Welcome to Lesson 1!

It looks like we are ready to go for lesson 1: Energy and Society. This lesson is going to teach us about energy! What is energy, and with which units do we measure energy? We will learn about the commonly used units we use to measure energy. There are different forms of energy that we use; for example, we use electrical energy or mechanical energy, like moving a car, etc., and we need to know the units in which we measure these different forms of energy. So we will also learn about forms of energy. We will learn about the units in which we measure these forms of energy, and also we will get into a very, very important distinction between energy and power. To be clear, that is the key concept in this lesson that I want you to concentrate on – power and energy. And once we know the difference, we know that using power, we can calculate energy, or if we know the energy and time, we can calculate power.

We will also look at some of those calculations. Once we know the power, we can calculate the energy. For example, a computer consumes some power, the rate at which energy is drawn, and if we use the computer for so many hours, what is the energy consumption by this computer? We can do the same thing for a refrigerator, or we can do it for any other appliance that you use at home. These are common appliances that we are using every day in our lives. When we add up the energy consumed by a computer, by a toaster, by an oven, by a refrigerator, by lighting, etc., at your place then you get energy consumption of all your equipment for a day. So we are going to do that and calculate energy consumption for a day, and then for a month, and we can calculate also the electric bill for one whole month -- that would be our objective in this lesson.

Be careful, again, because the distinction between energy and power is a very important concept. Forms of energy and the units in which we measure energy are the concepts that we will be looking at in this wonderful lesson. All Right! Why Wait? Let’s go and start our lesson.

Good Luck!

What is Energy?

When thinking about energy the following questions may come to mind:

• What is energy?
• How do we measure it?
• Where is it coming from?
• Do we have enough?
• What is the impact of energy use?

Energy is the lifeblood of any modern society. Energy is used in every walk of life. Without it, modern life would almost come to a standstill. From the moment of waking up in the morning with an alarm clock, we use energy for almost everything we do.

Energy is a property of matter that can be converted to work, heat, or radiation. It can move things or do work, produce heat even if it does not move anything, and be converted to light (or more accurately, radiation).

Lesson 1 Objectives

Upon completing this lesson, you should be able to:

• define energy
• articulate fundamental forms of energy
• know the different units of energy
• define and distinguish differences between energy and power
• classify Energy Sources

Checklist for Lesson 1

Please refer to the Calendar in Canvas for specific timeframes and due dates.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Six Basic Forms of Energy

Energy exists in a number of different forms, all of which measure the ability of an object or system to do work on another object or system. There are six different basic forms in which we use energy in our day-to-day life:

Mechanical Energy (Kinetic)

• Energy that a body possesses by virtue of its motion. A few examples are a baseball player pitching a ball, a plow being pulled by a tractor, and a hammer that is being used to pound nails.
• In the United States, we use about a third of our total energy for transportation or movement of people and goods.

Mechanical Energy (Potential)

• Energy that a body possesses by virtue of its position relative to a reference point. A few examples of mechanical energy include a pendulum, a bow (archery), a spring, and a hammer that is raised in preparation to pound nails.

Chemical Energy

• Energy locked in the bonds of molecules in the form of microscopic potential energy, which exists because of the electric and magnetic forces of attraction exerted between the different parts of each molecule.
  • It is the same attractive force involved in thermal vibrations.
  • The molecular parts get rearranged in the chemical reactions, releasing or adding to this potential energy.
• Some examples include a battery, burning wood, and glucose in the body.
• As of 2020, approximately 80% of the energy used in the U.S. comes from fossil fuels such as coal, oil, and natural gas.
  • All of these fuels store energy in the form of chemical energy.
  • When they are burned, these fuels release energy in the form of heat or thermal energy.

The glucose (blood sugar) in your body is said to have "chemical energy" because the glucose releases energy when chemically reacted (combusted) with oxygen. Your muscles use this energy to generate mechanical force (work) and also heat.

Thermal or Heat Energy:

• Energy that combines microscopic, kinetic, and potential energy of the molecules. Some examples of this include a hot beverage and boiling water.
• Temperature is really a measure of how much thermal energy something has: The higher the temperature, the faster the molecules are moving around and/or vibrating, i.e., the more kinetic and potential energy the molecules have.
• Fuels (chemical energy) are oftentimes burned and converted to thermal or heat energy, which is then converted to motion in an automobile or electricity.

Electrical Energy:

• Energy created through the movement of electrons among the atoms of matter.
• Although electricity is seldom used directly, it is one of the most useful and versatile forms of energy. Following are some examples. When electricity is:
  • put into a toaster, it can be converted to heat;
  • put into a stereo, it is converted into sound;
  • put into an electric bulb, it converts into light;
  • put into a motor, it converts into motion or movement (mechanical energy).
• Due to its versatility, electricity is in high demand; in the US, about 40% of the total primary energy used is converted into electricity for various uses.

Nuclear Energy:

• Energy produced when reactions occur in an atom, resulting in some type of structural change in the nuclei.
• Fusion occurs when two small nuclei join together to create one large nucleus or particle, and during this process, energy is released in the form of light and heat. An example is in the Sun: hydrogen nuclei fuse (combine) together to make helium nuclei, which release energy.
• Fission occurs when the nucleus of one big atom splits into two new atoms, and during this process, a tremendous amount of energy is released in the form of light and heat. An example is in a nuclear reactor or the interior of the earth: uranium nuclei split apart, causing energy to be released.

Radiation:

• Energy radiated or transmitted in the form of rays, waves, or particles. Some examples include:
  • visible light that can be seen by naked eye;
  • infrared radiation;
  • ultraviolet radiation (UV) that cannot be seen with the naked eye;
  • long wave radiation, such as TV waves and radio waves;
  • very short waves, such as x-rays and gamma rays.

Even things that we encounter in our every day life contain some radioactive material, either natural or man-made. Smoke detectors, compact fluorescent bulbs, some watches and granite countertops can emit some nuclear radiation. Even plane travel at high altitudes cause exposure from cosmic rays.

• Electromagnetic Radiation
  • Energy from the sun comes to the earth in the form of Electromagnetic radiation, which is a type of energy that oscillates (side to side) and is coupled with electric and magnetic fields that travel freely through space.
  • Electromagnetic radiation is composed of photons or particles of light, which are sometimes referred to as packets of energy.
  • Photons, like all particles, have properties of waves.

• Electromagnetic Spectrum
  • The “Electromagnetic spectrum“ is a representation of the wide range of wavelengths of electromagnetic radiation.
  • Photons are associated with visible light, which accounts for only a very limited part of the electromagnetic spectrum.
  • A great discovery of the nineteenth century was that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.

Please watch the following 5:00 video about the electromagnetic spectrum:

As depicted in the image above, the lower the energy, the longer the wavelength and lower the frequency, and vice versa.

The reason that sunlight can hurt your skin or your eyes is because it contains "ultraviolet light," which consists of high energy photons. These photons have short wavelength and high frequency, and pack enough energy in each photon to cause physical damage to your skin if they get past the outer layer of skin or the lens in your eye.

Radio waves, and the radiant heat you feel at a distance from a campfire, for example, are also forms of electromagnetic radiation, or light, except that they consist of low energy photons (long wavelength and high frequencies - in the infrared band and lower) that your eyes can't perceive. This was a great discovery of the nineteenth century - that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.

About 20% of the electricity used in the US is used to produce visible light for lighting purposes.

Can you identify the different forms of energy in the picture below? Enter your answer in the table below and click the "Check Answers" button to check your work.

The six fundamental forms of energy: Mechanical, Chemical, Thermal/Heat, Electrical, Nuclear, and Radiation.
Click link to expand for a text description of the figure

These things, listed below, represent the six fundamental forms of energy: Mechanical, Chemical, Thermal/Heat, Electrical, Nuclear and Radiation. Your task is to determine what form of energy is represented by each item.

• Light bulb in a lamp post powered by?
• Two women sitting at a picnic table drinking water. The arrow is pointing to the cups of water. One cup is sitting on the table and the other is in a woman's hand.
• A doctor looking at an X-ray produced with?
• A Frisbee flying through the air powered by?
• The sun power by?
• A man getting ready to hit a golf ball with a golf club. The arrow is pointing at the head of the golf club which is powered by?
• A little boy eating an ice cream cone. The arrow is pointing to the ice cream that provided what to the child?

Now spend some time trying to identify the different forms of energy that are at work in the above items. Once you have thought through this and have some answers, read on to see if you are correct.

Answers

Light bulb in a lamp post - Electrical Energy

Cups of water. One is sitting on a table and the other is in a woman's hand. - Thermal or Heat Energy

An X-ray - Nuclear Energy

A Frisbee flying through the air - Mechanical (kinetic) Energy

The sun - Radiation

A golf club getting ready to hit a ball - Mechanical (Potential)

The ice cream in an ice cream cone - Chemical

Energy can be converted from one form to another.

Examples:

• Gasoline (chemical) is put into our cars, and with the help of electrical energy from a battery, provides mechanical (kinetic) energy.
• Purchased electricity is fed into our TVs and is converted to light and sound.
• Similarly, purchased electricity goes into an electric bulb and is converted to visible light and heat energy.
• The image below shows examples of more conversions.

Examples of Day-to-Day Energy Transformations
Click link to expand for a text description of figure

Chemical Energy is converted to Electrical Energy (stove), Kinetic Energy (car), Electricity (power plant), and Mechanical Energy (space shuttle). Electrical Energy is converted to Kinetic Energy. Electricity is converted to Light (light bulb) and Sound and Light (TV). Chemical food energy is converted to Energy to Work (person running).

Units of Measurement

How is energy measured? It is measured in various units by various industries or countries, in much the same way as the value of goods is expressed in Dollars in the U.S. and Yen in Japan and Pounds in Britain.

The table below identifies different units for measuring energy. A lot of it also has some historical context. Our early studies of energy involved heating things up, so we name units based on how hard it was to heat things. Makes sense, right? Now we pass electrical energy to operate many devices, so now we use units that "better" capture this process.

Here is a fun way to understand your energy use

Prof. Bruce Logan of Penn State published a fascinating way to view your energy and climate impact. Using what you learned in this section, you can start to piece together just how much energy each of us uses to maintain our busy lifestyles.

The premise of this approach is to define (another!) unit of energy, but one with a bit more meaning. The daily energy unit, D. We are all supposed to eat about 2000 food Calories a day to survive. So, let’s set this amount of energy to equal 1 D. Now, how many Ds does the typical U.S. home each day (normally in KWh) or operate a car (normally joules or BTUs )?  This method of comparing energy consumption allows us to better understand the scale of our energy habits (which might be shocking!) and tell you how many big mac-powered humans it would take to do what your car does…

Here are a few examples he shows to give you an idea.

• Food for 1 day = 1 D
• Running a single 100 W light bulb all day = 1.03 D
• Average daily electricity use for a US house = 13 D
• 1 gallon of gasoline used in an average car (goes 18 miles) = 15.2 D
• Natural gas for daily heating a US house = 31 D

Once we tally up all the energy it takes to fuel our lifestyle (professional + personal uses), each person consumed about 101 D of energy! (remember this is daily) For comparison, a Swiss citizen consumes about 54 D. Check out his website for more comparisons. Watch this video (5 min 46 sec)

Energy is stored and is available in different forms and sources. The ~24,000 times more solar energy that is available than we need is not in a readily usable form. It needs to be concentrated.

For example, when oil (a concentrated fuel) is burned with air, the resulting gases can reach high temperatures. Solar energy, as it is, is not concentrated and cannot reach those high temperatures. Therefore, we use more concentrated energy sources. These sources are divided into two groups—renewable and nonrenewable.

Renewable Energy Sources:

• Energy sources that can be replenished over and over again; they are never depleted. Some examples include hydropower, solar, wind, tidal, geothermal energy from inside the earth, biomass from plants, and nuclear fusion.
• These types of energy sources are usually converted into electricity or thermal (heat) energy. 

Nonrenewable Energy Sources:

• Energy sources that we are using up and cannot produce in a short period of time. Some examples include fossil fuels (Petroleum Oil, Natural Gas, and Coal), Tar Sands, and Nuclear Fission.
• Another nonrenewable energy source is the element uranium, whose atoms we split (through a process called nuclear fission) to create heat, and ultimately, electricity.
• These types of energy sources are usually converted into electricity and mechanical energy.
• We get most of our energy from these nonrenewable energy sources.

Fossil Fuel Distribution

Fossil fuels, non-renewable energy sources formed over a million years, are not distributed uniformly over the earth’s surface. Depending on the climate conditions millions of years ago, certain parts of the land masses were favorable for organic matter to grow and thrive.

Over geological ages, these land masses moved, and certain regions are richer in fossil fuels than others. Review the information on the map below, and then answer the questions below the map based on your observations.

Fossil Fuel Distribution Activity

Credit: Roke [CC BY-SA 3.0], via Wikimedia Commons

Click link to expand for a text description of the image

Global Distribution of Natural Resources

The most abundant resources for various global regions are as follows:

• China is richest in coal
• Australia is richest in coal
• The Middle East is richest in petroleum
• The United States is richest in coal
• Russia is richest in natural gas

Human Use of Energy Sources

The activity below is a drag and drop. Select the items listed in the center of the image and drag them to the corresponding or matching energy type listed on the side. 

What is Power?

Click the "play" button below and observe what happens. (Note: The video has no audio.)

Power vs. Energy

Both cyclists did the same amount of work (they both pedaled 10 miles), and used the same amount of energy (218 calories). The blue cyclist, however, demonstrated the most power, because he did the equivalent amount of work as the red cyclist, but in a faster time.

