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Cooling Houses Naturally

Cooling Houses Naturally. We can cool houses by: Superinsulating them. Taking advantages of breezes. Shading them. Having light colored or green roofs. Using geothermal cooling. Using Solar Energy to Generate High-Temperature Heat and Electricity.

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Cooling Houses Naturally

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  1. Cooling Houses Naturally • We can cool houses by: • Superinsulating them. • Taking advantages of breezes. • Shading them. • Having light colored or green roofs. • Using geothermal cooling.

  2. Using Solar Energy to Generate High-Temperature Heat and Electricity • Large arrays of solar collectors in sunny deserts can produce high-temperature heat to spin turbines for electricity, but costs are high. Figure 17-15

  3. Trade-Offs Solar Energy for High-Temperature Heat and Electricity Advantages Disadvantages Moderate net energy Low efficiency High costs Moderate environmental impact Needs backup or storage system No CO2 emissions Need access to sun most of the time Fast construction (1–2 years) High land use Costs reduced with natural gas turbine backup May disturb desert areas Fig. 17-15, p. 397

  4. Producing Electricity with Solar Cells • Solar cells convert sunlight to electricity. • Their costs are high, but expected to fall. Figure 17-16

  5. Producing Electricity with Solar Cells • Photovoltaic (PV) cells can provide electricity for a house of building using solar-cell roof shingles. Figure 17-17

  6. Single solar cell Solar-cell roof – + Boron enriched silicon Roof options Junction Phosphorus enriched silicon Panels of solar cells Solar shingles Fig. 17-17, p. 398

  7. Producing Electricity with Solar Cells • Solar cells can be used in rural villages with ample sunlight who are not connected to an electrical grid. Figure 17-18

  8. Trade-Offs Solar Cells Advantages Disadvantages Fairly high net energy Need access to sun Work on cloudy days Low efficiency Quick installation Need electricity storage system or backup Easily expanded or moved No CO2 emissions High land use (solar-cell power plants) could disrupt desert areas Low environmental impact Last 20–40 years Low land use (if on roof or built into walls or windows) High costs (but should be competitive in 5–15 years) Reduces dependence on fossil fuels DC current must be converted to AC Fig. 17-19, p. 399

  9. Producing Electricity with Solar Cells

  10. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should the world greatly increase its dependence on solar cells for producing electricity? • a. No. Solar cells are too expensive and cannot substantially meet our electricity needs. • b. Yes. Solar cells are environmentally friendly and could supplement our energy needs.

  11. PRODUCING ELECTRICITY FROM THE WATER CYCLE • Water flowing in rivers and streams can be trapped in reservoirs behind dams and released as needed to spin turbines and produce electricity. • There is little room for expansion in the U.S. – Dams and reservoirs have been created on 98% of suitable rivers.

  12. Trade-Offs Large-Scale Hydropower Advantages Disadvantages Moderate to high net energy High construction costs High environmental impact from flooding land to form a reservoir High efficiency (80%) Large untapped potential High CO2 emissions from biomass decay in shallow tropical reservoirs Low-cost electricity Long life span Floods natural areas behind dam No CO2 emissions during operation in temperate areas Converts land habitat to lake habitat May provide flood control below dam Danger of collapse Uproots people Provides water for year-round irrigation of cropland Decreases fish harvest below dam Decreases flow of natural fertilizer (silt) to land below dam Reservoir is useful for fishing and recreation Fig. 17-20, p. 400

  13. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should the world greatly increase its dependence on large-scale dams for producing electricity? • a. No. Large hydroelectric dams harm the environment and should be replaced by renewable energy. • b. Yes. We need large dams to meet power demands, protect areas from flooding, and provide water.

  14. PRODUCING ELECTRICITY FROM THE WATER CYCLE • Ocean tides and waves and temperature differences between surface and bottom waters in tropical waters are not expected to provide much of the world’s electrical needs. • Only two large tidal energy dams are currently operating: one in La Rance, France and Nova Scotia’s bay of Fundy where the tidal amplitude can be as high as 16 meters (63 feet).

  15. PRODUCING ELECTRICITY FROM WIND • Wind power is the world’s most promising energy resource because it is abundant, inexhaustible, widely distributed, cheap, clean, and emits no greenhouse gases. • Much of the world’s potential for wind power remains untapped. • Capturing only 20% of the wind energy at the world’s best energy sites could meet all the world’s energy demands.

  16. PRODUCING ELECTRICITY FROM WIND • Wind turbines can be used individually to produce electricity. They are also used interconnected in arrays on wind farms. Figure 17-21

  17. Wind turbine Wind farm Gearbox Electrical generator Power cable Fig. 17-21, p. 402

  18. PRODUCING ELECTRICITY FROM WIND • The United States once led the wind power industry, but Europe now leads this rapidly growing business. • The U.S. government lacked subsidies, tax breaks and other financial incentives. • European companies manufacture 80% of the wind turbines sold in the global market • The success has been aided by strong government subsidies.

