经济学人下载:太空太阳能 老兄传下来吧

Science and technology
科学技术

Solar power from space
太空太阳能

Beam it down, Scotty
老兄，传下来吧

Harvesting solar power in space, for use on Earth, comes a step closer to reality
在太空获取太阳能以供地球之用:梦想距现实又近了一步

THE idea of collecting solar energy in space and beaming it to Earth has been around for at least 70 years.
在太空获取太阳能并传送回地球这一创意存在了至少有70年了。

In “Reason”, a short story by Isaac Asimov that was published in 1941, a space station transmits energy collected from the sun to various planets using microwave beams.
由艾萨克·阿西莫夫创作、1941年发表的短篇故事《推理》，描述了一个太空站将获取的太阳能以微波束的方式传送至多个星球的场景。

The advantage of intercepting sunlight in space, instead of letting it find its own way through the atmosphere, is that so much gets absorbed by the air.
相比于让阳光穿过大气层后再获取太阳能，在太空中截取太阳能的一大优点就是大气吸收的能量很少。

By converting it to the right frequency first a space-based collector could, enthusiasts claim, yield on average five times as much power as one located on the ground.
热衷者声称，首先通过调节阳光至适当频率，在太空中的太阳能收集器可以吸收五倍于地面收集器的能源。

The disadvantage is cost.
缺点在于成本高。

Launching and maintaining suitable satellites would be ludicrously expensive.
适用卫星的发射和维护成本会高得惊人。

But perhaps not, if the satellites were small and the customers specialised.
但也许不会—如果卫星足够小、且是为专门客户服务。

Military expeditions, rescuers in disaster zones, remote desalination plants and scientific-research bases might be willing to pay for such power from the sky.
军事远征队、灾区救援人员、偏远的脱盐工厂和科研基地也许会愿意为太空太阳能买单。

And a research group based at the University of Surrey, in England, hopes that in a few years it will be possible to offer it to them.
英国萨里大学的一个研究小组希望在未来几年内可以提供太空太阳能。

Heavenly power
天国能源

This summer, Stephen Sweeney and his colleagues will test a laser that would do the job which Asimov assigned to microwaves.
今年夏天，斯蒂芬·斯维尼和同事将测试一个激光器，该激光器用来完成阿西莫夫为微波“指派”的任务。

Certainly, microwaves would work: a test carried out in 2008 transmitted useful amounts of microwave energy between two Hawaiian islands 148km apart, so penetrating the 100km of the atmosphere would be a doddle.
当然，微波可以发挥作用：2008年进行的一项测试为相距148公里的夏威夷两岛传送了大量的微波能，所以穿越100公里的大气层应该易如反掌。

But microwaves spread out as they propagate.
但微波在传送过程中会扩散。

A collector on Earth that was picking up power from a geostationary satellite orbiting at an altitude of 35,800km would need to be spread over hundreds of square metres.
接收35,800公里外的地球同步卫星传送的能源所需的地面收集器需覆盖数百平方米。

Using a laser means the collector need be only tens of square metres in area.
而使用激光器则意味着收集器面积仅需达到几十平米。

Dr Sweeney's team, working in collaboration with Astrium,
斯维尼博士的团队正与卫星和太空公司Astrium合作。

a satellite-and-space company that is part of EADS, a European aerospace group, will test the system in a large aircraft hangar in Germany.
Astrium隶属于欧洲一航天集团欧洲宇航防务集团。斯维尼博士的团队将在德国一座大型飞机库测试该系统。

The beam itself will be produced by a device called a fibre laser.
光束将由光纤激光器发出。

This generates the coherent light of a laser beam in the core of a long, thin optical fibre.
该激光器利用细长的光纤核心汇聚激光束。

That means the beam produced is of higher quality than other lasers, is extremely straight and can thus be focused onto a small area.
这意味着产生的光束比其他激光器发射的光束质量更高，最直接，也因此可以汇聚到更小的区域内。

Another bonus is that such lasers are becoming more efficient and ever more powerful.
另外一个益处就是此类激光器效率正逐步提高、力量更大。

In the case of Dr Sweeney's fibre laser, the beam will have a wavelength of 1.5 microns, making it part of the infra-red spectrum. This wavelength corresponds to one of the best windows in the atmosphere.
斯维尼博士采用的光纤激光器发射的光束波长将达到1.5微米，从而使其达到红外线的光谱范围。该波长正处于大气最佳窗口之一。

The beam will be aimed at a collector on the other side of the hangar, rather than several kilometres away.
光束将瞄准飞机库另一侧的—而不是数公里之外的——收集器。

The idea is to test the effects on the atmospheric window of various pollutants, and also of water vapour, by releasing them into the building.
通过释放各种污染物以及水蒸气至机库中，该创意旨在测试这些物质对大气窗口的影响。

Assuming all goes well, the next step will be to test the system in space.
如果一切都进行顺利，下一步将是在太空中测试该系统。

That could happen about five years from now, perhaps using a laser on the International Space Station to transmit solar power collected by its panels to Earth.
这可能要在五年之后实现，或许会利用国际空间站上的激光器将空间站电池板收集的太阳能传送回地球。

Such an experimental system would deliver but a kilowatt of power, as a test.
作为测试，该试验系统将只传送一千瓦的能量。

In 10-15 years Astrium hopes it will be possible to deploy a complete, small-scale orbiting power station producing significantly more than that from its own solar cells.
Astrium 希望在未来10到15年的时间内能够建立一个完整的、小规模的、沿轨道运行的太阳能站，利用自身的太阳能电池发出大量电能。

Other researchers, in America and Japan, are also looking at using lasers rather than microwaves to transmit power through the atmosphere.
美日其他研究者也在考虑弃微波、用激光器，穿过大气层将能量传送回地球。

NASA, America's space agency, has started using them to beam energy to remotely controlled drones.
美国航天机构国家航空航天局已开始采用激光器传送能源至遥控飞机。

Each stage of converting and transmitting power results in a loss of efficiency, but with technological improvements these losses are being reduced.
能量转化、传送的每一个环节都会有一定的功耗，但随着技术的改进，损耗正在降低。

Some of the latest solar cells, for instance, can covert sunlight into electricity with an efficiency of more than 40%. In the 1980s, 20% was thought good.
例如，部分最新型的太阳能电池将阳光转换成电能的功率超过了40%。而在上世纪80年代，20%的功率就很高了。

Whether the Astrium system will remain a specialised novelty or will be the forerunner of something more like the cosmic power stations of Asimov's imagination is anybody's guess.
Astrium 系统将是一个专业用途的创新，还是某个更接近阿西莫夫想象中的太空太阳能电站的先导？一切都还是未知数。

But if it comes to pass at all, it will be an intriguing example, like the geostationary communications satellites dreamed up by Asimov's contemporary, Arthur C. Clarke, of the musings of a science-fiction author becoming science fact.
但倘若系统通过测试，它定将激起人们的兴趣，正如与阿西莫夫同一时代的科幻小说作家亚瑟·C·克拉克所梦想的地球同步通讯卫星一样——梦想最终成为了现实。