1. Alternative Energy Sources Chapter 11.4

2. Alternative Energy 1.Alternative Energy a.Energy that is derived from sources that do not deplete the natural resources or harm the environment. b.Alternative energy sources include solar energy, geothermal energy, water, and wind energy.

3. Solar Energy 2.Solar Energy a.Energy that is derived from the sun’s radiation. i.Every 15 minutes the earth receives enough energy from the sun to meet the energy needs of the entire world for 1 year. b.There are two ways of capturing solar energy, with a passive system or with an active system.

4. Solar Energy i.A passive system requires no working parts to collect solar energy. 1.An example of a passive system would be a brick house with windows that face the sun. Solar energy is collected by the bricks and transferred in the house.

5. Solar Energy ii.An active system requires the use of working parts, such as solar collectors and photovoltaic cells. 1.A solar collector is a box with a glass top, usually placed on the roof. Water runs through tubes in the collector and is heated. The heated water then runs to the house providing heat and hot water. 2.A photovoltaic cell converts sunshine directly into electricity.

6. Geothermal Energy 3.Geothermal Energy a.Energy derived from the heat of the earth’s interior. i.This process works when water flows through rock that is heated by a body of magma or by hot gases being released by the magma. This hot water, or steam, is a source of geothermal energy. 1.This energy (steam) can be used as a source of heat to power turbines and generate electricity.

7. Hydroelectric Energy 4.Hydroelectric Energy a.Energy derived from running water. i.At a hydroelectric plant, dams hold back running water and channel it through the plant. Inside the plant, the force of the water spins turbines which produce electricity.

8. Hydroelectric Energy ii.Tidal energy can also be used to generate electricity. When high tide occurs, dams trap water in, this water is then used to generate electricity at low tide.

9. Wind Energy 5.Wind Energy a.Energy derived from the wind. i.When the wind blows through the blades of a windmill, it spins the blades and the turbines, which produces electricity. ii.Through many areas of the US and off- shore sites, wind energy is being used to power homes, farms, and cities.