Sources of Energy pp.145-151

Nearly all the energy on Earth comes originally from the sun. Plants get energy for photosynthesis from sunlight. Animals get energy from food, including plants. Over time plant and animal remains changed into coal, oil and natural gas. Photovoltaics change solar power directly into electricity Heat from sunlight creates wind, which windmills change into electricity or mechanical energy.

Fossil Fuels Coal, oil and natural gas are called fossil fuels because they take millions of years to be created, like fossils. Fossil fuels are nonrenewable resources because we are using them much faster than they can be replaced. They will run out! Burning fossil fuels releases pollution into the air.

Fossil Fuels Coal comes from plants alive millions of years ago. Oil and natural gas come from animals and bacteria from millions of years ago. Coal comes from plants alive millions of years ago.

Nuclear Energy Nuclear energy comes from releasing the energy that holds the nucleus of a uranium atom together. This releases lots of heat (thermal energy). The nuclear fuel is still radioactive for millions of years after it’s removed from the power plant.

Hydroelectricity Uses the potential energy of water to generate electricity. The water has to be stored by a dam. Then it passes through the dam’s generators. Hydroelectricity is a renewable resource because the source can be replaced.

Inexhaustible Resources Inexhaustible means they can never run out! Examples include solar power, wind power and geothermal energy. These are also called alternative resources.

Geothermal Energy Underground temperature stays same year round Power plants pump water deep down to be heated to steam to generate electricity. Home Heat Pumps In summer: underground cooler than house so pump water down to cool it, then pump through house In winter: underground hotter than house so pump water down to heat it, then pump through house

Inexhaustible Resources Solar Power Wind Power Geothermal From sunlight Depends on weather Expensive Passive solar uses light to heat water Photovoltaics change light energy into electricity From kinetic energy of wind Depends on weather No pollution Not pretty to look at Can kill birds that fly into windmill From underground heat No pollution Expensive

Notes Nearly all the energy on Earth comes originally from the sun Coal, oil and natural gas are called fossil fuels. Nonrenewable resources are used faster than they can be replaced. (Examples: coal, oil, natural gas) Renewable resources can be replaced. (Example: hydroelectricity) Inexhaustible resources can never run out! (Examples: solar, wind, geothermal energy) Photovoltaics change sunlight to electric energy.

Fossil Fuels Advantages We already use them Portable

Fossil Fuels Limited amounts left We already use them Disadvantages Advantages Limited amounts left Need large amounts of fuel Releases lots of pollution Leaves lots of ash/residue We already use them Portable

Nuclear Energy Uses small amounts of fuel No air pollution Advantages Uses small amounts of fuel No air pollution Releases large amounts of energy

Nuclear Energy Limited amounts of uranium Uses small amounts of fuel Disadvantages Advantages Limited amounts of uranium Leaves radioactive waste Uses small amounts of fuel No air pollution Releases large amounts of energy

Hydroelectricity ADVANTAGES No pollution Available on demand

Hydroelectricity Can harm fish swimming upstream No pollution ADVANTAGES Disadvantages Can harm fish swimming upstream Drought can lower water level too low to generate power Expensive to build No pollution Available on demand

Solar Power Advantages Inexhaustible No pollution

Solar Power Inexhaustible No pollution Need sunlight (night, clouds) Advantages Disadvantages Inexhaustible No pollution Need sunlight (night, clouds) Expensive Needs large spaces

Wind Power Advantages No pollution

Wind Power No pollution Depends on weather Needs large spaces Advantages Disadvantages No pollution Depends on weather Needs large spaces Can kill birds Not pretty to look at

Geothermal Energy Advantages Available 24/7 No pollution

Geothermal Energy Available 24/7 No pollution Not available everywhere Advantages Disadvantages Available 24/7 No pollution Not available everywhere Expensive

Sources of Energy Nearly all the energy on Earth comes originally from the sun Coal, oil and natural gas are called fossil fuels. Nonrenewable resources are used faster than they can be replaced. (Examples: coal, oil, natural gas) Renewable resources can be replaced. (Example: hydroelectricity) Inexhaustible resources can never run out! (Examples: solar, wind, geothermal energy) Photovoltaic cells change sunlight directly into electricity. Fossil Fuels Advantages Disadvantages Already being used Limited amounts left Portable Causes much pollution Nuclear Energy Advantages Disadvantages No air pollution Radioactive waste for millions of years Need just small amount of fuel Limited amount of uranium Get large amount of energy

Hydroelectricity Advantages Disadvantages No pollution Can harm fish Always available Drought can lower water too far Expensive Need large amounts of space Solar Power Advantages Disadvantages No pollution Not available at night or cloudy days Inexhaustible Expensive Needs large amounts of space

Wind Power Advantages Disadvantages No pollution Depends on weather Needs large amounts of space Can kill birds Not pretty to look at Geothermal Power Advantages Disadvantages Reliable Not available everywhere No pollution Expensive