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News & Analysisphysicsworld.comInnovationSpin-out puts new spin on wind-energy technologyThe future of wind energy could in -volve huge blades spanning half akilometre that generate compressedair – which is then piped into giant,underwater balloons. That is thedream of Seamus Garvey, a mechan -ical engineer at the University of Not -tingham in the UK, who envisagesusing the pressurized air to inflatethe balloons, nestling about 500 mbelow the surface of the sea. Elec tri -city could then be generated, when re -quired, by releasing the air to drive aset of turbines.The advantage of Garvey’s techniqueis that several days’ worth ofenergy could be stored in the balloonswhile the wind is blowing – and thenreleased when there is no wind. Gar -vey has just formed a spin-out companycalled NIMROD Energy tocommercialize the technology, dub -bed Integrated Compressed Air Re -newable Energy Systems (ICARES),which he has been working on since2006. He has also received a 7310 000development grant from the energycompany E.ON.According to Garvey’s blueprint,the wind turbine’s blades would behollow and contain an internal piston.When the blade is pointing downwards,the piston is at the tip. As theblade slowly lifts skywards, the pistonChina has announced plans to generatean extra 100 GW of power from nuclearreactors – a 12-fold increase in nuclearcapacity. The plans, released in lateMarch by the Energy Bureau of theChinese National Development andReform Commission (NDRC), will see anadditional 75–80 GW of nuclear powercoming online by 2020, with a further25 GW of capacity still under constructionat that time. If the country completes itsplan, then nuclear power will accountfor about 5% of China’s electricity needsby 2020.Last year, nuclear power capacity inChina was 9.08 GW, accounting for only1.04% of the total power generation inthe country, according to the ChinaElectricity Council, which implementsgovernment energy policy. Original plansby the NDRC, published in October 2007,announced that China would increase itsfalls through the cylinder, compres -sing air. However, the blades must notrotate too fast or else the pistons willget pinned to the ends of the blades.Given that a blade’s rotation speed isinversely proportional to its length,Garvey’s scheme would only be practicalfor turbines bigger than about230 m in diameter, with 500 m beingthe ideal size.As for the storage balloons, Garveysays they should ideally be 20 m indiameter and lie anchored 500 mbelow the surface of the sea. He hasal ready begun to test prototype “en -ergy bags” and believes that that acommercial undersea storage systemwill be available by May next year.EnergyChina plans massive nuclear boost8Power to the peopleOne of two 1.75 GWEuropean PressurizedReactors that China isbuilding in TaishanCity, near Hong Kong.Bags of energySeamus Garvey fromthe University ofNottingham hasdesigned a way ofstoring wind energy inunderwater balloons.nuclear power capacity by 40 GW by2020 with a further 18 GW inconstruction. The revised plans almostdouble those figures.“We will be building as many as six toeight 1 GW nuclear power plants eachyear,” says Mu Zhanying, general managerof Chinese National Nuclear EngineeringGroup Company. Chinese authorities haveUniversity of NottinghamChina Guangdong Nuclear Power GroupAlthough Garvey believes that it willtake about 15 years to get the giantturbines up and running, he says hissystem could be as cheap to build as agas-turbine generator and have zerofuel costs.Compressed-air energy storage isnot a totally new idea. There are twofacilities – one in Germany and theother in the US – where surplusenergy is taken off the electrical gridand used to pump air undergroundinto disused salt mines. But Garveysays that underwater storage has twobenefits. It is not restricted to minelocations, plus the pressure in an un -dersea bag is constant, which lets turbinesgenerate electricity relativelyefficiently. An underground storagefacility, in contrast, has a fixed volume,meaning that the air pressuredrops as air is released.Garvey also thinks undersea bagscould store surplus energy from nuc -lear reactors or even natural gas.Jakob Mann, a wind-energy expert atRisø National Laboratory in Den -mark, says that the storage techniqueis “worthwhile trying” but warns thatthe undersea nature of the schemecould boost the cost. “Offshore is al -ways expensive,” he says.Hamish Johnston● See also page 14identified 30 possible sites that canaccommodate nuclear power stations.China is already building the world’slargest single nuclear power plant inTaishan City, on the southern coast of thecountry, close to Hong Kong. The 1.75 GWTaishan nuclear plant, costing $4.7bn, isthe first of two European PressurizedReactors to be built at Taishan and isexpected to come online in 2013, with thesecond following in 2014. Indeed,Sun Youqi, general manager of ChineseNational Nuclear Engineering GroupCompany, says that China is alreadybuilding more nuclear power capacitythan any other country in the world.However, some worry about China’sability to deal with nuclear-fuelreprocessing and high-level radioactivewaste once the reactors are operating.“We need to pay far more attention nowto researching techniques into fuelpost- processing”, says Li Yongjiang, theformer manager of the Qinshan NuclearPower Company.Jiao LiBeijingPhysics World May 2010