Ch. 17 Environmental Science Alternative Energy Sources

Solar Energy Sun is the source of all energy on earth Absorbed by plants and used by all organisms Also provides energy for Water cycle – flow of rivers Wind energy – warms earth surface and causes winds to blow

The Sun as fuel Sun obtains its energy from thermonuclear fusion – Hydrogen fuse and form helium – Converted to heat and light energy – Only one billionth of the energy reaches earth. – Fusion Energy Advances (6 min) Fusion Energy Advances (6 min)

Solar Energy Advantages – Free – Clean – Nonpolluting disadvantages - not constant – Size and cost of equipment – Energy from the sun (4 min) Energy from the sun

Passive Solar Energy Suns energy is collected, stored, and distributed naturally in an enclosed dwelling. – Greenhouse, car on a warm sunny day Not used to produce electricity – Reduces use of fossil and nuclear fuels

Passive solar heating in homes – Large windows that face south – Materials that absorb solar energy – Stone, brick, and concrete – May have glass enclosed areas – Insulation helps

Active Solar Energy Devices are used to collect, store, and circulate heat produced from solar energy – Tubes, tanks, fluids, pumps, fans Solar Collectors – On roofs – Flat-plate collectors – heat absorbed by fluid in tubes, fluid circulated into home Solar panels In this video segment adapted from NOVA, learn about photovoltaics and see how two families are using solar technologies in their homes. Solar power - This video segment from Vegas PBS shows the largest solar power system to date in the U.S. and explains how solar power can serve the needs of large-scale facilities and benefit the environment. (3 min)power

Photovoltaic Cells PV Cell – uses thin wafer of semiconductor material to produce electricity directly from solar energy – Made of silicon or selenium – Sunlight causes electrons to move and make an electric current – Used in calculators, watches, satellites – Lightweight, no pollutants – Photovoltaic Video (1 min) Photovoltaic Video (1 min)

17.2 Hydroelectric Energy Hydroelectric power – electricity produced from the energy of moving water Energy from flowing streams – Use dams to generate electricity – flowing water pushes turbines which make electricity Important in flood control Provide recreation/lakes Store water

Disadvantages of dams – Negatively impact ecosystems – Affect plant life – Flooding/erosion – Create a barrier/fish cannot spawn – Stored water develops cold bottom layer

Energy from tides Tides in the ocean have a large amount of energy – Use of tidal electrical generators is limited Concerned about the environment Difference in high and low tides not enough to produce large amounts of energy

17.3 Wind Energy Aerogenerators or wind turbine generators – Windmills used to generate electricity – Adv. and disadv. similar to solar power Adv. - Free, unlimited and nonpolluting Disadv – not constant, need storage devices

Two types of wind turbines – Traditional – 2 or 3 very long vanes – Darriues rotor – looks like upsidedown eggbeater

Wind farms – Need steady winds of at least 15 mph – Take up land – Interfere with radio and TV – Dangerous for birds – Wind energy (6 min) Wind energy (6 min) – Investing in carbon-free power Investing in carbon-free power

17.4 geothermal energy and nuclear fusion Geothermal energy – heat energy generated within Earth – Generated by the decay of radioactive elements deep beneath the ground. - as elements decay they give off energy in the form of heat.

Geothermal energy used where the source of energy is near he surface – 250 plants around the world – 65% of the homes in Iceland use it – In the US – Hawaii and California use it

Geothermal disadvantages; – Not enough in some areas to be worth the cost of extraction – Not easy to locate – Sulfide gas given off along with the heat – Pipes become corroded – Lack of water to produce the steam

Nuclear Fusion – two nuclei fuse to become one larger nucleus. Produce large amounts of energy Scientists have not yet learned to control and use it efficiently. Geothermal Power