Chapter 16. Renewable Energy Alternatives. Lecture Presentations prepared by Reggie Cobb Nash Community College Pearson Education, Inc.

Transcription

1 Chapter 16 Renewable Energy Alternatives Lecture Presentations prepared by Reggie Cobb Nash Community College

2 This lecture will help you understand: Reasons for seeking alternative fuels Major sources of renewable energy Solar energy Wind energy Geothermal energy Ocean energy Hydroelectric power Bioenergy Hydrogen fuel cells

3 Central Case Study: Germany Goes Solar Germany is the world s leader in production of photovoltaic (PV) solar power Yet the country is cool and cloudy Federal policies offer incentives to promote solar energy Feed-in tariff system Utilities must buy power from anyone who generates it from renewable sources

4 Central Case Study: Germany Goes Solar (cont d) German industries are world leaders in green tech Its leaders see renewables as a great economic opportunity It is a model for others

5 We have alternatives to fossil fuels Our global economy is powered by fossil fuels Oil, coal, and natural gas supply four-fifths of our energy They power two-thirds of the world s electricity Renewable sources Used relatively less for transportation Relatively more for generating electricity

6 We have alternatives to fossil fuels (cont d) Nations are looking for ways to move away from fossil fuels while ensuring a reliable energy supply Nuclear energy is the main nonrenewable alternative Renewables include hydroelectric power and biomass They are well established and widely used New renewables are not widely used and are still being developed to use in: Generating electricity, heating air or water, providing fuel for vehicles

7 Renewable energy offers advantages Renewable energy sources reduce air pollution and greenhouse gas emissions that drive global climate change Green-collar jobs Design, installation, maintenance, and management of renewable energy technologies

8 Policy and investment can accelerate our transition Although prices are falling, most renewable energy remains more expensive than fossil fuel

9 Policy and investment can accelerate our transition (cont d) Conventional sources get more government subsidies and tax breaks Policies keep fossil fuels cheap Which hurts renewables For America to remain a global leader: Political and financial support will need to be redirected toward renewable energy

10 The Science Behind the Story Comparing Energy Sources Mark Jacobson of Stanford University reviewed over 100 studies on alternative energy to calculate the impacts of various energy sources across their entire life cycle Findings: Wind power: most desirable alternative energy source Ethanol: least desirable

11 Solar energy Each square meter of Earth receives 17 times the energy of a lightbulb Passive solar energy collection Buildings are designed to maximize absorption of sunlight in winter

12 We collect solar energy using passive and active methods Active solar energy collection Uses technology to focus, move, or store solar energy Flat plate solar collectors Dark-colored, heat-absorbing metal plates mounted on rooftops Water, air, or antifreeze runs through the collectors, transferring heat throughout the building Heated water is stored and used later Over 200 million U.S. homes and businesses heat water with solar collectors Most is for swimming pools

13 We collect solar energy using passive and active methods

14 Concentrating sunlight focuses energy Concentrated solar power (CSP) Technologies that concentrate solar energy to generate electricity Mirrors track the sun s movement Solar cookers Simple, portable ovens that use reflectors to focus sunlight onto food

15 PV cells generate electricity Photovoltaic (PV) cells Convert sunlight directly into electrical energy Watches and calculators contain small PV cells On roofs, PV cells are arranged in modules Which comprise panels gathered into arrays

16 PV cells generate electricity (cont d) Thin-film solar cells PV materials are compressed into thin sheets Less efficient but cheaper Can be incorporated into roofing shingles, roads, etc. Producers of PV electricity can sell their power to a utility Net metering The value of the power the consumer provides is subtracted from the monthly utility bill Feed-in tariffs pay producers more than the market price of power, so power producers turn a profit

17 Solar energy offers many benefits Solar technologies use no fuels, are quiet, are safe, contain no moving parts, and require little maintenance They allow local, decentralized control over power Especially helpful in developing nations In developed nations, PV owners can sell excess electricity to their local utility Green-collar jobs are being created PV cells do not emit greenhouse gases and air pollution when up and running

