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博主胡德良:邢台学院外语系英语教授,中国译协专家会员,河北省译协常务理事,邢台市译协副会长。爱好翻译,内容涉及宇宙探秘、医疗卫生、家庭保健、生命科学、能源科学、地球科学、环境科学、散文小说和纪实文学等领域。所译文章曾见于《光明日报》、《科技日报》、《健康时报》、《健康报》、《英语世界》、《英语知识》、《科技英语学习》、《科学之友》、《科学与文化》、《世界科学》、《生命世界》等全国各大报刊。博客特色:英汉对照、图文并茂,融趣味性、科学性、知识性为一体。

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太阳能发电的另外一种方法(图)  

2009-10-06 15:54:50|  分类: 尖端科技 |  标签: |举报 |字号 订阅

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Energy: Think of solar power, and you probably think of photovoltaic panels. But there is another way to make electricity from sunlight, which arguably has even brighter prospects

提到太阳能,你很可能会想到光伏板。然而,还有另外一种利用太阳能发电的方法,根据论证,该方法有着更加光明的前景……

太阳能发电的另外一种方法(图) - 月亮飞船 - 月亮飞船的博客

西班牙塞维利亚附近的太阳能发电塔。

太阳能发电的另外一种方法(图) - 月亮飞船 - 月亮飞船的博客

来自抛物槽系统的电力

The other kind of solar power

Jun 4th 2009

From The Economist print edition     胡德良

 

IN THE past few months BrightSource Energy, based in California, has signed the world’s two largest deals to build new solar-power capacity. The company will soon begin constructing the first in a series of 14 solar-power plants that will collectively supply more than 2.6 gigawatts (GW) of electricity—enough to serve about 1.8m homes. But to accomplish this feat BrightSource will not use photovoltaic cells, which generate electricity directly from sunlight and currently constitute the most common form of solar power. Instead, the company specialises in “concentrating solar-thermal technology” in which mirrors concentrate sunlight to produce heat. That heat is then used to create steam, which in turn drives a turbine to generate electricity.

 在过去的几个月中,加州的亮源能源公司签署了世界上最大的两笔太阳能生意,准备扩大太阳能产量。该公司很快就要建造14个太阳能发电连锁站中的第一个电站,这些发电站建成投产后供电总量将达到26亿瓦特,足够大约180万家庭之需。光伏电池可以直接通过阳光来发电,是最为常见的一种太阳能形式。然而,为了完成这一壮举,亮源能源公司将不再使用光伏电池,相反,该公司深入研究了“太阳热能集中技术”——利用镜面将阳光集中起来,以便产生热能,然后利用热能产生蒸汽,再利用蒸汽驱动涡轮机来发电。

 Solar-thermal power stations have several advantages over solar-photovoltaic projects. They are typically built on a much larger scale, and historically their costs have been much lower. Compared with other renewable sources of energy, they are probably best able to match a utility’s electrical load, says Nathaniel Bullard of New Energy Finance, a research firm. They work best when it is hottest and demand is greatest. And the heat they generate can be stored, so the output of a solar-thermal plant does not fluctuate as wildly as that of a photovoltaic system. Moreover, since they use a turbine to generate electricity from heat, most solar-thermal plants can be easily and inexpensively supplemented with natural-gas boilers, enabling them to perform as reliably as a fossil-fuel power plant.

 跟光伏太阳能工程相比,太阳能热电站有好几个优点。太阳能热电站的建造规模通常要大得多,而且从历史上来讲,这种发电站建造成本也低得多。一家研究公司——新能源财经公司的纳撒尼尔·布拉德说:比起其他的可再生能源,太阳能热电很可能是公用事业单位电力负荷的最佳匹配。当天气最热、电量需求最大的时候,太阳能热电站的发电效率也最高。而且,太阳能热电站所产生的热能可以存储,所以其产量不象光伏发电系统波动得那么剧烈。此外,由于这种发电站通过热能驱动涡轮机来发电,多数太阳能热电站可以轻而易举地安装上天然气锅炉,花费也不大,然后就可以象化石燃料发电厂那样可靠地运行了。

 Besides these benefits, the main drivers for the growth of the solar-thermal industry are moves to limit carbon-dioxide emissions and requirements to increase the proportion of electricity produced from renewable sources. According to New Energy Finance, about 12GW of concentrating solar-thermal power capacity is being planned worldwide—a vast amount, given that only about 500 megawatts (MW) of such capacity has been built to date. To maximise the energy that can be collected from the sun, solar-power facilities are being constructed in regions that enjoy daily uninterrupted sunshine for much of the year. According to Mark Mehos of America’s National Renewable Energy Laboratory, solar-thermal power could in theory generate 11,000GW in America’s south-west. That is about ten times America’s entire existing power-generation capacity.

