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再生能源與材料科技

廖建勛 博士

元智大學 化材系

Dec. 16, 2010

大 綱

1. 能源與效率

2. 再生能源技術

3. 燃料電池與材料科技

4. 太陽能電池與材料材料

5. 儲能技術與材料科技

6. 熱電技術與材料科技

7. 未來能源技術

*Major fossil energy carriers (crude oil, natural gas, coal and uranium) as primary energy sources: limited reserves and resources along with emission problems *The worldwide demand for electrical energy has increased from 8.3 million GWh in 1980 to 18.9 million GWh in 2006, and is estimated to further increase to 30.7 million GWh in 2030.

Total world primary energy demand and supply Oil Production and Supply

* Popul. Environ. 24, 193 (2002).

The Future of Energy Supply: Challenges and Opportunities

*Angew. Chem. Int. Ed. 46, 52–66 (2007). *Science 315,796 (2007).

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Energy and Efficiency

*Sci. Am., Sep. 74 (2005)

Classical Heat-Engine Cycles

*Angew. Chem. Int. Ed. 48, 9230 (2009).

Carnot process and its limits

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21

in

out )(T

TTWW

)(2/3 21out TTRW

1in 2/3 RTW

hot

cold

hot

coldhot 1)(TT

TTT

The Carnot process consists of two adiabatic and two isothermal cycles. In the isothermal cycles, the steam is in contact with the combustion chamber T2 or with the capacitor T1. In the adiabatic cycles, the piston moves without heat contact. The efficiency of the Carnot cycle is a function of the temperatures T1and T2. T1 cannot be arbitrarily high owing to the properties of the materials, and T1 - T2 cannot be too large owing to heat conduction within the machine.

*Sci. Am., Dec. 52 (1994)

*Sci. Am., Mar. 62 (2005)

Electrochemical Versus Heat-Engine Energy Technology

*Sci. Am., Oct. 64 (2002)

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*Sci. Am., May 66 (2004)

Water vs EnergyWater is needed to generate energy. Energy is needed to deliver water. Both resources are limiting the other—and both may be running short.

*Sci. Am., Earth 3.0. 34 (2008)

Wij rijden op water

*Chem. Commun. 668 (2008)*Sci. Am., Earth 3.0. 34 (2008)

An Oil-free America

*Sci. Am., Sep. 74 (2005)

U.S. oil consumption and imports can be profitably slashed by doubling the efficiency of vehicles, buildings and industries (yellow lines in graph). The U.S. can achieve further reductions by replacing oil with competitive substitutes such as advanced biofuels and saved natural gas (green lines) and with hydrogen fuel (gray lines).

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Electricity Alternatives

*Sci. Am., Sep. 74 (2005)

Decentralized sources of electricity—cogeneration (the combined production of electricity and heat, typically from natural gas) and renewables (such as solar and wind power)—surpassed nuclear power in global generating capacity in 2002. The annual output of these low- and no-carbon sources will exceed that of nuclear power this year.

The Rise of Renewable Energy

No plan to substantially reduce greenhouse gas emissions can succeed through increases in energy efficiency alone. Because economic growth continues to boost the demand for energy — more coal for powering new factories, more oil for fueling new cars, more natural gas for heating new homes—carbon emissions will keep climbing despite the introduction of more energy-efficient vehicles, buildings and appliances. To counter the alarming trend of global warming, the U.S. and other countries must make a major commitment to developing renewable energy sources that generate little or no carbon.

*Sci. Am., Sep. 84 (2006)

A world of clean energy could rely on wind turbines and solar cells to generate its electricity and biofuels derived from switchgrass and other plants to power its vehicles.

*Sci. Am., Mar. 56 (2009)

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*Angew. Chem. Int. Ed. 46, 52–66 (2007).