18 Location, timing, and cost can be drawbacks Not all regions are sunny enough for solar energy Daily and seasonal variation also poses problems We need storage (e.g., batteries) and backup power Solar produces the most expensive electricity But prices have dropped and efficiency has increased

19 Solar energy is expanding Solar energy was pushed to the sidelines as fossil fuels dominated our economy Because of a lack of investment, solar energy contributes only a minuscule part of energy production But solar energy use has increased 30%/yr since 1971 Solar energy is attractive in developing nations Where hundreds of millions don t have electricity

20 Solar energy is expanding (cont d) China leads the world in PV cell production The U.S. may recover its leadership As a result of tax credits and state initiatives Solar energy use should increase as a result of: Falling prices Improved technologies Economic incentives

21 Wind turbines convert kinetic energy to electrical energy Wind energy Energy derived from movement of air An indirect form of solar energy Wind turbines Devices that convert wind s kinetic energy into electric energy Wind blowing into a turbine turns the blades The nacelle contains the generator Towers are 260 feet tall Wind farms may contain hundreds of turbines

22 Wind power is growing fast 5 nations produce 75% of the world s wind power But dozens of nations now produce wind power U.S. growth in wind power has been haphazard A long-term federal tax credit would encourage growth

23 Offshore sites hold promise Wind speeds are 20% greater over water than over land, with less air turbulence over water Costs to erect and maintain turbines in water are higher But more power is produced and is more profitable Currently, turbines are limited to shallow water The first U.S. offshore wind farm will have 130 turbines Off Cape Cod, Massachusetts

24 Wind power has many benefits Wind produces no emissions once installed Prevents the release of CO 2, SO 2, NO x, mercury It is more efficient than conventional power sources Turbines produce 20 times more energy than they consume Turbines use less water than conventional power plants Local areas can become more self-sufficient Farmers and ranchers can lease their land Allows them to receive extra revenue while still using the land

25 Wind power has many benefits (cont d) Advancing technology is also reducing the cost of wind farm construction 85,000 employees now work in the wind industry Over 100 colleges and universities offer programs and degrees that train people for jobs in renewable energy

26 Wind power has limitations Wind varies from time to time and place to place It can be one of several sources of electricity Batteries or hydrogen fuel can store the energy Wind sources are not always near population centers that need energy Transmission networks need to be expanded Local residents often oppose wind farms Turbines kill birds and bats when they fly into rotating blades

27 U.S. wind-generating capacity Mountainous regions have the most wind and turbines

28 We harness geothermal energy for heating and electricity Geothermal energy Thermal energy from beneath Earth s surface Radioactive decay of elements under high pressures deep inside the planet generates heat Heat rises through magma, fissures, and cracks Heated groundwater erupts as geysers or submarine hydrothermal vents Hot water can directly heat building Geothermal power plants use hot water or steam to generate electricity

29 We harness geothermal energy for heating and electricity (cont d) Geothermal power plants harness naturally heated water and steam to generate electricity

30 Heat pumps make use of temperature differences We can take advantage of natural temperature differences between the soil and air Soil temperatures vary less than air temperatures Ground-source heat pumps (GSHPs) Geothermal pumps heat buildings in the winter by transferring heat from the ground to the building In summer, heat is transferred from the building to the ground More than 600,000 U.S. homes use GSHPs

31 Heat pumps make use of temperature differences (cont d) GSHPs heat and cool spaces more efficiently They reduce electricity and emissions

32 Geothermal power has pros and cons Geothermal power reduces emissions It is not sustainable if the water is withdrawn faster than it can be recharged Patterns of geothermal activity in the crust shift Dissolved salts and minerals corrode equipment and pollute the air It is limited to areas where the energy can be tapped

33 Geothermal power has pros and cons (cont d) Engineers are working to overcome the limitation of geothermal availability Enhanced geothermal systems (EGS) Water is put into deep holes When heated, it is withdrawn to generate electricity It could be used in many locations But EGS can trigger minor earthquakes So, our use of geothermal power will stay localized

34 We can harness energy from tides, waves, and currents Kinetic energy from the natural motion of ocean water can generate electrical power Tidal energy Dams cross the outlets of tidal basins Water is trapped behind gates Tidal currents turn turbines to generate electricity Tidal stations don t release emissions But they change the area s ecology