 除了上述优点之外,发展太阳能热电产业的主要促进因素是:要采取行动限制二氧化碳的排放,也需要提高利用可再生能源进行发电的比例。根据新能源财经公司提供的数据:在全球范围内,正在计划之中的、通过集中太阳热能进行发电的产量大约为120亿瓦特。鉴于到目前为止太阳能热电产量仅为大约500兆瓦特,计划中的产量是巨大的。为了使取自太阳的能量最大化,太阳能设施正在建设于那些在一年当中多数日子里阳光可以持续照射的地区。美国国家可再生能源实验室的马克·梅霍斯称:从理论上讲,美国西南部的太阳能热电产量可达11万亿瓦特。这个电量大约相当于美国目前发电总量的10倍。

 Simple techniques for concentrating sunlight to generate heat date back thousands of years. In China and ancient Greece, people focused the sun’s rays with mirrors or glass to light fires. In times of war, the same approach is said to have been used to set enemy ships ablaze. By the early 20th century several scientists had built simple machines that could run on concentrated heat from the sun.

 利用集中太阳光来获取热量的简单技术可以追溯到几千年以前。在古代中国和古希腊,人们曾经利用镜子或透镜来聚集太阳光线,以此来点火。据说在战争时期,同样的办法曾经用来点燃敌人的战船。到20世纪初期时,几位科学家制造了简易的机器,这些机器可以靠集中起来的太阳热能来运行。

 A significant milestone was reached in 1913 when Frank Shuman, an American inventor, created the first large solar-thermal pumping station in Meadi, Egypt. He designed a system based on five large reflectors, each 62 metres long and made of glass mirrors arranged to form a trough in the shape of a parabola. Each parabolic trough focused sunlight onto a tube running along its length, heating the water inside it. The resulting steam powered an engine connected to a pump capable of delivering 6,000 gallons of water a minute from the Nile to nearby fields.

 1913年是一个重要的转折点。美国的发明家弗兰克·舒曼在埃及的米阿迪(Meadi)建造了第一座大型的太阳热能抽水站。他设计的系统以五个大型的反光镜为基础,每个反光镜长62米,是由砌成抛物槽状的玻璃镜做成的,每个抛物槽式的反光镜都将阳光聚集在跟抛物槽等长的一根管子上,致使管子内的水升温,形成的水蒸汽驱动一个跟水泵连接的发动机,该水泵每分钟可以把6000加仑的水从尼罗河中抽到附近的田野里。

 Do try to concentrate

 想方设法集中能量

 The modern history of solar-thermal power began after the oil crises of the 1970s, which prompted many nations to start to investigate clean and renewable energy sources as alternatives to fossil fuels. Over the following decades America, Spain and a handful of other countries built solar-thermal pilot plants for research purposes. The first company to implement the technology on a commercial scale was Luz International, an Israeli company founded in 1980.

 20世纪70年代爆发了石油危机之后,太阳能热电的当代史便揭开了序幕。石油危机促使许多国家开始研究可替代化石燃料的清洁能源和可再生能源。在接下来的几十年里,美国、西班牙和少数其他国家为了研究而建造了太阳能热电试验站。第一个以商业化的规模实施该技术的公司是鲁兹国际公司,这是成立于1980年的一家以色列公司。

 Drawing on prior research, Luz began building a series of solar-thermal power stations in California’s Mojave desert in the mid-1980s. Like Mr Shuman before, the company used parabolic troughs to focus sunlight on to liquid-filled tubes, but instead of water they used oil as the heat-transfer fluid. Once it reached a temperature of about 390°C, the hot oil was pumped to a so-called “power block” where it went through a series of heat exchangers, turning water into steam and powering a conventional steam-turbine. The turbine then turned a generator to produce electricity.

