CHAPTER 18 RENEWABLE ENERGY

SECTION 18.1 RENEWABLE ENERGY TODAY

RENEWABLE ENERGY TODAY Renewable energy is energy from sources that are constantly being formed. Examples: solar, wind, moving water and Earth’s heat Many countries plan to increase their use of renewable sources.

SOLAR ENERGY: POWER FROM THE SUN Passive solar heating Active solar heating Uses the sun’s energy to heat something directly Examples: large windows facing the sun Uses collectors on the roof Used to heat water or the building SOLAR ENERGY: POWER FROM THE SUN

SOLAR ENERGY: POWER FROM THE SUN ALL RENEWABLE ENERGY COMES DIRECTLY OR INDIRECTLY FROM THE SUN. THIS ENERGY IS ENOUGH TO POWER THE WIND, PLANT GROWTH, AND WATER CYCLE.

Photovoltaic cells Solar cells that use a semiconductor. They convert the sun’s energy into electricity. Meeting the needs of a small city would require covering hundreds of acres of solar panels. Energy production from solar cells has doubled. They are becoming more efficient and less expensive.

WIND POWER: CHEAP AND ABUNDANT CONVERTS THE MOVEMENT OF WIND INTO ELECTRIC ENERGY. FASTEST GROWING ENERGY SOURCE IN WORLD. (QUADRUPLED FROM 1985-2000) NEW TURBINES ARE COST-EFFECTIVE.

Wind FARMS Large array of wind turbines. Take up little space Convenient for farmers. Problem is transporting electricity from rural areas to urban centers. In future, electricity may be used on the wind farm to produce hydrogen from water.

Biomass: power from living things Plant materials, manure, any organic matter that is used as energy is called biomass fuel. Renewable biomass fuels would include wood and dung. (Used for heating and cooking) Habitat loss, deforestation, and soil erosion are disadvantages of biomass fuel.

methane Methane can be used to generate electricity and heat. Biogas digesters ferment manure and produce methane. Dung-fired power stations produce electricity. Methane from landfills can generate electricity.

Alcohol Ethanol can be made by fermenting fruit or agricultural waste. In U.S. corn is major source. Gasohol is a blend of gas and ethanol for cars Produces less air pollution

Hydroelectricity: power from moving water Hydroelectric energy is energy produced from moving water. Accounts for 20 percent of the world’s electricity. A dam is built across a river to hold the reservoir of water. When water is released, it turns a turbine, which generates electricity.

advantages disadvantages Disadvantages of Hydroelectric energy Benefits of hydroelectric energy Inexpensive to operate No air pollution Last longer than fossil fuel plants Dams can provide flood control, and water for drinking, agriculture, industry, and recreation. Fertile sediment builds up behind the dam. Floods habitats above the dam. Disrupts ecosystem downstream. People can be displaced. If dam bursts, people can die Farmland below dam becomes less productive. Some plant matter trapped in reservoir can release greenhouse gases. advantages disadvantages

Modern trends in hydroelectricity Brazil, India and China still building large dams. Micro-hydropower is electricity produced in a small stream without building a big dam. Turbine floats, not blocking river Cheaper than large dam projects

Geothermal energy: power from the earth Geothermal energy uses heat from the Earth’s interior. Geothermal power plants pump heated water or steam from rock formations and use the water or steam to power a turbine that generates electricity. U.S. is the world’s largest producer of geothermal energy

Geothermal heat Pumps: Energy for homes Geothermal heat pumps use stable underground temperatures to warm and cool homes. Summer: ground is cooler than air and fluid is used to cool home. Winter: ground is warmer than air and fluid is used to warm home.

That’s all for 18.1 Time for a reading quiz!

Section 18.2 Alternative Energy and Conservation

Alternative energy and conservation Alternative energy describes energy sources that are still in development. These sources must prove to be cost effective. Environmental effects must be acceptable.

Tidal power Used to generate electricity in France, Russia, and Canada. Works like a hydroelectric dam. As the tide rises, water is trapped behind the dam. At low tide, water rushes through the dam and spins a turbine, which generates electricity.

Ocean thermal Energy conversion (OTEC) Produces electricity using the temperature difference between two layers of water. Water boils at low temperatures when it is under low pressure in a vacuum chamber. Boiling water turns to steam, which turns turbine, generating electricity.

Problems with OTEC Hawaii and Japan have tried this alternative source. Can’t generate electricity cost-effectively. Power needed to pump cold water up from deep ocean uses 1/3 of the electricity plant produces Environmental effects are unknown.

Hydrogen: a future fuel source? Most abundant element in the universe. Can be burned as fuel Is used in fuel cells. Does not release pollutants when burned Produces water as by-product.

The challenge of hydrogen fuel Current methods to produce hydrogen are not very efficient. Require a lot of energy, are expensive, and cause pollution. A lot of hydrogen is needed to produce the same amount of energy as a tank of gasoline. Hydrogen must be compressed to fit into vehicle.

Fuel cells Produce electricity chemically by combining hydrogen fuel with oxygen from the air. Hydrogen and oxygen combine, producing electricity, and water as a byproduct. Fuel cells can be fueled by natural gas, alcohol, or even gasoline

Energy efficiency Is the percentage of energy put into a system that does useful work. Most of the devices we use are fairly inefficient. Energy conservation includes lifestyle changes.

Examples of ways to be more energy efficient Vehicles with efficient engines. Increase the use of public transportation Insulate buildings Use of fuel cells Use fluorescent bulbs Wash in cold water

Hybrid car Uses an efficient gas engine and an electric motor. Convert energy of braking into electricity Store this energy in battery. When car is idling, gas engine shuts off Lightweight so need less energy to accelerate. Cost less to fuel and produce less harmful emissions.

That’s all for 18.2 Time for a reading quiz.