Measuring Power

Units of Power are not the same as units of energy (i.e., Btus, calories). Units of power are measured in terms of units of energy used per some unit of time.

Examples of Units of Power include:

• Watt (W) = 1 joule of energy per second or 1 J/S
• BTU per hour (BTUs/h) = 1,055J
• Horsepower (hp) = 550 foot-pounds per second or 550 ft lb/S
• Calories per second (cal/sec)
• Kilowatt (kW) = 1,000 watts

Calculating Power

Power can be determined by the following formula:

Power & Cost of Energy

We can also use a version of the Power formula to determine Cost of Energy:

Calculating Energy Use

How is energy use of Home Appliances calculated?

You just learned in a previous discussion on power that:

By modifying this formula slightly, we can determine Energy Consumption per Day:

Where:

• Energy Consumption will be measured in Kilowatt hours (kWh) - like on your utility bills.
• Power Consumption will be measured in Watts
• Hours used per Day will be the actual time you use the appliance.

Since we want to measure Energy Consumption in Kilowatt hours, we must change the way Power Consumption is measured from Watts to Kilowatts (kWh). We know that 1 kilowatt hour (kWh) = 1,000 Watts hours, so we can adjust the formula above to:

What is the energy consumption of a refrigerator with a wattage rating of 700 Watts when it is operated for 24 hours a day?

Step 1

To solve, use the following formula:

Where:

Energy Consumption = Watt Hours (Wh) or KiloWatt Hours (kWh)

Power Consumption = Watts (W) or kW (KiloWatts)

Number of Hours Operated = Hours (h) For the example above:

Energy Consumption = 700 W x 24 h

Energy Consumption = 16800 W h

Step 2

To convert from Wh to kWh, remember that 1kWh = 1000 Wh

To solve, set up as a ratio and use linear algebra to solve for ?.

Locating Wattage

You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.

You can find the wattage information on the bottom or back of many appliances.

Credit: thefamily8 from flickr is licensed under BY CC 2.0

A refrigerator, although turned "on" all the time, actually cycles on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals.

To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

The table below shows wattage of some typical household appliances.

Amperes and Voltage

If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance.

Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage.

If not, find an ammeter to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment.

Take a reading while the device is running; this is the actual amount of current being used at that instant.

Phantom Loads

Also note that many appliances continue to draw a small amount of power when they are switched "off."

These "phantom loads" occur in most appliances that use electricity, such as VCR, televisions, stereos, computers, and kitchen appliances.

Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance.

Review

Watch this 3 minute 41 second video review Lesson 1

Extra Resources

For more information on topics discussed in Lesson 1, see these selected references:

• Energy Information Administration ("Energy Kid's Page")
• A Consumer's Guide to Energy Efficiency and Renewable Energy

Welcome to Lesson 2!

You are already to Lesson 2: Energy Supply and Demand. These energy supply and demand lessons will explore more about energy resources. Basically, you will be able to appreciate global and national consumption patterns. We will go over what kinds of energy we have been consuming, how much we have been consuming, and how we compare with the rest of the world, etc., over the past few decades. Based on those patterns, we can also deduce some information about how much energy we use to do a job; energy intensity. What kind of energy sources we will be needing, and how much we will be needing based on the past trends?

We will also look at energy reserves. Do we have those? Will we need more renewables, batteries, coal, more oil, or more gas? Can we (sustainably) use any of those resources? If we can, great, if not, what do we do? We will be doing those kinds of energy analysis. So, obviously, you are going to see a lot of numbers and statistics. One of the questions that I always get is: Hey, do I have to remember all these numbers? In 2019, petroleum and natural gas accounted for 69 % of energy consumption in this country, and renewables accounted for 11% of the electricity generated by utility companies.

Do we have to remember these numbers? My advice is, you don’t have to remember everything but you need to get the main message behind these numbers. In other words, you have to know the fact that petroleum and natural gas are the main energy sources. Similarly, over 75% of our oil products or petroleum products are used for transportation. So, we need to know that transportation is basically run by petroleum; petroleum is mostly used for transportation. That is the message. You don’t need to remember the exact numbers. But if there is something that has very insignificant or significant quantities, you should note that. For example, renewable energy sources supply about 10% of our energy source (although the exact number is about 11%). That is the message. You don’t need to worry about whether it is 9.2 or 9.5 or 8.5 or 11.2%. So just to give you a clue, you don’t have to worry about the exact numbers, but the message that is conveyed using these numbers is what you have to concentrate on. And we will also have one numerical type of problem in this lesson. That problem will be predicting the energy needed for the future. The problem follows an exponential function, and we will talk about that, and there will be a few numerical problems for you to practice.

See the Calendar tab in Canvas for due dates/times.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Energy consumption numbers are always reported a few years behind, so we are always looking into the past before we plan for the future. As of 2021, The world's total primary energy consumption was about 176,000 TWhs (580 Quadrillion Btus).

Table 2.1 below shows various regions and total primary energy consumption history.

From the Table 2.1, it can be seen that the energy consumption is high for the Far East and Oceania. The amount of energy used depends on the economic prosperity of the nation and the population of the country. The North American region includes Canada, the United States, and Mexico. The Far East and Oceania include developed nations such as Japan and Australia, and densely populated developing nations such as China and India. Obviously, due to highly populated countries like China and India, total energy consumption does not reflect the quality of life of the people in those countries. Figure 2.1 shows the energy per capita consumption over the last 30 years. As can be seen from the graph that Far East and Oceania used a lot of energy as a region, but per capita energy consumption is relatively low implying that if each person in that region would consume as much as in North America, that Region's energy consumption would skyrocket.

Per Capita Energy Consumption (MMBTU/person) every ten years.

Credit: Sarma Pisupati

The productivity of a country is measured by the total value (dollars) of goods and services, called Gross Domestic Product (GDP), produced by its people. Therefore, the average value of goods and services produced by each person - the GDP per capita of a country - is an indicator of the quality of life.

Energy intensity is the relationship between energy consumption and growth in gross domestic product (GDP), and it is an important factor that affects changes in energy consumption over time.

• In industrialized countries, history shows the link between energy consumption and economic growth to be a relatively weak one, with growth in energy demand lagging behind economic growth.
• In developing countries, however, the link between energy consumption and economic growth have been more closely correlated with energy demand growing in parallel with economic expansion.

The total primary energy consumption of the world in 2015 was 570 Quadrillion Btus and in 2017 it increased to 582.4

Energy Consumption as a Function of Quality of Life in Industrialized Countries

Credit: Sarma Pisupati

Energy Consumption as a Function of Quality of Life in Developing Countries

Credit: Sarma Pisupati

Global Energy Consumption and GDP per person

In general, as the GDP (Gross Domestic Product) per person of any country increases, the amount of energy that is consumed is also expected to increase.

• For developing nations, the correlation is much stronger.
• For developed nations, the correlation is weak.

For example, Iceland, Finland, the United States, and the Netherlands, with similar GDP per capita, have significant differences in energy consumption per capita. In other words, to produce one dollar's worth of goods and services, the U.S. uses twice the energy of the Netherlands. Similarly, Iceland uses four times the energy of the Netherlands.

Energy Intensity

Credit: Sarma Pisupati

Energy Consumption Differences

The differences in energy consumption among countries are the result of:

• efficiency of industrial, transportation, commercial, and residential energy,
• climatic and geographical areas of a country,
• lifestyles (use of more gas guzzling cars and SUVs and bigger sized houses), and
• the nature of the products produced by the nation's industries.

New York City

Credit: Superheros and Villains by Andreas Komodromo is licensed under CC BY-NC 2.0

Bangladesh

Credit: Signs on the river bank by abrinsky is licensed under  BY-NC-SA-2.0

Click here ot see Global Average Change in Energy Production by Fuel 

and determine production of energy which energy sources decreased over the last 5 decades.

The world energy requirements are projected by several energy companies such as British Petroleum and Exxon Mobil and international agencies like International Energy Agency (IEA) and US Energy Information Administration (EIA). The United States Department of Energy projects strong growth for worldwide energy demand over the 28-year projection period from 2012 to 2040. Although these projections or forecasts are based on the same principles, they differ slightly. They are also often wrong! For example, the rate of renewable adoption is continuously underestimated. Detailed projections of each organization can be seen through the following external links.

• International Energy Agency
• British Petroleum
• Exxon Mobil
• US Energy Information Administration (EIA)

According to International Energy Outlook 2019,

• Manufacturing centers are shifting toward Africa and South Asia, especially India, resulting in energy consumption growth. Most economic growth happens in non-OECD countries, where GDP per person nearly triples from 2018 to 2050.
• The total world energy consumption is likely to increase from 591 quadrillion Btus in 2016 to 910 quadrillion Btus in 2040, an increase of 54%.
• Most economic growth happens in non-OECD countries, where GDP per person nearly triples from 2018 to 2050. Most energy-intensive manufacturing shifts to non-OECD Asia and, increasingly, to India.

The world's GDP (expressed in purchasing power parity terms) rises by 2.4%/year from 2018 to 2040. The fastest rates of growth are projected for the emerging, non-OECD countries, where combined GDP increases by 3.5%/year. In OECD countries, GDP grows at a much slower rate of 1.5%/year over the projection period.

The World’s energy supply sources

Before the global pandemic, the World’s energy supply sources followed long-term trends, with new fuels increasing in share and old fuels losing ground. Below, you can see consumption history for the years 1990 to 2018.

Figure 2.3. Global Energy Supply by Source. ktoe means kiltons of oil equilivents.

(https://www.iea.org)

Here we can see the role of renewables and natural gas quickly growing.

Figure 2.3a. Global Energy Supply By Percent.

(https://www.iea.org)

Three of the world’s largest energy sources

Energy Consumption and Electricity Projections

According to International Energy Outlook 2019, the strongest growth in electricity generation is projected to occur among the developing, non-OECD nations. Increases in non-OECD electricity generation average 2.5%/year from 2012 to 2040, as rising living standards increase demand for home appliances and electronic devices, as well as for commercial services, including hospitals, schools, office buildings, and shopping malls. In the OECD nations, where infrastructures are more mature and population growth is relatively slow or declining, electric power generation increases by an average of 1.2%/year from 2012 to 2040.

Fig 2.5 World energy consumption by type.

Credit: www.EIA.gov

Projections of Energy consumption by use.

https://www.eia.gov/outlooks/ieo/pdf/ieo2020.pdfmage credit here

 As can be seen from the figures, the role of renewables are expected to change dramatically in the coming years.  What a transition!

Nuclear Power

Worldwide, electricity generation from nuclear power is projected to remain largely unchanged into 2040.

According to International Energy Outlook projections by US Department of Energy (US DOE), there is still considerable uncertainty about the future of nuclear power, and a number of issues could slow the development of new nuclear power plants. Issues related to plant safety, radioactive waste disposal, and proliferation of nuclear materials continue to raise public concerns in many countries and may hinder plans for new installations. Although the long-term implications of the disaster at Japan's Fukushima Daiichi nuclear power plant for world nuclear power development are unknown, Germany, Switzerland, and Italy have already announced plans to phase out or cancel all their existing and future reactors. In contrast, developing Asia is poised for a robust expansion of nuclear generation. Most of the increase is by China's addition of 139 gigawatts (GW) of nuclear capacity from 2012 to 2040.

In a nuclear plant, heat is produced by nuclear fission (splitting of an atom's nucleus into many new atoms) inside uranium fuel. As a result of fission, heat energy is released and the steam spins a turbine generator to produce electricity.

Renewables

Sizable growth in the world’s consumption of renewable energy resources is projected over the next 25 years. Much of the projected growth in renewable generation is expected to result from the completion of solar installations all throughout the world. Dramatic reductions in the cost of solar panels has led to this source being one of the cheapest forms of electric power generation as of 2020. In 2020, 90 % of all new electric power generation installations were renewable across the globe.

In hydroelectricity, mechanical energy from the water being pulled downward by gravity is converted to electrical energy. More specifically, a hydroelectric generator directs the flow of water through a turbine, which extracts the kinetic energy from the movement of the water and turns it into electricity through the rotation of electrical generators. Hydropower is the largest single renewable electricity source today, providing 16% of world electricity at competitive prices. It dominates the electricity mix in several countries, developed, emerging, or developing. However, wind and solar are quickly catching up.

For a long time, growth in the world and the U. S. energy consumption as a function of time, follow what is known as exponential function. Now it looks like we have switched to linear growth, but time will tell if this is a permanent change.  The exponential increase is characterized as follows. The amount of change (increase in energy consumption) per unit time is proportional to the quantity (or consumption) at that time.

$$\frac{\Delta N}{\Delta t}\propto N$$

or

$$\frac{\Delta N}{\Delta t}=\lambda N$$

Where Greek letter Δ(delta) is the change or increment of the variable and λ (lambda) is the growth rate. After some mathematical methods, it can be shown that the equation changes to the form

$$N=N_0{e}^{\lambda t}$$
where e is a constant = 2.71

We can determine how long it takes for N0 to become 2N0 (twice its original number or double). That time period is called doubling time. After some mathematical steps it can be written as:

Until so far that the energy requirement is going to increase in the future and also that the U.S. and the rest of the world will depend to some extent on fossil fuels. These fossil fuels are non-renewable fuels with a finite lifetime. So, the question is: Will we have enough supply for future energy requirements?

The answer to this question depends on the quantity of fossil fuels we have in the ground. Energy sources that have been discovered but not produced cannot be easily measured. Trapped several feet below the surface, they cannot be measured with precision. There are several terms used to report the estimates of the energy resources. The most commonly used terms are “reserves” and “resources.”

