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