Chapter 13 Achieving Energy Sustainability

1. Chapter 13 • Achieving Energy Sustainability

2. Key Ideas • Define renewable energy resources. • Describe strategies to conserve energy and increase energy efficiency. • Compare and contrast the various forms of biomass energy.

3. Key Ideas • Explain the advantages and disadvantages of hydroelectricity, solar energy, geothermal energy, wind energy and hydrogen as energy resources. • Describe the environmental and economic options we must assess in planning our energy future.

4. What is Renewable Energy? • Renewable energy can be rapidly regenerated, and some can never be depleted, no matter how much of them we use. This includes potentially renewable and nondepletable resources. • Nonrenewable- energy from resources that are depletable • Potentially renewable- sources of energy that can be regenerated rapidly • Nondepletable- the source of energy will always be available

5. Renewable and Nonrenewable Energy Resources Fossil fuels and nuclear fuels are nonrenewable energy resources. Renewable energy resources include potentially renewable energy sources such as biomass, and nondepletable energy sources, such as solar and wind.

6. Energy Use Global energy use, 2007 US energy use, 2008

7. Review Questions • What are some common kinds of nondepletable, potentially renewable, and nonrenewable energy resources? • How do you know if an energy resource is nondepletable, potentially renewable, or nonrenewable? • What are the most important differences between renewable and nonrenewable energy resources?

8. How Can We Use Less Energy? • Energy conservation- finding ways to use less energy. For example, lowering your thermostat during the winter or driving fewer miles. • Energy efficiency- getting the same result from using a smaller amount of energy.

9. Reducing Energy Use Ways you can reduce your energy use inside and outside the home.

10. Saving Energy in Existing Buildings • About one-third of the heated air in typical U.S. homes and buildings escapes through closed windows and holes and cracks. Figure 17-11

11. Thermographic photography offers clues to where energy is being wasted in this older house in Connecticut. Red and yellow patches indicate escaping heat, while new double-pane windows appear cool blue. By sealing in warmth, the windows cut heating costs, which can account for up to half a family's energy bill. (Nat Geo, 3/09)

12. Benefits of Conservation and Efficiency • Many energy companies have an extra backup source of energy available to meet the peak demand, the greatest quantity of energy used at any one time. • An important aspect of energy conservation is reducing peak demand. • Variable price structure- utility customers can pay less to use energy when demand is lowest and more during peak demand.

13. Energy Efficient Home Incorporates proper solar orientation and landscaping as well as insulated windows, walls and floors. Southern exposure allows the house to receive more direct rays from the Sun in winter when the path of the Sun is in the southern sky.

14. SustainableDesign • Sustainable design- improving the efficiency of the buildings we live and work in. • Passive solar design- taking advantage of solar radiation to maintain a comfortable temperature in a building • Thermal inertia- the ability of a material to retain heat or cold. Stone and concrete have high thermal inertia

15. Passive Solar Energy • Using passive solar energy can lower your electricity bill without the need for pumps or other mechanical devices. • Building the house with windows along a south-facing wall which allows the Sun’s rays to warm the house would be an example.

16. Passive Solar Design Roof overhangs make use of seasonal changes in the Sun’s position to reduce energy demand for heating and cooling. High-efficiency windows and building materials with high thermal inertia are also components of passive solar design.

17. Passive Solar Heating

18. Other Types of Sustainable Design • Building a house into the side of a hill • Using green roofs • Use recycled building materials • Take advantage of natural lighting using windows and skylights • Installing solar panels

19. The California Academy of Sciences The design maximizes the use of natural light and ventilation. The building generates much of its own electricity with solar panels on its roof and captures water in it rooftop garden.

20. Living Roofs • Roofs covered with plants have been used for decades in Europe and Iceland. • These roofs are built from a blend of light-weight compost, mulch and sponge-like materials that hold water. Washington, DC

21. Review Questions • How can we use less energy as individuals and as societies? • What is peak demand, and how does it relate to energy conservation? • How can building design contribute to energy conservation and efficiency?

22. Biomass is Energy from the Sun • The Sun is the ultimate source of almost all types of energy, and is incorporated into plant tissue via photosynthesis • Biofuels- biomass that is processed or refined into liquid fuels, such as ethanol and biodiesel.