  19. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should the United States (or the country where you live) greatly increase its dependence on wind power? • a. No. Wind turbines need research and mass-production before they will be competitive in the energy market. • b. Yes. Wind power is becoming competitive and produces more clean energy than most other energy sources.

  20. Trade-Offs Wind Power Advantages Disadvantages Moderate to high net energy Steady winds needed High efficiency Backup systems needed when winds are low Moderate capital cost Low electricity cost (and falling) High land use for wind farm Very low environmental impact No CO2 emissions Visual pollution Quick construction Noise when located near populated areas Easily expanded Can be located at sea May interfere in flights of migratory birds and kill birds of prey Land below turbines can be used to grow crops or graze livestock Fig. 17-22, p. 403

  21. PRODUCING ENERGY FROM BIOMASS • Plant materials and animal wastes can be burned to provide heat or electricity or converted into gaseous or liquid biofuels. Figure 17-23

  22. Solid Biomass Fuels Wood logs and pellets Charcoal Agricultural waste (plant debris) Timbering wastes (wood) Animal wastes (dung) Aquatic plants (kelp and water hyacinths) Urban wastes (paper, cardboard, combustibles) Conversion to gaseous and liquid biofuels Direct burning Liquid Biofuels Gaseous Biofuels Ethanol Methanol Gasohol Biodiesel Synthetic natural gas (biogas) Wood gas Fig. 17-23, p. 404

  23. Solid Biomass Fuels Wood logs and pellets Charcoal Agricultural waste (stalks and other plant debris) Timbering wastes (branches, treetops, and wood chips) Animal wastes (dung) Aquatic plants (kelp and water hyacinths) Urban wastes (paper, cardboard), And other combustible materials Conversion to gaseous and liquid biofuels Direct burning Gaseous Biofuels Synthetic natural gas (biogas) Wood gas Liquid Biofuels Ethanol Methanol Gasonol Biodiesel Stepped Art Fig. 17-23, p. 404

  24. PRODUCING ENERGY FROM BIOMASS • The scarcity of fuelwood causes people to make fuel briquettes from cow dung in India. This deprives soil of plant nutrients. Figure 17-24

  25. Trade-Offs Solid Biomass Advantages Disadvantages Large potential supply in some areas Nonrenewable if harvested unsustainably Moderate to high environmental impact Moderate costs CO2 emissions if harvested and burned unsustainably No net CO2 increase if harvested and burned sustainably Low photosynthetic efficiency Plantation can be located on semiarid land not needed for crops Soil erosion, water pollution, and loss of wildlife habitat Plantations could compete with cropland Plantation can help restore degraded lands Often burned in inefficient and polluting open fires and stoves Can make use of agricultural, timber, and urban wastes Fig. 17-25, p. 405

  26. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should we greatly increase our dependence on burning solid biomass to provide heat and produce electricity? • a. No. Increased utilization of solid biomass may result in net greenhouse gas emissions, deforestation, and competition for valuable farmland. • b. Yes. Biomass incineration would decrease the landfilling of wastes.

  27. Converting Plants and Plant Wastes to Liquid Biofuels: An Overview • Motor vehicles can run on ethanol, biodiesel, and methanol produced from plants and plant wastes. • The major advantages of biofuels are: • Crops used for production can be grown almost anywhere. • There is no net increase in CO2 emissions. • Widely available and easy to store and transport.

  28. Case Study: Producing Ethanol • Crops such as sugarcane, corn, and switchgrass and agricultural, forestry and municipal wastes can be converted to ethanol. • Switchgrass can remove CO2 from the troposphere and store it in the soil. Figure 17-26

  29. Case Study: Producing Ethanol • 10-23% pure ethanol makes gasohol which can be run in conventional motors. • 85% ethanol (E85) must be burned in flex-fuel cars. • Processing all corn grown in the U.S. into ethanol would cover only about 55 days of current driving. • Biodiesel is made by combining alcohol with vegetable oil made from a variety of different plants..

  30. Trade-Offs Ethanol Fuel Advantages Disadvantages High octane Large fuel tank needed Lower driving range Some reduction in CO2 emissions Low net energy (corn) Much higher cost High net energy (bagasse and switchgrass) Corn supply limited May compete with growing food on cropland Reduced CO emissions Higher NO emissions Can be sold as gasohol Corrosive Hard to start in cold weather Potentially renewable Fig. 17-27, p. 407

  31. Case Study: Producing Ethanol • Biodiesel has the potential to supply about 10% of the country’s diesel fuel needs. Figure 17-28

  32. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Do the advantages of using liquid ethanol as fuel outweigh its disadvantages? • a. No. Liquid ethanol is costly to produce and reduces vehicle performance. • b. Yes. Liquid ethanol is a renewable fuel and can reduce carbon dioxide and carbon monoxide emissions and our dependence on imported petroleum.