35 We can harness energy from tides, waves, and currents (cont d) Wave energy The motion of waves is harnessed and converted from mechanical energy into electricity Many designs exist but need to be tested Ocean currents, such as the Gulf Stream, can be used Underwater turbines have been erected off of Europe

36 The ocean stores thermal energy Each day, tropical oceans absorb solar radiation equal to the heat content of 250 billion barrels of oil Ocean thermal energy conversion (OTEC) Uses temperature differences between the surface and deep water Warm surface water evaporates chemicals, which spin turbines to generate electricity Or, warm surface water is evaporated in a vacuum and its steam turns turbines Costs are high and no facility operates commercially yet

37 Hydroelectric power (hydropower) Hydropower uses the kinetic energy of moving water to turn turbines to generate electricity Hydropower uses three approaches Storage technique Water stored in reservoirs behind dams passes through the dam and turns turbines Run-of-river approach Generates electricity without disrupting the river s flow Water flows through a pipe then returns to the river Useful in remote areas away from electric grids Pumped-storage Water is pumped to a high reservoir and flows downward through a turbine

38 Hydroelectric power (hydropower) (cont d)

39 Hydropower is clean and renewable, yet has impacts Hydropower has two clear advantages over fossil fuels for producing electricity It is renewable: as long as precipitation fills rivers we can use water to turn turbines It is clean: no carbon dioxide is emitted Hydropower is efficient It has an EROI of 10:1 As high as any modern-day energy source

40 Hydropower is clean and renewable, yet has impacts (cont d) Damming rivers destroys wildlife habitats Upstream areas are submerged Downstream areas are starved of water Natural flooding cycles or rivers are disrupted Downstream floodplains don t get nutrients Water temperatures are changed, eliminating fish species Dams block passage of fish, fragmenting the river and reducing biodiversity

41 Hydroelectric power is widely used, but it may not expand much more Dams have helped many nations develop Canada, Brazil, Norway, Austria, Switzerland, etc. China s Three Gorges Dam is the world s largest dam But hydropower isn t likely to expand much more Most of the world s large rivers have already been dammed People have grown aware of the ecological impact of dams and resist more construction 98% of U.S. suitable rivers have been dammed The rest are protected

42 Bioenergy Bioenergy (biomass energy) Energy obtained from biomass (organic material from living or recently living organisms) Includes wood, charcoal, agricultural crops, manure The sustainable use of bioenergy requires careful consideration of the biomass source Over 1 billion people use fire for heat, cooking, and light

43 Bioenergy (cont d) We harness bioenergy by burning biomass for heating, using biomass to generate electricity, and processing biomass to create liquid fuels for transportation

44 We use biomass to generate electricity Biopower Biomass sources are burned in power plants This generates heat and electricity Waste products of industries or processes Woody debris, pulp mill waste, crop residues Bioenergy crops Fast-growing willow trees, bamboo, switchgrass Combustion strategies Co-firing combines biomass and coal in a specialized boiler Gasification turns biomass to steam Pyrolysis produces a liquid fuel

45 Benefits and drawbacks Biopower increases efficiency and waste recycling It reduces CO 2 emissions Capturing landfill gas reduces methane emissions It reduces sulfur dioxide emissions when used to replace coal But burning crops deprives the soil of nutrients The soil becomes progressively depleted

46 Biofuels can power vehicles Biofuels Liquid fuels used to power automobiles Ethanol A biofuel made by fermenting carbohydrate-rich crops is added to U.S. gasoline to reduce emissions In 2013, 13.3 billion gallons of were made in the U.S., mostly from corn Congressional mandates will increase ethanol production

47 Biofuels can power vehicles (cont d) Flexible-fuel vehicles run on E-85 85% ethanol, 15% gasoline Over 15 million cars are in the U.S. Most gas stations do not yet offer this fuel Almost all new Brazilian cars are flexible-fuel vehicles Bagasse Crushed sugarcane residue used to make ethanol It is in half of all fuel that Brazil s drivers use

48 Using ethanol for fuel may not be sustainable Environmental scientists don t like corn-based ethanol Growing corn impacts ecosystems Pesticides, fertilizers, irrigation Takes up precious land Using the corn crop to produce ethanol drives up food prices Growing corn requires energy for equipment, pesticides, fertilizers, transportation to processing plants Its EROI ratio is about 1.5:1, so it is inefficient

49 Using ethanol for fuel may not be sustainable (cont d) To produce all automotive fuel used in the U.S. with ethanol from U.S. corn, the nation would need to expand its already immense corn acreage by more than four times

50 Frequently Asked Question If we substitute ethanol for gasoline, won t that solve most of our problems with oil dependence?