U.S. Plan for 2050: Solar Power Provides 69% of electricity and 35% of total energyBy 2050 vast photovoltaic arrays in the Southwest would supply electricity instead of fossil-fueled power plants and would also power a widespread conversion to plug-in electric vehicles. Excess energy would be stored as compressed air in underground caverns. Large arrays that concentrate sunlight to heat water would also supply electricity. A new high-voltage, direct-current transmission backbone would carry power to regional markets nationwide. The technologies and factors critical to their success are summarized at the right, along with the extent to which the technologies must be deployed by 2050. The plan would substantially cut the country’s consumption of fossil fuels and its emission of greenhouse gases (below). We have assumed a 1 percent annual growth in net energy demand. And we have anticipated improvements in solar technologies forecasted only until 2020, with no further gains beyond that date.

*Sci. Am., Jan. 64 (2008) *Sci. Am., Mar. 56 (2009)

*Nature 447,1046 (2007).

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Biofuels from biomassCarbohydrates from biomass will almost certainly provide the source of carbon-based fuels of the future. But the fuel of choice and the method of production are still uncertain. In the absence of an optimal process, there is a vigorous debate over whether the biomass conversion system should be thermochemical (using heat and metal catalysts) or biological (using enzymes and microorganisms). The fuels produced reflect the process involved: ethanol is the product of biological conversion, whereas synthetic diesel (a mixture of saturated hydrocarbons known as alkanes) is that of thermochemical methods.

*Nature, 447, 914 (2007)

Biofuels from Biomass or Coal Hybrid routes to biofuels

*Nature, 447, 982 (2007)

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Hybrid routes to biofuels

*Nature, 447, 9824 (2007)

燃料電池與材料科技

*Sci. Am., Mar. 62 (2005)*Nature 414, 345 (2001)

Electrochemical reactions for various fuel cells

Type Anode Reaction Cathode Reaction

AFC H2+2OH-→2H2O+2e- 1/2O2+H2O+2e-→2OH-

PEMFC H2→2H++2e- 1/2O2+2H++2e-→H2O

PAFC H2→2H++2e- 1/2O2+2H++2e-→H2OPAFC H2 2H 2e 1/2O2 2H 2e H2O

MCFC H2+CO32-→H2O+CO2+2e- 1/2O2+CO2+2e-→CO32-

SOFC H2+O2-→H2O+2e- 1/2O2+2e-→O2-

DMFC CH3OH+H2O→CO2+6H++6e- 3/2O2+6H++6e-→3H2O

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PEM Fuel cell

a) PEM fuel cell, with current connection, membrane (PEM), carbon-supported catalyst, and gas diffusion layer (GDL). b) Crosssection of a membrane electrode assembly (MEA), SEM image of a standard MEA, with platinum nanoparticles on Vulcan XC72, and a Nafion membrane as standard PEM.

*Aangew. Chem. Int. Ed. 48, 9230 (2009).

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*Sci. Am., Apr. 81 (2007) *Nature 414, 353 (2001)

The Photovoltaic Effect 光生電流程序

Schottky junction and single layer PV device

Energy diagram of a metal1/semiconductor/metal2 Schottky barrier under open circuit conditions, when the metals have different work functions (workfunction, vs electron affinity; IP ionization potential; Eg bandgap,W depletion width). Charge generation process in a single layer PV device under short circuit conditions in the MIM model. VB valence band, CB conduction band, Egbandgap, P+, P- positive and negative polarons.

Photovoltaic device efficiency

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太陽能電池功率效率 太陽能電池效率

Roll-to-roll process for thin-film solar cells Solar Emission Spectrum

Absorption coefficients for various semiconductors 太陽能電池電費 cost down

*Science 319, 718 (2008)

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太陽能電池電費 cost down

*Science 285, 692 (1999)

Solar electricity cost and efficiency

*Science 315, 798 (2007)

光化學太陽能電池染料敏化太陽能電池

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Principle of Photoelectrochemical cells

*Nature 414, 338 (2001) *Nature 451, 652 (2008).