  33. Trade-Offs Biodiesel Advantages Disadvantages Reduced CO emissions Slightly increased emissions of nitrogen oxides Reduced CO2 emissions (78%) Higher cost than regular diesel Reduced hydrocarbon emissions Low yield for soybean crops Better gas mileage (40%) May compete with growing food on cropland High yield for oil palm crops Loss and degradation of biodiversity from crop plantations Moderate yield for rapeseed crops Potentially renewable Hard to start in cold weather Fig. 17-29, p. 408

  34. Video: MTBE Pollution PLAY VIDEO • From ABC News, Environmental Science in the Headlines, 2005 DVD.

  35. Case Study: Biodiesel and Methanol • Growing crops for biodiesel could potentially promote deforestation. • Methanol is made mostly from natural gas but can also be produced at a higher cost from CO2 from the atmosphere which could help slow global warming. • Can also be converted to other hydrocarbons to produce chemicals that are now made from petroleum and natural gas.

  36. Trade-Offs Methanol Fuel Advantages Disadvantages High octane Large fuel tank needed Some reduction in CO2 emissions Half the driving range Lower total air pollution (30–40%) Corrodes metal, rubber, plastic Can be made from natural gas, agricultural wastes, sewage sludge, garbage, and CO2 High CO2 emissions if made from coal Expensive to produce Can be used to produce H2 for fuel cells Hard to start in cold weather Fig. 17-30, p. 408

  37. GEOTHERMAL ENERGY • Geothermal energy consists of heat stored in soil, underground rocks, and fluids in the earth’s mantle. • We can use geothermal energy stored in the earth’s mantle to heat and cool buildings and to produce electricity. • A geothermal heat pump (GHP) can heat and cool a house by exploiting the difference between the earth’s surface and underground temperatures.

  38. Geothermal Heat Pump • The house is heated in the winter by transferring heat from the ground into the house. • The process is reversed in the summer to cool the house. Figure 17-31

  39. Basement heat pump Fig. 17-31, p. 409

  40. GEOTHERMAL ENERGY • Deeper more concentrated hydrothermal reservoirs can be used to heat homes and buildings and spin turbines: • Dry steam: water vapor with no water droplets. • Wet steam: a mixture of steam and water droplets. • Hot water: is trapped in fractured or porous rock.

  41. Trade-Offs Geothermal Energy Advantages Disadvantages Very high efficiency Scarcity of suitable sites Moderate net energy at accessible sites Depleted if used too rapidly Lower CO2 emissions than fossil fuels CO2 emissions Moderate to high local air pollution Low cost at favorable sites Noise and odor (H2S) Low land use Low land disturbance Cost too high except at the most concentrated and accessible sources Moderate environmental impact Fig. 17-32, p. 410

  42. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should the United States (or the country where you live) greatly increase its dependence on geothermal energy to provide heat and to produce electricity? • a. No. Most sites in the U.S. would not benefit from geothermal power. • b. Yes. Geothermal energy has environmental advantages. Potentially suitable sites for geothermal power plants exist in Hawaii, Alaska, California, and several other states.

  43. HYDROGEN • Some energy experts view hydrogen gas as the best fuel to replace oil during the last half of the century, but there are several hurdles to overcome: • Hydrogen is chemically locked up in water an organic compounds. • It takes energy and money to produce it (net energy is low). • Fuel cells are expensive. • Hydrogen may be produced by using fossil fuels.

  44. Converting to a Hydrogen Economy • Iceland plans to run its economy mostly on hydrogen (produced via hydropower, geothermal, and wind energy), but doing this in industrialized nations is more difficult. • Must convert economy to energy farming (e.g. solar, wind) from energy hunter-gatherers seeking new fossil fuels. • No infrastructure for hydrogen-fueling stations (12,000 needed at $1 million apiece). • High cost of fuel cells.

  45. Trade-Offs Hydrogen Advantages Disadvantages Can be produced from plentiful water Not found in nature Energy is needed to produce fuel Low environmental impact Negative net energy Renewable if from renewable resources CO2 emissions if produced from carbon-containing compounds No CO2 emissions if produced from water Nonrenewable if generated by fossil fuels or nuclear power Good substitute for oil High costs (but may eventually come down) Competitive price if environmental & social costs are included in cost comparisons Will take 25 to 50 years to phase in Short driving range for current fuel-cell cars Easier to store than electricity Safer than gasoline and natural gas No fuel distribution system in place Nontoxic Excessive H2 leaks may deplete ozone in the atmosphere High efficiency (45–65%) in fuel cells Fig. 17-33, p. 412

  46. A SUSTAINABLE ENERGY STRATEGY • Shifts in the use of commercial energy resources in the U.S. since 1800, with projected changes to 2100. Figure 17-34

  47. Wood Coal Natural gas Contribution to total energy consumption (percent) Oil Hydrogen Solar Nuclear Year Fig. 17-34, p. 413

  48. A SUSTAINABLE ENERGY STRATEGY • A more sustainable energy policy would improve energy efficiency, rely more on renewable energy, and reduce the harmful effects of using fossil fuels and nuclear energy. • There will be a gradual shift from large, centralized macropower systems to smaller, decentralized micropower systems.

  49. Small solar-cell power plants Bioenergy power plants Wind farm Rooftop solar cell arrays Fuel cells Solar-cell rooftop systems Transmission and distribution system Commercial Small wind turbine Residential Industrial Microturbines Fig. 17-35, p. 414

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