位于纽约尼什卡纳的通用电气全球研究中心，一名研究人员正在分析碲化镉太阳能电池。碲化镉是一种比硅更便宜的光伏材料。
The sun packs some serious power. Even taking into account the all the energy that’s lost in space, enough still reaches Earth in an hour to power the entire planet, theoretically, for a year.
太阳拥有无穷无尽的能量。即便除去辐射到茫茫太空中的大部分，每小时到达地球的能量理论上仍可供人类使用一年。
So why doesn’t the world harness all this energy?
☀ 人类为何不充分利用这些太阳能呢？
The truth: Capturing that power, and putting it to work in the form of electricity, is relatively expensive.
It’s true that the cost of solar electricity has declined over the past ten years. Along the way, the popularity of solar electricity has risen. A decade ago, fewer than 25,000 solar cells and modules were shipped in the United States every year. In 2008, that number had skyrocketed to more than 500,000. But that is still a drop in the bucket. Only about one-tenth of 1 percent of the energy consumed in the United States came from solar sources in 2008.
In Germany, a country with a much more robust government incentive program, solar’s share is much larger, but still only 1.1 percent of that nation’s electricity.
And, while most scientists agree solar power will be an important part of the future energy mix, there’s no clear consensus on when it will be able to compete on a large scale. In fact, the experts don’t even agree on how much solar electricity costs today.
答案是：捕获太阳能并利用它来发电相对较贵。
过去的十年里，太阳能发电的成本在不断下降，太阳能的使用率也越来越高。十年前，美国每年装运的太阳能电池和模块不足两万五千块。但到了2008年，这个数字上升到了五十万。不过这仍然只是杯水车薪，2008年太阳能仅占美国能源消耗的0.1%。德国拥有更多太阳能刺激项目，太阳能发电的比例要高得多，即便在这里，这个比例也仅有1.1%。
大部分的科学家都认为太阳能是未来能源的重要组成部分，但是何时才能实现大规模发电，大家尚未形成一致的意见。事实上，专家们甚至都还无法确定目前太阳能发电的成本有多大。3
Calculating the Sun’s Power
☀ 如何计算太阳能发电的成本
The problem: Solar electricity isn’t just one thing.
Think about any simple item, like a shirt. A shopper may know how much he or she paid for it, but that doesn’t mean the consumer knows how much a shirt, in general, costs. That number can vary quite a bit, depending on the type of shirt and where it is purchased.
Solar electricity is similar. The cost varies based on the technology being used, and on where it is being installed. The situation looks much different in Phoenix, Arizona, than it does in Albany, New York, and looks much different in Seville, Spain, than in Leipzig, Germany.
The reasons for those differences are fairly easy to figure out, but sunlit geography is only the beginning, says Seth Darling, a scientist at the U.S. Department of Energy (DOE) Argonne National Laboratory in Illinois.
难点在于：太阳能发电涉及众多方面。
任何一件简单的东西如衬衫，买家或许知道他应该付多少钱，但这并不代表他知道一件衬衫值一般多少钱。因衬衫类型和购买地的不同，一件衬衫的成本可能会相差很大。太阳能发电也是这样。依据其所选用的技术和安装场地的不同，成本千差万别。比如在亚利桑那州的凤凰城和纽约的奥尔巴尼就不一样，再比如在西班牙的塞维利亚和德国的莱比锡也有所差别。
伊利诺斯州美国国家能源部阿尔贡国家实验室的科学家塞斯•达灵说道，产生这些差异的原因很简单：阳光照射的角度不同，但这也仅仅是一个方面。5
A standard way of thinking about the cost of electricity is “total system levelized cost”—basically, how much a power producer would have to charge for electricity to earn back the money spent building a new generating facility.
“But what’s surprising is that there’s no one accepted way to do a levelized cost calculation,” Darling said. “That’s the gorilla in the room and it’s a big reason there’s so much confusion about the cost” of solar photovoltaics (PV).
Figuring out the levelized cost requires a number of guesses: How well the solar energy system will perform, how long it will last, and even how much sunshine it will get over the next 30 years. It’s possible to make good guesses. But, right now, everybody makes different ones and it’s hard to say who’s right.
