Chapter 16: Energy Efficiency & Renewable Energy

Transcription

1 Chapter 16: Energy Efficiency & Renewable Energy

2 Energy Units Power = Energy/Time = Work/Time: watts Energy = Power x Time: watt-hour kwh = kilowatt-hour (10 3 ) MWh = megawatt-hours (10 6 ) GWh = gigawatt-hours (10 9 ) TWh = terrawatt-hour (10 12 ) The Joule is another common energy unit 1 kwh = 3,600,000 Joules

3 Energy Efficiency Improving the percentage of total energy input that does useful work. A lot of energy is lost due to the Law of Thermodynamics: In every energy transfer, some energy is transferred to a less useful type (usually )

4 Energy Efficiency Lighting uses 19% of the world s energy There are 4.4 billion incandescent bulbs in the US. Law to phase them out was If 1.2 million households replaced a 60 watt incandescent bulb with a 15 watt compact fluorescent bulb for light used 4 hrs/day, ~ kwh/year would be saved enough energy for homes.

5 We could save as much as 43% of all the energy we use by improving energy efficiency. Energy Inputs System Outputs 9% 7% Four widely used devices that waste a large amount of energy: Incandescent light bulb Motor vehicle with an internal engine power plant -fired power plant 85% 8% 4% 3% U.S. economy Nonrenewable fossil fuels Nonrenewable nuclear Hydropower, geothermal, wind, solar Biomass 41% 43% Useful energy Petrochemicals Unavoidable energy waste Unnecessary energy waste

6 Energy Efficiency Net energy efficiency: the net efficiency of the entire energy delivery process is determined by the efficiency of each in the energy conversion process.

7 Ways to Improve Energy Efficiency (Combined Heat and Power- CHP): the production of two useful forms of energy from the same fuel source Example: waste heat from generator used to heat water. Better insulated homes Use of energy efficient lighting & appliances Increase the fuel efficiency of motor vehicles

8 Energy Efficient Homes

9

10 Renewables are increasing rapidly

11 Change in Electric Power Generation by State: Use of coal down in states, only 1 has an increase (KY) Natural Gas has increased (ex. DE) Many Renewables have increased, although they are still relatively a small ews&utm_content=

12 United States Electricity Sources % from fossil fuels Of the % in the renewable (non-hydro) category, 67% is biomass Percentage of total US energy consumption used to generate electricity: 1940: % 1970: % 2010: % Nation s electric bill = $247 Billion Average cost/kwh = $0.07 $247 billion/$0.07/kwh = ~3.5 TWh (3.5 x )

13 America s Grid US has ~10,000 power plants Average efficiency ~ % Majority of plants are > years old Newer plants using can have efficiencies of 65-90%

14 America s Grid 157,000 miles of high voltage transmission lines decrease voltage for use in homes, etc. and distribution losses increased from ~5% in 1970 to ~9.5% in 2001, due to heavier use and more frequent congestion of the grid transmission lines have lower losses, but are 10x more expensive to build and are harder to maintain Substation

15 America s Grid : Electricity Infrastructure Demand has increased by since 1990 Construction of new lines has decreased by Resulting congestion of transmission pathways create bottlenecks, and higher costs because customers cannot get access to lower-cost electricity supplies Estimated cost of power outages and power quality disturbances due to congestion is $25-$180 billion per year Increased use of information technologies has decreased public for power quality problems Construction of new facilities is often tied up in America s aging infrastructure versus increased demand for power will require large investments to upgrade the system

16 Renewable Energy Resources Original Energy from Sun: Solar power (dams, waves, solar ponds) Wind power Biomass Energy Independent of Sun: power Fuel (maybe) Tidal Energy (mostly)

17 Solar Energy solar Sunlight is captured directly within a structure & converts it into low temperature heat for space heating. Heat is stored in walls & floors & is released slowly throughout the day. A passive solar & superinsulated is the cheapest way to heat a home in regions where sunlight is available more than 60% of daylight hours.

18 Passive Home Design /09/26/business/energyenvironment/26smart.html?e mc=eta1&pagewanted=print

19 Solar Energy solar heating solar collectors absorb solar energy & a fan or pump supplies the building s space or water heating needs

20 Pros Active & Passive Solar Heating solar energy is free net energy yield is high for & moderate for technology is well developed & easily installed takes up little space does not emit polluting or greenhouse gases Cons need to secure solar collectors are ugly to some people active systems are

21 Solar Energy to Produce Electricity solar energy can be converted into electrical energy by cells sunlight striking atoms creates an electrical current electrical energy is stored in for use when the sun is not shining, or excess energy is sent back to the grid ( )

22 Solar Energy : selling excess electricity generated by solar back to the grid. Gives financial incentive to homeowners, and does not waste electricity when it is produced. Solar Farm

23 Solar Energy: Producing Electricity Ways to Generate Electricity from Sunlight (CST) Solar collectors reflect light. And are used to heat a liquid that can spin a turbine to generate electricity.