Batteries, Fuel Cells, and SupercapacitorsRechargeable battery systems

Energy storage capability of battery system電池發展歷程

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二次電池分類與特性

小型二次電池特性

EV二次電池特性

二次電池材料組成 二次電池應用

鋰離子二次電池原理 鋰離子二次電池組成材料

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鋰離子二次電池組成材料 鋰離子二次電池正極材料

鋰離子二次電池負極碳材結構

Criteria for Li+ intercalated anode:

•High Li+ intercalation capacity

•High effective dischargeable capacity

•Little expansion/shrinking on charging/discharging

圓筒型與角柱型鋰離子二次電池

鋰離子二次電池優點

• High energy density: 300~320 Wh/dm3; 125~130 Wh/kg• High output potential: 4.1~4.2 V(initial); 3.6~3.7

V(average); 3 times of Ni-Cd & Ni-MH• No memory effect• Wide use temperature range

L lf di h t 10% i th h lf f Ni Cd &• Low self discharge rate: ~10% in month; half of Ni-Cd & Ni-MH

• Long cycling life• High charging/discharging efficiency• Fast charging speed• Easily indicative existing capacity• Maintenance free

鋰離子二次電池缺點

• High resistance due to use of non-aqueous electrolyte and lack of large current capacity– To enlarge electrode area by coating active materials on

electrode

• Breakdown from excessive chargingg g– A control circuit to prevent excessive charging in a battery pack

• Deterioration from excessive discharging– A control circuit to prevent excessive discharging in a battery

pack

• Three times higher cost than Ni-MH– Substitute LiCoO2 cathode material with LiNiO2 or LiMn2O4

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Nanomaterials used in the batteriers Organic batteries from biomass

Lithium-air batteries 3D lithium-ion battery

Ragone plot for electrical energy storage devices

Specific power against specific energy, also called a Ragone plot, for various electrical energy storage devices. If a supercapacitor is used in an electric vehicle, the specific power shows how fast one can go, and the specific energyshows how far one can go on a single charge. Times shown are the time constants of the devices, obtained by dividing the energy density by the power.

*Nature Mater. 7, 815 (2008)

Electric double layer carbon supercapacitores

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Properties of Carbon supercapacitors

*Chem. Soc. Rev., 38, 2520 (2009)

Carbon structure for double layer capacitors

Pseudocapacitore (Redox capacior)

C = d(q)/d(V)

Improvement of electrochemical capacitors

Thermoelectric devices

*Nature 413, 517 (2001)

Thermoelectric devices

*Naure Mater. 7, 105 (2008)

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Figure-of-merit zT of thermoelectric devices Crystal structure with low lattice thermal conductivity

Thermophotovoltaics

Semiconductors that convert radiant heat to electricity may prove suitable for lighting remote villages or powering automobiles.

*Sci. Am. Sep. 18 (1998)

未來能源技術- Plan B for energy

If efficiency improvements and incremental advances in today’s technologies fail to halt global warming, could revolutionary new carbon-free energy sources save the day? Don’t count on it—but don’t count it out, either.

*Sci. Am., Sep. 102 (2006)

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Biofuels from Algae 核融合技術

Space-based solar energy A Global supergrid

Revolutionary energy sources need a revolutionary superconducting electrical grid that spans the planet “ A basic problem with renewable energy sources is matching supply and demand,” Hoffert observes. Supplies of sunshine, wind, waves and even biofuel crops fade in and out unpredictably, and they tend to be concentrated where people are not. One solution is to build long distance transmission lines from superconducting wires. When chilled to near absolute zero, these conduits can wheel tremendous currents over vast distances with almost no loss. In July the BOC Group in New Jersey and its partners began installing 350 meters of superconducting cable into the grid in Albany, N.Y. The nitrogen-cooled link will carry up to 48 megawatts’ worth of current at 34,500 volts. “We know the technology works; this project will demonstrate that,” says Ed Garcia, a vice president at BOC. At a 2004 workshop, experts sketched out designs fora “SuperGrid” that would simultaneously transport electricity and hydrogen. The hydrogen, condensed to a liquid or ultracold gas, would cool the superconducting wires and could also power fuel cells and combustion engines. With a transcontinental SuperGrid, solar arrays in Australia and wind farms in Siberia might power lights in the U.S. and air conditioners in Europe. But building such infrastructure would most likely take generations and trillions of dollars.

科幻能源技術