氣候變化與新能源(Climate change and New Energies)_圖文

1、Climate change and New EnergiesCarlo RubbiaInstitute for Advanced Sustainability StudiesPotsdam, GermanyCERN,Geneva, SwitzerlandBeijing_Nov20101Innovation: the key to a successful developmentIn order to reconcile sustainable development and economic growth with the threat of environmental decay cohe

2、rent strategic choices have to be made, relaying on truly innovative scientific and technological developments.The huge progress in the fields of Solar, Wind, Biomass and Geothermal energies does not need to be here further discussed.In this short presentation some other tentative, novel, new and pe

3、rhaps less known developments will be briefly described: 1.Energy production from fossils without CO2 emissions, as analternative to Carbon Capture and Sequestration (CCS. 2.Recovering the vast amounts of already accumulated CO2 togenerate a liquid substitute to Oil. The “Methanol economy”.3.Unconve

4、ntional, huge resources of Natural Gas fromClathrates.4.An almost inexhaustible novel Nuclear Energy from Thorium.Energy production from fossils without CO2 emissionsThe consequences of Climate Changes are irreversible Anthropogenic CO2 and other emissions and their predictable effects on the climat

5、e changes are a major concern: it is therefore necessary to develop new solutions for curbing the growing combustion of fossils,and the related CO2 emissions.The idea that anthropogenic CO2 releases will affect the climate of the earth for hundreds of thousands of years has not reached general aware

6、ness of the public and of the scientific community.Residual amounts of fossil C :17-33% after 1000 years1015% after 10000 years7% after 100000 yearsResidual, for everPre-industrialCO2 sequestration: but 1000 years ?An alternative: burning Natural Gas without CO2 emissions?The ordinary combustion of

7、Natural Gas (NG implies the production of vast amounts of CO2.A way of temporarily removing the CO2 from the atmosphere is to concentrate and sequester it either under the ocean or underground (CCS for a long time (?. A very significant amount of additional energy is however wasted in the process.An

8、 alternative process is however possible in which NG conversion into H2 is made without CO2 emissions, namely:CH4 2H2 + C.This is the pyrolysis or spontaneous thermal decomposition (TDM at high temperatures of NG into H2 and black solid carbon. The energy is then generated by burning the H2.The blac

9、k carbon can kept sequestered or eventually sold on the market as a material commodity, or reduce costs by marketing the carbon as a filler or construction material.CH 4 => H 2 conversion in an empty, hot tubeCH 4+heat at 1600 °C "C +2H 2Passing through a hot tube, CH 4 quickly splits s

10、pontaneously into hydrogen and black carbon.The process can be performed at lower temperatures with the help of Catalysers A plasma torchThe idea The process is extremely fast,milliseconds !10 msComparing reforming and pyrolysis of NG for H2 productionStandard process Thermal PyrolysisH2 Plasma Blac

11、k C Reactor (KVAERNER ENGINEERINGThe plasma-arc process separatesat temperatures of 1600°C,hydrocarbons into pure carbon andhydrogen. with cooling water andelectricity.A pilot plant produces about 500kg/h pure carbon (carbon blackand 2000 Nm3/h hydrogen from1000 Nm3/h natural gas (37.08GJ/h and

12、 2100 kWel (7.56 GJ/h.and 1000kW high temperaturesteam.The next step is the planned constructionof a plant capable of producing a yearlycapacity of 120 x 106 Nm3 H2 and a costestimated to be somewhere in thevicinity of 300 Mil DM.A liquid substitute to Oil The “Methanol economy”The inevitable risks

13、of a future Oil crisisOil will not be exhausted current reserves representing many years worth of supply but market forces will inevitably drive prices up as demand surpasses supply, creating a true and lasting Oil crisis of incalculable and even dramatic economic consequences.We must prepare adequa

