Renewable Energy Resources

Transcription

1 Visualizing Environmental Science Renewable Energy Resources Chapter 18 Chapter 7 [chapter opener image] Copyright

2 Reducing Heat Loss Two strategies to decrease reliance on fossil fuels Developing alternative energy sources Reducing energy use Thermal images show heat escaping from a building Dark blue and green represent cold Reds and yellows represent heat Allow homeowners to detect where heat is escaping their home and insulate, caulk, replace old windows

3 Energy Consumption Direct solar energy Always available, not like fossil and nuclear fuels Solar energy must be collected and transformed into other forms for it to be useful as an energy source for human use

4 Energy Consumption Heating buildings and water Active solar heating Collectors absorb solar energy and pumps and fans distribute the collected heat Primarily used for heating water Household use Swimming pools Can provide a family with hot water year-round More than 8% of energy consumed in the U.S. goes toward heating water Not used as much for space heating, but may become more important as oil, gas, electricity prices rise

5 Energy Consumption Active Solar Heating

6 Energy Consumption Passive solar heating Does not require mechanical devices to distribute the collected heat Design features are used to warm buildings in the winter and keep them cool in the summer South facing windows receive more sunlight Sunlight provides heat, stored in floors and walls Heat is transmitted by convection Must be well-insulated to maintain heat Passive heating can save as much as 80% of heating costs About 7% of new homes built have passive heating

7 Energy Consumption House designed with passive solar heating

8 Photovoltaic solar cells A wafer/thin film of solid-state materials; treated with certain metals it generates electricity when solar energy is absorbed Energy Consumption

9 Energy Consumption No pollution, minimal maintenance Absorbs sunlight even on cloudy or rainy days Currently limited by low efficiency Large-scale power generation requires too much land to generate sufficient electricity Can be economical in rural areas of developing countries vs. installing power lines

10 Energy Consumption Cost of manufacturing PV units has steadily decreased over the past 35 years PV cells incorporated into roofing tiles may provide substantial power production in future California residents have installed over 1000MW solar capacity on roofs by late 2012 Japan considering policy requiring PV on new building rooftops by 2030

11 Energy Consumption Solar thermal electric generation Means of producing electricity in which the sun s energy is concentrated via mirrors or lenses onto fluid-filled pipes Becoming cost-competitive with fossil fuels No pollution, acid deposition, or climate change Does require alternate energy source (natural gas) at night or on cloudy days

12 Energy Consumption Solar-generated hydrogen Hydrogen fuel of the future Abundant, easily produced Electricity from any source can split water into oxygen and hydrogen gases Hydrogen itself is a clean fuel Produces water and heat as byproducts Potential to provide energy for transportation, heating buildings, producing electricity Solar electricity must be used immediately, whereas hydrogen can be stored and transported by pipeline

13 Indirect Solar Energy Some renewable energies use the sun s energy indirectly Combustion of biomass (organic matter) Plants use solar energy for photosynthesis and store the energy as biomass Wind energy Uses wind to generate electricity Hydropower Uses dammed rivers and streams to generate electricity

14 Indirect Solar Energy Biomass energy Plant and animal material used as fuel Crop wastes, sawdust, wood, charcoal, peat, animal dung At least half of the world s population relies on biomass fuel Wood is the primary fuel for cooking and heat in many developing countries

15 Indirect Solar Energy Biogas Biomass can be converted into a mixture of gases Mostly methane Biogas digesters produce gas for cooking and lighting, by microbial decomposition of wastes Several million used in China and India Solid remains can be used as fertilizer Biogas has the potential to power fuel cells to generate electricity

16 Indirect Solar Energy Biomass can also be converted into liquid fuels Methanol Ethanol can replace gasoline in internal combustion engines Biodiesel made from plant or animal oils Biomass is attractive to politicians and consumers as source of energy

17 Power Generation from Wood Chips 12-17

18 Indirect Solar Energy Problems with biomass Use of land and water that might be dedicated to food production Higher food prices Reduced food supplies Unsustainable use of wood Trees are cut faster than replanted Severe damage to environment Erosion, desertification, deforestation, etc. Harm to soil quality Crop residues are not left for conservation tillage Increases likelihood of erosion and mineral depletion Reduces productivity