24 Large-scale Solar Power Generation Pros: No greenhouse emissions and reliable net energy yield Plentiful supply in some areas Cons: Currently Large land area required Only some parts of country suitable Electricity for night or cloudy day use

25 We Can Cool Buildings Naturally Too Technologies available: Superinsulation and high-efficiency Overhangs or awnings on windows Light-colored Reflective insulating foil in an attic pumps Plastic earth tubes underground

26 Producing electricity from water Hydroelectric dams Hoover Dam

27 Grand Coulee Dam Built ft high Required 12 million cubic yards of concrete largest hydroplant in the world) Generates over 4.1 billion kwh in electricity each year, enough for 2.3 million households in 11 states

28 Three Gorges Dam: China 607 ft high, 1.4 miles long 1,200 towns and villages Chinese government says in addition to providing needed energy will help control flooding on Yangtze 18,200 Megawatts

29 Hydropower Production US is 4 th in the world for hydropower production Columbia River basin provides of the US s hydroelectric capacity Norway gets the highest percentage from hydropower

30 Hydropower Pros No emission of greenhouse gases net energy yields Technology well-developed, inexpensive once in place Cons Dams flood habitats & alter downstream habitats Dams interfere with runs Requires abundant water & large elevation differences Water supplies are often In arid areas, high loss of water in reservoirs due to

31 Producing electricity from water Tides Pros: No greenhouse emissions Cons: new/developing technology, few areas with enough tidal or wave energy, Potential disturbance of tidal and fish Limited useful areas Tides only moving fast enough ~10 hours/day

32 Producing electricity from water Waves Pros: No greenhouse emissions Can run, as long as waves are large enough Does not disturb near-shore ecosystems/animals Cons: often must transmit energy to shore Must be in areas with significant wave action

33 Producing electricity from water Ocean thermal energy conversion & solar ponds Pros: no greenhouse emissions Cons: not currently, moderate energy yields, large space required

34 Producing electricity from wind Pros unlimited source of energy at favorable sites moderate to high net energy yield to build & expand emit no pollutants or greenhouse gases land can also be used for agriculture or

35 Solutions: Wind Turbine and Wind Farms on Land and Offshore Advantage of offshore sites: winds less, and often more Disadvantage: Obstructed of ocean. Corrosion in seawater.

36 Producing electricity from wind Cons economical only in areas with winds (Grid can not currently handle transport) back up energy sources are necessary since winds are not always steady (doesn t run 24/7) mass production takes up a great deal of land space pollution may interfere with migrating birds

37 Geothermal Energy Using water heated from volcanic activity to create electricity.

38 Geothermal Energy Pros: No greenhouse emissions Plentiful supply in volcanic areas Moderate net energy yields Can run Iceland

39 Geothermal Energy Cons: Heat must be to surface to be useful Scarcity of easily sites Extraction of water can cause land to Costly in all but most concentrated sources

40 TRADE-OFFS Geothermal Energy Advantages Very high efficiency Moderate net energy at accessible sites Lower CO 2 emissions than fossil fuels Low cost at favorable sites Low land use and disturbance Moderate environmental impact Disadvantages Scarcity of suitable sites Can be depleted if used too rapidly Environmental costs not included in market price CO 2 emissions Moderate to high local air pollution Noise and odor (H 2 S) High cost except at the most concentrated and accessible sources

41 Geothermal Heat Pumps: The ground temperature stays relative year round. Geothermal pumps move a fluid through underground tubes that will be heated in the winter and cooled in the summer.

42 Producing energy from biomass

43 Pros Producing energy from biomass Using wood or other plants a renewable energy resource high net energy yield if burned near source Less need for imported oil Cons currently exploited in nonrenewable & unsustainable ways single species biomass plantations reduce burning wood produces air pollutants such as particulates Biofuels have a lower yield than fossil fuels Using arable land for biomass production may reduce available lands for

44 Biodiesel Produced from vegetable oil. Sources: Palm oil, Rapeseed, Soybeans 95% of biodiesel produced in the. Yield L/ha US gal/acre Algae ~3,000 ~300, Palm oil Coconut Rapeseed [ Soy (Indiana) Jatropha Shrub Palm Oil Production 2006

45 Palm Oil Production The downside Increases rate of clear cutting of forests in areas Endangered Orangutan in Borneo Palm Oil Plantation