14、tely to alternatives especially for transport, which today is the most Oil dependent (97% sector of our economy, together with industry (42% on Oil.New ways must be envisaged with the associated goal of de-carbonization, in order to avoid the “business as usual”alternative of extracting in the futur

15、e massively the needed Oil from shales, tar sands, heavy oils, Coal based liquids which will vastly multiply the CO2 emissions. In our view the necessary future substitute to Oil for transport must be liquid, containing primarily H2,O2 and CO2Fossil methanol from H 2 and CO 2The most promising alter

16、native in this respect is what has been called the “methanol Economy ” which combines the use of H 2produced by some mean of cleavage through the process from already spent CO 2 and H 2 : CO 2+3H 2 -> CH 3OH+H 2O.Methanol is a convenient liquid fuel for transportation.Methanol can also be readily

17、 converted into many other chemicals like ethylene, propylene and others.Hydrogen production in turn is an important chapter, especially from Natural Gas,in three main ways: the classic steam reforming CH 4+2H 2O -> CO 2+4H 2, which however produces CO2, the “coking process ” with no CO2 emission

18、s: CH 4 -> C+2H 2and formation of solid Black Carbon. A third alternative could be direct transformation of the bi-reforming of Olah et al. 3CH 4+2H 2O+CO 2 -> 4CH 3OH.Transforming CO2 from a liability to an assetspent CO2 recoveryMethanol derived chemical products (OlahIn practice, allchemica

19、lproductsassociated toOil may be alsoproduced fromMethanolNew unconventional sources ofNatural GasExpanding the exploitation of NG with new sourcesThe process of progressive de-carbonization of fossils goes necessarily through an increased use of methane.Methane it is the fossil fuel with the highes

20、t de-carbonization, whose full combustion produces 2.5 times less CO2 than coal for the same energy.But how can we increase the future availability of NG ? Beside the conventional supply of NG, it is worth underlying that there are extremely vast quantities of methane trapped in the form of oceanic

21、hydrate deposits, called clathrates.As already pointed out, if associated with the alternative process in which methane is converted into hydrogen and black carbon, we should be able to achieve the “dream” of burning fossils without additional CO2 emissions.Clathrates ?Methane hydrate is the most ab

22、undantnatural form of clathrate, a uniqueclass of chemical substances in which molecules of one material (in this case, water form an open solid lattice that encloses, without chemical bonding, appropriately-sized molecules ofanother material (in this case,methane.While it is stable at a temperature

23、 ofup to around 0°C, at higher pressures methane clathrates remain stable up to18 °C. One litre of methane clathratesolid would contain, on average, 168litres of methane gas (at STP.“Burning ice"Natural Gas production from Clathrates ?The subject appeared to be purely academic until r

24、ecently when scientists realized that, given the ubiquity of both methane (the common by-product of bacterial breakdown of organic matter and water in nature, methane hydrate could be present in vast quantities in any environment with suitable pressures and temperatures.Methane clathrates are common

25、 constituents of the shallow marine geosphere and they occur both in deep sedimentary structures, and as outcrops on the ocean floor.The potential amount of methane in natural gas hydrate is enormous, with current estimates converging around a conservative value of about 10000 Gigatons of methanecar

26、bon. 40 times NGAs a comparison the total estimates for conventional Natural Gas and Oil are of the order of a few hundred Gigaton.Locations where clathrates have been observed Reservoirs of methane, located globally within 2000 m of the solid surface and observed in a large number of locations are

27、of major interest as a potential novel energy resources.Thorium:an almost inexhaustible new energy from NucleiNew Nuclear EnergiesAlthough the exact amount of exploitable Uranium ores are not exactly known and depend on the lowest levels of recovery, as long as used with todays methods and at the pr

28、esent level of consumption (6.5 % of primary energy, there are probably left no more reserves of Uranium than of Oil and Gas.Particularly interesting are fission reactions without U-235 in which a natural element is firstly bred into a fissionable one.These sources of energy available from exploitab