一个衡量电力成本的标准方法就是：整个系统的平准化成本。它是指能源供应商该收多少电费才可以赚回安装发电设备所花的钱。达灵说道：“但是令人惊讶的是，暂时尚无一个普遍认可的计算方法，但是又要必须面对这个问题，所以大家对于光伏发电的成本的都还很困惑”。要估算出平准化成本需要很多的假设：太阳能系统运行状况，运行时长以及三十年内受阳光照射的时间。事实上给出假设很容易，问题是每个人给出的都不一样，并且很难说谁是正确的。
That said, there’s wide agreement that solar electricity is pricey. The U.S. DOE’s Energy Information Administration (EIA) estimates that it’s the most expensive form of electricity among current technologies for new electricity generation, about $396 per megawatthour for PV. That’s more than double EIA’s estimate of the total system levelized cost of wind, and almost four times the cost of conventional coal.
And that analysis looks at large-scale solar, the kind usually owned by utility companies. Small installations on home rooftops are even more expensive, because they don’t take advantage of buying—or installing—in bulk. To be fair, over 20 years, a homeowner will earn back between 76 percent and 109 percent of the system’s cost in the form of lower electricity bills, because the fuel that powers solar energy is free, according to a 2009 report on financing solar installations in the residential sector by the U.S. DOE National Renewable Energy Laboratory.
但是大家一致认为太阳能发电非常昂贵。据美国国家能源部能源信息部估计，太阳能发电是所有发电技术中成本最高的，每兆瓦约396美元。那是风能平准化成本的两倍，燃煤发电的四倍。并且这种分析的假设是公司运营的大规模发电。而装在屋顶的小型装置成本更高，因为它们没有批量购买和安装的优势。美国能源部可替代能源国家实验室2009年发布的一份关于资助太阳能设施安装的报告称，考虑到阳光照射时免费的，一个家庭仍需要二十年才能赚设备安装成本的76%至 109%。
With such a broad range in the potential rate of return, it isn’t always easy to find a bank that will make that loan, says Ed Regan, assistant general manager of strategic planning at Gainesville Regional Utilities (GRU) in Gainesville, Florida. GRU helped Gainesville residents get around that problem by implementing a feed-in tariff, a system where a utility offers solar panel owners a 20-year contract to buy solar electricity, guaranteeing the owners will make a set profit on their decision to go solar. There are other alternative financing options—such as letting the utility or a third party buy and own the solar system, while the homeowner hosts it on the roof—but these options aren’t available everywhere.
因为回收成本的风险太高，所以很少有银行愿意发放贷款，埃德•瑞根说道。他是位于佛罗里达州盖恩斯维尔地方公共事业部门（GRU）分管战略策划的经理。 GRU给盖恩斯维尔的居民提供电价补贴，帮助它们解决相关问题，并给太阳能电板拥有者提供二十年的合同，保证他们能够在太阳能发电方面获得稳定收益。当然也有其它的激励措施，比如让设备商或第三方拥有太阳能设施，而居民只需将其放在屋顶即可。不过这种方式并不是适用于所有地方。
It’s All in the Material
☀ 材料是关键
So why is solar so expensive?
Converting light into electricity with no moving parts is a profoundly different enterprise than turning a turbine to make power—the technology that is at work in coal, natural gas, nuclear, hydropower plants and, most visibly to the public, at wind farms.
“Wind power is the same technology as it’s been for 1,000 years,” said Tom Meyer, a professor of chemistry at the University of North Carolina at Chapel Hill. “There’s nothing to invent. It just needs to be improved.” The makers of wind turbines have made huge cost reductions in recent decades with relatively small tweaks to an otherwise familiar system.
That’s not yet true for solar, experts say. Most solar cells are made from silicon—the same semiconductor material that is at the heart of computers. The cells are expensive to produce because it takes a great deal of energy to purify the silicon. And, while the computer industry has made enormous strides in making cheaper silicon devices, those advancements don’t translate to the solar industry.
