APES

2. Energy Efficiency and Renewable Energy Resources APES

3. A. What is Energy Efficiency? • 84% of all commercial energy in used in the US is wasted • Energy efficiency- the percentage of total energy input that does useful work • Life cycle cost- the initial cost plus lifetime operating costs • The net efficiency of the entire energy delivery process is determined by the efficiency of each step in the energy conversion process. • The three least energy efficient using devices are incandescent light bulbs, vehicles with internal combustion engines, and nuclear power plants producing electricity for space heating.

4. B. Why it is important to reduce energy waste? • 1. make nonrenewable fossil fuels last longer • 2. gives us more time to phase in renewable energy resources • 3. decreases dependence on oil imports • 4. lessens the need for military intervention in the oil-rich and politically unstable Middle East • 5. Reduces local and global environmental damage • 6. Is the cheapest and quickest way to slow projected global climate change • 7. Saves more money, provides more jobs, improves productivity and promotes more economic growth per unit of energy than other alternatives. • 8. Improves competitiveness in the international marketplace

5. B. Why it is important to reduce energy waste? • The reason there is not more emphasis on improving energy efficiency is the glut of low-cost underpriced fossil fuels. • A second cause is huge government subsidies

6. II. Ways to Improve Energy Efficiency • A. How can we use waste heat? • Energy cannot be recycled (2nd law of thermodynamics) • For a house: insulate it, eliminate air leaks and equip it with an air-to-air heat exchanger

7. B. How can we save energy in industry? • Cogeneration- production of two useful forms of energy from the same fuel source. (Efficiency can be increased to approx. 90%) • Replacing energy-wasting electric motors; use adjustable-speed drives • switch to high efficiency lighting

8. C. How can we save energy in producing electricity? The Negawatt Revolution • The negawatt revolution is known as demand-side management - reducing demand for electricity

9. D. How can we save energy in Transportation? • 1. Increase the fuel efficiency of motor vehicles • There is little interest in fuel-efficient vehicles when gasoline is so cheap • 2. Electric cars - pollution to recharge batteries is produced elsewhere • Electric cars are not very efficient • 3. Hybrid cars– run on both internal combustion engines and electric motors with batteries charged by the internal combustion engine • 4.Hydrogen fuel cell car– run on electric motors with electricity (produced with hydrogen) from a fuel cell • 5. Shift to more energy efficient way to move people and freight http://www.topgear.com/uk/videos/electric-shocker http://auto.howstuffworks.com/engine3.htm

10. E. How can we save energy in buildings? • Superinsulated houses; air-to-air heat exchangers • Use the most energy-efficient ways to heat houses: passive solar heating and high-efficiency natural gas furnaces. [electric resistance heating is the most wasteful] • Heat Pumps work in warm climates·        For existing homes add insulation, plug leaks and install energy saving windows • Use the most energy-efficient ways to heat water (using electricity is the least efficient) • Use the most energy-efficient appliances and lights • Rebates or tax credits for building energy-efficient buildings, etc.

11. III. Solar Energy • Pros: • Save money • Create jobs • Less pollution • Increase national security • Cheaper than nuclear

12. III. Solar Energy • Cons • Initial cash investment

13. A. Using Solar Energy to Heat Houses and Water • Passive Solar Heating - captures sunlight directly within a structure and converts it into low-temperature heat for space heating • a. Thermal mass stores collected energy as heat and releases it day and night

14. A. Using Solar Energy to Heat Houses and Water • Active Solar Heating - special collectors absorb solar energy; a fan or pump is used to circulate the hot water • a. Net energy yield is moderate; CO2 not emitted; land disturbance is minimal • b. Owners need solar legal rights

15. B. How Can Solar Energy Be Used to Generate High-Temperature Heat and Electricity? Central Receiver System (Power Tower) • Heliostats - computer controlled mirrors • Solar Thermal Plant (distributed receiver system) • Parabolic dish collectors • Non-imaging optical solar concentrator • Solar cookers • Central Receiver System (Power Tower)

16. Solar Power Tower Fig. 15.21a, p. 374

17. Solar Thermal Plant Fig. 15.21b, p. 374

18. Nonimaging Optical Solar Concentrator Fig. 15.21c, p. 374

19. Solar Cooker Fig. 15.21d, p. 374

20. C. Producing Electricity from Solar Cells - The PV Revolution Pros • Reliable, quiet, No moving parts, Lasts 20-30 years, Produce no_____________, • Can be on individual homes or power plants, All US power needs could be met if 6% of land is covered by them, Low pollution to _____________, Ideal for isolated homes and villages, Can be attached to a ___________Cons • $ .30 Kw/hour, expensive to put in – about $15,000 to outfit a home, battery storage for night is large and _____________________·       

21. Photovoltaic Cells (Solar Cells) - Sunlight falling on a wafer thin silicon sheet releases a flow of electrons creating an electric current. • a. High net energy yield; works in __________ • b. Cost of PVs is high, but going down • C. Storage of electricity produced is a problem • . Batteries are expensive • . Flywheels are promising