• "Reserves" represent that portion of demonstrated resources that can be recovered economically with the application of extraction technology available currently or in the foreseeable future. Reserves include only recoverable energy.
• “Resources” represent that portion of the energy that is known to exist or even suspected to exist, irrespective of technical or economic viability. So reserves are a subset of resources.

As of 2016, total world proved recoverable reserves of coal were estimated at 948 billion short tons.

Five countries have nearly 73% of the world's coal reserves:

• United States—28%
• Russia—18%
• China—13%
• Australia—9%
• India—7%

Based on data from OPEC (Oil Producing and Exporting Countries), the highest proved oil reserves including non-conventional oil deposits are shown in the graphic below.

OPEC share of world crude oil reserves, 2018

Source: Opec

Based on data from BP (British Petroleum), proved gas reserves were dominated by three countries: Iran, Russia, and Qatar, which together held nearly half the world's proven reserves. According to the US CIA The World Factbook, the US has the 5th largest reserves of natural gas. Due to constant updates about the shale gas estimates, these are difficult to say with certainty.

How Long Will the Reserves Last?

How long these reserves do last depends on the rate at which we consume these reserves. For example, let’s assume that we have $100,000 in the bank (reserves) and if we draw 10,000 dollars every year (consumption) the reserve will last for 10 years (\$100,000/\$10,000 per year). However, in this case, we are assuming that we do not add any money to our deposit, and we do not increase our withdrawal.

This is generally not true in the case of life of an energy reserve. We may find new reserves, and our energy consumption or production can also increase. In the case of energy reserve, although we know that we might find new resources, we do not know how much we could find. But the consumption can be predicted with some accuracy based on the past rates.

Lifetime of current reserves at constant consumption

We can calculate the life of current petroleum reserves by dividing the current reserves by current consumption.

• At the current rate of consumption, the approximate lifetime of the world’s petroleum, natural gas, and coal reserves is 50 years, 52.8 years, and 153 years, respectively. (BP Statistical Review of World Energy)
• At the current rate of consumption, the current U. S. petroleum, natural gas, and coal reserves will last approximately for 4.88 years, 12.2 years, and 258 years, respectively.

It is important to note that the entire U.S. petroleum consumption is not coming from the U.S. reserves because we import more than one half of the consumption. Because we import more than one half of the consumption, the petroleum reserves at the current rate will last about 11 years. If the consumption increases in the future, the life will be less. However, there is also a chance of adding more reserves with more exploration and discoveries. The increase in consumption can change depending on the price of petroleum and other alternative fuels. Likewise, us moving to electric cars and harnessing unconventional oil reserves can extend the lifetime of these reserves.

Therefore, these lifetimes are not carved in stone. It can be debated whether the U.S. reserves will last for 6 years or 10 years or even 20 years, or we may never run out! But there is increasing consensus that we must change our lifestyle. Even if we won't run out, the environmental consequences of continued use are pushing us to change anyway, but more on that later..

The R/P ratio can change from year to year, similar to our bank balance. We can add more if we make more or consume more. That changes the time we can draw on the balance.

The following figures illustrate that these ratios changed.

Fig Variation of R/P ratio Over Time for Oil

Credit: Data from British Petroleum

Therefore, we must conserve, innovate (get more with less), or learn to live without these resources.

US Energy Supply and Demand

When focusing on the energy supply and demand, it can be helpful to see where the energy is going. Which of our daily activities consume the most energy? Several agencies track this very closely.

The 2019 energy flow chart released by Lawrence Livermore National Laboratory details the sources of energy production, how Americans are using energy and how much waste exists.

Source for a clearer image: Lawrence Livermore National Laboratory (LLNL)

Globally, many interesting transitions are occurring. While the U.S. was once the top consumer of energy, China claimed this title in 2009.

As a result of innovations in oil and gas extraction, U.S. imports have dropped considerably. 

US Energy Imports between 1950 and 2019

Credit: EIA Energy Explained

Looking at the U.S. Energy Profile,  It can be seen from the imports profile that the US Crude oil imports have significantly reduced between 2005 and 2019 from a peak of 25 Quadrillion BTUs. Another significant change that can be noted is that the US is now exporting natural gas (below zero on the y axis) instead of importing it. Although crude oil is imported, US exports finished petroleum products resulting in less net imports. As a matter of fact, US total energy exports exceeded the imports in 2019 since 1950.

The top five countries (sources) of US total petroleum in 2019 were Canada (49%), Mexico (7%), Saudi Arabia (6%), Russia (6%) and Columbia (4%).

The U.S. also ranks:

• first in worldwide reserves of coal;
• sixth in worldwide reserves of natural gas;
• eleventh in worldwide reserves of oil.

US Energy Consumption by Source and the chart of the US Energy consumption by source and user sector shows each energy source and the amount of energy it supplies in British thermal units (BTU). Petroleum is the leading source of energy in the US in 2019 with 36.72 quadrillion BTUs. Next is natural gas with 32.10 quadrillion BTUs. Coal supplies 11.31 quadrillion BTUs of energy. Renewable energy and nuclear power are responsible for 11.46 and 8.46 quadrillion BTUs respectively. Of the total petroleum consumption, 72% is used for transportation and another 23% is used by the industrial sector. Similarly, 35% of the natural gas (largest fraction) is used for power generation. On the other hand, 76% of the residential and commercial energy needs are met by natural gas. The actual percentages are not required to be memorized but answers to the questions such as: Which fuel is most used by power plants for power generation? Which sector uses petroleum the most? Approximately what fraction of the electricity is generated by renewable energy? (10, 25, 50 or 90) What is the primary purpose of coal use? etc. need to be answered.

US Energy Consumption by Source and Sector

The graph shows how dependent the U.S. is on our petroleum supply, as it accounts for almost 37% of our energy. Our next two highest sources of energy, like petroleum, are non-renewable and include natural gas and coal. Only about 11%  of our energy comes from renewable energy sources such as wood and water (hydroelectricity). According to Energy Information Administration, US renewable energy consumption surpassed coal for the first time in over 130 years in 2019. Of the 4.12 trillion kWh of electricity generated in the US, 38% was from natural gas, coal accounted for about 23% and nuclear adding another 20%. Renewable sources contributed to 17% of the total electricity generated.

In 2019, fossil fuels made up 81% of total U.S. energy consumption, the lowest fossil fuel share in the past century. According to EIA projections, the percentage declines to 76.6% by 2040. Policy changes or technology breakthroughs that go beyond the trend improvements could significantly change that projection. In 2019, the renewable share of energy consumption in the United States was its largest since the 1930s at nearly 11.7%. The greatest growth in renewables over the past decade has been in solar and wind electricity generation. Liquid biofuels have also increased in recent years, contributing to the growing renewable share of total energy consumption. 2020 was the first year that renewables surpassed coal consumption in the U.S.

US Energy Consumption Over Time

US Primary Energy Consumption History in Quadrillion BTUs

Credit: US EIA, Energy Monthly Review Jan. 2021

The most significant decline in recent years has been coal: U.S. coal consumption fell by 41% since 2009 in a decade, from 997 million tons to 587 million tons. Biomass, which includes wood as well as liquid biofuels like ethanol and biodiesel, remain relatively flat, as wood use declines and biofuel use increases slightly. In contrast, wind and solar are among the fastest-growing energy sources in the projection, ultimately surpassing biomass and nuclear.

Net U.S. imports of energy declined from 30% of total energy consumption in 2005 to 13% in 2013 and down to 7.6 % in 2017, as a result of strong growth in domestic oil and dry natural gas production from tight formations and slow growth of total energy consumption.

US Energy Consumption History

The plot of US energy consumption shows the relative amounts of each type of energy that was consumed for each year.  The history of the energy consumption profile of the United States indicates that petroleum makes the largest part of the energy demand over the past seven decades. Natural gas has taken the second over the past decade with the production of gas from shale. Coal has been replaced by renewable energy and natural gas for electricity generation. Among the renewable energy sources, biomass has the larger share followed by wind energy. Wind energy and solar energy are the fastest growing energy sources.

Growth of Renewables in the U.S.

EIA.gov

U.S. energy consumption projections by source and by sector.

https://www.eia.gov/outlooks/aeo/

Answers to the following questions need to be looked for in the material presented above.

• Of all the renewable energy sources, which renewable source is used most?
• Which of the renewable sources is used most for transportation?
• Approximately what fraction of the electricity is generated by nuclear energy? (10, 20, 50 or 90)

US Vehicle Fuel Consumption

The table below shows the vehicle fuel consumption and travel between 1960 and 2018.

Electricity

US electricity generation is expected to grow from 3.7 trillion kilowatthours in 2015 to 4558 trillion kilowatthours in 2035. Visit the webpage US electricity explained - Sources and profiles

Examine for 

• Sources of U,.S electricity generation
• What are the notable changes in the major sources for  electricity generation between 1950 and 2019?
• Role of renewable energy in the electricity generation.

Growth in electricity use for computers, office equipment, and electrical appliances in the residential and commercial sectors is partially offset by improved efficiency in these and other, more traditional electrical applications, by the effects of demand-side management programs, and by slower growth in electricity demand for some applications, such as air conditioning.

Most capacity additions over the next 10 years are renewables and natural gas, increasing the natural gas share to 26 percent and lowering the coal share to under 20 percent.  The nuclear generation (about 9 percent of total electricity supply in 2012) is projected to remain at about 9 percent in 2050.

Review

Watch the following 4 minute 50 second video Review for Lesson 2.

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. Why is the energy use per person in the world increasing?
2. The United States, with 5% of the world's population, uses about 25% of the world's energy and contributes 25% of the world's greenhouse gas emissions. Explain.
3. List the reasons why the United States per capita energy consumption is the highest of any other region in the world.
4. List reasons why the United States energy consumption per dollar of GDP is higher than most of the industrialized nations.
5. What is the difference between reserves and resources?
6. List the changes that you would make in your personal lifestyle if you were mandated to reduce your energy consumption by 25%.
7. What variables determine the lifetime of a nonrenewable resource?

Extra Resources

For more information on topics discussed in Lesson 2, see these selected references:

1. Hinrichs, R. A., “Energy,” Saunders College Publishers, Philadelphia, PA, 1992.
2. Aubrecht, G. L., “Energy,” Prentice Hall, Inc., Englewood Cliffs, NJ, 1995.
3. Fay, J.A. and Golomb, D. S., “Energy and the Environment,” Oxford University Press, New York, NY, 2002.
4. Christensen, J. W., “Global Science: Energy Resources Environment”, 4th edition, Kendall/Hunt Publishing Company, Dubuque, IA, 1996.
   Energy Information Administration, Annual Energy Review, U.S. Department of Energy, 2004.
5. Energy Information Administration, Annual Energy Outlook, DOE/EIA 0383 (2004), U.S. Department of Energy, Washington D.C., 2004.
6. Energy Information Administration, International Energy Outlook, DOE/EIA 0484 (2004), U.S. Department of Energy, Washington D.C., 2004.

Welcome to Lesson 3!

Alright, we are into lesson 3. Lesson 3 basically deals with energy efficiency. Upon completing this lesson, you will really get a quantitative feel for what energy efficiency is and also how to calculate energy efficiency with a conversion device. A conversion device can be anything – an automobile or a power plant or any device that converts one form of energy to another form.

And we will also understand the concept of entropy. Entropy is disorder. Because of entropy, our efficiencies are lower than what we normally expect. And we will look at the operating principle of a heat engine. A heat engine is a device that converts heat to work. Particularly, automobiles are all heat engines, and they are notoriously inefficient. We will see 2 examples and calculations of why these automobiles are notoriously inefficient.

We can also calculate the efficiency of a whole process from the step efficiencies. For example, if it involves 2 or 3 steps like in a relay race. You know you have 3 or 4 players taking the baton and one lap by each of the athletes. So, what is the overall or team efficiency if we know the efficiency of each of those steps or the efficiency of each of those players? That is a very important concept in this chapter.

While doing this, we will also learn about temperature scales; Kelvin scale, Fahrenheit, and also Celsius. So there will be a lot of numerical problems in this lesson.

Alright! Good luck!

Lesson 3 Objectives

Upon completing this lesson, you should be able to:

• define and calculate efficiency of an energy conversion device;
• articulate the concept of entropy;
• explain operating principles of a heat engine; and
• calculate overall efficiency from step efficiencies.

See the calendar in Canvas for due dates/times.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

In the first lesson, we saw that energy can be transformed from one form to another, and during this conversion, all the energy that we put into a device comes out. However, all the energy that we put in may not come out in the desired form.

For example, we put electrical energy into a bulb and the bulb produces light (which is the desired form of output from a bulb), but we also get heat from the bulb (undesired form of energy from an electric bulb).

Electrical energy conversion to light and heat.

Therefore, energy flow into and out of any energy conversion device can be summarized in the diagram below:

Energy Flow Diagram for an Energy Conversion Device

When all forms of energy coming out of an energy conversion device are added up, it will be equal to the energy that is put into a device. Energy output must be equal to the input. This means that energy can not be destroyed or created. It can only change its form.

In the case of an electric bulb, the electrical energy is converted to light and heat.

Self Check

Instructions: Identify the useful energy output(s) and undesirable energy output(s) in the energy conversion devices below. Enter your answers in the fields provided, and click the "Check" button to check your work. 