51 Biodiesel powers engines Biodiesel Produced from vegetable oil, cooking grease, animal fat, soybeans, oil palms, rapeseed Vehicles can run on 100% biodiesel B20: 20% biodiesel Biodiesel reduces emissions Its fuel economy is good It costs a bit more than gasoline Crops are specially grown Using land, leading to deforestation

52 Novel biofuels are being developed Other crops can be used as biofuels Wheat, sorghum, sugar beets, hemp, grasses Algae Produce lipids that can be converted to biodiesel Their carbohydrates can be fermented to make ethanol Can be grown in ponds, tanks, or photobioreactors Grow fast and can be harvested every few days

53 Novel biofuels are being developed (cont d) Cellulosic ethanol Produced from structural plant material (e.g., cornstalks) that has no food value

54 Is bioenergy carbon-neutral? In principle, biomass energy releases no net carbon Photosynthesis removes carbon that is released when biomass is burned Burning biomass is not carbon-neutral: If forests are destroyed to plant bioenergy crops If we use fossil fuel energy (tractors, fertilizers, etc.) International climate change policy does not encourage sustainable bioenergy approaches Only emissions from energy use (not land use changes) are counted toward controlling emissions

55 Weighing the Issues Biofuels Do you think producing and using ethanol from corn is a good idea? Do the benefits outweigh the drawbacks? Explain why or why not Should we invest billions of dollars into developing nextgeneration biofuels such as algae and cellulosic ethanol? Can you suggest ways of using biofuels that would minimize environmental impacts?

56 Hydrogen and fuel cells Hydrogen fuel could store energy cleanly and efficiently By using the world s simplest and most abundant element (hydrogen) as fuel Hydrogen is an energy carrier, not an energy source Electricity produced from intermittent sources (sun, wind) would be used to produce hydrogen Fuel cells (hydrogen batteries) would use hydrogen to produce electricity to power cars, homes, computers, etc. Governments are funding research into hydrogen and fuel cell technology

57 Hydrogen fuel cell

58 Hydrogen fuel may be produced from water or from other matter Hydrogen gas does not exist freely on Earth Energy is used to force molecules to release the hydrogen Electrolysis electricity splits hydrogen from water 2H 2 O 2H 2 + O 2 It may cause pollution, depending on the source of electricity Hydrogen production s impact depends on the source of electricity used in electrolysis and the hydrogen source Using methane produces the greenhouse gas CO 2 CH 4 + 2H 2 O 4H 2 + CO 2

59 Fuel cells can produce electricity Once isolated, hydrogen gas can be used as a fuel to produce electricity within fuel cells The chemical reaction is the reverse of electrolysis: 2H 2 + O 2 2H 2 O

60 Hydrogen and fuel cells have costs and benefits Costs Needs massive and costly development of infrastructure Leakage of hydrogen can deplete stratospheric ozone Benefits We will never run out of hydrogen It can be clean and nontoxic to use It may produce few greenhouse gases and pollutants If kept under pressure, it is no more dangerous than gasoline in tanks Hydrogen fuel cells are up to 90% energy-efficient Hydrogen fuel cells are silent and nonpolluting, and they don t need recharging

61 Conclusion We need to shift to renewable energy Biomass energy sources include wood and newer biofuels They can be carbon-neutral but are not strictly renewable Hydropower is a renewable, pollution-free alternative But it is nearing maximal use and can involve substantial ecological impacts Renewable sources such as solar, wind, geothermal, and ocean energy sources and hydrogen fuel are promising They need funding for research and development