 20世纪80年代中期,鲁兹国际公司开始在加州的莫哈韦沙漠建造一系列的太阳能热电站。跟以前的舒曼先生一样,该公司使用抛物槽式镜面将阳光聚集在装满液体的管子里,但是他们使用的传热液体不是水,而是油。一旦油温达到大约摄氏390摄氏度时,热油就被抽到所谓的“单元机组”里,在这里热油经过一系列的换热器,把水变成蒸汽,为一个传统的蒸汽涡轮机提供动力,然后涡轮机转动一个发电机来发电。

 By 1990 Luz had constructed nine plants with a total capacity of 354MW. At the time, solar-thermal power was producing about 90% of all solar electricity in the world, says Arnold Goldman, the former chief executive of Luz, who is now chairman of BrightSource. But when the price of natural gas fell and America’s tax incentives for solar power were not renewed, the industry came to a grinding halt. For nearly two decades no new commercial solar-thermal plants began operating. In the meantime, solar-photovoltaic technology slowly took over the market, and by 2007 worldwide installed capacity reached 9.2GW. Although it is more expensive per kilowatt-hour, solar panels can be deployed in small, modular systems, and thus require much less capital investment. Moreover, they can generate power off the grid, which turned out to be an important market for solar power in its early days.

 1990年,鲁兹国际公司建造了九个发电站,总产量达到354兆瓦。鲁兹国际公司的前董事长阿诺德·戈德曼现在是亮源能源公司的董事长,他说:当时,太阳能热电约占全世界太阳能发电的90%。但是在天然气价格下降之后,美国对于太阳能没有新的税务激励措施出台,太阳能热电产业突然停产。在将近二十年的时间里,没有商业化的太阳能热电站投入运行。同时,太阳能光伏技术慢慢地占领了市场,到2007年装机容量达到92亿瓦特。利用该技术每度电的价格更高,但是由于太阳能光伏板可以安装在小小的模块化系统中,因此需要的资本投入要少得多。况且,这种技术可以在远离电网的地方发电,这些地方正是早期太阳能的重要市场。

 Now, as the solar-thermal industry is experiencing a revival, parabolic-trough projects are garnering much of today’s investment money because of their proven track record. To improve the economics still further, SkyFuel, a firm based in New Mexico, is replacing curved glass mirrors, which are expensive to make, with a thin, reflective low-cost film. And other competing solar-thermal technologies that were developed in parallel with trough-based systems, but never commercialised, are also ready to be deployed.

 现在,太阳能热电产业正在处于复苏阶段。由于历年来抛物槽式工程的效率已经得到证实,因此这类工程目前占有着大量的资金投入。为了进一步提高经济效益,新墨西哥州的天空燃料公司正在利用低价的反光薄膜来代替造价昂贵的曲面玻璃镜。有些具有竞争力的其他太阳能热电技术是跟抛物槽式系统同时开发的,但从未进入商业化运行,目前也准备投入使用。

 Among them is an approach that BrightSource uses, in which a field of small, flat mirrors called “heliostats” redirect and concentrate sunlight onto a central receiver at the top of a tower. The tower contains a fluid, typically water, which boils and the resulting steam is then transferred to a nearby “power block”, where it spins a conventional turbine. The advantage of this “power tower” approach is that it can produce steam at a temperature of 550°C and can thus achieve a higher thermal-to-electric efficiency than trough-based systems, says John Woolard, the chief executive of BrightSource. In addition, he says, power-tower systems suffer from fewer pumping losses than trough-based designs. The first commercial power-tower began operating in Spain in 2007.

 其中一项技术就是亮源能源公司使用的方法。在该技术中,一片被称为“定日镜”的小块平镜将太阳的光线反射并集中到塔顶的一个中心接收器上,塔上含有一种液体,通常为水,水沸腾后产生的蒸汽被传送到附近的“单元机组”中,在这里驱动一个传统的涡轮机。亮源能源公司的执行总裁约翰·伍拉德指出:这种“发电塔”式技术的优点在于,所产生的蒸汽温度可达550摄氏度,因此可以获得比抛物槽式系统更高的热电转换效率,此外,比起抛物槽式设计,发电塔式系统的泵损也较少。2007年,第一个商业发电塔在西班牙开始运行。

 Another advance that makes solar-thermal power more economically and technologically viable than in the past is the ability to use a large number of smaller and less expensive mirrors, steered by computer systems, to ensure more accurate and automatic tracking and redirection of sunlight than was ever possible before. Bill Gross, the chief executive of eSolar, a developer of “power tower” technology based in Pasadena, California, says his firm is using software to turn thousands of flat mirrors and shape them into a continuously evolving parabola around the tower.

