ChemicalChallengesinRenewableenergy在可再生能源化工的挑战

1、Mean global energy consumptions Total 13.8 TW, US 3.3 TW, Italy 0.25 TW The less expensive fossil sources represent the lions share! Than it appears that renewable resources will not play a large role in primary power generation unless, or until: . Cost breakthroughs in carbon-free technologies are

2、achieved. . Externalities are introduced , such as environmentally driven carbon taxes. Actually also if there are reassuring resources of fossil fuels, geopolitical and regional factors can affect significantly the price of energy. Can we supply the energy needed in the future with fossil fuel? Qui

3、te probable yes. Current global energy consumption = 13.8 TW By 2050 consumption = 25 TW. Need abot 10 TW. Fossil fuels: Can produce extra 10 TW only at risk to environment. Wind/Geothermal/Biomass/Hydroelectric: Cannot produce 10 TW. (But should be implemented where appropriate: energy is extensive

4、) Nuclear: Requires massive investment today to provide power plant infrastructure (10 TW = 10,000 new 1 GW reactors, in 50 years). The employment of geological reservoirs is potentially feasible but it arises problems for maintaining a low rate of of CO2 leaking. Besides for the cost of plants and

5、infrastructures an increase of expences of 15% is predicted. In conclusion it appears to be a promising option with uncertainties in his : technical and economical ASPECTS. Carbon dioxide sequestration Renewable The total rate (TW) is shared between different categories: -hydroelectric 0.3 pv=1.5 -g

6、eothermal 0.03 pv=12 -eolic 0.074 pv=7 -biomass 1.3 (+) -solar 0.03 pv= 600 (+) due to the low efficiency of photosynthesis about 17% of the of the terrestrial area land is required to produce 10TW. Light Fuel Electricity Photosynthesis Fuels Electricity Photovoltaics H O OH 2 22 sc M e sc e M CO Su

7、gar H O O 2 2 2 Semiconductor/Liquid Junctions conversion strategies Solar energy appears to be the only source able to supply 10-20 TW carbon-free power needed at 2050. What is the area needed to generate the required power? -The full energy consumed in the world can be produced in a tropical land

8、with a squared area with a side of 500 Km . -The present energy employed in Italy can be produced in a land area with a side of 60 Km -It is sufficient to cover about 0.17 % of the territory. Solar is expensive Typical levelized cost by source 0 10 20 30 40 50 SolarCoalNuclearGasWindOil 25-50 2-4 2-

9、7 4-6 2-6 6-8 (US cents/kWh) Solars typical range of 25-50 cents/kWh is much higher than other sources It competes with grid price not generator cost 4 4 7 9 13 17 18 25 0102030 China India South Korea US UK Germany Italy Japan Average residential grid price (US cents/kWh) Much easier to compete wit

10、h grid price than generation cost. Silicon technology dominates the market: 93% for crystalline Si (single-, multi-, poly-, nano-) Market share for Si and thin film technologies were continuously decreasing during last 10 years Market share by technology 10 Prices and predictions of photovoltaic mar

11、ket Module efficiencyLab scale Max efficiency HIT heterojunction intrinsic thin film Many different technologies on the market rushing for high efficiency & low costs Shockley-Queisser analysis (1961) It is based on four assumptions: 1- single p-n junction 2- one electron-hole pair excited for incom

12、ing photon 3- thermal relaxation of the electron-hole pair energy in excess of the bandgap 4- illumination with unconcentrated sunlight Maximum yield of 31% is obtained. S-Q limit can be exceeded by violating one or more of its premises. A- Intermediate-band solar cells B- Quantum-well solar cellsl

13、C-Multiple junctions cells C C Employment of organic materials LUMO=Lowest Unoccupied Molecular Orbital HOMO=Highest Occupied Molecular Orbital XSC : Exciton Solar Cells Unsaturated Molecoles and fullerenes for : - harvesting solar radiations -to give rise to a fast charge transfer -to limit the ret

14、urn to the ground state Plastic Cells: Scale-up using Roll-to-Roll Techniques Printed or coated inexpensively on flexible materials using roll-to-roll manufacturing Can be produced with varying degrees of translucency so that it is customized for specific markets Environmentally friendly Easily scal

15、ed up Utilizes wide spectrum of light 16 Solar electricity cost as a function of module efficiency . I- Wafers of silicon. II- Thin films of amorphous silicon , tellurides, selenides III- Research goals: carrier multiplication, multiple junctions, sun light concentration, new materials (organic). Si

16、licon Si Eg = 1,1 eV Gallium Arsenide AgAs Eg = 1,5 eV Titanium Dioxide TiO2 Eg = 3,2 eV TiO2 fulfils the requirement but it absorbs only the ultraviolet radiation, that is only 3% of the available solar energy. SC semiconductor (photocatode) M metal (anode) Water photodissociation occurs if h2.97 e

