EME 807
Technologies for Sustainability Systems

2.1 Technology as a part of anthropogenic environment

How do we define technology? In this course, specifically, we need to look at a particular technology, process, or product as an active part (component) of an anthropogenic system. In such context, a technology is not simply a piece of human knowledge implemented through design and engineering principles, it is considered a "living" part of a bigger organism. Here we use the word "living" because our interest will be to assess the entire lifecycle of a technology: development, adaptation, operation, interactions with natural and technical environment, aging, and death (in some cases). Further on, we will try to understand how technology development impacts the viability of the whole system.

The common definition of the term technology is quite broad and multi-colored. The most simplistic one is -application of scientific knowledge for practical purpose. And as an extension of it, the tool or device enabling that application is typically also referred to as technology. You can read more on the history and usage of this term in a Wikipedia article on Technology. You may recognize that the meaning strongly depends on the context and the professional area you are in. However, in this course, we need to distill this broad perception of technology to a more specific entity that can be used for practical analysis.

The most important ability of almost any technology is conversion. A technology uses inputs of energy or matter to create outputs of energy or matter of a different quality. In a general case, any technology can be represented by the following scheme (Figure 2.1):

input of energy and matter conversion using technology output of energy and matter
Figure 2.1. Energy and matter conversion defined as a function of technology.
[Credit: Mark Fedkin]

So technology typically serves as a conversion portal in a system. We use energy to produce materials; or use raw materials to produce some more complex products; or we use matter to convert forms energy; etc. Note that conversion can also be performed by natural systems or mechanisms; but we only define technology as a human-made conversion system.

Here are some simple examples:

  • Chemical energy of fuel >>> Car >>> Kinetic energy
  • Sunlight >>> Solar panel >>> Electric energy
  • Electric energy >>> Phone >>> Waves: sound, light
  • Contaminated water >>> Water treatment facility >>> Clean water
  • Electric energy >>> Furnace >>> Thermal energy
  • Flour, water >>> Baking machine >>> Bread
  • Organic waste >>> Composting >>> Fertilizer
  • Electricity, mechanical energy >>> Electric guitar >>> sound
  • … etc.

Conversion efficiency

The key characteristic of any conversion process is efficiency. Efficiency is estimated based on the amount of useful output per unit input. In that sense, it is a subjective value which depends on a particular goal or purpose of a technological process, and a particular input resource we are concerned about. Hence, efficiency has widely varying meanings in different disciplines.

For example, efficiency is a very common metric in the field of energy conversion. According to the energy conservation law, the total energy entering a conversion device should be equal to the total energy output by the device:

Ein = Eout

Some of the output energy can be useful (based on the purpose of conversion) and some of it can be attributed to losses:

Eout = Eout(useful) + Eout(loss)

So, efficiency determines the fraction of the useful energy as follows:

Efficiency = Eout(useful)/Ein × 100%

Efficiency is important in the sustainability context because it indicates how much of the resource is put to work, and how much of the resource is wasted in the process. The reasons for losses are process dependent and should be analyzed specifically for each application. A big part of the technological research is aimed at increasing efficiency of the conversion process via minimizing losses.


To illustrate how this concept works, for example, let us estimate the efficiency of a photovoltaic panel. Photovoltaic technology converts visible solar radiation (energy-in) into electric power (energy-out). So, for this estimation, we need to know or to measure these two quantities.

Let us assume that the efficiency is measured in the middle of a sunny day, and the panel is installed perpendicular to the incident rays. Under those conditions, the typical incident radiation power density is ~1000 W/m2. We can take this number as the measure of energy-in per unit of time.

Now let us assume that the panel outputs the power density 120 W/m2 at its peak performance. Usually, this value can be obtained by measuring the voltage and current density of the panel (power = voltage x current).

Then, the efficiency value can be calculated as follows:

Efficiency = Eout(useful)/Ein × 100% = 120 W/m2 / 1000 W/m2 × 100% = 12%

This value means that 88% of total solar energy reaching the panel is lost, and only 12% is converted to electricity due to technology limitations or environmental factors. As you can see, efficiency estimations require data on technical performance of the system, so we will be paying attention to how performance of different technologies can be measured and interpreted.