 太阳能热电塔的另外一个先进之处使其在经济上和技术上比以往更为可行,那就是现在可以利用大量较小、较便宜的镜子,由计算机系统调节方向,以确保镜面能够更加准确地自动跟踪和反射太阳光线。这在以前是无法做到的。地处加州帕萨迪纳的太阳能电力公司(eSolar)是一家“发电塔式”技术的开发商,该公司的执行总裁比尔·格罗斯称:他的公司目前使用软件转动成千上万块平面镜,使它们在发电塔周围形成一个不断变化的抛物面。

 Storage and hybrids

 热能存储与混合能源

 Both power-tower and parabolic-trough systems can store thermal energy in the form of hot, molten salt. It is then possible to generate steam, and thus electricity, even when the sun is not shining. Solar-thermal plants without storage can operate about 30% of the year; but with storage that number could climb to 70% or higher. Unfortunately storage is expensive, and is only economical when regulators provide incentives. In Spain, for example, producers of solar-thermal power receive a guaranteed feed-in tariff. That makes it particularly appealing for Spanish plants to have storage capabilities, to maximise their ability to sell electricity to utilities. In America the main incentives for solar-thermal projects are a 30% investment-tax credit or an equivalent cash grant. As a result, American plants have to be built more cheaply in order to make a profit, and thus typically do not include storage.

 发电塔式系统和抛物槽式系统都可以以高温熔盐的形式存储热能,因此即使在没有太阳照射的情况下,也能够产生蒸汽来发电。在一年当中,没有热存储设施的太阳能热电厂大约可以运行30%的时间,而具有热存储设施的电厂运行时间可增加到70%或更长。遗憾的是,热存储的投资很大,只有政府管理人员提供激励措施时才能节省投资。例如,西班牙的太阳能热电生产商可以享受到有保障的回购电价补贴,这一招特别具有吸引力,使西班牙的发电厂纷纷投资于热存储能力,力求对公共事业单位的售电能力最大化。在美国,对太阳能热电项目的主要激励措施是减免30%的投资税额或等值的现金补贴。结果,美国的电厂为了获利而不得不减少投资,因此通常没有热存储设施。

 A cheaper alternative to storage is hybridisation. All the original Luz plants also have natural-gas boilers that can generate steam when the sun is not shining. Because solar-thermal plants have a power block and turbine already in place, the extra cost is marginal. Hybridisation could also be done the other way around, by using steam generated from solar-thermal collectors to help drive the turbines at existing coal or gas plants. The Electric Power Research Institute, based in Palo Alto, is studying the feasibility of this approach as a means of reducing fuel costs and emissions at existing power stations.

 热存储投资较少的一个可替代办法是利用混合能源。最初,鲁兹国际公司的所有电厂都兼有天然气锅炉,在没有太阳照射的情况下也可以产生蒸汽。由于太阳能热电厂已经装有单元机组和涡轮机,因而额外的花费只是少量的。混合能源发电还可以通过另外一个途径来实现,利用太阳热能采集器产生的蒸汽来帮助驱动现有煤电厂或气电厂的涡轮机。加州帕洛阿尔托市的电力研究所正在研究这种途径的可行性,研究该途径是否可以在现有的发电站中成为一种减少燃料花费和减少排放的手段。

 In addition to parabolic troughs and power-towers there is also a third solar-thermal technology, which combines curved, dish-shaped mirrors with heat engines. In a dish-engine design, the mirrors concentrate sunlight to generate heat, which then typically powers a Stirling engine—a machine that converts heat into mechanical energy by compressing and expanding a fixed quantity of gas. The change in pressure drives the engine’s pistons, which drive a shaft that turns a generator to produce electricity.

 除了抛物槽和发电塔之外,还有一项太阳能热电技术,这项技术把曲面镜和碟形镜跟热机结合在一起。在碟形镜跟热机的设计中,镜面聚集阳光产生热量,然后通常为一台斯特林发动机提供动力。斯特林发动机是通过压缩和扩张定量气体来把热能转化为机械能的机器,压力变化驱动发动机的活塞,活塞驱动一个机械轴,机械轴驱动发电机进行发电。

 Although they are highly efficient, Stirling engines have seen little practical use since their invention nearly two centuries ago, and so far there are no commercial solar-thermal systems that use this approach. Critics of the technology say it involves too many moving parts, making it more complex and expensive to operate and maintain than competing technologies. Stirling Energy Systems, based in Phoenix, Arizona, hopes to prove the doubters wrong. It has signed two large power-purchase agreements, for up to 1,750MW, and plans to fulfil them using dish-engine systems built in conjunction with its sister company, Tessera Solar. Both projects are due to start construction as early as 2010.