Efficiency is the useful output of energy. To calculate efficiency, the following formula can be used:

$$Efficiency=\frac{UsefulEnergyOutput}{TotalEnergyOutput}$$

The previous example about an electrical motor is very simple because both mechanical and electrical power is given in Watts. Units of both the input and the output have to match; if they do not, you must convert them to similar units.

Practice 2

The United States' power plants consumed 39.5 quadrillion Btus of energy and produced 3.675 trillion kWh of electricity. What is the average efficiency of the power plants in the U.S.?

Energy Efficiencies

Energy efficiencies are not 100%, and sometimes they are pretty low. The table below shows typical efficiencies of some of the devices that are used in day to day life:

From our discussion on national and global energy usage patterns in Lesson 2, we have seen that:

• about 40% of the US energy is used in power generation;
• about 27% of the US energy is used for transportation.

Yet the energy efficiency of a power plant is about 35%, and the efficiency of automobiles is about 25%. Thus, over 62% of the total primary energy in the U.S. is used in relatively inefficient conversion processes.

Why are power plant and automobile design engineers allowing this? Can they do better?

There are some natural limitations when converting energy from heat to work.

Thermal energy is energy associated with random motion of molecules. It is indicated by temperature, which is the measure of the relative warmth or coolness of an object.

A temperature scale is determined by choosing two reference temperatures and dividing the temperature difference between these two points into a certain number of degrees.

The two reference temperatures used for most common scales are the melting point of ice and the boiling point of water.

• On the Celsius temperature scale, or centigrade scale, the melting point is taken as 0°C and the boiling point as 100°C, with the difference between them being equal to 100 degrees.
• On the Fahrenheit temperature scale, the melting point is taken as 32°F and the boiling point as 212°F, with the difference between them being equal to 180 degrees.

It is important to realize, however, that the temperature of a substance is not a measure of its heat content, but rather, the average kinetic energy of its molecules resulting from their motions.

When water molecules freeze at 0°C, the molecules still have some energy compared to ice at -50°C. In both cases, the molecules are not moving, so there is no heat energy.

So what is the temperature at which all the molecules have absolutely zero energy? A temperature scale can be defined theoretically, for which zero degree corresponds to zero average kinetic energy. Such a point is called absolute zero, and such a scale is known as an absolute temperature scale. At absolute zero, the molecules do not have any energy.

The Kelvin temperature scale is an absolute scale having degrees the same size as those of the Celsius temperature scale. Therefore, all the temperature measurements related to energy measurements must be made on Kelvin scale.

Energy conversions occurring in an automobile are illustrated below:

Energy Conversions in an Automobile

Any device that converts thermal energy into mechanical energy—such as an automobile or a power plant—is called a heat engine. In these devices, high temperature heat (thermal energy) produced by burning a fuel is partly converted to mechanical energy to do work and the rest is rejected into the atmosphere, typically as a low temperature exhaust.

Heat Engine

A general expression for the efficiency of a heat engine can be written as:

$$\text{Efficiency =}\frac{\text{Work}}{{\text{HeatEnergy}}_{Hot}}$$

We know that all the energy that is put into the engine has to come out either as work or waste heat. So work is equal to Heat at High temperature minus Heat rejected at Low temperature. Therefore, this expression becomes:

$$\text{Efficiency=}\frac{{\text{Q}}_{\text{Hot}}{\text{-Q}}_{\text{Cold}}}{{\text{Q}}_{\text{Hot}}}$$

Where, Q_Hot = Heat input at high temperature and Q_Cold= Heat rejected at low temperature. The symbol (Greek letter eta) is often used for efficiency this expression can be rewritten as:

$${\eta }^{\prime }\left(\%\right)=1-\frac{Q_{Cold}}{Q_{Hot}}\times 100$$

The above equation is multiplied by 100 to express the efficiency as percent.

French Engineer Sadi Carnot showed that the ratio of Q_HighT to Q_LowT must be the same as the ratio of temperatures of high temperature heat and the rejected low temperature heat. So this equation, also called Carnot Efficiency, can be simplified as:

The Carnot Efficiency is the theoretical maximum efficiency one can get when the heat engine is operating between two temperatures:

• The temperature at which the high temperature reservoir operates ( T_Hot ).
• The temperature at which the low temperature reservoir operates ( T_Cold ).

In the case of an automobile, the two temperatures are:

• The temperature of the combustion gases inside the engine ( T_Hot ).
• The temperature at which the gases are exhausted from the engine ( T_Cold ).

It's like taxes. The more money you earn (heat), the more money is taxed (cold), leaving you with less money to take home (efficiency). However, if you could earn more money (heat) and find a way to have less taxes taken out (better engine material), you would have more money to take home (efficiency).

Below is a table showing two temperature scales. The scale labeled "HOT," shows the range of temperatures for the combustion of gases in a car engine. The scale labeled "COLD," shows the range of temperatures at which gases are exhausted from the car engine.

Car Engine Temperatures: red indicates combustion temperatures and blue indicates exhausted temperatures.

Instructions: Look carefully at the efficiency numbers in the body of the table. How do the Hot and Cold temperatures' effect on the efficiency.

Answer the following questions based on the information in the Car Engine Efficiency table above.

Let’s look at an example of how temperature differences are used to generate power. Power plants convert chemical energy into electrical power. Here is a video overviewing the operation of a geothermal energy system, a classic thermal power generation plant.

Below are two temperature scales. The scale labeled "HOT," shows the range of temperatures for the combustion of gases in a power plant. The scale, "COLD," shows the range of temperatures at which gases are exhausted from the power plant.

Power Plant Temperatures: red indicates power plant combustion temperatures and blue indicates exhausted gas temperatures.

Instructions: Look carefully at the efficiency numbers in the body of the table. How do the Hot and Cold temperatures' effect on the efficiency.

Answer the following questions based on the information in the Power Plant Efficiency table above.

Calculating Overall Efficiency

Using the energy efficiency concept, we can calculate the component and overall efficiency:

$$OverallEfficiency=\frac{Electrica\mathrm{l }Energ\mathrm{y }Output}{Chemica\mathrm{l }Energ\mathrm{y }Input}$$

Here the electrical energy is given in Wh and Chemical Energy in Btus. So Wh can be converted to Btus knowing that there are 3.412 Wh in a Btu.

This overall efficiency can also be expressed in steps as follows:$$OverallEfficiency=\underset{Efficienc\mathrm{y }oftheBoiler}{\underbrace{\left[\frac{Therma\mathrm{l }Energy}{ChemicalEnergy}\right]}}\times \underset{Efficienc\mathrm{y }o\mathrm{f\; }th\mathrm{e }Turbine}{\underbrace{\left[\frac{Mechanica\mathrm{l }Energy}{ThermalEnergy}\right]}}\times \underset{EfficiencyoftheGenerator}{\underbrace{\left[\frac{ElectricalEnergy}{MechanicalEnergy}\right]}}$$

$$OverallEfficiency=Boile\mathrm{r, }\eta \times Turbin\mathrm{e, }\eta \times Generato\mathrm{r, }\eta$$

Applying this method to the above power plant example:

$$\begin{array}{l}OverallEfficiency=\left[\frac{88Btus}{100Btus}\right]\times \left[\frac{36Btus}{88Btus}\right]\times \left[\frac{35Btus}{36Btus}\right]\\ \\ =0.88\times 0.41\times 0.97\\ \\ =\mathrm{0.35 }o\mathrm{r }35\%\end{array}$$

It can be seen that the overall efficiency of a system is equal to the product of efficiencies of the individual subsystems or processes. What is the implication of this?

Steps of Overall Efficiency

We have been looking at the efficiencies of an automobile or a power plant individually. But when the entire chain of energy transformations is considered—from the moment the coal is brought out to the surface to the moment the electricity turns into its final form—true overall efficiency of the energy utilization will be revealed. The final form at home could be light from a bulb or sound from a stereo. The series of steps as shown in the figure below are: 1) Production of coal (Mining), 2) Transportation to power plant, 3) Electricity generation, 4) Transmission of electricity, and 5) Conversion of electricity into light (Use).

Efficiency of a Light Bulb

If the efficiency of each step is known, we can calculate the overall efficiency of production of light from coal in the ground. The table below illustrates the calculation of overall efficiency of a light bulb.

Efficiency of an Automobile

A similar analysis on automobile efficiency is shown in the Figure below.

>

Overall Automobile Efficiency

The table below shows that only about 10% of the energy in the crude oil in the ground is in fact turned into mechanical energy moving people.

Review

Please watch the 5:30 Lesson 3 Review below:

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. A heat engine has Carnot efficiency of 30%. Useful output from the engine is 1000J. How much heat is wasted?
2. How can we improve the Carnot efficiency of a heat engine by changing the hot and cold reservoir temperatures?
3. Most of the energy conversion devices that we use in our day-to-day life can be classified as Heat Engines. Give two examples.

Extra Resources

For more information on topics discussed in Lesson 3, see these selected References:

1. Hinrichs, R. A., “Energy,” Saunders College Publishers, Philadelphia, PA, 1992.
2. Aubrecht, G. L., “Energy,” Prentice Hall, Inc., Englewood Cliffs, NJ, 1995.
3. Fay, J.A. and Golomb, D. S., “Energy and the Environment,” Oxford University Press, New York, NY, 2002.
4. Christensen, J. W., “Global Science: Energy Resources Environment."

Welcome to Lesson 4!

Lesson 4 deals particularly with Energy and the Environment. As mentioned before in the unit overview, this lesson is divided into 3 parts. Part A is basically looking at the products that are formed when we burn fossil fuels and the environmental effects of these fossil fuels products. In part B we are going to look at global effects of using fossil fuels and how they are changing the environment. We will also look, some other climate issues like acid rain, ozone layer destruction up above in the stratosphere. Go through part A, part B, and part C; together there will be one quiz for this lesson. 

Lesson 4 Objectives

Upon completion of this lesson, you will be able to:

• demonstrate a familiarity with fossil fuel composition;
• describe basic combustion chemistry;
• explain the quantitative implications of fossil fuel combustion;
• state the health and environmental effects of products of combustion; and
• describe the effects of primary and secondary pollutants.

See the Calendar tab in Canvas for due dates/times.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Review

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. What is the difference between primary and secondary pollutants?
2. How can scientists extrapolate historical climate changes by analyzing ice cores?
3. What is the greenhouse effect? Explain the difference between greenhouse effect and global warming? Which gases contribute to the greenhouse effect?
4. Explain how ozone is formed at the ground level with the help of the basic reactions. Which end users of energy are responsible for the emissions of the compounds involved?
5. Explain how the stratospheric ozone layer is being destroyed. Which sector is responsible for the emission of the gases that are responsible for this?
6. What is acid rain? How is it formed? What are the effects of acid rain?
7. List five steps that you, as an individual, can take to reduce potential global warming, and explain how each of these steps will reduce the emissions.
8. List 5 ways in which you, as an individual, can reduce gaseous emissions that contribute to acid rain.
9. State the arguments that scientists are making who say that global warming is not due to burning of fossil fuels.
10. What are the effects of ground level ozone?
11. Briefly describe the methods by which information is gathered and used to show that the planet is warming up.

Welcome to Lesson 5!

Welcome to the Appliances lesson! This is the most important one for most students--most important in the sense that it can make a difference in both energy consumption and environmental protection because we use a lot of appliances at home. We use a lot of energy for these appliances. In this chapter we are going to learn the basic operating principles of most of the residential big ticket items, for example refrigerators, or water heaters. Water heaters are one of the most energy-consuming appliances. And we will talk about clothes washers and dryers. We are not going to look at how to do the laundry, but we are going to look at the basic operating principles. In other words, how these things really operate. What are all the things that govern energy consumption, and what are all the things we need to look for when we buy some of these appliances?

We'll also learn how to do a cost benefit analysis. To do that, we will learn how to read energy guide labels. Energy guide labels are the yellow, ugly looking labels on appliances that give you the amount of energy that a model consumes. So when you go shopping (I'm sure you are all going to do that with your significant others in a few years) you're going to compare different options. You are going to look at a couple of models -- 3, 4 or 5 models, and say, "Okay, this is better than this; this is worse than this," and so on.

What are the factors that go into comparing several models and picking the right one, both with respect to energy consumption and environment protection? I will show you what kind of information you can get from these energy guides and how these can be used to compare model A vs. model B. For example, model A may cost $1000 and Model B may cost $1500. What you are basically deciding is, is it worth it to pay $500 extra to get the benefits that this model will give? In other words, the more expensive model obviously "should" give you more features that you want, or it should give you energy savings in the long run -- for example, cutting your energy bill by $50 every month. So it's going to really take about 10 months to recover the $500 you are paying up front. This kind of analysis is basically called life cycle analysis--what it would cost to buy a piece of equipment and to operate that over its lifetime. And we do that calculation for two models and see, in the long run, that one model is going to be cheaper and environmentally friendlier than another model. So we are going to learn how to do that. That discussion will be very common for all the appliances, and this calculation of payback period is the key for most of this lesson as well as the lessons to come. We will also look at refrigerators and calculate the efficiency of these refrigerators and how to use the efficiency we need to calculate how much energy these things consume. We will do that with clothes washers and dryers.

From here on you will also encounter some acronyms and energy efficiency terms, so you will need to pay attention to those. And, as I told you, these calculations and the use of the energy guides are the most important concepts in this lesson.

Lesson 5 Objectives

Upon completing this lesson, you should be able to:

• Explain the operating principles of day-to-day residential appliances
• Read and use Energy Guide labels
• Calculate life-cycle analysis of appliances
• Recommend ways to save energy and money based on good operating practices

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Most homes have a variety of appliances with a wide range of operating costs. Typical costs of operation of basic household appliances are shown in the graph below.

