| A | B |
|---|
| renewable energy | energy from sources that are constantly being formed |
| passive solar heating | the use of sunlight to heat buildings directly |
| active solar heating | the gathering of solar energy by collectors that are used to heat water or heat a building |
| biomass fuel | plant material; manure, or any other organic matter that is used as an energy source |
| hydroelectric energy | electrical energy produced by falling water |
| geothermal energy | the energy produced by heat within the Earth |
| alternative energy | energy that does not come from fossil fuels and that is still in development |
| ocean thermal energy conversion (OTEC) | the use of temperature difference in ocean water to produce electricity |
| energy efficiency | the percentage of energy put into a system that does useful work |
| energy conservation | the process of saving energy by reducing energy use and waste |