17、V Photoelectrochemistry (Photo)chemical Water Splitting: 2 H2O O2 + 2H+ + 2e- +H2 Operation principles of a dye-sensitized mesoporous heterojunction solar cell. (Gratzel) Gray dots : mesoscopic oxide particles covered with a monolayer of dye. The development of energetic technologies arises new and

18、stimulating challenges for chemical sciences : -Complex systems including many degrees of freedom .What is the real cost of the silicon solar energy? .How important will the burning of coal be to global warming? - Chemistry of small molecules, implied in: . Atmospheric chemistry . Combustion .New fu

19、el synthesis. .Excitaction and transfer of electrons. - Chemistry of CO2 involving: .New applications on large scale processes -Design of new catalytic systems , involved in energy production, such as. .Activation of methane to methanol CH4 + (1/2)O2 CH3OH .Photoreduction of CO2 to methanol CO2 + 6H

20、+ +6e- CH3OH .Improvement of the slow catodic processes reactions .Fuel cells operating with metanol CH3OH + H2O CO2 + 6H+ + 6e- Hydrogen Methanol Syncrude Olefins Chemicals Dimethhyether (DME) Fuels Naphta Diesel Jet Fuel Lubricants Ammonia Refinery products CO+2H2 (Synthesis gas) Existing routes v

21、ia syngas Prospective direct routes being researched The discover of new catalytic systems opens important perspective in the synthesis of new fuels. A secure energy future depends on wether chemists will discover efficient catalysts for the production of alternative fuels . Photosyntesis has immens

22、e appeal for the closed cycle capture of energy from the sun. The prospect of non biological photosyntesis , that is through bio-inspired chemical reactions , deserves new research. Photosynthesis Two massive protein complexes split water and carbon dioxide and forge new energy-storing bonds in suga

23、r molecules. How to design photosyntetic systems with artificial reaction centers? Biominspired approach (BP) -Chemical Antenna for harvesting solar energy -Chemical Structure able to transfer the excited electron at fast speed.(0,1-1 ns) ET photosyntesis BP interfaces Gas-solid (PV) Liquid-solid Re

24、levance of electron transfer processes ET Interdisciplinary approach including physics,chemistry ,biology and engineering, aimed to design and build simplified biological catalytic systems with high efficiency. In nature the metabolic pathways are connected in complicated networks that have evolved

25、for organisms survival and reproduction and not for fuel production. The relevant steps might be isolated and connected directly to produce fuels such as hydrogen, methane and alcohols. Post petroleum economy. Syntetic Biology Craig Venter : Science on line, july 2007 The genome of one bacterium has

26、 been succesfully replaced with that of a different bacterium. Then synthetic biology seems to make possible new cell functions by fusing existing genomes. Fall out on energy problems: To develop an anaerobic species that will digest cellulose into To develop an anaerobic species that will digest ce

27、llulose into ethanol , thus generating a fuel from biomass.ethanol , thus generating a fuel from biomass. From the analysis of the carbon free options it comes out that: -Fossil fuelsFossil fuels are penalized by carbon dioxide sequestration -Nuclear fissionNuclear fission requires high investiments

28、 and nevertheless it does not yet represent an alternative to fossil fuels, unless new technological breakthrogh will emerge -Eolic, geothermic and biomassEolic, geothermic and biomass energies can only give an integrating support to the wide incoming energy requirements -Solar energySolar energy is

29、 promising but it requires a deep transformation of the energy system Though it be honest, it is never good to bring bad news. (Shakespeare) Stabilization triangle divided in sectors each of one corresponding to an advisable reduction of the emitted carbon. Big importance is attributed to the improv

30、ement of efficiency! Conclusions External limitations on carbon dioxide emissions imply the adoption of precautions that will be introduced through the adoption at local level of a mix of different carbon free technologies in a mutual integrated system ( energy saving, increase in the employment of

31、natural gas instead of carbon, increase of renewable sources, nuclear, .) THE ENDTHE END THANK YOUTHANK YOU The employment of geological reservoirs is potentially feasible but it arises problems for maintaining a low rate of of CO2 leaking. Besides for the cost of plants and infrastructures an incre

32、ase of expences of 15% is predicted. In conclusion it appears to be a promising option with uncertainties in his : technical and economical ASPECTS. Carbon dioxide sequestration Light Fuel Electricity Photosynthesis Fuels Electricity Photovoltaics H O OH 2 22 sc M e sc e M CO Sugar H O O 2 2 2 Semiconductor/Liquid Junctions conversion strategies Solar energy appears to be the only source able to supply 10-20 TW carbon-free power needed at 2050. Silicon technology dominates the market: 93% for crystalline Si (single-, multi-, poly-, nano-) Market share for Si and thin film technologies wer