23. Sources and Energy Types The Sun is the ultimate source of almost all types of energy

24. Modern Carbon vs. Fossil Carbon • Modern carbon- carbon that is in biomass • Fossil carbon- carbon that is found in fossil fuels • Carbon neutral- any activity that does not change atmospheric CO2 concentrations

25. Modern Carbon vs. Fossil Carbon • Many people are confused how burning biomass such as wood is better then burning coal. • The carbon found in biomass was in the atmosphere as carbon dioxide, taken in by the tree, and by burning it we put it back into the atmosphere • Burning coal is carbon that has been buried for millions of years and was out of circulation until we began to use it. This results in a rapid increase in the concentration of carbon dioxide in the atmosphere.

26. Biomass • Wood is commonly used in developing countries for fuel, also known as fuelwood. If forests are removed faster than they can grow back, there is net removal of the forest. • Wood, Charcoal (made from wood) and Manure- used to heat homes throughout the world. • Ethanol and Biodiesel (biofuels)- used as substitutes for gasoline and diesel fuel. • Ethanol is made from corn or sugar cane, but corn is a food crop. Switchgrass might be a good alternative • Biodiesel is made from plant oils, such as soybean or vegetable oils or algae.

27. An area of land after it has been denuded for charcoal production. Many people in developing countries rely on charcoal for cooking and heating

28. Converting Plants and Plant Wastes to Liquid Biofuels: An Overview • Motor vehicles can run on ethanol, biodiesel, isobutanol 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 IF land is not cleared to grow crops used specifically for biofuel. • Widely available and easy to store and transport.

29. Biodiesel from Algae Closed-Tank Bioreactor Process Vertical growth/Closed Loop Process rexresearch.com smartplanet.com science.howstuffworks.com science.howstuffworks.com

30. Biodiesel has the potential to supply about 10% of the country’s diesel fuel needs. Figure 17-28

31. 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

32. 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.

33. Waste Products • When biomass is burned, it releases carbon dioxide. Some of this carbon dioxide is absorbed by plants. • Sometimes when waste is burned it releases harmful gases and ash. • Biodiesel has nitrogen oxide emissions that are about 10% higher than regular fuel.

34. Review Questions • What are the major forms of biomass energy? • Why is energy from modern carbon potentially carbon neutral? • Why is it important to find abundant sources of biomass energy? What are the advantages and disadvantages of different forms of biomass energy?

35. The Kinetic Energy of Water Can Generate Electricity • Hydroelectricity- electricity generated by the kinetic energy of moving water. This is the second most common form of renewable energy in the world. • The amount of energy produced depends on flow rate and the vertical distance the water falls

36. How a Dam Works Water flows through the intake and turns the turbine, which spins the generator, which generates electricity. Dam operators control flow rate by opening and closing the dam.

37. Types of Hydroelectric Power Systems • Run-of-the-river systems- water is held behind a dam and runs through a channel before returning to the river. • Water impoundment- water is stored behind a dam and the gates of the dam are opened and closed controlling the flow of water. • Tidal systems- the movement of water is driven by the gravitational pull of the Moon.

38. Is Hydroelectricity Sustainable? • Advantages: generate large quantities of electricity, less expensive than nuclear, natural gas or solar, no air pollution • Reservoir provides recreation and water sources during drought

39. Is Hydroelectricity Sustainable? • Disadvantages: a free-flowing river must be blocked, people must be displaced, valuable land is flooded, habitat is destroyed, and alteration of stream dynamics downstream • Blocks needed sediments from flowing downstream, interferes with migrating fish • A number of hydroelectric dams are being removed

40. Review Questions • How can water be used as a renewable energy resource? • What are the types of hydroelectricity generation systems? • What are the trade-offs associated with using hydroelectricity compared with biomass energy?

41. Solar Energy • Active solar energy- capturing the energy of sunlight with the use of a pump or photovoltaic cell and generating electricity. • Solar water heating systems • Photovoltaic systems • Concentrating solar thermal electricity generator

42. Solar Hot Water System A nonfreezing liquid is circulated by an electric pump through a closed loop of pipes. It moves from a water storage tank to a solar collector on the roof, where it is heated, then back to the tank.

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

44. 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

45. 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

46. Producing Electricity with Solar Cells

47. 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

48. 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

49. Concentrating Solar Thermal Energy These glass panels focus the heat from the Sun (infrared light) onto a tube filled with oil. The heated oil is then pumped to an adjacent generating plant that uses the heat to make steam, which then pushes on turbines hooked to electric generators. When done on a large scale, thousands or millions of watts of electricity can be generated from the free energy of the Sun.

50. Concentrating Solar Thermal Power Plant Mirrors and reflectors concentrate the Sun’s energy onto a “power tower” filled with salt, which uses the sunlight to heat water and make steam for electricity generation.