46 TRADE-OFFS Biodiesel Advantages Reduced CO emissions Reduced CO 2 emissions (78%) High net energy yield for oil palm crops Moderate net energy yield for rapeseed crops Reduced hydrocarbon emissions Better gas mileage (40%) Potentially renewable Disadvantages Increased NO x emissions and more smog Higher cost than regular diesel Environmental costs not included in market price Low net energy yield for soybean crops May compete with growing food on cropland and raise food prices Loss and degradation of biodiversity from crop plantations Can make engines hard to start in cold weather

47 Ethanol Sources: Corn Sugar Cane Cellulosic (switch grass, crop residue) is the Saudi Arabia of sugar cane ethanol. - Saved 50% on oil import costs since the 70 s

48 TRADE-OFFS Advantages High octane Ethanol Fuel Some reduction in CO 2 emissions (sugarcane bagasse) High net energy yield (bagasse and switchgrass) Reduced CO emissions Can be sold as E85 or pure ethanol Potentially renewable Disadvantages Lower driving range Low net energy yield (corn) Higher CO 2 emissions (corn) Much higher cost Environmental costs not included in market price May compete with growing food and raise food prices Higher NO x emissions and more smog Corrosive Can make engines hard to start in cold weather

49 Electric Cars Electric Motor Note: from a pro-tesla website Combustion Engine

50 Electric Cars Based on grid emissions (i.e. amount of fossil fuels used to generate electricity by region Source: Union of Concerned Scientists: vs-electric-global-warming-emissions- 953?utm_source=fb&utm_medium=fb&utm_cam paign=fb

51 Electric Cars Pros: CO 2 emission-free while driving Electricity is cheaper than gas Cons: Limited Time to charge vs. time to fill with gas Lack of (nationwide rapid-charging stations) Currently expensive Most electricity is currently produced from Tesla Model 3 (2017) Battery replacement/disposal But many of these cons are changing fairly rapidly as the technology progresses

52 Hydrogen Fuels Energy is used to split water into hydrogen and oxygen The hydrogen is stored in fuel cells The hydrogen then combusts with oxygen to produce water Fig Note: Law of Conservation of : The energy required to split H 2 O to make H 2 = amount of energy obtained by combusting H 2 to make water

53 Hydrogen Fuel Pros: the source of hydrogen, water, is plentiful when burned, hydrogen produces no carbon dioxide, but instead water vapor & nitrogen oxides reduce problems & greenhouse gas emissions Cons: requires energy source to split hydrogen from water currently nonrenewable energy sources are used to produce hydrogen, negating many benefits Hydrogen is highly flammable (but less explosive than gasoline) some hydrogen fuel is produced from (CH 4 ), a greenhouse gas

54 TRADE-OFFS Hydrogen Advantages Can be produced from plentiful water Low environmental impact Renewable if produced from renewable energy resources No CO 2 emissions if produced from water Good substitute for oil Competitive price if environmental and social costs are included in cost comparisons Easier to store than electricity Safer than gasoline and natural gas Nontoxic High efficiency (45 65%) in fuel cells Fuel cell Disadvantages Not found as H 2 in nature Energy is needed to produce fuel Negative net energy CO 2 emissions if produced from carboncontaining compounds Environmental costs not included in market price Nonrenewable if generated by fossil fuels or nuclear power High costs (that may eventually come down) Will take 25 to 50 years to phase in Short driving range for current fuel-cell cars No fuel distribution system in place Excessive H 2 leaks may deplete ozone in the atmosphere Fig , p. 430

55 Solutions Hydrogen Fuel use renewable sources of energy, most notably, to produce hydrogen for combustion currently it costs more to use solar energy than other non-renewable energies Sandia currently is experimenting with nanodevices that use sunlight to split water ( For more info on the future of hydrogen in the US, go to

56 Solutions Hydrogen Fuel Iceland is planning to be fossil fuel-free within the next few decades by using energy to produce hydrogen fuel Hydrogen fuel station in Reykjavik, Iceland, December, 2011 Photos by Weston

57

58 Renewable Energy Solutions Improve Diversify the : use many different energy sources so that we are not too reliant on any one source Give to individuals, cities, energy utilities to use renewable energy Create to support renewables Develop new technologies to improve the implementation/feasibility of renewables Wave Power Energy from Wind Farm

59 Solutions: Battery Technology Most renewables energy sources cannot run 24/7. Diversifying the grid is a good solution, but in the long-term, creating batteries that can store enough energy to power a city could revolutionize the grid. Daily winter heat demand Daily electricity demand Home battery system

60 New Ideas: Battery Technology For Your Home Tesla Powerwall: a home battery that charges using electricity generated from solar panels, or when utility rates are low. Can provide a backup electricity supply if there s a power outage. energy storage capacity, sufficient to power most homes during powerwall the evening using electricity generated by solar panels during the day. Multiple batteries may be installed together for homes with greater energy needs.