The (relatively) easy part
But the challenges of renewable energy are still daunting
Henrik poulsen, boss of Ørsted, a big Danish wind developer formerly known as Dong Energy, has a dream that may scare sailors and seabirds, but warms the hearts of renewable-energy advocates. He reckons there is scope to install 600,000 megawatts (mw) of offshore wind capacity in relatively shallow waters off Europe’s Atlantic, Baltic and North Sea coasts, which could supply 80% of Europe’s electricity. “You could turn the northern seas into one large power factory over the next 10-15 years,” he says.
丹麦大型风能开发商沃旭能源［Ørsted，早先叫丹能集团（Dong Energy）］的老板亨利克·普尔森（Henrik Poulsen）有一个梦想。它可能会吓到水手和海鸟，却会温暖可再生能源倡导者的心。据他估计，在欧洲的大西洋、波罗的海和北海沿岸相对较浅的海域可以安装 600,000 兆瓦（MW）的海上风电容量，可以提供欧洲电力的 80%。「你可以在未来 10 到 15 年内将北海变成一个大型发电厂。」他说。
As yet, only 16,000mw of offshore wind has been installed in Europe, and already people are talking about space constraints, as with onshore wind and solar farms. Partly in response, Norway’s Equinor, an energy company, is using its deepwater-oil technology to build floating wind turbines tethered to the ocean floor, which could be installed far from land in the North Sea, off the west coast of America and in East Asia. So far it has built one 30mw project off the coast of Scotland, and is considering another to power North Sea oilfields. But Mr Poulsen says the cost of floating turbines, up to four times that of fixed ones, may be prohibitive.
到目前为止，欧洲仅安装了 16,000 兆瓦的海上风电，而人们已经开始谈论空间限制，就像陆上风电和太阳能发电场一样。挪威的能源公司 Equinor 正在利用其深水石油技术建造拴在海底的浮动风力涡轮发电机，可安装在远离北海陆地的地方，以及美国西海岸和东亚，算是部分回应了这个问题。迄今它已在苏格兰沿海建造了一个 30 兆瓦的项目，并正在考虑另一个项目来为北海油田提供动力。但普尔森表示，浮动涡轮机的成本高达固定涡轮机的四倍，可能令人望而却步。
The price of offshore wind generated by his turbines, he says, fell by 60% in 2013-17 as they doubled in size to 8-9mw apiece without needing large increases in their foundations, cabling and installation time. By the mid-2020s he expects each of them to have a capacity of 15mw, but such growth is still not fast enough to meet Europe’s climate goals. The same is true elsewhere.
他说，他的涡轮机发出的海上风电价格在 2013 到 2017 年间下降了 60%，因为它们的产能翻了一番，达到单台 8 至 9 兆瓦，却不需要大幅扩展底座及增加布线和安装时间。他预计到本世纪 20 年代中期，单台产能将达到 15 兆瓦，但这种增长仍然太慢，不足以满足欧洲的气候目标。在其他地方也是如此。
Almost all agree that a lot more electricity, all of it carbon-free, will be the backbone of efforts to decarbonise the energy system. The Energy Transitions Commission (etc) says that electricity’s share of final global energy demand, currently about 20%, could rise to 60% by mid-late century, with bioenergy and hydrogen providing most of the rest. That entails demand for electricity quadrupling to about 100,000 terawatt-hours over the same period to power vehicles, heating and other users of energy. A quarter of that would be just to make hydrogen.
几乎所有人都同意，大幅增加全部无碳的电力将成为使能源体系脱碳的关键。能源转型委员会（ETC）表示，电力在终端能源需求中的份额目前约为 20%，到本世纪中叶可能会上升到 60%，由生物质能和氢能提供其余的大部分能源。这就需要在这一时期内让电力需求翻两番，达到大约 100,000 太瓦时，以满足车辆、供暖和其他能源用户的需求。而其中有四分之一将用于制氢。
Figures from bp, an oil company, show that last year less than 35% of the world’s electricity was generated from non-carbon sources, including nuclear and hydro, and only 8.4% from non-hydro renewables. The etcestimates that in order to produce all electricity by renewables in 2050, the annual deployment rate of solar and wind power would have to rise tenfold. Yet it is not necessary that all electricity should come from a mixture of renewables and batteries, even if it were possible. Some argue persuasively that it is cheaper to include non-renewable sources in the power mix to stabilise the system. Nestor Sepulveda at mit and others argue in a recent paper that it is far more cost-effective to mix intermittent renewables with “firm” (ie, not intermittent) low-carbon resources such as nuclear, natural gas with carbon capture, and bioenergy. Without these, costs rise rapidly as the electricity system gets closer to full decarbonisation, even with storage and the ability to flex demand to cope with surpluses and shortages of power.
英国石油公司（BP）的数据显示，去年全球不到 35% 的电力来自非碳源，包括核电和水电，而非水电的可再生能源只占 8.4%。ETC 估计，为了在 2050 年通过可再生能源生产所有电力，太阳能和风能的年度部署速度必须提高十倍。然而，哪怕有可能做到这一点，电力也不必定要全部来自可再生能源和电池的搭配。一些人的观点很有说服力，认为在动力组合中加入不可再生能源来稳定系统会更便宜。麻省理工学院的内斯特·塞普尔韦达（Nestor Sepulveda）等人在最近的一篇论文中指出，将间歇性可再生能源与「稳定的」（即非间歇性）低碳资源（如核能、带碳捕获的天然气，以及生物能源）混合在一起会经济得多。如果没有这些，随着电力系统接近完全脱碳，即便拥有蓄电能力和调节需求以应对电力盈余和短缺的能力，成本也会迅速上升。
Savings in the total use of electricity could be made by using it more efficiently, lowering the amount of energy needed to produce each unit of gdp. Energy intensity declined at an average rate of 2% a year in 2010-16, which helped reduce greenhouse-gas emissions, though they have since risen again. Tightening new constructions standards, retrofitting existing buildings and managing consumption better would all help. At the same time electricity consumption in the developing world still lags far behind, averaging around a third of that in rich countries. Moreover, as energy efficiency increases, consumers may simply use more of it.
要节约总耗电量，还可通过更高效地利用电力，降低生产每单位 GDP 所消耗的能源。2010 至 2016 年，能耗强度以每年平均 2% 的速度下降，这有助于减少温室气体排放，尽管此后它们又再度上升。收紧新建筑标准，改造现有建筑物以及更好地管理能耗也会有所帮助。与此同时，发展中国家的电力消耗仍远远落后，平均约为富裕国家的三分之一。此外，随着能源利用效率的提高，可能消费者就是会用得更多。
There is an outside chance that a “breakthrough” technology will emerge to replace fossil fuels with a steady source of electricity. Ernest Moniz, who was America’s energy secretary in the Obama administration, says he has never seen so much interest in new nuclear fission technologies. Some continue to hold out hope for nuclear fusion. But as the price of renewables falls, hydrogen is looking more attractive as a way to store electricity over longer periods and distances than batteries. It could have even more uses with further development of carbon capture and storage.