Chapter 17.1 Solar Energy

Solar energy ● It is energy from the sun and used as fuel by virtually every organism. ● It drives both wind energy and the water cycle.

● The upside to solar energy is it is free, clean, and non-polluting ● The negatives are that the equipment may cost more than the benefits and that light is in limited supply.

Passive Solar Energy ● The sun's energy is collected, stored and distributed naturally in an enclosed dwelling. ● This can be seen in modern day greenhouses and some homes.

Active Solar Energy ● There is many more parts to an active solar energy system. ● It uses devices to collect, store, and circulate heat produced from solar energy.

Photovoltaic Cell ● The only solar energy device that produces electricity directly. ● It uses thin wafers of semiconductor material to produce electricity directly from solar energy. ● Ex.: satellites, calculators ● No moving parts or pollutants.

Chapter 17.2 Hydroelectric Energy

Hydroelectric Power ● Electricity that is produced from the energy of moving water. ● It is a non-polluting and less expensive than fossil fuels and nuclear power.

History of Hydroelectric Power ● For hundred of years water wheels were used to grind grain. ● Water turbines were used in the 1800's to make electricity.

Modern Hydroelectric Power ● Today huge dams are used to produce up to twenty percent of the world's energy. ● Water is directed into at blades that turn coils of wire through a magnetic field producing electricity. ● They also provide flood control, ship navigation, and recreation.

Negatives ● By altering the depth of bodies of water the it effects the natural plant life of streams. ● It can also erode the shoreline. ● Fish especially salmon are caught in the turbines or their migrating paths are disrupted, temperature changes also effect the fish.

Tidal Energy ● The tides produce large amounts of energy. The same concept of turbines can be used for tidal energy. ● This unfortunately also effects benthic and wetland ecosystems.

17.3 Wind Energy ● Aerogenerators are windmills used to generate electricity. ● Some still use windmills to grind grain and pump water. ● Wind power is free clean and non- polluting.

Today's Windmills ● The traditional looks like the propeller of an airplane and can produce the most amount of electricity. ● The Darrieus rotor looks like an upside down eggbeater and turns on a vertical axis. It can produce electricity at a much lower speed.

Wind Farms ● These sites contain many windmills and are located in open areas where windy conditions are favorable. ● Problems  Bird injuries  Equipment is expensive  Takes a lot of land  Disturbs cell phone and TV reception

17.4 Geothermal Energy ● The sun is the main source of energy for Earth, but the earth creates a lot of energy itself. ● Deep in the Earth’s core the decay from radioactive elements produces energy.

Geothermal Energy ● Geothermal energy is heat energy generated at the Earth’s core. ● The temperature rises between 30 to 45 degrees c with every kilometer down. It has to level off somewhere and the center is probably between 3 and 5 thousand.

Methods of Extracting ● In areas where bedrock is heated by magma known as hot rock zones, explosives are used to break the rock. Then water is poured onto the hot rocks. This produces steam that turns turbines.

Negatives ● Most places are not suited to have a geothermal plant. This is due to heavy pollution in some areas that gives off hydrogen sulfide gas and toxins corrode the pipes.

Nuclear Fusion ● This occurs when two atomic nuclei fuse together to become one larger nucleus. ● This is the source of the sun’s energy. ● Technology is not advanced enough to harness this energy.