2.  The sun constantly gives off energy in the form of light and heat.  Earth receives enough solar energy to meet the energy needs of the entire world for 40 years.  Advantages: 1. It does not cause pollution 2. Abundant availability, It will not. Disadvantages: 1. Its only available when the sun is out and it is very spread out.

3.  Solar Plants: Rows of giant mirrors focus the sun’s rays to heat a tank of water. The water boils, making steam that is used to generate electricity.  Solar Cells: consists of a “sandwich” of very thin layers of the element silicon and other materials.

5.  Passive: converts sunlight into thermal energy without using pumps of fans.  Active: captures the sun’s energy, then uses fans and pumps to distribute the heat.

7.  Wind energy is an indirect form of solar energy.  The differences in pressure cause winds as air moves from one area to another.  Wind can be used to turn a turbine and generate electricity.

10.  Hydroelectric power is electricity produced by flowing water.  It is the most widely used source of renewable energy in the world today.  Advantages: 1. It is inexpensive. 2. No pollutions 3. Provides a steady supply of energy.

12.  Tides are another source of moving water.  The gravity of the moon and sun causes the water on Earth’s surface to rise and fall on its shores.  A few tidal power plants have been built to take advantage of this regular motion.

14.  The oldest fuel used for heat and light is wood.  Other biomass fuels are leaves, food, wastes and manure.  Biomass materials can be converted into other fuels; 1. Gasohol-corn makes alcohol, add alcohol to gasoline produces fuel for cars. 2. Bacteria decomposes turns into methane gas is used to heat buildings.

17.  Intense heat from Earth’s interior.  Geothermal energy is an unlimited source of cheap energy.  Disadvantages: 1. Only a few places where magma comes close to Earths surface. (Iceland) 2. Need to drill deeper wells (expensive)

19.  Energy of the future: 1. Burns cleanly 2. Water is its only by-product 3. It creates no smog, smoke or acid rain. 4. Can be handled and transported through pipelines. 5. Exists on Earth in large supply. Disadvantage: Almost all of Hydrogen is combined to Oxygen