PrintEnergy Efficiency Introduction
There are several terms related to this topic that are important to know. For this lesson, we will touch on energy efficiency, distributed energy and microgrids, and the future of the way energy is delivered, which includes smart grids and demand side management.
Credit: Eight Electrical Metric Meters by Tim Mossholder is licensed under CC BY-NC-ND 2.0
Energy Efficiency
Energy efficiency is the amount of useful energy you get from any type of system. It is calculated as the useful energy output divided by the total energy input. For example, a light bulb converts electricity to light and heat. Typically, the light is the "useful" output, and the heat is a byproduct. Because only five to eight percent of the energy used by a standard incandescent light bulb is converted to light, the rest is dissipated as heat.
Stated another way, energy efficiency generally means how effectively we use energy to accomplish a function. For example, a refrigerator that uses less energy than another model to keep the same amount of food cold is said to be “more efficient” than the other model. Another aspect of energy efficiency is how much of the energy provided is used as compared to that which is wasted. For example, with a steam boiler, the higher the percentage of the heat generated by burning fuel that is translated to the heat output in steam, the more efficient it is said to be.
The traditional grid is relatively inefficient because so much energy is lost in transmission between the power plant and the ultimate user. This is in part due to heat loss generated by the resistance of the transmission lines. Without getting into physics here, suffice to say that long distance transmission and traditional power plants lose energy as waste, usually as heat, between initial generation and delivery to your home. These losses average 6 to 8%, and minimizing these losses, combined with managing how much energy you use, serves as the foundation for the energy use efficiency movement. This doesn’t sound like much, but when you consider the losses at the power plant simply from burning a fuel to generate power, you will start to get a sense of how much energy it takes to make electricity and how important it is to be as efficient as possible from generation to transmission to end use.
The term "energy efficiency" is also used with a more broadly scoped meaning, such as this previously published definition from the World Energy Council: "energy efficiency improvements refer to a reduction in the energy used for a given service (heating, lighting, etc.) or level of activity. The reduction in the energy consumption is usually associated with technological changes, but not always, since it can also result from better organization and management or improved economic conditions in the sector ('non-technical factors')."
In this sense, a programmable thermostat may help with "energy efficiency." Simple steps such as remembering to turn off the lights is a non-technical behavior that can also improve energy efficiency. These are examples of energy efficiency in its broader meaning, related to the smarter use of energy for a specific purpose.
Energy efficiency helps in many ways. Recall our four attributes- security, reliability, accessibility, and sustainability. Energy efficiency, which fundamentally is using less energy when possible, is one of the few approaches that supports all four. By using less energy, there is more in the system increasing reliability and accessibility (in part, due to reduced cost of power from lower demand). Needing less energy means less use of fossil fuels and other environmental impacts. And using less energy makes us less dependent and therefore more secure.
Some content on this page came from an earlier version of this course and was written by Vera Cole.
EGEE 401: Energy in a Changing World by Vera Cole via the Pennsylvania State University is licensed under CC BY-NC-SA 3.0