Typical energy costs for various appliances

Credit: U.S. Department of Energy

Household appliances, cooking, and lighting consume 33% of the energy at home as shown in the pie chart below. Water heating (not included in the appliances) is the second largest energy expense after home heating and cooling. It typically accounts for about 14% of the utility bill.

All major home appliances must meet the Appliance Standards Program set by the US Department of Energy (DOE). Manufacturers must use standard test procedures developed by DOE to prove the energy use and efficiency of their products. Test results are printed on yellow Energy Guide labels (pictured below) which manufacturers are required to display on many appliances. This label provides the necessary information to perform a Life Cycle Analysis when comparing different models.

Instructions: View detailed descriptions about the information found on Energy Guide labels.

Energy Guide Labels

Credit: Energy Guide Label by Federal Trade Commission

The Federal Trade Commission's Appliance Labeling Rule requires appliance manufacturers to put these labels on refrigerators, freezers, dishwashers, clothes washers, water heaters, furnaces, boilers, central air conditioners, room air conditioners, heat pumps, and pool heaters. The law requires that the labels specify:

• the capacity of the particular model—for refrigerators, freezers, dishwashers, clothes washers, and water heaters;
• the energy efficiency rating and the estimated annual energy consumption of the model—for air conditioners, heat pumps, furnaces, boilers, and pool heaters;
• the range of estimated annual energy consumption, or energy efficiency ratings, of comparable appliances.

How to Use the Labels

A worksheet on how to use the labels in choosing a cost-effective and environmentally friendly appliance is given below.

Heat is continuously flowing from the tank of the water heater and the pipes to the room because the water heater is always at a higher temperature than the surroundings (basement or garage). Thermal energy flows from high temperature to low temperature. Heat is lost whether you use water or not.

Like most appliances, water heaters have improved greatly in recent years. Today's models are much more energy efficient, and you will be able to purchase a more efficient water heater that will save you money on energy each month. The average life expectancy of a water heater is 13 years. Therefore, the initial purchase price should not be an important factor in selecting a water heater.

Costs of Water Heaters

Just like other appliances, there are two costs associated with water heaters - initial purchase price and operating costs. Water heaters typically last for about 13 years, after which they need to be replaced. Also, each month, you pay for the fuel you use. An energy-efficient model could save hundreds of dollars in the long run in the energy costs and may offset the higher initial purchase price.

It can be compared to automobile mileage—some cars get 15 miles to a gallon, while other, more efficient, vehicles can go 30 miles or more on a gallon of gas. In the same way, some water heaters use energy more efficiently.

One should buy an energy-efficient water heater and spend less money each month to get the same amount of hot water.

Typical Water Use at Home

The table below shows typical water use for various purposes at home.

Energy costs increase with water temperature. Dishwashers require the hottest water of all household uses, typically 135ºF to 140ºF. However, these devices are usually equipped with booster heaters to increase the incoming water temperature by 15ºF to 20ºF. Setting the water heater between 120ºF and 125ºF and turning the dishwasher’s booster on should provide sufficiently hot water while reducing the chances for scalding.

Refrigerators are heat movers, which move heat from a low temperature (inside the refrigerator) to a high temperature (outside the refrigerator into the kitchen). Heat movers do not produce any heat, but just move from one location to another. (Note: The animation has no audio.)

How Does a Refrigerator Work?

The principle of operation of a refrigerator is similar to an air conditioner. It moves the heat energy from inside to outside. There are four basic components in a refrigerator and their functions are as follows:

• Expansion valve - A liquid refrigerant at high pressure flows through an expansion valve. As the refrigerant moves through the expansion valve, it moves from a high-pressure zone to a low-pressure zone. The decrease in pressure corresponds with a decrease in temperature.
• Evaporator or heat exchanging pipes - A set of coiled tubes carrying the low pressure, expanded refrigerant. In the evaporator, the liquid refrigerant also expands and evaporates. The evaporation of liquid takes away heat, creating cold gas in the coils. The cold refrigerant flowing through the coils absorbs heat from the refrigerator. The food gets cold. However, the refrigerant warms up because of the absorption of heat.
• Compressor - A device that pressurizes the warm refrigerant and makes it hot (hotter than the kitchen temperature). This hot refrigerant goes into the condenser.
• Condenser or second heat exchanger coil - Located at the back of the refrigerator where it gives off the heat to the air in the kitchen.

Click the “play” button to learn how a refrigerator works.

Types and Features

There are four types of refrigerators: top-freezer (or top-mount), bottom-freezer (or bottom-mount), side-by-side, and built-in (as shown below).

Refrigerators also come in four size categories: small (7 to 9.9 cubic feet), medium (10 to 13.9 cubic feet), large (14 to 19.9 cubic feet), and extra large (20 to 29 cubic feet).

Types of Refrigerators: Top Mounted, Bottom Mounted, and Side-by-Side.

Clothes washers and dryers account for 10 percent of the residential energy consumption, with most of the energy consumed for hot water used for washing.

• An estimated 85 percent to 90 percent of the energy is used for heating the water.
• Relatively, 10 percent to 15 percent of the energy is used by the clothes washer itself to operate the motor and controls.

A typical household does nearly 400 loads of laundry a year, and each load in a conventional washer uses 40 gallons of water. Therefore, any reduction in energy consumption for clothes washing application would involve reduction in hot water use.

Types of Clothes Washers

The basic principle for cleaning clothes has remained unchanged—wet the garment, agitate it to loosen the dirt from the cloth fibers, and then use more water to rinse the dirt off. What has changed over the millennia is the method of agitation? Pounding garments with stones was common for several thousand years, and along the way someone also figured out that using heated water got out a lot more dirt.

Clothes washers come in two types: Horizontal axis (h-axis) or front loading and Vertical axis (v-axis) or top loading (shown below).

Horizontal axis (front loading) and a Vertical axis (top loading)

Credit: Energy Star

Most clothes washers produced for the U.S. consumer are vertical axis (v-axis) washers with a central agitator. While there are variations, most v-axis washers suspend the clothes in a tub of water for washing and rinsing.

As an alternative, the horizontal axis (h-axis) washer tumbles the wash load repeatedly through a small pool of water at the bottom of the tub to produce the needed agitation. This tends to reduce the need for both hot and cold water.

The h-axis washer, popular in Europe, has a very limited market share in the United States at present. Yet, estimates have shown that a large quantity of energy and water could be saved through the replacement of conventional v-axis washers with the h-axis design.

H-axis washer

H-axis or tumble-action machines repeatedly lift and drop clothes, instead of moving clothes around a central axis. H-axis washers also use sensor technology to closely control the incoming water temperature. To reduce water consumption, they spray clothes with repeated high-pressure rinses to remove soap residues rather than soaking them in a full tub of rinse water.

Click the "play" button to see how an H-axis washing machine works. (Note: The animation has no audio.)

In a study conducted by Oak Ridge national Laboratory (ORNL) in 1998 for U.S. Department of Energy, it was found that, on average, the h-axis washer used 62.2 percent of the water used by the v-axis washer, and this yielded total water savings of 37.8 percent. Moreover, the average h-axis washer consumed 42.4 percent of the energy used by a typical v-axis washer in the study, resulting in energy savings of 57.6 percent.

Features of the h-axis washer include:

• Auto temperature. The machine will mix hot and cold water to a preset "warm" and "cold" so that the water is warm enough for the detergent to dissolve and optimally perform. During the winter in many parts of the country, cold tap water can be too cold to wash your clothes well.
• Water level settings. Some of the very high-end machines sense the amount of clothing and automatically adjust the water level, but all except the most basic machines offer at least four settings.
• Capacity. If you have a large household or athletes who produce an astounding amount of laundry each week, a larger capacity machine is a must. The front loaders generally hold more because they don't have the agitator. A definite minus for the front loaders, however, is the actual loading because you have to bend over to put in the clothes. To minimize this fact, the machines and their matching dryers are often displayed in stores on a raised platform.

A clothes dryer dries wet clothes in a rotating drum through which hot air is circulated.

• The hot air removes the residual moisture from the clothes.
• The humid air from the dryer is vented out of the house.
• The drum is rotated with the help of a motor at relatively slow speeds to create a tumbling effect.

Clothes dryers can be of two types: electric and gas.

• In an electric dryer, electrical energy is used for both the motor to rotate the drum and heating the air.
• In a gas dryer, the motor requires electrical energy but the air is heated by natural gas.

Energy Efficiency of Dryers

Dryers work by heating and aerating clothes. The efficiency of clothes dryer is measured by a term called the Energy Factor. It is similar to the miles per gallon for a car, but in this case the measure is pounds of clothing per kilowatt-hour of electricity.

The minimum Energy Factor rating for a standard capacity electric dryer is 3.01. For gas dryers, the minimum energy factor is 2.67. The rating for gas dryers is provided in kilowatt-hours though the primary source of fuel is natural gas.

Unlike most other types of appliances, energy consumption does not vary significantly among comparable models of clothes dryers. Clothes dryers are NOT required to display EnergyGuide labels.

Clothes Dryers: Your “Power” in the Environmental Protection

• Locate your dryer in a heated space. Putting it in a cold or damp basement will make the dryer work harder and less efficiently.
• Make sure your dryer is vented properly. If you vent the exhaust outside, use the straightest and shortest metal duct available. Flexible vinyl duct isn't recommended because it restricts the airflow, can be crushed, and may not withstand high temperatures from the dryer.
• Check the outside dryer exhaust vent periodically. If it doesn't close tightly, replace it with one that does in order to keep the outside air from leaking in. This will reduce heating and cooling bills.
• Clean the lint filter in the dryer after every load in order to improve air circulation and reduce risk of fire. Regularly clean the lint from vent hoods.
• Dry only full loads, as small loads are less economical; but do not overload the dryer.
• When drying, separate your clothes and dry similar types of clothes together. Lightweight synthetics, for example, dry much more quickly than bath towels and natural fiber clothes.
• Dry two or more loads in a row, taking advantage of the dryer's retained heat.
• Use the cool-down cycle (permanent press cycle) to allow the clothes to finish drying with the residual heat in the dryer.
• In good weather, hang clothes dry outside. This the ultimate energy saver for clothes drying

A dishwasher typically uses the equivalent of 700–850 kilowatt-hours of electricity annually, or nearly as much energy as a clothes dryer or freezer. About 80 percent of this energy is used, not to run the machine, but to heat the water for washing the dishes.

• Older dishwashers use about 8–14 gallons of water for a complete wash cycle.
• Newer dishwashers, built in the past 10 years, have been using 7–10 gallons per cycle.

The dishwasher is the only device at home that requires a water heater temperature that is about 140°F. The units built recently have supplemental heaters in the dishwashers to bump up the temperature so that the main water heater temperature can be set at 120°F or less. Remember that each 10°F reduction in water heater temperature lowers the water heater energy cost by 3 percent to 5 percent.

How a Dishwasher Works

A dishwasher is essentially an insulated water tight box. The dirty dishes are systematically arranged in the dishwasher. As shown below, hot water is sprayed on to the dishes as jets. Repeated jets of water emanating from a spray arm clean the dishes. Some models have two spray arms: one at the bottom of the dishwasher (lower spray arm) and one at the top (upper spray arm). The dirty water passes through a filter and re-circulates until the dishes are finished. Fresh water is then spayed during the rinse cycle to remove the soapy water. Then the dishes are dried with either electric heat or simply with air.

Inside of a dishwasher

Inside of a dishwasher by Ryan from Louisville, USA is licensed under CC BY-SA 2.0

Press the “play” button to see how a dishwasher works. This is also described in the paragraph above. (Note: The animation has no audio.)

Features of a Dishwasher

Dishwashers can be built-in or portable. Built-ins are mounted under a kitchen countertop usually next to a sink. Portables are on wheels with finished tops and sides. Most models can be converted into under-counter mounting. However, because of the additional connection hardware and finished sides, portables usually cost more than similar built-in models.

Some of the additional features that are offered are:

• Interior layout—configuration of sliding racks, baskets, and trays. Does the washing arm reduce the amount of loadable space?
• Water heating—Most homes have water heaters set to 110 degrees. However, to clean well, a dishwasher should use water at 140 degrees. Many budget units now offer a water heating feature.
• Number of cycles—light cycles, normal, heavy or pans, and rinse and hold to remove food if dishes will sit in the washer a while before the wash cycle is run.
• Water-saving cycles—If you live in an area where fresh water is scarce, you’ll want to consider this feature.
• Sound insulation—The sound level will vary from one model to another. Consider how important a quiet wash cycle is before you purchase.
• Build in food disposers—will grind up food similar to in-sink units, allowing the user to spend less time cleaning dishes before they go into the dishwasher.
• Controls—Entry-level machines feature knob and dial controls. On mid- to upper-end models, you will find push-button switches hidden behind smooth, one-piece, plastic console covers. Some of the highest priced dishwashers feature electronic touchpad controls with lighted displays for an uncluttered, high-tech look. And the highest-end European models now integrate controls on the top of the door so they can't be seen when the machine is closed.
  • Countdown timer — lets you know how much time is left in a cycle.
  • Clean light — signals that cycle is complete and dishes are clean.
  • Soil sensors — take the guesswork out of cycle selection. Sensors optically analyze dirtiness of water and adjust water level and wash length accordingly.
  • Delay-start — timer that allows starting dishwasher automatically; lets you take advantage of late-night off-peak power rates or run the dishwasher after everyone has taken a shower.
• Color and Appearance—Does the dishwasher fit in your kitchen? Do you like its appearance?
• Delay Start Timer—Allows the user to load the washer and have it start a few hours later.

