Defining the Renewables
The term renewable energy refers to electricity supplied from sources that are replenished by nature, including as wind and solar power, geothermal, hydropower, and various forms of biomass.
Biomass, burning of wood, corn, and other vegetation is renewable, because we can always grow more. But converting biomass to heat energy creates as many problems as it solves and while trees may be considered renewable, forests are not.
Hydropower is a pollution free source of electricity, but it forces long term changes on streams and rivers and their ecosystems.
Solar power technology is still too expensive for wholesale deployment, but it is an important source of clean energy.
Wind power is a viable alternative, but windmill sites must be chosen carefully, because locations near flyways have killed thousands of birds and bats.
Geothermal energy is derived from the Earth’s hot inner core, which heats the earth’s surface and warms the water and rocks beneath. This steaming water and rock can be used to generate heat and electricity.
The earth’s core contains more energy than all the oil and gas reserves in the world, making geothermal energy abundant, available, and affordable. Already, geothermal provides enough electricity to power nearly four million U.S. homes.