【经济学人】清洁太阳能丨2016.12.10丨总第765期

THAT solar panels do not emit greenhouse gases such as carbon dioxide when they are generating electricity is without question. This is why they are beloved of many who worry about the climate-altering potential of such gases. Sceptics, though, observe that a lot of energy is needed to make a solar panel in the first place. In particular, melting and purifying the silicon that these panels employ to capture and transduce sunlight needs a lot of heat. Silicon’s melting point, 1,414°C, is only 124°C less than that of iron.

太阳能板在发电的时候不会排放类似二氧化碳的温室气体，这是毋庸置疑的。这也是那些担心二氧化碳可能会引发气候改变风险的人偏爱太阳能的原因。然而，一些怀疑者发现制作太阳能板需要消耗大量能量，尤其是太阳能板中用来收集和转化太阳能的硅的融化和提纯过程需要很高的温度。硅的熔点为1414°C，仅比铁的熔点低124°C。

• Transduce [trænz'djuːsə] 转换（能、信号等）

Silicon is melted in electric furnaces and, at the moment, most electricity is produced by burning fossil fuels. That does emit carbon dioxide. So, when a new solar panel is put to work it starts with a “carbon debt” that, from a greenhouse-gas-saving point of view, has to be paid back before that panel becomes part of the solution, rather than part of the problem. Observing this, some sceptics have gone so far as to suggest that if the motive for installing solar panels is environmental (which is often, though not always, the case), they are pretty-much useless.

在电炉中用来熔化硅的热量大多来自化石燃料燃烧产生的电力，而燃料燃烧会产生二氧化碳。（期待您的翻译，明天会有针对这句话的读者试译详解哟~）从这点来看，一些怀疑者过于偏激，他们认为如果安装太阳能电板是为了环保（通常是为了环保，但也不总是），那太阳能电板是毫无用处的。

• Furnace  ['fɜːnɪs]  炉

Wilfried van Sark, of Utrecht University in the Netherlands, and his colleagues have therefore tried to put some numbers into the argument. As they report in Nature Communications, they have calculated the energy required to make all of the solar panels installed around the world between 1975 and 2015, and the carbon-dioxide emissions associated with producing that energy. They also looked at the energy these panels have produced since their installation and the corresponding amount of carbon dioxide they have prevented from being spewed into the atmosphere. Others have done life-cycle assessments for solar power in the past. None, though, has accounted for the fact that the process of making the panels has become more efficient over the course of time. Dr Van Sark’s study factors this in.

因此荷兰乌得勒支大学的Wilfried van Sark和他的同事尝试用具体数据来支撑他们的论点。正如他们在《自然-通讯》上的报道：他们计算出了1975至2015年间世界各地所有太阳能板安装所需的能量及生产这些能量所排放二氧化碳的量。他们也研究了这些太阳能板自安装以来所产生的能量及它们所阻止的排放到大气中二氧化碳的量。其他研究者评估了太阳能电板的生命周期。然而这些数据没有说明制作技术随时间推移变得更加高效。Van Sark博士的研究也支持这一说法。

• Spew  [spjuː] 放出，喷出

To estimate the number of solar panels installed around the world, Dr Van Sark and his team used data from the International Energy Agency, an autonomous intergovernmental body. They gleaned information on the amount of energy required to make panels from dozens of published studies. Exactly how much carbon dioxide was emitted during the manufacture of a panel will depend on where it was made, as well as when. How much emitted gas it has saved will depend on where it is installed. A panel made in China, for example, costs nearly double the greenhouse-gas emissions of one made in Europe. That is because China relies more on fossil fuels for generating power. Conversely, the environmental benefits of installing solar panels will be greater in China than in Europe, as the clean power they produce replaces electricity that would otherwise be generated largely by burning coal or gas.

为了估计全球安装的太阳能板的数量，Van Sark和他的团队查阅了国际能源机构（一个独立的政府间的机构）的数据。他们从多篇发表的研究报告中收集到了关于生产太阳能电板所需能量的信息。在不同的地区和不同的时期，生产太阳能电板所排放的二氧化碳量有所不同。而它减少二氧化碳排放量的多少则取决于电板安装的地区。举个例子，在中国生产一块电板所排放的二氧化碳量接近欧洲的两倍。这是因为中国更多地依赖化石燃料发电。因为太阳能板代替了燃烧煤或气来发电，所以相反地在中国安装太阳能电板所带来的环境效益比欧洲大。

• Autonomous [ɔː'tɒnəməs] 独立自主的

• Glean [gliːn] 收集（资料）

Once the team accounted for all this, they found that solar panels made today are responsible, on average, for around 20 grams of carbon dioxide per kilowatt-hour of energy they produce over their lifetime (estimated as 30 years, regardless of when a panel was manufactured). That is down from 400-500 grams in 1975. Likewise, the amount of time needed for a solar panel to produce as much energy as was involved in its creation has fallen from about 20 years to two years or less. As more panels are made, the manufacturing process becomes more efficient. The team found that for every doubling of the world’s solar capacity, the energy required to make a panel fell by around 12% and associated carbon-dioxide emissions by 17-24%.

曾有个团队研究时考虑了所有因素，他们发现太阳能板对现今的温室效应也负有责任。在太阳能电板的使用年限内（估计为30年，而不管是何时生产的），平均每转化1千瓦时的电，就会排放20克的二氧化碳。这个数字从1975年的400-500克降到了现在的20克。而且补偿生产太阳能板过程中消耗的能量所需的时间从20年降到了2年甚至更短。随着太阳能板的不断制作，其制作过程也越来越高效。该团队发现，全球的太阳能板的量平均每增加一倍，生产一块电板所消耗的能量大约会减少12%，相应地二氧化碳排放量会减少17-24%。

• Capacity  [kə'pæsɪtɪ] 生产量

The consequence of all this number-crunching is not as clear-cut as environmentalists might hope. Depending on the numbers fed into the model, global break-even could have come as early as 1997, or might still not have arrived. But if it has not, then under even the most pessimistic assumptions possible it will do so in 2018. After that, solar energy’s environmental credentials really will be spotless.

这些数据处理的结果并不像环保主义者希望的那样明确。根据输入模型的数据来看，全球盈亏平衡可能早在1997年就该有了，又或许还没到。如果没有到来，即使是最悲观的估计是可能在2018年出现。之后太阳能的环保效益将会是无可争议的。

• number-crunching [krʌn(t)ʃ] 数字运算，数字处理

• clear-cut 清楚的，明确的

• spotless ['spɒtlɪs] 无可挑剔

• credential [krɪ'denʃ(ə)l] 成绩

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