Renewable Energy Alternatives

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1 Renewable Energy Alternatives

2 Reasons for Alternative Energy Fossil fuels won t last forever Renewable unlikely to run out Decrease air pollution and greenhouse gas emissions Less dependent on other nations Creates jobs

3 Oil, coal, and natural gas supply 80% of U.S. energy and 2/3 of world electricity Renewable sources growing faster than nonrenewable Wind growing most rapidly Reserves of fossil fuels reducing Citizens want cleaner environment Can t yet produce enough power

4 Biomass Energy produced from living things Wood, manure, grain Mainly used in developing nations Biofuels Liquid fuel Ethanol Produced mainly from corn Gasohol gas and alcohol mix that produces less pollutants than pure gasoline Biodiesel Vegetable oil that produces less emissions Biopower Burning biomass for electricity Sawdust, timber, woody debris, manure Breakdown of waste creates methane (landfill gas) to be burned as fuel

5 Biomass Benefits No net carbon in atmosphere Distributed worldwide Reduce dependence on other nations Costs Take up land Deforestation, soil erosion, desertification Inefficient needs substantial amount of energy input for farm equipment Creates indoor air pollution

6 Geothermal High pressure and breakdown of radioactive elements creates heat Hot springs and geysers Steam from geysers or wells dug to heated rocks and water Steam turns blades of turbine, which turns generator to create electricity Steam cooled and returned to aquifers Cool water can also be pumped into ground to create steam Hot water from ground can be pumped into pipes ground source heat pumps Few feet underground the temp stays the same year round Heats water in the winter and cools water in the summer

7 Geothermal Benefits Less air pollution Less greenhouse gas emissions Costs Can run out of water Hot springs contain chemicals that damage equipment and add to pollution Trigger earthquakes Limited to areas where heated groundwater can be tapped easily

8 Hydropower Kinetic energy of moving water to turn turbines Dam water passes through dam and turns turbine Flows back into rivers Reservoir provides steady supply of water River Flowing water turns turbines May be diverted through a pipe Doesn t disturb the ecosystem

9 Hydropower Benefits Doesn t pollute or release greenhouse gases Relatively inexpensive Dams control floods Costs Dams and reservoirs interrupt natural flow and disrupt ecosystems Fish populations reduced Cause erosion Prevent nutrient-rich sediment from getting further down river

10 Ocean Tidal Movement of tides to produce electricity Dam built, high tide moves in, low tide moves out, turbines turn when water recedes Benefits Doesn t pollute and no greenhouse gas emissions Costs Not many ideal locations (long, narrow bays) Harms ecology Thermal Ocean water near equator absorbs solar radiation equivalent to 250 million barrels of oil OTEC (ocean thermal energy conversion) Warm surface water circulates around pipes with ammonia that boil at lower temps than water Substance evaporates and turns turbines High costs

11 Solar Solar heating does not produce electricity Passive solar heating Heat homes and buildings Design buildings to collect and store sun s energy naturally Greenhouses Windows facing south and east Active solar heating Technology to collect, move, and store heat Flat-plate solar collector made of black, heatabsorbing metal with glass cover Heat warms metal, which warms a fluid in tubes that pass through collector and moves fluid through pipes in building

12 Solar Photovoltaic cells 2 plates made of silicon Sunlight hits one plate full of electrons, which knocks them loose and attracts to other plate Movement of electrons creates electricity CSP (concentrating solar power) Hundreds of mirrors focus sunlight on a power tower in center of mirrors Heats up a fluid in the receiver of the tower, which produces steam to turn turbines

13 Solar Benefits Endless source No fuel Quiet and safe No greenhouse gases Doesn t pollute Little maintenance Reduce dependence on power plants Creates jobs Costs Making devices creates pollution Some regions not sunny enough expensive

14 Wind Unequal heating of air masses Wind turbine turns from wind s kinetic energy connected to a gearbox that connects to a generator Wind speeds 20% greater over water than land Offshore wind turbines more common More expensive but produce more power

15 Wind Benefits No pollution Highly efficient Create 23x more energy than used Local areas more self-efficient Less expensive once running Costs No control over wind Clutter landscape Noisy Birds killed in blades

16 Hydrogen Hydrogen-containing compounds must release hydrogen atoms Requires input of energy Electrolysis Water molecules broken down into oxygen gas and hydrogen gas from an electric current No greenhouse gases or pollution Costly Breakdown of methane Hydrogen taken from methane in natural gas Produces carbon dioxide Looking in to heat from nuclear reactors or using algae

17 Hydrogen Benefits Most abundant gas Produces few greenhouse gases and pollutants Water and heat only products from reactions Can be stored and transported Costs Requires energy input Expensive Fuel cells Hydrogen gas used to make electricity Reverse of electrolysis Hydrogen and oxygen molecules form water Can be used to power cars