Environmental Science Chapter 18 Section 1

 Energy from sources that are constantly being formed.  Examples: ◦ Solar ◦ Wind ◦ Water ◦ Earth’s heat

 Only a small fraction of the sun’s energy reaches the Earth.  The energy is enough to power the wind, plant growth, and the water cycle.  All forms of energy come either directly or indirectly from the sun.

 Passive Solar Heating ◦ Uses the sun’s energy to heat something directly. ◦ May use windows facing the direction where the sun strikes most directly in order to heat a building. ◦ Could potentially eliminate heating bills, but can definitely greatly reduce them.

 Active Solar Heating ◦ Energy from the sun is gathered by collectors and used to heat water or to heat a building. ◦ Collectors are usually mounted on a roof and capture the sun’s energy. ◦ Used primarily for water heating.

 Photovoltaic Cells ◦ Convert the sun’s energy into electricity. ◦ Solar cells have no moving parts. ◦ Solar cells produce a very small electrical current, so it cannot meet all of our energy needs. ◦ Solar energy production has doubled every four years since ◦ Provide energy for more than 1 million households in the developing world.

 Wind Farms ◦ Large arrays of wind turbines. ◦ In CA, supply electricity to 280,000 homes. ◦ Wind turbines take up little space, so can be placed on farms where the land can still be used for other purposes.

 An Underdeveloped Resource ◦ Scientists estimate that the windiest spots on Earth could generate more than ten times the energy used worldwide. ◦ One problem is transporting the electricity from rural areas where it is generated to urban centers where it is needed.

 Biomass fuel ◦ Plant material, manure, and any other organic matter that is used as an energy source. ◦ Renewable: wood and dung. ◦ Nonrenewable: fossil fuels.

 Methane ◦ A byproduct of bacteria decomposing organic waste. ◦ Gas that is used for heating and cooking. ◦ Some landfills in the U.S. use the produced methane to generate electricity. ◦ Britain opened the first dung-fired power station in 2002.

 Alcohol ◦ Ethanol can be made by fermenting fruit or agricultural waste. ◦ Corn is a major source of ethanol. ◦ Cars and trucks can run on gasohol (a blend of gasoline and ethanol).

 Hydroelectric energy ◦ Energy produced from moving water. ◦ Renewable resource that accounts for about 20% of the world’s electricity. ◦ Canada, U.S., Brazil, China, Russia, and Norway are the major producers (in decreasing order).

 The Benefits of Hydroelectric Energy ◦ Hydroelectric dams are expensive to build, but relatively inexpensive to operate. ◦ Do not release air pollutants that cause acid precipitation. ◦ Tend to last longer than fossil fuel-powered plants. ◦ Provide benefits such as flood control and water for drinking, agriculture, industry, and recreation.

 Disadvantages of Hydroelectric Energy ◦ A dam changes a river’s flow. ◦ A reservoir floods large areas of habitat above the dam and ecosystems downstream are disrupted by reduced water flow. ◦ Fertile sediment does not travel as far downriver. ◦ If a dam bursts, people may perish and property may be destroyed.

 Geothermal energy ◦ Deposits of water in the Earth’s crust are heated by energy within the Earth. ◦ The heat below Earth’s crust can be used to generate electricity. ◦ Geothermal power plants pump heated water or steam from rock formations and use the water or steam to power a turbine that generates electricity. ◦ The water is returned to the Earth’s crust where it can be heated and used again.

 Geothermal Heat Pumps: Energy for Homes ◦ More than 600,000 homes in the U.S. are heated and cooled using geothermal heat pumps. ◦ Temperature of the ground is nearly constant year- round. ◦ Heat pump is a loop of piping that circulates a fluid underground.  In summer, the ground is cooler.  In winter, the ground is warmer.