Core Case Study: The Coming Energy-Efficiency and Renewable-Energy Revolution

1. Core Case Study: The Coming Energy-Efficiency and Renewable-Energy Revolution • The heating bill for this energy-efficient passive solar radiation office in Colorado is $50 a year. Figure 17-1

3. Passive Solar Heating • Passive solar heating system absorbs and stores heat from the sun directly within a structure without the need for pumps to distribute the heat. Figure 17-13

4. Direct Gain Ceiling and north wall heavily insulated Summer sun Hot air Super- insulated windows Warm air Winter sun Cool air Earth tubes Fig. 17-13, p. 396

5. Greenhouse, Sunspace, or Attached Solarium Summer cooling vent Warm air Insulated windows Cool air Fig. 17-13, p. 396

6. Earth Sheltered Reinforced concrete, carefully waterproofed walls and roof Triple-paned or superwindows Earth Flagstone floor for heat storage Fig. 17-13, p. 396

7. Trade-Offs Passive or Active Solar Heating Advantages Disadvantages Energy is free Need access to sun 60% of time Net energy is moderate (active) to high (passive) Sun blocked by other structures Quick installation Need heat storage system No CO2 emissions Very low air and water pollution High cost (active) Very low land disturbance (built into roof or window) Active system needs maintenance and repair Moderate cost (passive) Active collectors unattractive Fig. 17-14, p. 396

8. 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.

9. Wind • Energy conversion – kinetic to electrical • Benefits – pollution-free, source is free (used in West Texas, Hawaii, California, and more) • Costs – can only be used in places with lots of wind

10. 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.

11. 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

12. 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.

16. Biomass • Description – any type of organic matter (forest products, crop wastes, animal wastes, people wastes, etc.) that can be used to produce energy; currently used for about 5% of U.S. energy • Energy conversion – chemical to electrical or heat • Benefits – cheap, less toxic pollutants, using wastes effectively, currently used in Rio Grande Valley with the burning of sugar cane residue, also produces food, feed, and fiber • Costs – we don’t have all the technology needed to use this well right now, not useful in every location, some pollution is produced

17. 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

18. 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

19. 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

20. Water • Energy conversion – kinetic to electrical or heat • Benefits – already have the technology to do this, pollution free, dams are also useful as water sources and flood controls; world’s largest source of electrical power • Costs – there are environmental costs to building new dams, there are not rivers located everywhere • Read James Bay Watershed Transfer Project Miller Page 304

21. 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.

22. 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

23. Geothermal • Description – heat from deep within the earth is used to produce electricity • This is the only energy source that doesn’t come from the sun! • Energy conversion – thermal to electrical and heat • Benefits – pollution-free, used near Waco and in Iceland • Costs – not available everywhere, we don’t have all the technology needed to use it

24. 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.

25. 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