 尽管斯特林发动机效率很高,但是自从发明这种机器以来还没有投入实际应用,而且到目前为止,在商业上根本没有太阳能热电系利用这种发动机。对该技术持批评态度的人员说,其中包含太多的活动部件,使其运行起来和保养起来比同类技术更为复杂、更为昂贵。亚利桑那州凤凰市的斯特林能源系统公司希望证明那些怀疑者是错误的。该公司签署了两项重大的电力订购协议,共计1,750兆瓦,计划利用碟式热机系统,联合其姊妹公司——泰色拉太阳能公司,共同来完成合同任务。两个项目都即将在2010年开始建设。

 One obstacle hampering the growth of the entire field is the difficulty of obtaining financing for solar-thermal projects in the current economic climate, says Thomas Mancini, programme manager for concentrating solar-power at Sandia National Laboratories. As a result, some announced projects may be delayed or perhaps never be built. The situation has prompted some companies to change their business models: Ausra, a solar-thermal company based in Mountain View, California, has switched from being an independent power-producer to being mostly an equipment supplier, for example.

 桑迪亚国家实验室太阳能集热的项目经理托马斯·曼西尼说:阻止整个领域发展的一个障碍是,在目前的经济形势下,难以搞到太阳能热电工程所需的资金。结果,一些宣布要建设的项目可能会拖延,甚至有可能永远也建不起来。这种状况促使一些公司改变了经营模式,例如:在很大程度上,加州山景城的太阳能热电公司——奥斯拉公司从独立的电力生产商转变为设备供应商。

 Although solar-thermal power produces no carbon-dioxide emissions, it can have some negative environmental impacts. Both power-tower and trough-based systems are typically water-cooled, and require millions of gallons of water annually. That can cause big problems, especially in desert environments. The California Energy Commission recently urged NextEra Energy Resources, a renewable-energy company, to consider dry cooling instead of using water for its proposed solar-thermal power project in Kern County, California. (Stirling-engine designs do not require water for cooling.) Another potential problem when building power plants in remote locations is a lack of transmission lines, since it is difficult and expensive to get new transmission lines approved and built.

 尽管太阳能热电技术不会产生二氧化碳的排放,但还是可能会对环境产生一些其他的负面影响。通常,太阳能塔式系统和抛物槽式系统都是利用水来冷却的,每年需要的水量达几百万加仑。这会引起严重的问题,尤其是在沙漠环境中。最近,加州能源委员会催促可再生能源公司——新纪元能源公司在加州科恩县的太阳能热电计划项目中考虑使用空冷技术来代替水冷。(在斯特林发动机的设计中,不需要用水来冷却。)由于审批和架起新的输电线路困难大、代价高,在偏远的地方建造太阳能发电厂的另一个潜在问题是:缺少输电线路。

 Despite these problems, many people think a massive scale-up of the industry is imminent. Among them is Mr Woolard, who believes that solar-thermal power could regain its historical lead over the solar-photovoltaic approach. Competition from photovoltaic systems for large-scale power generation should not be underestimated, however. According to Mr Bullard, thin-film solar-cell modules are rapidly falling in price, and can generate electricity more cheaply than solar-thermal power in some situations. But no matter which approach comes out on top, competition between the two technologies is sure to foster continued innovation, and a growing supply of clean electricity, in the years to come.

 虽然存在上述问题,很多人仍然认为太阳能产业的规模即将大幅度扩大。伍拉德先生就是其中之一,他认为太阳能热电技术可能会超过太阳能光伏技术,重新获得其历史上曾经拥有的领先地位。然而,也不应低估来自光伏系统大规模发电的竞争。布拉德先生指出:薄膜太阳能电池模块的价格下降很快,利用该技术所发的电在某些情况下可能比太阳能热电更便宜。但是在未来的几年中,不管哪种方法处于领先地位,两种技术的竞争肯定会不断地促进技术革新,使洁净电能的供应越来越多。

译自:《经济学家》杂志纸质版

原著:不详

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