19 Indirect Solar Energy Wind energy Wind turbines are huge, and becoming more efficient (100m tall) $0.40/kwh in 1980 to $ /kwh now Cost competitive with most conventional energy Most profitable in areas with consistent winds Coastal areas, mountain passes, islands, grasslands U.S., Germany, Denmark are main wind electricity producers Denmark produces 21% of its energy by wind China expanding wind energy capacity

20 Indirect Solar Energy Best locations for wind energy in U.S. ND, TX, SD, MT, NE, WY, OK, MN, IO, KS If we developed wind energy in ND, TX, and KS, we could supply enough electricity to meet the current needs of the entire U.S. Projects are underway Currently, wind power is captured and placed in regional electricity grids Requires development of distribution methods No waste, clean energy Every kwh of wind electricity reduces release of 2.2lb of CO 2 from fossil fuels into the air

21 Indirect Solar Energy Problems with wind turbines Can cause bird kills if turbines are on bird migration pathways (Altamont Pass, CA) Can be corrected by not placing turbines on those sites, painting blades, using anti-perching devices, and shutting down during peak migration periods Developers currently conduct voluntary wildlife studies to locate sites away from bird and bat routes Aesthetic issues Maple Ridge Wind Farm in Upstate NY Some residents welcome extra money from wind leases Others complain that turbines ruin their view of Adirondacks Nantucket Sound residents oppose off-shore wind project in MA, because tourists may find it offensive

22 Indirect Solar Energy Hydropower Potential energy of water held back by a dam can be converted into electricity More efficient than any other source of energy 90% of potential energy is converted to electricity Generates about 19% of world s electricity 7% in U.S.

23 Indirect Solar Energy Problems with hydropower Dams change natural flow of rivers Water backs up, floods large areas of land to form reservoir, destroys plant and animal habitats Downstream lands no longer receive nutrient-rich silt Earthquakes may occur and damage dams in areas of seismic activity In some areas, there is greater evaporation of water Displaces people when reservoir is created

24 Other Renewable Resources Geothermal energy Energy from the Earth s interior, used for space heating or generation of electricity Just 1% of the heat contained in the uppermost layer of the Earth s crust is 500 times the energy contained in all of Earth s oil and natural gas resources

25 Other Renewable Resources U.S. is largest producer of geothermal electricity The Geysers geothermal power plant, in CA provides electricity to 1.7 million consumers Geothermal energy is renewable on a human timescale Water used to transfer energy is not inexhaustible Some geothermal systems recirculate water back to underground reservoir Considered environmentally benign

26 Other Renewable Resources Heating and cooling buildings with geothermal energy Ground-effect heat pumps (GHPs) take advantage of the difference in temperature between Earth s surface and subsurface Underground pipes with circulating liquids extract natural heat in winter, transfer excess heat underground in summer Heating systems can be modified to provide supplemental hot water

27 Energy Consumption Electricity generation costs

28 Other Renewable Resources Tidal energy Tides are caused by the gravitational pull of the moon and sun A dam across a bay can harness the energy of large tides to generate electricity Water at high tide gets trapped on land side, as tide recedes, the water falls through the dam s spillway and turns a turbine France, Russia, China, Canada have tidal power plants Problems Few places in the world have tides large enough to support this mode of energy High economic cost Potentially high environmental costs in estuaries

29 Energy Solutions Energy conservation Using less energy; reducing energy use and waste Energy efficiency Using less energy to accomplish a given task Consumption trends and economics Even though U.S. has become more energy efficient, consumption has increased

30 Energy-efficient technologies Refrigerators today use 80% less energy than in early 1970s Automobile efficiency has improved dramatically since 1970s lighter materials and dragreducing design Energy Solutions Fuel efficiency doubled between mid 70s and mid 80s Declined after that as larger vehicles became popular Autos with fuel efficiencies of 60 mpg will be possible in next decade

31 Energy Solutions Energy-efficient technologies Appliances, automobiles, buildings, industrial processes CFLs produce light comparable to that of incandescent light bulbs, but require only 25% of energy and last up to 15% longer Condensing furnaces require 30% less fuel Superinsulated buildings use 70 90% less energy

32 Potential Renewable Energy Mix 12-32