那么为什么太阳能发电如此昂贵呢？
在没有运动部件的情况下，将光能转换成电能和燃煤，天然气，核能，水力以及常见的风力发电所采用的传统的涡轮机发电的方式有很大不同。北卡罗来纳大学查普尔山分校化学系教授汤姆•梅耶说道，“风能的利用技术千年未变，已经没有什么可发明的了，只能进行一些小的改进。” 几十年来风力涡轮机的制造商们就是通过这些小的改进极大地降低了成本。但是专家们表示，这在太阳能发电并不可行。大部分的太阳能电池是用硅制造的，它是一种用于生产计算机核心部件的半导体材料。因为纯化硅要消耗很多能量，所以太阳能电池的成本很高。虽然计算机工业在降低制造硅器件的成本方面取得了长足的进步，但这并不适用于太阳能工业。5
“It’s kind of comparing apples and oranges,” says Hugh Hillhouse, a professor of chemical engineering at the University of Washington. “The semiconductor industry makes minutely patterned silicon. You’d have to look at it under an electron microscope to see the intricate structure. Their advancements have been about how to design and fabricate that intricate structure cheaply. And the solar cell: That’s completely not intricate. It’s simply a few layers of semiconductor. It changes the economics dramatically since the manufacturing cost is more closely tied to the cost of the material, not the patterning.”
What may really help to lower the cost of solar are new materials—especially semiconductors made from the compound cadmium telluride. It’s cheaper to make “thin-film solar cells” with cadmium telluride than with silicon.
华盛顿大学化学工程系的教授休•希尔豪斯说道，“它们之间并无可比性，半导体工业主要是制作微小的特定图形的硅，需要在电镜下才能看清它的复杂结构。它们的进展主要是关于如何低成本地设计和制备这些精细结构的。但是太阳能电池并不精细，它只是简单的几层半导体。这样情况就完全不一样了，因为它们的成本直接跟材料的成本相关，而非制作特定图形的成本。而真正能降低太阳能发电成本的就是使用新材料——比如使用碲化镉制成的半导体材料。用碲化镉制作薄膜太阳能电池比硅更便宜。
But that still leaves what experts call “soft costs,” everything from permitting fees to the hardware that mounts solar panels onto a roof. Even though there’s disagreement over how much of the price of solar is tied up in these soft costs, they are clearly an important factor. In fact, Ryne Raffaelle, director of the National Center for Photovoltaics at the National Renewable Energy Laboratory, says the solar array itself accounts for only half the cost of a solar system today.
Innovations that could cut both hard and soft costs are being made all the time, but they don’t necessarily reach customers quickly. For one thing, not every great idea that works in a lab can be replicated on a mass production scale. And it can take a long time to iron out technological kinks on an apparatus that the manufacturer wants to be sure will last a long time.
“Different industries have different speeds from discovery to marketing. Consumer electronics is relatively quick. But it can be seven or eight years for the auto industry,” said Paul Friley, an energy economist at U.S. DOE’s Brookhaven National Laboratory in Upton, New York. “With solar, you have 20-year warrantees. You want it to work and be durable. And that means you have to spend a long time testing it.”
此外还有专家们所谓的”软成本“尚未考虑，它是指在屋顶安装太阳能板所需其它硬件的成本。甚至太阳能发电的价格和这些软成本的关系也不甚明了，而这显然又是一个很重要的因素。可替代能源国家实验室光伏中的主任瑞恩•拉法尼说道，事实上，太阳能阵列的成本只占整个系统成本的一半。
虽然技术创新能同时降低软硬成本，但太阳能发电离消费者依然很远。一方面，实验室的伟大构想不一定可在大规模生产中应用。另一方面，制造商们要保证它们的设备能长期稳定使用，而解决这种技术难关需要花很长时间。位于纽约阿普顿的美国能源部布鲁克海文国家实验室的能源经济学家保罗•弗赖利说道，”从发现到市场化，不同的工业速度是不一样的。消费电子工业比较快，而汽车工业却需要七到八年。太阳能发电设施必须要二十年的质保，它们必须很耐用。那就意味着你要花很长时间来测试它。“
Seeking an Even Footing
☀ 寻找应用领域
Expensive as it is, solar electricity can already be competitive in a limited way.
