Renewable Energy

Renewable Energy—energy from sources constantly being formed --Like the sun, wind, moving water, heat of the Earth, and growing plants --Governments plan on increasing use of them: --to reduce environmental problems --to ensure long-lasting energy

 Our sun is a medium-sized star  Energy (light/heat) produced by nuclear fission:  Combining of nuclei  Opposite of nuclear power plants  Can’t make on Earth – too hot to contain/control  Only a small fraction of its energy reaches us

 “Passive Solar Heating” sun heats something directly:  Long eaves shade house in summer  South-facing windows in winter let in light/heat  Thick insulation to keep heat in  “Active Solar Heating” gathered by collectors:  Gather heat on roof and heat water  8% of U.S. energy use is to heat water

 “Photovoltaic Cells”  PRO:  Convert sunlight directly into electricity  No moving parts (less friction, less energy lost)  No pollution  CON:  Produce small amounts of electricity  Hundreds of acres to power a small city  Need long periods of sunlight  Stored in battery  Increasing in efficiency; decreasing in cost  Great for developing countries  low energy need

 Energy from sun warms Earth unevenly  Wind  Windmills convert moving air into electricity  Are cost effective and quick to build  Wind generated electricity has quadrupled (4x) from year 1995 to 2000  Wind Farms  large array of wind turbines  Can add easily to land and roofs

 Windiest spots on Earth could generate more than 10x the energy used worldwide  Possible Problems: Getting electricity to others from remote areas and animal impacts

 Any organic matter (living or once part of living system)  Fossil Fuels are buried and compressed biomass  Renewable biomass is being cycled through biosphere continually  Developing Countries use biomass (wood and dung) for primary heating of homes and cooking  Use of wood too fast = deforestation, soil erosion, habitat loss, and air pollution

 Methane  Gas made when bacteria decompose organic waste  Can be burned to make heat or electricity  Dung-powered power plant in Britain in 2002  Landfills produce methane as trash breaks down  Alcohol  Fermenting fruit and farm waste = alcohol  Corn produces ethanol  replaces gasoline  “Gasohol” makes less air pollution

 Energy from the sun causes the water cycle  As water moves across the land it can be used  Accounts for 20% of world’s electricity  Leading Countries: Canada, U.S., Brazil, China, Russia, and Norway

 PRO:  Inexpensive to operate  No air pollution  Dam lasts longer than power plant  Flood control, water for drinking, agriculture, industry, and recreation

 CON:  Expensive to build  Changes a river’s flow  Floods behind the dam  Disrupts ecosystems  Stops sediments from reaching other land  Reduces water flow down-river

 New Trend is Micro-hydropower:  Mini-dams that float on the river  Smaller scale using small streams

 Under Earth’s crust is heated  This heat can be used to heat water to power a generator:  Leading Countries: U.S. (California), Philippines, Iceland, Japan, Mexico, Italy, and New Zealand  Heated area must be managed so its not depleted  Heat Pump  Soil underground stays warmer than topsoil  Water pipes go underground to heat water for homes