29、le ores are comparable to the one for the D-T fusion reaction (ITEREnergies from nucleifor many millenia to comeHow much Thorium is available?Thorium, (Th-232 is a huge but unexploited energy resource. The total abundance is estimated to be 120 Trillion tons, i.e.1.2 x 1014 tons. Soil commonly conta

30、ins an average of around 6 parts per million (ppm of Thorium. The Monazite black sand deposits are composed from 2 to 22 percent of Thorium.Estimates of available Th resources vary widely. The 2007 IAEA-NEA publication Uranium 2007: Resources, Production and Demand gives 4.4 x 106 tons of known Th r

31、esources, but this excludes data from much of the world.For instance China produces 120 kton/year of Rare Earth Metals (REEs, with 12 kton/year of recoverable Th “waste”.With well designed Th burners the 2007 electricity of China(3.2 Trillion kWh requires burning only 443 ton/year ofTh.2008 Figures

32、from the US Geological Survey give for China8.9 x 107 ton of REE basic reserves, adequate for 20000 years of today Chinas Th electricity and no import reliance.Main features of a breeder.In a pure Th breeder reactor, two neutrons are required in order to close the energy producing cycle namely: One

33、neutron is transforming the initial element into the fissionable one, through the chain Th 232Pa 233U 233A second neutron is required to fission the U-233 with production of energy and of new neutrons:Thermal Fast = 2L-Na Resonance region Molten salts Several alternatives for Th232/U233L-PbOnly Fast

34、 n for U238/Pu239Practical alternativesThe very small excess above the two needed neutrons makes the standard operation as a critical reactor practically impossible, due to the presence of growing neutron losses due to finite reactor size, the emergence of capturing fission products, fuel cladding a

35、nd so on. Two solutions are possible: One can maintain criticality with the help of continuouson-line reprocessing of the fuel and an adjacent chemicalplant on-line.One can close the sub-critical cycle adding the missingneutron contribution with an external source. This isachieved with a particle ac

36、celerator (ADS system.Practical ADS scenarios are under active consideration:A fast neutron driven ”Energy Amplifier“, where ordinaryfuel pins are cooled in a molten metal, i.e. Pb, Pb-Bi or Na.A “molten salt Liquid Fluoride” Fuel: LiF, BeF added toactinide (Th,U-233 fuel from 6,5% to 20 %.Accelerat

37、or driven congurationsEnergy Amplifier: Fast neutron on Pb Molten salt: Liquid Fluoride FuelThe Thorium driven sub-critical systemClosed loopFuel flowShort half-lives of nuclear waste and Fuel reprocessingAn uninterrupted operation of about 10 years, in whichthe only waste are Fission fragmentsTheir

38、 radio-activity of the material isintense, but limited to some hundredsof years.Actinides are recovered withoutseparation and are the “seeds” of thenext load, after being topped withabout 10 ÷ 15 % of fresh breedingelement (Th or U-238 in order tocompensate for the losses ofelement.A small frac

39、tion of Actinides is notrecovered and ends with the “waste”The cycle is “closed” in the sense that the only material inflow is the natural element and the only “outflow” are fission fragments.OrdinaryPWRTh-basedEA cycleMagneticFusionWaste may return to the environmentComparing alternativesTo continu

40、ously generate a power output of 1GW electric for one year requires:200 tonnes of Uranium Low CO 2 impact but challenges with reprocessing very long-term storage of hazardous wastes Proliferation Enrichment 3,500,000 tonnes of coalSignificant impact upon the Environmentespecially CO 2 emissions PWR

41、1 tonne of Thorium Low CO 2 impact Can eliminate Plutonium and radioactive waste Reduced quantity and much shorter duration for storage of hazardous wastes No enrichment No proliferationIn short:Item Thorium breeder Safety Not critical, no meltdown Credibility Proven at zero powerFuel Natural ThoriumFuel Avail