In Hawaii and some parts of the Southwest, solar has already dipped below “grid parity.” Essentially, that means solar energy can be produced and sold for less than the average, going electric rate. That works because electricity is already expensive in those places, and because locations are ideal for producing solar electricity—lots of clear, sunny days.
Friley offers another option. Even in places where the average cost of electricity is low, that cost varies with the seasons and the time of day. Peak load electricity—the power that consumers draw on in the middle of a hot summer afternoon, for instance—costs a lot more than a region’s average cost of electricity. Peak load times happen to coincide with the peak hours for sunshine. If the system were designed to encourage the use of solar to cover peak load, the cost savings would be substantial, he says.
It’s also important to point out why fossil fuel electricity is relatively cheap in the United States: The behind-the-scenes costs of burning fuel that produces carbon dioxide and noxious pollutants—health care costs, environmental cleanup, and the current and future expenses of adapting to a warmer world—are not included in the U.S. electric bill. Solar would naturally reach grid parity faster under policies that accounted for those costs by putting a tax or price on carbon.
尽管很贵，太阳能发电在一些特定领域仍然拥有竞争力。
在美国西南部以及夏威夷，太阳能发电已经可以和普通电网媲美了。也就是说，太阳能产生的电力的销售价格已经低于平均价格了。那是因为这些地方的电价比较贵并且光照时间长。弗赖利还提到了另外一种情况。即便在一些电价较低的地方，成本价也会随季节和每日的时间而不同。在用电高峰期，如夏日的午后，电价会比成本价高很多。而此时又常常恰好是阳光最强烈的时候。如果鼓励在用电高峰期用太阳能发电，那样成本也会大幅下降。
另外我们要清楚的是为什么化石燃料发电的成本很低：因为很多隐性成本并没有包括到美国的电价中。化石燃料发电会排放二氧化碳和有毒污染物，这些都会增加医药卫生，环境清理和气候暖化的成本。因此，在征收碳排放税的政策鼓励下，太阳能发电最终会更快地接入电网。
How Long Must Consumers Wait?
☀ 消费者还要等多久？
But the question for most consumers is when it will make sense to put a solar panel on the roof.
Partly because of the issues in estimating levelized cost, there’s not a clear answer right now. In fact, the right answer could change over time. For instance, cadmium telluride thin film panels could help solar reach grid parity sooner than silicon panels could, but tellurium—a key ingredient—is fairly rare. If production of cadmium telluride solar panels increases substantially, it could trigger a scarcity of tellurium, raising the price for that type of panel. If the solar industry has become dependent on the short-term low-cost cadmium telluride option, long-term scarcity could end up moving solar electricity back out of grid parity for many people.
Thanks to the rising cost of coal and natural gas—as well as the short-term cost benefits of cadmium telluride, and falling costs of silicon and other solar options—the National Renewable Energy Laboratory estimates that solar energy could reach nationwide grid parity by 2017. That’s without any subsidies and with only small, incremental improvements on current technology.
But Seth Darling at Argonne says the United States won’t be likely to see hundreds of gigawatts of solar running at grid parity until 2025, at the earliest.
消费者最关心的问题是：我何时才能在自家屋顶上装上太阳能板？
因为平准化成本无法估计等原因，这个问题尚无明确答案。不过实际情况会随时间改变。比如， 碲化镉薄膜电板可能会加速太阳能发电接入电网。但是元素碲非常稀有。如果碲化镉电板被大量生产，它可能使碲变得更加稀有，从而带来电板价格的上扬。如果太阳能工业依赖于这种暂时低价的碲化镉，从长远角度看，它最终还是会远离消费者的。
得益于煤和天然气价格的上升，短期低价的碲化镉和硅成本的降低等综合因素，可替代能源国家实验室估计，在没有政府津贴和当前技术仅有稍稍改进的情况下，太阳能发电将会于2017年接入国家电网。不过塞斯•达灵说，美国最早也要等到2025年才能实现千亿瓦量级的太阳能发电。