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. Describe three operating practices in using refrigerators that can save energy and money.
2. List the five main components of a refrigerator, and explain how a refrigerator works.
3. Describe five ways in which you, with good operating practices, can reduce energy consumption of water heaters at home.
4. Explain the advantages and disadvantages between Storage and Demand water heaters.
5. What are the various methods in which solar energy can be collected for water heating?
6. What is EF? And how does it describe the efficiency of a water heater?
7. How do electric and gas compare for water heating?
8. Why are ENERGY STAR appliances better in terms of efficiency, and how can they help the environment?
9. What are Energy Guide Labels? What information can be obtained from these labels, and how can this information can be used to select an environmentally friendly appliance?
10. Briefly describe five ways in which we can save energy in using clothes washers and dryers.
11. Compare and contrast the v-axis (top loading) and h-axis (front loading) water heaters.
12. Explain how energy efficiency of clothes washers is evaluated.
13. What are good operating practices for clothes dryers?
14. How can you describe the energy efficiency of dishwashers?
15. Describe appliance-operating practices that can help the environment.
16. Calculate the amount of heat energy required to heat 200 lbs of water that is heated from 55 degrees F to 130 degrees F.
17. 200 gal of water is heated in a heater from 60 degrees F to 120 degrees F every day by a family of four. What is the annual energy requirement?
18. An electric water heater heats 250 gallons of water per day from 58 degrees F to 140 degrees F. How many kWh of energy are required? Recall that, 3412 Btus =1 kWh.
19. If the temperature of the water heater was reduced to 120 degrees F, what percent of energy can be saved?
20. What is the cost of operating the water heater in Problem 3, if electricity cost is $0.08 per kWh?
21. A water heater heats 200 gal of water a day from 55 degrees F to 130 degrees F using natural gas. How many CCF of natural gas are required every month?
22. What would be the monthly cost of natural gas in problem 6?
23. What would be the monthly cost of energy if electricity was used for heating the water in problem 6?
24. If the temperature of the water heater was reduced to 120 degrees F in Problem 6, how many kWh could be saved and what would be the cost savings?
25. Estimate the % energy savings of an electric water heater that heats 100 gallons per day when the temperature is set back at 110 instead of 120 F. The basement is heated and is at 65 F. The life of the water heater is expected to be about 15 years.
    • Use an appropriate cost for electricity, and compare the operating expenses with the approximate initial cost of the water heater (from the lectures).
    • Heat required (BTUS) = m x Cp x (Temperature Difference)
    • Where Cp is the heat capacity of water (1 Btu/lb/F)
    • And m is the mass of the water (Assume 1 gal has 8.3 lb of water and the 3,412 Btus = 1 kWh)
26. An old refrigerator consumed 150 W of power. Assuming that the refrigerator operates for 20 hours in a day, what is the annual operating cost, assuming the cost of electricity to be $0.06 per kWh?
27. Suppose that an oven lasts for 10 years. For a given heating effect, the least efficient oven draws 1,000 W. The most efficient one uses 450 Watts. Assuming that the oven uses 700 W annually, and that the local energy cost is 0.06 per kWh, can you save any money? If so, how much money over its lifetime? If the more efficient oven costs $100 more than the least efficient one, would you buy the more efficient model?
28. Suppose you are comparing two refrigerators, both of which last for 10 years. The least efficient refrigerator draws 275 W of power. The most efficient one uses 250 Watts. Assuming that the refrigerator operates 4000 hours annually and that the local energy cost is 0.06 per kWh, can you save any money with the energy efficient model? If so, how much money over its lifetime? If the more efficient refrigerator costs $100 more than the least efficient one, would you buy the more efficient model?

Welcome to Lesson 6!

Welcome to the lesson on lighting. In this chapter, we are basically going to look at basic lighting principles and definitions. Light can be generated in several ways, and we are going to look at the ways in which we can generate light and discover which is the most efficient of all these methods. We will also learn a little bit about some of the definitions, like how light is measured and what the intensity is, and how to measure the efficacy or efficiency of lighting and so on and so forth.

We will also look at the different types of bulbs that are available around for us to use. The U.S. is currently in a transition to more efficient lightbulbs. 10 years ago, incandescent lightbulbs dominated the market, but now ~100 % of all lightbulb replacements are some form of energy efficient model. Some of you may be familiar with light emitting diode (LED) and compact florescent (CFL) bulbs, and we will be looking at how each of these types work and also how the light is generated. What is the efficiency with which we generate lighting?

As far as calculations are concerned, we will be doing the most important calculation in this chapter again, and that is life cycle analysis. Life cycle analysis is, as I mentioned in the last chapter, the total cost over the life cycle of a product. The life cycle begins the moment you buy and lasts until the moment the product dies or is put to retirement. Until then, what does it cost? In other words, the costs would be to buy it and to feed it the electricity or the energy, and then if there are any maintenance costs, they are also involved. So we have to calculate all of these aspects over the lifetime of a particular bulb, and then compare bulb A with bulb B. That life cycle analysis is what you will have to spend quite a bit of time with and make sure you understand it.

We'll also consider the way we measure the efficiency and the efficacy of lighting, and also improved lighting controls. If we have an existing home or existing system, what can we add; how can we improve the efficiency? How can we get more light for less energy? So this is a chapter where we can work to save a lot of energy. And we spend about, almost 40 billion dollars a year in this country on lighting, so easily we can save about 20 billion dollars and the associated energy that is involved and the impact. Think about it -- the impact that we can make on the environment by using more efficient light. So let’s get started.

Lighting

These are some statistics on lighting in the US. Information like this does not get updated often (The U.S. hasn't been spending money on these types of studies), so here is where we were as of 2015:

• Lighting accounts for 5 to 10 percent of all electricity consumed in the United States.
• An average household dedicates ~4 percent of its energy budget to lighting. Commercial establishments consume about ~20 percent of their total energy just for lighting.
• Technologies developed during the past 15 years can help us cut lighting costs 30 to 75 percent while enhancing lighting quality and reducing environmental impacts.

Variety of Lighting Use in the United States

Lesson 6 Objectives

Upon completing this lesson, students will be able to:

• explain basic lighting principles and definitions;
• list the various types of lighting and explain how each type works;
• describe energy efficient lighting options;
• calculate life cycle costs (LCC) for different types of lighting.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

When most people buy a light bulb, they look for watts (W). Recall that watt is a unit of power, (i.e., the rate at which energy is consumed from the electricity supplier). It does not say anything about the light.

The most common measure of light output (or luminous flux) is the lumen. All lamps are rated in lumens, as shown in the figure below, and every bulb has 3 parameters listed on the package:

• Lamp lumen output or light output
• Power consumption in watts
• Life of the bulb in hours

Parameters listed on a light bulb.

Watch this video (1:44) below to find out more about lumens.

Footcandles

A footcandle (fc) is the Standard unit of measure for illumination on a surface. It is a lumen of light distributed over a 1-square-foot (0.09-square-meter) area.

Footcandle

The average footcandle level on a square surface is equal to the amount of lumens striking the surface, divided by the area of the surface.

Example

A 40 watt bulb produces about 505 lumens and has a life of about 1,000 hours. When this bulb is used to light a room of 10 x 10 feet, these 505 lumens are distributed over 100 square feet of floor area. What is the illumination?

505 lumens of light/100 ft²= 5.05 lumens per ft² or 5.05 fc

$$1Footcandle=1Lumen/f{t}^2 =1Lux\left(metric\right)$$

How much light is needed in a room depends on the task(s) being performed (contrast, requirements, space, size, etc.). There are three different types of task-oriented lighting: Ambient, Task, and Accent. The light requirement also depends on the ages of the occupants and the importance of speed and accuracy of the task.

• Ambient lighting is general purpose lighting—an example is the lighting used in hallways for safety and security. An illumination of 30–50 fc is generally the maximum that one needs for this purpose.
• Task lighting is lighting that is designed for specific tasks. Reading and writing are the most light-intensive tasks and require about 50 fc at home. Tasks like cooking, sewing, or repairing a wrist watch require more -- about 200–300 fc. However, the area with this level of illumination will be small. Increasing the light everywhere is not required and is a waste of energy.
• Accent lighting is the lighting that is provided to highlight certain objects or areas, for example, the use of floodlights to highlight a painting or a statue. Accent lighting also illuminates walls, so they blend more closely with naturally bright areas like ceilings and windows. Accent lighting can be high intensity or subtle.

Color Rendering Index

Lamps are assigned a color temperature (according to the Kelvin temperature scale) based on their "coolness" or "warmness." The human eye perceives colors as cool if they are at the blue-green end of the color spectrum, and warm if they are at the red end of the spectrum.

Instructions: Click "play" to see examples of the light sources that temperatures represent. (Note: The video has no audio.)

The ability to see colors properly is another aspect of lighting quality. Objects' colors appear to be different under different types of light. The color rendering index (CRI) scale is used to compare the effect of a light source on the color appearance of its surroundings. A scale of 0 to 100 defines the CRI. A higher CRI means better color rendering, or less color shift.

Instructions: Move the drag button in the center of the picture below to see the difference between low CRI and high CRI.

Factors Affecting the Number of Lamps Required

Instructions: Click on the hot spots below to determine the factors that affect the number of lamps required:

There are five basic types of lighting:

• Incandescent
• Fluorescent
• High-intensity discharge
• LED

Incandescent Bulbs

Thomas Alva Edison invented the incandescent light bulb with reasonable life. Lewis Latimer has perfected it with the use of carbon filament.

The incandescent bulb consists of a sealed glass bulb with a filament inside. When electricity is passed through the filament, the filament gets hot. Depending on the temperature of the filament, radiation is emitted from the filament.

The filament's temperature is very high, generally over 2,000º C, or 3,600º F. In a "standard" 60-, 75-, or 100-Watt bulb, the filament temperature is roughly 2,550º C, or roughly 4,600º F. At high temperatures like this, the thermal radiation from the filament includes a significant amount of visible light.

This principle of obtaining light from heat is called ‘incandescence.” At this high temperature of 2,000º C, about 5 percent of the electrical energy converts into visible light and the rest of it is emitted as heat or infrared radiation.

Instructions : Press play to see how an incandescent light bulb works. (Note: The animation has no audio.)

Let’s now look at several different types of incandescent bulbs.

Standard incandescent bulbs

Standard incandescent bulbs are most common and yet are the most inefficient. Larger wattage bulbs have a higher efficacy (more lumens per Watt) than smaller wattage bulbs.

Instructions: Click the “graph” button below to create a graph comparing Watts and efficiency, and then answer the question below.

Tungsten halogen bulbs

Tungsten halogen is an incandescent lamp with gases from the halogen family sealed inside the bulb and an inner coating that reflects heat back to the filament. It has similar light output to a regular incandescent bulb, but with less power. Halogens in the gas filling reduce the material losses of the filament caused by evaporation and increase the performance of the lamp.

A tungsten halogen lamp

Tubular tungsten-halogen bulbs

Tubular tungsten-halogen bulbs are commonly used in “torchiere” floor lamps, which reflect light off of the ceiling, providing more diffused and suitable general lighting.

Although these provide better energy efficiency than the standard A-type bulb, these lamps consume significant amounts of energy (typically drawing 300 to 600 W) and become very hot (a 300-W tubular tungsten-halogen bulb reaches a temperature of about 2600° C compared to about 600° C for a compact fluorescent bulb). Because Tungsten-halogen lamps operate at very high temperatures (high enough to literally fry eggs), they should not be used in fixtures that have paper- or cellulose-lined sockets.

Tubular tungsten-halogen lamp.

Halogen bulbs

A halogen bulb is often 10 to 20 percent more efficient than an ordinary incandescent bulb of similar voltage, wattage, and life expectancy. Halogen bulbs may also have two to three times as long a lifetime as ordinary bulbs. How much the lifetime and efficiency are improved depends largely on whether a premium fill gas (usually krypton, sometimes xenon) or argon is used. The image below shows a picture taken with an Infrared camera comparing the heat produced by a halogen and a compact fluorescent light bulb. The red and white color zones are extremely hot, and the blue zones are cooler.

A comparison of heat generated by a Halogen and CFL light bulbs.

Credit: Lawrence Berkeley Laboratory

Reflector Lamps

Reflector Lamps - Light waves from a bulb spread in all directions. The light that goes toward the back is not useful when the light is most needed in the front. Reflector lamps (Type R) are designed to spread light over specific areas.

Reflector lamps have silver coating on the sides, like any mirror, and therefore all the light waves passing through the sides or the back are reflected to the front. Therefore, they are called reflector lamps and are also called floodlighting, spotlighting, and down lighting bulbs.

Instructions: Click the buttons below to see the difference between a regular and reflective lamp light bulb:
(Note: The animations have no audio.)

Parabolic aluminized reflector (PAR) lamps

Parabolic aluminized reflector (PAR) lamps (shown in the image below) are also available with halogen technology to operate at 120 volts. A standard 150-W incandescent spotlight can be replaced with a lower wattage halogen lamp, reducing electricity consumption by up to 40 percent.

A Reflector Lamp (Type R) light bulb.

