Chapter 18
Renewable Energy Today Renewable Energy energy from a source that is constantly being reformed. Many governments are planning to increase their use of renewable energy resources. This will reduce environmental problems of nonrenewable energy sources. Examples Solar Wind Hydro Geothermal
Solar Energy Power from the Sun The sun is a medium sized star that radiates energy via nuclear fusion. Only a small portion of the suns energy ever makes it to earth. This energy directly or indirectly powers all of earths weather, and photosynthetic life.
Types of energy from the Sun
Uses of Solar Energy Heat Light Photosynthesis Electricity
Passive Solar Heating Uses the suns energy to directly heat an object In the northern hemisphere southern facing walls and windows receive the most energy from the sun. Large windows are often used in passive solar heating. Passive cooling techniques are also used. While most homes use these techniques they are not the sole methods of heating and cooling.
Active Solar Heating Energy from the sun is gathered to heat water. Solar collectors are mounted on the roof to capture the energy of the sun. Hot water is then pumped through the house and or a heat exchanger. 8 percent of the energy in the in the US is used to heat water.
Photovoltaic Cells Aka Solar Cells Convert the energy of the sun into electricity. They are used to power many different electronic devices large and small. Pros They have no moving parts so they are easy to maintain. They produce no pollution. Cons Produce a very small electrical charge. Need long period of sunlight. Difficult to store energy in batteries. Expensive
Wind Power Energy from the sun warms earth s surface unevenly causing wind. Converts the kinetic energy of the wind into electrical energy. Wind Farms large groups of wind turbines. Pros Wind turbines take up little space and the land can still be used for other purposes.
Future of Wind Energy Scientist estimate that the windiest locations on earth can produce 10 times more energy then currently used. Cons It is difficult to transport energy. Eye soar
Biomass Power from Living Things Plant material, manure, and any other organic material that is used as an energy source. Fossil fuels are nonrenewable biomass fuels. Renewable biomass fuels include: Wood Dung Methane Alcohol
Methane Byproduct of decomposition of organic wastes by bacterial. Can be burned to produce heat or electricity. Methane was once considered a dangerous waste product that was simple burned off to prevent explosions. Land fills now collect the methane produced from decomposing trash and burn it to create energy.
Alcohol Liquid fuel derived from biomass. Created by the fermentation of fruit, grain or agricultural waste. Cars can run on ethanol of gasahol Gasahol a mixture of ethanol and gasoline. Gasahol produces less air pollution than fossil fuels do.
Hydroelectricity - Power from Moving Water Flowing water has kinetic energy. The kinetic energy of water can be converted into electricity using a turbine. Hydroelectricity is a renewable resource that makes up 20% of the worlds electricity. Many developed countries use this energy source.
Benefits of Hydroelectricity Relatively inexpensive to run. Do not release air pollution. Flood control Drinking water Agriculture Industry Recreation
Disadvantages of Hydroelectric Expensive to build Changes river flow Floods large areas Reduces water flow down stream Prevents the migrations of animals People are displaced Dam failure Sediment deposits Plant matter trapped in the reservoir produce greenhouse gases
Modern Trends In developed countries the time of large scale dam building is over. Developing countries are still building large scale dams. Micro-hydropower Electricity which is produced in a small stream without building a large dam. The may even float preventing flooding and stream blockage. Cheaper in cost.
Geothermal Power The energy of heat in the earths crust. Ground water is heated by the internal energy of the earth. This heated water and steam is used to turn turbines and produce electricity. Water is then returned to the ground to be reheated. Ground water must be carefully monitored.
Geothermal Heat Pumps: Energy for Homes The temperature of the ground is nearly constant all year long. The heat pump uses this ground temperature to heat and cool the home. A heat pump is a series of pipes located under the ground through which fluid is pumped.
Alternative Energy Energy sources that are still in development. For alternative energy sources to become viable in the future they must prove to be cost effective. They must also be environmentally sound. Government investment is often the only way these technologies can be developed.
Tidal Power Tide the movement of the water in the ocean caused by the gravitational attraction of the moon and the sun. Tides happen twice a day. High and low. The power of the tides is use to produce electricity. Works similar to a hydroelectric plant Pros No pollution Renewable Cons Cost is high Few suitable locations
Ocean Thermal Energy Conversion (OTEC) Uses the temperature difference between the ocean s water surface and the deep ocean. Water boils at lower temperatures when it is under pressure. Pumping warm surface water into the deep ocean causes it to boil and produce steam to turn turbines. Pros No Pollution Cons In efficient 1/3 of energy used to pump water, Unknow effects of changing the ocean temp.
Hydrogen Most abundant element Can be burned for fuel Does not release pollutants associated with fossil fuels Byproduct is water and a small amount of nitrogen oxides. Water can be split to produce hydrogen. But it takes a lot of energy to produce hydrogen gas. Hydrogen gas must be stored in tanks or transported via pipeline.
Fuel Cells Produces energy by combining hydrogen and oxygen to make water.
Energy Efficiency The percentage of energy put into a system that does not do useful work. Energy out/energy in times 100 Most of our current electrical devices are extremely inefficient. More than 40% of the energy used in the US is wasted.
Efficient Transportation Mass Transportation Fuel efficient personal vehicles Gas prices are a driving force
Hybrid cars Use both gas and electric engines. Regenerative braking to charge batteries. Aerodynamic Light weight Cost less to fuel Release fewer emissions
Cogeneration The production of two useful forms of energy from the same fuel source. Using heat that is generated as a byproduct to create steam to produce electricity.
Energy Conservation Means saving energy Can be done by: Using energy efficient devices Using less energy Insulating Plugging leaks Washing using cold water Turning off appliances when you are not using them