Ch. 18: Renewable Energy Ch 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 and 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 10x 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 California- produces 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