The fluorescent lamp is a major advancement and a commercial success in small-scale lighting since the original tungsten incandescent bulb. These bulbs are highly efficient compared to incandescent bulbs. Fluorescence is the phenomenon in which absorption of light of a given wavelength by a fluorescent molecule is followed by the emission of light at longer wavelengths. Please watch the following 2:19 presentation about fluorescent bulbs:

Types of Lighting, Fluorescent

These fluorescent bulbs that you are seeing, the long tubes, basically have two electrodes on the sides. And you pass electric current, and that creates an arc between the two electrodes, and that tube is filled with inert gasses. The inert gasses are argon or an argon plus krypton mixture. No air in there. Just an argon plus krypton mixture, and you spark it with a little bit of mercury in there. When you generate that arc between two electrodes, on the two sides of that tube, that arc excites these mercury atoms to a higher state. And then when they are coming back to the ground state, they have to release that excess energy that they absorbed, and they release it as non-visible UV light.

UV light is not visible. UV light is dangerous. Remember, UV light is what comes out when the mercury atoms are coming back to the ground state. But you know this tube is coated on the inside. The inside wall is coated with a different material, a special material called phosphorous. And those particles that are coated have a unique ability to absorb this UV light that is released when the mercury atoms are coming to the ground state. So that is absorbed, and that phosphorous coating will give out visible light. It absorbs UV light and gives out visible light. So without that phosphorous coating in there, a fluorescent bulb would not work. Fluorescence is absorbing UV light in the phosphorous and giving out visible light.

So, change of frequency, or change of energy status, is called fluorescence and a bulb that uses this principle is called a fluorescent bulb.

A fluorescent bulb consists of a glass tube with a phosphorus coating, a small amount of inert gas (usually argon or krypton), mercury, and a set of electrodes. Contact points on the outside of the tube carry electricity into the bulb.

Instructions: The animation below (1:04) shows a step-by-step depiction of how fluorescent lamps provide light. You may replay the video to review steps. (Note: The animation has no audio.)

Fluorescent lamps are about 2 to 4 times as efficient as incandescent lamps at producing light at the wavelengths that are useful to humans. Thus, they run cooler for the same effective light output. The bulbs themselves also last a lot longer—10,000 to 20,000 hours versus 1,000 hours for a typical incandescent.

Fluorescent lights need ballasts (devices that control the electricity used by the unit) for starting and for circuit protection. Ballasts require energy, and for some type of ballasts, efficiency is only achieved if the fluorescent lamp is left on for long periods of time without frequent on-off cycles.

The image below shows a picture of a full-size fluorescent lamp fixture. The energy savings for existing fluorescent lighting can be increased by:

• re-lamping (e.g., replacing an existing lamp with one of a lower wattage);
• replacing ballasts;
• replacing fixtures with more efficient models.

Full-size fluorescent lamp fixture

Full-size fluorescent lamps are available in several shapes, including straight, U-shaped, and circular configurations. Lamp diameters range from 1" to 2.5". The most common lamp type is the four-foot (F40), 1.5" diameter (also called T12) straight fluorescent lamp. More efficient fluorescent lamps are now available in smaller diameters, including the 1.25 " (also called T10) and 1" (also called T8).

Fluorescent lamps are available in color temperatures ranging from warm (2700 K) "incandescent-like" colors to very cool (6500 K) "daylight" colors.

Cool white (4100 K) is the most common fluorescent lamp color. Neutral white (3500 K) is becoming popular for office and retail use.

Compact Fluorescent Lamps

Compact Fluorescent Lamps are miniaturized fluorescent lamps that usually have premium phosphors, which often come packaged with integral or modular ballast, as shown in the image below.

Types of compact fluorescent bulbs available on the market

Compact fluorescent lamps (CFLs) come in a variety of sizes and shapes including (a) twin-tube integral, (b and c) triple-tube integral, (d) integral model with casing that reduces glare, (e) modular circline and ballast, and (f) modular quad-tube and ballast. CFLs can be installed in regular incandescent fixtures, and they consume less than one-third as much electricity as incandescent lamps.

Credit: United States Department of Energy

Compact Fluorescent Lamps have the following characteristics. They:

• Typically have a standard screw base that can be installed into nearly any table lamp or lighting fixture that accepts an incandescent lamp.
• Come in a variety of sizes and shapes and are being used as energy saving alternatives to incandescent lamps.
• Have a much longer life—6,000 to 20,000 hours (10 to 20 times longer), compared to 750 to 1000 hours for a standard incandescent.
• Can replace incandescent bulbs that are roughly 3 to 4 times their wattage, but can cost up to 10 times more than comparable incandescent bulbs.
• produce ~70 lumens per watt.
• Are an energy-efficiency investment. Although they cost more, they are very economical in the long run.

Compact Fluorescent Bulbs

High-intensity discharge (HID) lamps are similar to fluorescents in that an arc is generated between two electrodes. The arc in an HID source is shorter, yet it generates much more light, heat, and pressure within the arc tube.

Below are HID sources, listed in increasing order of efficacy (lumens per watt):

• mercury vapor
• metal halide
• high-pressure sodium
• low-pressure sodium

Like fluorescent lights, HID also requires ballasts, and they take a few seconds to produce light when first turned on because the ballast needs time to establish the electric arc.

Originally developed for outdoor and industrial applications, HID lamps are now used in office, retail, and other indoor applications. Their color rendering characteristics have been improved, and lower wattage have recently become available (as low as 18 watts).

When HID lamps reach "restrike" time, the gasses inside the lamp are too hot to ionize, and time is needed for the gasses to cool and pressure to drop before the arc will restrike. This process of restriking takes between 5 and 15 minutes, depending on which HID source is being used. Therefore, good applications of HID lamps are areas where lamps are not switched on and off intermittently.

Types of High-Intensity Discharge Lamps

Mercury vapor lamps

Mercury vapor lamps are widely used to light both indoor and outdoor areas such as gymnasiums, factories, department stores, banks, highways, parks, and sports fields.

Mercury vapor lamps consist of an inner arc discharge tube constructed of quartz surrounded by an outer hard borosilicate glass envelope. Shortwave UV, a result of the decay of mercury atom electrons from an excited to a stable state, is readily transmitted through the inner quartz tube but is virtually blocked by the outer glass envelope during normal operation.

Mercury Vapor Lamp

Metal Halide lamps

Metal Halide lamps are similar to mercury vapor lamps but use metal halide additives inside the arc tube along with the mercury and argon. These additives enable the lamp to produce more visible light per watt with improved color rendition.

Wattages range from 32 to 2,000, offering a wide range of indoor and outdoor applications. The efficacy of metal halide lamps ranges from 50 to 115 lumens per watt, typically about double that of mercury vapor.

Because of the good color rendition and high lumen output, these lamps are good for sports arenas and stadiums. Indoor uses include large auditoriums and convention halls. These lamps are sometimes used for general outdoor lighting, such as parking facilities, but a high-pressure sodium system is typically a better choice.

High-Pressure Sodium (HPS) Lamp

The high-pressure sodium (HPS) lamp is widely used for outdoor and industrial applications. Its higher efficacy makes it a better choice than metal halide for these applications, especially when good color rendering is not a priority.

HPS lamps differ from mercury and metal-halide lamps in that they do not contain starting electrodes; the ballast circuit includes a high-voltage electronic starter. The arc tube is made of a ceramic material which can withstand temperatures up to 2,372°F. It is filled with xenon to help start the arc, as well as a sodium-mercury gas mixture.

The efficacy of the HPS lamp is very high (as much as 140 lumens per watt.) For example, a 400-watt high pressure sodium lamp produces 50,000 initial lumens. The same wattage metal halide lamp produces 40,000 initial lumens, and the 400-watt mercury vapor lamp produces only 21,000 initially.

Sodium, the major element used, produces the "golden" color that is characteristic of HPS lamps. Although HPS lamps are not generally recommended for applications where color rendering is critical, HPS color rendering properties are being improved. Some HPS lamps are now available in "deluxe" and "white" colors that provide higher color temperature and improved color rendition. The efficacy of low-wattage "white" HPS lamps is lower than that of metal halide lamps (lumens per watt of low-wattage metal halide is 75-85, while white HPS is 50-60 LPW).

As we mentioned before, LED stands for light emitting diode. This type of lighting is completely different than the other types of lighting we have discussed so far. They do not need specific gases, filaments or moving parts because they are made from semiconducting materials, which makes and LED a semi-conducting device that produces light. The underlying principles of an LED light are the opposite function of a photovoltaic system. An LED semiconductor chip form an junction between and n-type and p-type semiconductor materials. N-type materials pass charge using electrons, and p-types pass charge using holes. See the figure below for a description of the circuit.

Basic LED circuit

Lightingdesignlab.com

LEDs do not directly produce white light. Due to this quirk, LEDs were originally used for colored light applications such as traffic lights and exit signs.

LED Traffic Light

popularmechanics.com

Because of their extremely high efficiencies (150 lumens per watt!!, and up to 90 % more efficient than incandescent light bulbs), researchers found ways to convert their outputs to white light. As such, they are one of the highest efficiency lighting options available.

Here are three examples:

• Phosphor conversion, in which a phosphor is used on or near the LED to convert the colored light to white light
• Color-mixed systems, in which light from multiple monochromatic LEDs (e.g., red, green, and blue) is mixed, resulting in white light
• A hybrid method, which uses both phosphor-converted (PC) and monochromatic LEDs.

Methods of making white light from LEDs. Credit DOE.

 These innovations have allowed these bulbs to be suitable for general lighting in residential applications. These bulbs last for 5-10 years depending on their usage.  Now, you can find them in almost every store, and they look something like this.

General purpose whitelight LED lights.

homedepot.com

Performing a life-cycle cost analysis (LCC) gives the total cost of a lighting system—including all expenses incurred over the life of the system. This analysis can be applied not only to lighting but for most of the appliances, automobiles, heating systems, and so on, when two systems are compared to determine the most cost effective options.

There are two reasons to do an LCC analysis:

1. To compare different systems, or bulbs in this case.
2. To determine the most cost-effective system or a bulb.

For some lighting systems, one of two situations may exist:

1. The initial cost may be high, but the energy costs will be low over its lifetime.
2. The initial cost to buy a bulb or a system and the energy or the maintenance costs may be low, but the useful life of such a bulb or system may be short. (In this case, we may have to replace the appliance several times to get the same useful life as the other option.)

Therefore, a life-cycle cost (LCC) analysis can be helpful for comparing the total costs incurred over the lifetime of a lighting system. It is, in essence, calculating all the costs incurred to buy, maintain, and run the system over its lifetime.

In the formula above,

• Cost to buy is the purchase price of the bulb or the system.
• Cost to maintain is the cost incurred to maintain it in good operating condition. (For example in the case of a car, an engine oil change every 3,000 miles is part of maintenance costs.)
• Cost of energy is the energy or the fuel it takes to run the appliance or bulb for its lifetime.
• Replacement cost is the cost to replace the bulb. If bulb A has a life of 1000 hrs and bulb B has a life of 10,000 hours, then Bulb A needs to be replaced 10 times to get the same useful life period as that of bulb B. Therefore, 10 A bulbs need to be purchased for each B Bulb.

The table below shows a life cycle cost analysis in comparing an incandescent bulb and a CFL.

This analysis shows clearly that each incandescent bulb replaced with a CFL that would fit into a regular incandescent bulb fixture would save about $39.25 over 10,000 hours of operation. Imagine the number of bulbs that you have at home: living room, kitchen, bathrooms, bedrooms, table lights, floor lamps, ceiling lights, closets, garage, basement, and so on. There are energy saving options all over the home.

Although they save energy, there are some disadvantages with CFLs:

• They are often physically larger than the incandescent bulbs they replace, and simply may not fit the lamp.
• The light is generally cooler—less yellow—than incandescent light bulbs. This may result in less than pleasing contrast with ordinary lamps and ceiling fixtures. Newer models have been addressing this issue.
• Some types (usually iron ballasts) may produce an annoying flicker.
• Ordinary dimmers cannot be used with compact fluorescents.
• Like other fluorescents, operation at cold temperatures (under around 50–60 degrees F) may result in reduced light output.
• There may be an audible buzz from the ballast.

Efficacy is the ratio of light output from a lamp to the electric power it consumes, and is measured in lumens per watt (LPW).

Efficacy of Light Bulbs
Click for a text description of the image.

Below is a list of different types of light bulbs and the light output of each (measured in lumens per watt):

• Incandescent: 8 - 22
• Mercury: 22 - 58
• Fluorescent: 30 - 38
• Metal Halide: 74 - 132
• High Pressure Sodium: 74 - 132
• Low Pressure Sodium: 70 - 152
• LED: 10-200

Conventional incandescent lamps in a single four-way traffic light consume roughly 85 kWh of electricity per day and cost about $1,600 per year to operate. LED lights use just 10 percent of the electricity that incandescent lamps use, so the opportunity for savings is enormous.

Lighting controls give you the flexibility to design a space for multiple use and easy access. They should be a part of the lighting plan for every room. Both manual and automatic controls can cut energy costs by making it easier to use lights only when and where they are needed.

Controls used with high-wattage incandescent bulbs are especially effective for saving energy, but they should be considered for use with any lights that might be left on when no one is using them.

Always choose controls that are compatible with the bulb and ballast. Try to obtain the best quality, so the controls will perform well over time.

Types of Lighting Controls

Switches

The simple on-off switch, whether mounted on a wall or on the light fixture, should always be obvious and convenient.