Table 2.1 lists some known efficiencies of various energy technologies for comparison. These are just a few examples to demonstrate the variety of converters. We should note that generally efficiency of a process or technology is not necessarily measured in terms of energy. If the useful output of the converting technology is, for example, some form of matter (e.g., water electrolyzer in this table), the calculation can be made in terms of mass. Sometimes efficiency analysis is also used to estimate the maximum theoretical efficiency, which cannot be practically exceeded due to inherent physicochemical limitation of the system. Finding maximum theoretical efficiency requires detailed knowledge of how the process works and what unavoidable losses occur in conversion.

Process or Technology Input Output Conversion efficiency
Table 2.1. Efficiencies of some energy conversion processes and technologies. Note: values for a specific system may vary due to operational conditions and component development [Source: Wikipedia]
Gas turbine Gas flow Electricity 40%
Water turbine Water flow Electricity 90%
Solar cell Light Electricity 15-40%
Fuel cell H2(gas), O2(gas) Electricity up to 85%
Water electrolyzer Electricity H2(gas), O2(gas) 50-70%
Combustion engine Fuel (gasoline) Motion (kinetic energy) 10-50%
Geothermal electric plant Heat Electricity 10-23%
Solar thermoelectric generator Sun radiation Electricity 15%
Electric motor Electricity Motion (kenetic energy) 30-90%
Electric heater Electricity Heat up to 100%
Refrigerator Electricity Negative heat 20-40%
Fluorescent lamp Electricity Light 8-15%
Photosynthesis Light Biomass, O2(gas) 3-6%
Muscle Metabolic energy Kinetic energy 18-25%

Probing Question

Can energy conversion efficiency be more than 100%? Click on answer below.


Incorrect :( Efficiency above 100% would mean that energy output of a system is greater than energy input. This contradicts the Law of energy conservation.


Correct!Output cannot be greater than in the input according to the energy conservation Law.

Yes, but only in an ideal zero-loss system

Incorrect! Zero losses would mean 100% efficiency, but not higher.

Probing Question

Can you calculate the efficiency of an electric motor that consumes 150 W of electrical power and produces 120 W of mechanical power? Click on answer below.


Try again - divide the useful output of the system by total energy input.


Try again - divide the useful output of the system by total energy input.


Correct! Dividing 120/150 = 0.8 (i.e. 80%)


Efficiency cannot theoretically go above 100%.

Technology Adaptation

To become part of society life, technology needs to be adapted. Not all technologies invented go through successful adaptation, and there are several critical barriers that need to be overcome in order to create a working interface between technology and society.

Stacked diagram: Technology surrounded by environment and infrastructure, that’s surrounded by market, everything's surrounded by society
Figure 2.2. Technology adaption stages
Credit: Mark Fedkin

Consider the following stages of technology adaptation:

  1. Technical Adaptation. Research and development, design, and demonstration. (yellow)
  2. Adaptation to natural environment: matter and energy exchange, use of resources, and absorption of the impact (green).
  3. Adaptation to the technical environment: development of infrastructure and supporting technologies (brown).
  4. Market Adaptation. Development of economic algorithm. Proof of profit and long-term feasibility (peach).
  5. Social Adaptation. Acceptance by target society groups, based on ethical, environmental, cultural, and economic considerations (blue).

The first three stages of adaptation can be reflected in more detail through the Technology Readiness Level scale (TRL) on page 2.2 of this lesson. The fourth stage of adaptation closely related to economic assessment, which should answer the question if the technology can support itself and make a profit in the short term or in the long term. Finally the fifth stage of adaptation includes multiple social factors - how ready consumers are to accept this new technology, and what socal benefits it promises (for example, higher standard of living, job creation, convenience, faster service, improved health, etc.). The sustainability analysis should be comprehensive enough to cover all of these layers of adaptation and recognize connections and feedbacks between them.