22. Producing Electricity from Moving Water and from Heat in Stored Water    Hydroelectric Power a. Large-scale hydroelectric project (large dam) b. Small-scale hydroelectric project - a low dam with no _______________ c. Pumped storage hydropower systems - water reservoirs at two different levels

23. ·        Hydroelectric Power • Advantage: All have Moderate to high net energy yield, downstream flooding is reduced, provides year-round irrigation water, cheap, reservoir can be used for recreation, produces no _______________ • Disadvantage: Flood vast areas, destroy wildlife habitat, uproots people, loss of water to evaporation, mass of water can cause earthquakes, expensive to build, fish migration disrupted, danger of collapse, downstream deprived of nutrient rich silt, no more dam-able rivers left ___________________

24. Producing electricity from Tides and Waves • Using the tidal flow & energy waves to produce electricity • Pros No polluting No carbon dioxide Cons Easily damaged Few areas with the right conditions expensive

25. Producing electricity from heat stored in water • a. OTEC (Ocean thermal energy conversion) • b. Saline solar ponds • c. Freshwater solar ponds

26. V. Producing electricity from Wind • Wind turbines produce ____________ • Currently 25,000 of them in world • Wind-farms are large groups of them

27. V. Producing electricity from Wind • Pros Cons * Unlimited source of energy *Only economical in areas • Easily built & expanded Steady wind • High net energy Need back –up power when • No air pollution wind dies down • No CO2 Visual & noise pollution • Cheap Interferes with flight of _______ • Farming could take Kills birds of prey place underneath

28. VI. Producing Energy from Biomass • Biomass: organic matter in plants • Can be burned directly or… • Converted to bio fuels • Biogas Digester: bacteria digest plant material to produce methane fuel & ethanol • Can be used in place • of gasoline or mixed • with gasoline (gasohol)

29. VI. Producing Energy from Biomass • Pros • Can be renewable if not harvested faster than they grow back • No net increase in CO2 • Add less SO2 & NO2 than coal • Cons • W/out effective land – use controls = soil erosion, flooding, loss of habitat • Wood is heavy to haul • Expensive • Produces air pollution: particulates and PAH poly aromatic hydrocarbons

30. VI. Producing Energy from Biomass • Biomass Plantation: plant large # of fast growing trees that will be burned directly or converted to bio fuels • Problem: requires lots H20 & fertilizer, & large areas of land, reduces • Using wood in fireplaces – 4% in U.S. get their heat from this = problem is it results in net energy loss of wildlife habitat

31. Burning Agriculture Waste: Bagasse: sugarcane residue- low oxygen burning produces a gas that can be used for electricity and the ash used for fertilizer. Organic matter can be burned directly as a solid fuel, or converted into gaseous or liquid biogas Potentially renewable if managed properly. Biogas (60% methane, 40% CO2); liquid methanol; liquid ethanol Biomass Plantations of Btu Bushes: burned directly or converted to alternative fuels • ·        Requires large areas of land • ·        Burning Wood • a. contains pollutants known to cause cancer, bronchitis, emphysema • b. Need efficient wood-burning stoves Burning agricultural or urban wastes • ·      Bagasse residue left after harvesting and processing sugar cane.

32. VII. Solar Hydrogen Revolution • Water can be split by electricity into hydrogen and oxygen • Solar energy can be used to produce this electricity • Hydrogen can be used in fuel cells to produce electricty to run cars, cell phones, computers, homes

33. VII. Solar Hydrogen Revolution • Cons: • It takes energy to produce it • To make it you need to react natural gas and electricity which makes CO2 • Cost is $.65 to $.92 a gallon to make • Requires energy from coal or nuclear power to produce, the only way it could be • Sustainable would be if solar power were used to make it • Requires larger gas tanks in cars

34. VII. Solar Hydrogen Revolution • Pros • Easy to store • Doesn’t pollute like gasoline • Will not explode • Does not produce CO2

35. VII. Solar Hydrogen Revolution • Why haven’t we done it? • -economics • -we need to convince governments and companies to make financial investments and phase out fossil fuels. • -politics

36. VIII. Geothermal Energy • Geothermal: heat contained in underground rocks and fluids • - dry steam, wet stream, hot h2o is extracted and used to turn a turbine • - 20 countries have geothermal sites http://www1.eere.energy.gov/geothermal/

37. VIII. Geothermal Energy • Pros Cons • Vast, reliable - not many available sites • renewable - can be depleted • moderate net energy - can degrade ecosystems • 96% fewer co2 - causes land to emissions sink • competitive - noise, odor, climate change

38. IX. Sustainable Energy Strategy • improved energy efficiency • chose projects carefully • we cannot continue to depend on a single nonrenewable energy source. • What the government can do: • a. increase fuel efficiency standards for motor vehicles • b. establish energy-efficiency standards for buildings and appliances • c. increase government sponsored R&D to improve energy efficiency • d. give tax credits and exemptions for purchases of energy efficient vehicles, houses, buildings and appliances • e. phase in full-cost pricing to include the environmental impact