Ch 18 Renewable Energy Ch 18 1 Renewable

Ch. 18: Renewable Energy Ch. 18. 1 Renewable Energy Today

What is renewable energy? • Energy from sources that are constantly being formed • 5 forms of Renewable Energy: – Solar energy – Wind energy – Hydroelectricity – Biomass – Geothermal energy

Misconception: • Many believe that using renewable energy is better for the environment than nonrenewable energy. • However, ALL SOURCES OF ENERGY affect the environment

Solar Energy • Power from the sun • Sun radiates energy (fusion) • Only a small fraction reaches Earth • Used Directly & indirectly

Direct & Indirect Use of Solar Energy • Direct: sun shines in a window and heats a room- the room is being heated by solar power • Indirect: solar energy generating electricity in solar cells

Passive Solar Heating • Uses the sun’s energy to heat something directly • Simplest form of solar energy • Buildings must be oriented according to yearly movement of sun & must be well insulated • Ex: Cliff dwellings

Active Solar Heating • Energy from the sun gathered by collectors and used to heat water or a building

Photovoltaic Cells • AKA: Solar cells • Convert the sun’s energy into electricity • Solar cells have no moving parts and they run on nonpolluting power.

So…why don’t solar cells meet our energy needs? • Produces a very small electrical current; therefore, would need hundreds of acres of solar panels just to meet needs of a small city • Require extended period of sunshine to produce electricity • Energy stored in batteries and supply electricity when the sun is not shining

Solar Cells Today • Despite limitations: – Solar cells have become increasingly efficient and less expensive – Potential for developing countries – Currently: provide energy for more than 1 million households in the developing world

Wind Power • coverts the movement of wind into electric energy • Fastest growing energy source in the world • Turbines-cost effective and can be quickly built

Wind Farms • Large arrays of wind turbines • Don’t take up a lot of room • Farmers can add them to their land still use the land for other purposes • Allows them to sell their electricity to local utility co.

An Underdeveloped Resource • Scientists estimate that the windiest spots on Earth could generate more than 10 x the energy used worldwide • Problem? – Transporting electricity from rural areas where it is generated to urban centers where it is needed

Biomass • Power from living things • Plant material, manure, and any other organic matter that is used as an energy sources is called biomass fuel • Fossil Fuels are organic-are they a biomass energy source? – Yes-but they are nonrenewable

Examples • Wood • Dung

Methane • Bacteria decompose organic wastes and one of the byproducts is methane gas. • Can be burned to generate heat and electricity • Cow manure power plant in Britain • Some US landfills generate electricity from decomposing trash

Alcohol • Liquid fuels can be derived from biomass • Ethanol can be made by fermenting fruit or agricultural waste • US=corn is major source of ethanol • Cars and trucks can run on gasohol=ethanol + gasoline

Gasohol • Produces less air pollution than fossil fuels • Some US states require the use of gasohol in vehicles

Geothermal Energy • Power from the earth • Energy form heat in the Earth’s crust • In some areas, deposits of water in the crust are heated by energy within the Earth

Geothermal power plants • How does it work? – 1. steam rises through a well – 2. Steam drives turbines-generates electricity – 3. Leftover liquid water is pumped back into the hot rock

Geothermal Energy • United States – Largest producer of geothermal energy – Largest in world: The Geysers in Californiaproduces electricity for about 1. 7 million households • Although geothermal energy is considered a renewable resource, the water in the rock formations must be managed carefully so that it is not depleted.

Hydroelectricity • Power from Moving Water • As rainwater flows across the land, the energy in its movement can be used to generate electricity-hydroelectric energy • 20% of the world’s electricity

Benefits of Hydroelectric Energy • Hydroelectric dams – Do not release air pollutants – Last longer than fossil fuel-powered plants – Provide flood control – Provide water for drinking, agriculture, industry, and recreation

Disadvantages • Dams change the flow of rivers • Disrupts ecosystems downstream – Salmon have been prevented from swimming upstream to spawn • • Land behind dam is flooded-people are displaced Dam Failure-if it bursts, people can be killed Farmland below dam can become less productive Decay of plant matter trapped in reservoirs can release large amounts of greenhouse gases

Micro-hydropower • Electricity produced in a small stream without having to build a big dam • Cheaper than large dam projects • Permits energy to be generated from small streams in remote areas