February 19, Chapter 17: Energy Efficiency and Renewable Energy

Transcription

1 Chapter 17: Energy Efficiency and Renewable Energy

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3 Energy conservation - reducing or eliminating unnecessary waste of energy Energy efficiency - one way to conserve by using less to accomplish same task (more work/unit of energy) *Quickest, cheapest, cleanest way to provide more energy.

4 *net energy efficiency February 19, 2014

5 Some strategies to improve energy efficiency in industry Cogeneration or combined heat and power (CHP) systems 2. Replace energy-wasting electric motors 3. Switch from incandescent to fluorescent lighting

6 Strategies for improving energy efficiency in transportation 1. Fuel economy standards (CAFE--corporate average fuel economy standards) 2. More fuel-efficient cars hindered by low gas prices (subsidies and tax breaks, military protection) government $ to allow people to buy fuel-efficient vehicles 3. Redesign urban transportation system

7 Hybrid Vehicles gasoline-powered motor + electric motor Plug-in hybrid 2nd battery to plug in and charge *where does electricity come from?

8 Fuel cell in cars 2H2 + O2 2H2O Advantages?

9 Green Architecture: Energy efficient buildings Capture solar energy block out sun to reduce cooling costs use efficient lighting thermostats insulation living roofs LEED: Leadership in Energy and Environmental design > certifies buildings based on standards > *tax breaks, rebates, grants to encourage meeting LEED standards?

10 Alternative Forms of Energy Solar Hydropower* Wind* Biomass* Geothermal Hydrogen *Indirect form of solar energy

11 Hydropower Water flowing from higher to lower elevation Dams Reservoir Turbines *US largest producer of electricity from hydropower > 7% US, 50% west coast > Little room for expansion: 98% rivers already dammed, some need to be taken down (silt) micro-hydrogenerator *Not true for US

12 Hydropower Tides > Need big difference in high/low tide > expensive Waves Ocean thermal energy conversion (OTEC) > Large temperature difference between surface and deep water in tropical oceans

13 Windpower difference in solar heating of earth Taller = more reliable wind February 19, 2014

14 Windpower: expansion? Anemometers > wind speed at different heights Locations? > land in US: midwestern states could potentially supply all of nation's electricity needs > offshore* winds are stronger and steadier sounds high cost February 19, 2014

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16 Biomass Directly burn organic materials (plants, animal waste) or convert into liquid/gaseous biofuels mostly burned for heat not to generate electricity 95% energy in poorest countries

17 Biomass Plants are potentially plentiful > sustainable harvest > biomass plantation depletes soils, degrade biodiversity Other sources? > crop residue > animal manure February 19, 2014

18 Biomass: Liquid biofuels Ethanol produced by fermentation and distillation of sugars (starch and cellulose can be broken down) > microbes > cellulosic ethanol > sugar cane and switchgrass rather than corn? Replace gasoline and diesel Environmental impacts? *Made affordable by government subsidies!

19 Biodiesel alcohol + vegetable oil *Environmental impacts of conventional farming

20 Geothermal Energy Heat stored in soil, underground rocks, and fluids in earth's mantle > original formation > radioactive decay Using just 1% stored heat in uppermost 5km of earth's crust provide 250x more energy than in all earth's oil and natural gas reserves *US biggest producer *Geothermal energy most available at volcanoes: boundaries of plates and hot spots

21 Geothermal Energy Hydrothermal reservoirs > dry steam > wet steam > hot water February 19, 2014

22 Geothermal Energy Geothermal heat pump (GHP) difference in surface and underground temperature fluid flowing through pipes Winter: Heat from underground to home Summer: Heat from home to underground

23 Geothermal Energy Geothermal heat pump (GHP) energy-efficient, reliable, environmentally clean no pollutants, no CO2

24 Turning Geothermal Energy into Electricity 1. Dry steam 2. Flash steam 3. Binary cycle

25 *Recirculate hot water back into ground to slow depletion

26 Hydrogen gas (H2) H2 + O2 H2O Where is the hydrogen? > Locked up in water, organic compounds > Energy and money to produce* low energy yield > Fuel cells are expensive > Whether it produces less air pollution than fossil fuel depends on how hydrogen is produced burning fossil fuels v. hydro/wind/solar power

27 Hydrogen How to apply technology? > home fueling units > energy farmers not energy hunter-gatherers > nanomaterials > store hydrogen in tanks or carbon nanofibers February 19, 2014

28 Sustainable Energy Strategy Takes at least 50 years + $$ to phase in new energy alternatives to 10-20% total energy use Things to consider: > Resource > Net energy yield > $$ required? > Government research and subsidies > Environmental effects *US

29 Trends: shift from large centralized macropower systems to smaller, decentralized micropower systems > diversity of energy resources energy efficiency + natural gas + sustainably produced biofuel to transition to renewable-energy resources continued use of fossil fuels + reduce harm while phase-in renewable energy

30 Policy to shift to more sustainable energy resources 1. Keep price of sustainable energy resources low > research subsidies, tax breaks 2. Keep energy prices artificially high to discourage use of a resource > eliminate tax breaks and subsidies, restrictive regulation, add tax on use 3. Consumer education

31 Tuesday (2/18): Guest presentation on using solar power Finish up chapter 17 Thursday (2/20): Start Chapter 18 Monday (2/24): Unit 6 Test (Chapter 16 and 17) *including calculations