Chapter 18 Renewable Energy Section 18 1 Renewable

Chapter 18 Renewable Energy

Section 18 -1 Renewable Energy Today

Discussion Prompt l List 3 reasons you think we have not completely switched over to renewable energy to meet our energy needs.

Renewable Energy l Renewable energy: energy from sources that are constantly being formed l Solar l Wind l Moving water l Geothermal (Earth’s heat)

Solar Energy l Sun: medium-sized star that radiates energy from nuclear fusion reactions in its core. l Only a small fraction of this energy reaches the Earth yet it is enough to power the wind, plant growth, and the water cycle. l Already l Water commonly used cycle l Photosynthesis l Wind l Sunshine warming a room

Passive Solar Heating l Passive solar heating: Use sun to heat something directly l Example: Northern hemisphere homes l Large, south facing windows absorb heat in winter l Overhangs block sunlight in the summer l Helps save money on energy bills l Insulation is important also

Active Solar Heating l Active Solar Heating: Sun’s energy is gathered by collectors to heat a building or water l. A liquid is heated by the sun and flows through solar collectors l Solar water heaters l Water heated on roof l Hot water used to heat water supply

Active Solar Heating, cont. l Photovoltaic cells: convert the sun’s energy into electricity l No moving parts, no pollution l Need many cells to produce decent yields l Great potential in developing countries which have lesser energy demands l Store energy in batteries

Wind Power l Air is heated unevenly by the sun, creating wind l Wind power is the fastest growing source of energy l Quadrupled l Cost between 1985 and 2000 effective to build wind turbines l Cost of wind power has declined

Wind Farms l See Figure 7 on p. 495 l 280, 000 homes in CA powered by wind l Take up little space l Farmers add windmills to farm l Sell power to cities

Currently Underused l Windiest areas on earth could generate 10 times the energy used worldwide. l Difficult to transport the energy l Wind farms may make hydrogen from water in the future. Hydrogen could be used as fuel.

Biomass l Biomass Fuel: Plant material, manure, other organic matter used as fuel l Different than fossil fuels which are nonrenewable l Ex: wood and dung l Half of wood cut down is used for heating and cooking (developing countries) l Challenges l Trees – renewable, but must be managed l Burning wood or manure – air pollution

Methane l Methane (CH 4) is created when bacteria decompose organic wastes l Can be burned for heat or electricity l China – 6 million homes use methane for heating and cooking l England – Methane from cow manure as fuel for electricity l USA – electricity from methane generated by landfills

Alcohol l Ethanol: made by fermenting fruit or agricultural waste l Corn is a major source in the US l Gasohol l mix of gasoline and ethanol l Produces less pollution when burned l Some states require (including GA)

Hydroelectricity l Hydroelectricity: Energy produced from moving water l 20% of world’s electricity l How it works (see p. 497) l Reservoir behind a dam holds water l Flowing water turns turbines l Turbines’ energy transferred to generator l Generator turns movement into electricity

Benefits of Hydroelectricity l Expensive to build but cheap to operate l No air pollution l Last longer l Flood control l Water for drinking, agriculture, industry, and recreation

Disadvantages of Hydroelectricity l Disrupts river flow l Ecosystems flooded behind dam l River flow diminished below dam l Displaces people l Farmland downstream less productive l Decay in reservoir releases greenhouse gases

Modern Hydroelectricity l No new dams in the USA l Brazil, India, and China still building large dams (developing countries) l Micro-hydropower: small streams are used to move turbines without building dams l Cheaper l Can provide energy to remote areas

Geothermal Energy l Geothermal Energy: Energy from the heat in Earth’s crust l How it works (see p. 498) l Steam rises to turn turbines through a well l Steam drives turbines, generating electricity l Leftover liquid water pumped back into hot rock l The Geysers in CA powers 1. 7 million homes (US uses more than any country) l Philippines, Iceland, New Zealand, Japan, Mexico, and Italy

Geothermal Heat Pumps l See Figure 12 on p. 499 l Temperature underground is constant l Pumps use stable underground temperatures to warm and cool homes l Loop of fluid in a pipe underground and into house l In summer, the fluid in the loop is cooler, so it cools the home l In winter, the fluid in the loop is warmer, so it warms the home

Section 18 -2: Alternative Energy and Conservation l. Discussion Prompt: Contrast alternative energy, renewable energy, and nonrenewable energy.

Alternative energy l Alternative Energy: Still in development l Some renewable energy was once alternative energy (Ex: geothermal). l Government investments are vital to development. l Need to research

Tidal Power Tides are the movement of l Drawbacks water caused by the l Expensive gravitational attraction l Few suitable locations between the Earth, sun, and moon l Currently used in France, Russia, and China l Benefits l Tides happen 2 times a day l Generates electricity like hydroelectric dams l

Ocean Thermal Energy Conversion (OTEC) Energy is created from l Drawbacks the difference in temp. l Not cost effective of the surface of ocean l Uses 1/3 of the energy it produces to pump water and deep ocean the cold water up to water the surface to be l Benefits boiled l Cold water boils at low temp in vacuum chamber l Steam can turn a turbine l l Environmental effects unknown

Hydrogen Can be burned as fuel l Benefits l The most abundant element in the universe l No air pollutants when burned l Obtain by running electricity through water or from plants (more cost effective) l l Drawbacks Generating it uses energy, money, and makes pollution l Takes a lot of hydrogen to create as much energy as gasoline so it must be compressed l l l dangerous Explosive and dangerous

Fuel Cells l See Figure 16 on p. 502 l Produce electricity chemically l Combine H 2 and O 2 and electricity is produced. l Water is only byproduct l Space shuttles use

Energy Efficiency l Energy Efficiency: percentage of energy put into a system that does useful work l What you get out vs. what you put in l %Energy l Read efficiency = Useful energy out Energy in x 100 p. 502 to 503 and summarize energy efficiency today

Efficient Transportation l Read p. 503. l Describe how transportation could be made more efficient.

Cogeneration l Production of 2 useful forms of energy from 1 fuel source l Example: use waste heat from a furnace to turn a turbine

Energy Conservation l Energy l Use Conservation: saving energy efficient devices l Wasting less energy l Read about on p. 504 and 505

Cities and Towns l Osage, l 3, 600 IA people saved $1 million/year l Sealed doors and windows l New efficient furnaces l Insulated water heaters l Businesses moved to the area l Unemployment is down

Around the Home l Spend $1, 500/year on energy costs l Much is wasted l Insulation l Efficient windows l Weather stripping l Wash clothes in cold water