• On fixtures with pull-cord switches, attach an object at the end that is easy to see and grasp.
• Install multiple wall switches in areas that have more than one entrance, such as hallways, staircases, and large rooms.
• Ensure that these switches should be easy to find as well by adding devices such as oversized toggles or switch plates that glow in the dark.
• A small indicator light near a switch can signal when lights that are out of sight—in the basement or outdoors, for example—have been left on.
• If a main switch in a room controls several lights, each fixture should have its own switch, so individual lights can be turned off if they are not needed.
• In rooms such as kitchens, where lights are used for different purposes, overhead ambient lights, counter, or island lights should be on separate switches.
• A three-level switch in lamps is a simple way to use one fixture for several lighting needs. When the higher levels are not necessary, switch it to the lowest level to save energy.

Photocells

A photosensor measures the light level in an area and turns on an electric light when that level drops below a set minimum. They are most effective with lights that stay on all night long, such as some outdoor fixtures or night lights. If a light does not need to remain on throughout the night, use a timer or motion detector.

Timers

Timers are an inexpensive way to control the amount of time a light stays on inside the home or outdoors. They can be located at a light switch, at a plug, or in a socket. Some models are turned on manually and set to turn off after a designated number of minutes or hours. Others can be programmed to turn on and off at specified times. Both mechanical and solid-state timers are available, and some offer the option of a manual override. Some screw-base compact fluorescent bulbs cannot be used with timers, so check the manufacturer's recommendations.

Be careful not to set timers so a light might turn off in an area when someone could be left in the dark. Or, install a glow-in-the-dark switch plate or a very low-wattage night-light with a photosensor near the switch, so it is easy to find.

Motion or Occupancy Sensors

Motion detectors, or occupancy sensors, have proven to be an excellent way to save energy, especially in bathrooms and bedrooms where lights are frequently left on. They are also popular outdoors for walkways, driveways, and as security lights.

Sensors can operate automatically to turn lights on when movement is detected, then off after a specified period of no motion, or they can have manual on or off switches. Some models feature dimmers that reduce light to a preset level rather than turn completely off when there is no movement; others come with photo sensors that turn lights on only when the light level is below a preset point and motion is detected.

Follow manufacturer's instructions for installing sensors to ensure the proper coverage area. Also, be sure the lights are compatible with the sensors. Some compact fluorescents should not be used with motion detectors, nor should high intensity discharge lights because of their inability to relight quickly.

Dimmers

Dimming fluorescent lamps is not all that easy to do. If you reduce power to the lamp, the filaments will not be as hot, and will not be able to thermionically emit electrons as easily. If the filaments get too cool by dimming the lamp greatly, usually the lamp will just go out. If you force current to continue flowing while the electrodes are at an improper temperature, then severe, rapid degradation of the thermionic material on the filaments is likely. To effectively, reliably, and safely dim fluorescent lamps below around half brightness or so, you need special equipment that may only work properly with a specific lamp. Such equipment typically gives some power to the filaments to keep them at a workable temperature, while the current flowing through the bulb is greatly reduced.

Manual dimming controls allow occupants of a space to adjust the light output or illumination. This can result in energy savings through reductions in input power, as well as reductions in peak power demand, and enhanced lighting flexibility.

Fluorescent lighting fixtures require special dimming ballasts and compatible control devices. Some dimming systems for high-intensity discharge lamps also require special dimming ballasts.

Incandescent
Bulb

Incandescent Bulbs:

• do not require a ballast
• have a warm color appearance with a low color temperature and excellent color rendering (CRI 100)
• are a compact light source
• require simple maintenance due to screw-in Edison base
• are a less efficacious light source
• have a shorter service life than other light sources in most cases
• have a filament that is sensitive to vibrations and jarring
• can get very hot during operation
• must be properly shielded because incandescent lamps can produce direct glare as a point source
• require proper line voltage, as line voltage variations can severely affect light output and service life

Fluorescent
Bulb

Fluorescent Bulbs:

• require a ballast
• have a range of color temperatures and color rendering capabilities
• have low surface brightness compared to point sources
• have a cooler operation
• are more efficacious compared to incandescent
• ambient temperatures and convection currents can affect light output and life
• all fixtures installed indoors must use a Class P ballast that disconnects the ballast in the event it begins to overheat; high ballast operating temperatures can shorten ballast life
• have options for starting methods and lamp current loadings
• require compatibility with ballast
• low temperatures can affect starting unless a "cold weather" ballast is specified

High
Intensity
Discharge
(HID)
Bulb

High Intensity Discharge (HID) Bulbs:

• require a ballast
• ambient temperature does not affect light output, although low ambient temperatures can affect starting, requiring a special ballast
• are a compact light source
• are high lumen packages
• are a point light source
• have a range of color temperatures and color rendering abilities depending on the lamp type
• have a long service life
• are highly efficacious in many cases
• have line voltage variations, possible line voltage drops, and circuits sized for high starting current requirements which must be considered

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. How is light measured?
2. What factors determine the amount of light that is needed in a room?
3. What are the three main methods of producing light?
4. Explain the difference between incandescence, fluorescence, and high intensity discharge.
5. What are the common ways in which we can improve energy efficiency?
6. A 60-watt light bulb produces 3 watts of radiant energy and 57 watts of heat energy. What is its efficiency?
7. A 100-watt light bulb is left on all day (24 hours). How much did it cost to operate the light bulb if electricity costs 5 cents per kWh?
8. A 100 watt incandescent light bulb is operated for 12 hours, and a 15 watt fluorescent light bulb is operated for the same period of time. At 10 cents per kWh, what are the cost savings of the fluorescent bulb?
9. Jackie Smith, who is very conscious about the environment, would like to know how much energy she can save by switching to fluorescent bulbs. Estimate the total energy savings for Jackie, who uses a light bulb fixture, by comparing the total costs to own and operate a 23-Watt CFL bulb instead of the 100 Watt incandescent bulb that she has been using. The expected life of incandescent and CFL bulbs is 1000 h and, 8000 hours. The purchase price of an incandescent bulb is \$0.50 and the CFL is \$7.50. If Jackie Smith replaces 24 bulbs at home with CFLs, what would her savings be if the electricity cost is \$0.085 per kWh?

Extra Resources

For more information on topics discussed in Lesson 6, see these selected references:

1. Energy.gov Office of Energy Efficiency and Renewable Energy
2. GE Consumer Lighting
3. Don Klipstein's Lighting
4. Home Energy Saver
5. Energy.gov Building Technologies Office

Welcome to Lesson 7!

We are into Lesson Seven now: home heating basics. This is a very interesting and very important chapter. Let me warn you about one thing: this chapter has a lot of calculations, and in the entire course this is the most, I would say, calculation-oriented chapter. So I want you to pay attention to this one.

Basically, if you have a house, you will be losing (or gaining) heat from various places like windows, like the ceiling, the roof, the walls, the doors, through the floor, everywhere. So in this chapter, we will be looking at how much heat transfer occurs and by what means you will be losing or gaining it. Let's say we have this wonderful mansion, and we want to keep the interior at, let's say, 70 degrees all the time. And we have a little furnace that puts out heat and that keeps the interior at 70 degrees even when outside it's, let's say, 10 degrees Fahrenheit. Heat always tends to get out. It can actually go through those solid walls, or if we have windows, it can go through windows or even the roof. And when you open doors and windows, air might leak in and out, so that's another way of losing heat. So there are several ways in which heat is lost to the outside.

How much heat the furnace has to put out to keep the temperature constantly at 70 degrees inside can easily be calculated or known when we know how much heat is escaping. If somehow, ideally, we can seal off this entire place without any heat loss, then once you bring this house to 70 degrees you can turn on the furnace, and it will remain at 70 degrees for the rest of the season. But you and I both know that is not the case. So in this chapter, you're going to learn how much heat is escaping through various surfaces here. And obviously, whatever is escaping, that is the amount of energy that the furnace has to put out. Which means we have to buy energy and put it into the furnace in the form of fuel. So if we are losing a million BTUs like this through all these areas, we have to get a million BTUs made up from this furnace. And we also know that the furnaces are not 100% efficient, either. If we need to get 100,000 BTUs, or 1 million BTUs from the furnace, we cannot expect a furnace to put out if we put in 1 million BTUs. So if we want 1 million BTUs as output, obviously we have to put more in, in the form of fuel. So to know how much fuel we have to put in, we have to know how much heat loss we actually have in the house.

So we will be looking at residential heat loss, how to calculate that, and in what ways we lose heat in this first chapter of Lesson Seven. We will understand the mechanisms of heat transfer and also calculate the heating degree days for a heating season, which is basically the number of degrees that we have to heat our air. If the outside temperature is low, obviously we have to heat our air to a higher temperature or higher number of degrees. That's more degrees of heating. So we will calculate how many degrees we have to heat per day and per season, and so on and so forth. And if we know that, we can calculate the heat loss from a solid wall. That is conduction heat loss. We will talk about conduction, convection, and radiation -- those three mechanisms of heat loss.

And also, once we have a wall, not all walls are the same. Some walls resist more heat loss than the others. So we define a property of a wall, a property of a solid material, that tells us how much the material resists the heat loss. That's called R-value. So we will understand and articulate the concept of R-value here. And we can also increase the R-value of a wall by increasing its thickness or by going to a different material, and so on. And if we were to have a wall with lower R-value, which means lower resistance, we would be losing more heat to the outside. And we would be requiring more heat or more fuel to heat that place. So we'll talk about the cost of various fuels for a given heat loss. Seeing 1 million BTUs that we lose, if we were to heat with natural gas to get that same 1 million BTUs, what would it cost? Or if we use electricity, what would it cost to get 1 million BTUs? Or if we use propane, what would it cost? But the heat loss is always 1 million BTUs. For the same amount of heat loss, which fuel happens to be cheaper fuel or more expensive fuel? That's what we will be determining here.

We will also understand that if we have to install more insulation, we will need to borrow more money. And if we borrow more money and put in more insulation, can we save enough through heat loss to pay back that money that we borrowed? That is payback period. You already know the concept. We will do some calculations to see whether it is wise to borrow money and put more into insulation. All right, that's basically part A here. And we will also look at part B, which is insulation and home heating fuels. And in this part, we will talk about various types of insulation materials and how we can improve a wall's performance by adding more and more layers to that wall. So if we have a wall that has four different materials together, we'll see that, for example, inside we would have drywall that we could paint easily. And behind the drywall we have the framework, like a wooden frame with wooden studs that are used for structural integrity. And between those studs, you always pack some insulation material. And outside the insulation material is not visible because we'll have a plywood or sheathing outside. And even sheathing doesn't look good outside, so on top of that we put a siding, a vinyl siding or brick or whatever it is.

So when we have different materials together, one right behind the other, they will all together resist the heat loss. So we will calculate the heat loss resistivity or R-value of a wall that has different layers of insulation. And if we have that, we can find how much energy we can save or how we can cut the heat loss, et cetera. And also we will talk about the efficiencies, the furnaces, and how we can distribute the heat in the house into various rooms, et cetera, of different heating systems. We'll talk about that later on in the next chapter. So this is basically a calculation-oriented and problem-based kind of chapter or lesson. And if we have any more difficulties in this one, I also added on top of this the practice questions, a bunch of practice problems which explain you how to do numerical problems. For example, I have given here a bunch of problems, actually, using the formulas that we'll be looking at here for practice. There are a bunch of problems -- about 30 problems or so.

Those of you who are comfortable with the material can do these problems yourselves and see if you got them correct by going to this answers page, where the same problems are given with answers. So you can actually look at whether you got the same answer or not. If you got it right, you are happy. If you don't, you may feel lost. If that's the case, what you do is click on this third one here, where for every problem we have a solution, actually, like audio that I'm speaking to you right now. I have made some movies again for each of these problems that will explain to you like a blackboard, or white board rather. 

So there are a bunch of problems like this that you can look at. And most of the problems have solutions like this. So I've tried to make your life simpler. Lesson Seven is a two-week lesson, which means you will have a quiz at the end of two weeks after the lesson is assigned. And you take the quiz at the end of the lesson.

Good luck.

Home Heating

Home heating is the single highest energy expense for a household.

• Energy spent for residential space heating accounts for about 10 percent of the total energy consumed in the United States.
• The average household consumes 92 million BTUs, and 46 percent of that is used for home heating.
• According to EnergyStar.gov, average annual energy expenses were $2,060. Home energy use also accounted for 20 percent of the greenhouse gas emissions.

Therefore, reduction of energy consumption in home heating results in substantial monetary savings and reduction in air pollution. With appropriate improvements, average home heating costs can be reduced by 30 percent (i.e., about $500 a year).

Lesson 7 Objectives

Upon completing this lesson, you will be able to:

• understand the mechanisms of heat transfer;
• calculate heating degree days for a heating season and articulate significance of Heating Degree Days (HDD);
• calculate heat loss from a home using conduction equation;
• understand the concept of R-value and its importance in home heating;
• compare the cost of various fuels for a given heat loss;
• understand the significance and be able to calculate the pay-back period.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Houses are heated to keep the temperature inside at about 65°F when the outside temperature is lower. A house requires heat continuously because of the heat loss. Heat can escape from a house through various places; some are well known and some are not noticeable. Heat can escape from the roof, walls, doors, windows, basement walls, chimney, vents, and even the floor.

Heat Loss Examples

The more heat the house leaks, the more the furnace has to put out to make up for the loss. For the furnace to generate more heat to compensate the heat loss, more fuel needs to be put into the furnace, hence higher fuel or heating costs.

Heat Loss Flow Chart

As you will recall from Lesson 3, not all energy conversion devices are efficient. Thus, it is important to note that furnaces are not 100 percent efficient. When a furnace’s efficiency is lower, the fuel consumption for the same amount of heat output will be even higher.

Where Does Heat Loss Occur?

Participate in the following activity to find out where the most heat loss occurs.