人工光合作用：誘人的清潔能源技術(shù)

Nature boasts some nifty technology. A leaf is one such miraculous machine, able to turn one form of energy into another: it takes in carbon dioxide, plus water, and uses sunlight to convert it all into carbohydrates.

大自然擁有一些奇妙的科技。葉子就是能將一種形式的能量轉(zhuǎn)化為另一種的神奇機(jī)器：葉子吸收二氧化碳和水分，并利用陽(yáng)光將其轉(zhuǎn)化為碳水化合物。

For years, scientists have tried to emulate the process of photosynthesis. Finally, those efforts are blooming. The magazine Scientific American, together with experts from the World Economic Forum, has named the artificial leaf one of the breakthrough technologies of 2017.

多年來(lái)，科學(xué)家們一直試圖模仿光合作用。這些努力終于有了成果?！犊茖W(xué)美國(guó)人》(Scientific American)雜志與世界經(jīng)濟(jì)論壇(WEF)的專(zhuān)家們將人工葉子評(píng)為2017年的突破性技術(shù)之一。

Laboratory-based efforts are attempting to go one better on nature by generating not plant food but fuels that can be stored for later use. Such projects offer the promise of making new forms of energy while mopping up carbon dioxide, an unwanted greenhouse gas, from the atmosphere. That makes artificial photosynthesis one of the potentially cleanest technologies on the energy horizon.

實(shí)驗(yàn)室研究人員正試圖比自然更勝一籌：不是生成植物養(yǎng)分，而是產(chǎn)生能夠儲(chǔ)存起來(lái)供以后使用的燃料。這類(lèi)項(xiàng)目帶來(lái)了一種前景：在生產(chǎn)新型能源的同時(shí)，從大氣層吸走二氧化碳這種不受歡迎的溫室氣體。這使人工光合作用有望成為能源領(lǐng)域最清潔的技術(shù)之一。

Daniel Nocera and Pamela Silver, from Harvard University, have taken early steps along this road. Their system — the “leaf” is actually a container — uses a catalyst, activated by sunlight, to split water molecules into hydrogen and oxygen molecules. The container is home to hydrogen-eating bacteria, which feast on the newly liberated molecules plus carbon dioxide to churn out liquid fuel.

哈佛大學(xué)(Harvard University)的丹尼爾•諾切拉(Daniel Nocera)和帕梅拉•西爾弗(Pamela Silver)是這條道路上的先行者。他們的系統(tǒng)，或者說(shuō)“葉子”，實(shí)際上是一個(gè)容器，該系統(tǒng)利用一種由陽(yáng)光激活的催化劑，把水分子分解成氫分子和氧分子。這個(gè)容器中有以氫為食的細(xì)菌，這些細(xì)菌吞噬新釋放出的氫分子，再加上二氧化碳，來(lái)產(chǎn)出液體燃料。

While even the fastest-growing plants manage to convert about 1 per cent of sunlight into food, the Harvard scientists managed an efficiency of 10 per cent when using pure carbon dioxide. The efficiency drops to about 4 per cent when pulling carbon dioxide from the air.

即使是生長(zhǎng)最快的植物，也只能將大約1%的陽(yáng)光轉(zhuǎn)化為養(yǎng)分，而哈佛大學(xué)的這兩位科學(xué)家研發(fā)的系統(tǒng)在利用純二氧化碳時(shí)，達(dá)到了10%的能量轉(zhuǎn)化效率。不過(guò)，如果從空氣中抽取二氧化碳，效率就會(huì)下降至約4%。

The sun is shining for solar fuels more widely. The US Department of Energy runs a specialist hub, the Joint Center for Artificial Photosynthesis, that brings together a host of academic institutions such as Caltech and the Lawrence Berkeley National Laboratory.

還有其他一些人在進(jìn)行利用陽(yáng)光制造太陽(yáng)能燃料的研究。美國(guó)能源部(US Department of Energy)旗下有一個(gè)專(zhuān)門(mén)進(jìn)行這方面研究的中心——人工光合作用聯(lián)合中心(Joint Center for Artificial Photosynthesis)，匯集了加利福尼亞理工學(xué)院(Caltech)和勞倫斯伯克利國(guó)家實(shí)驗(yàn)室(Lawrence Berkeley National Laboratory)等一批學(xué)術(shù)機(jī)構(gòu)。

Its mission is to develop a scalable technology that converts carbon dioxide, water and sunlight into renewable transportation fuels (even in a green future, trucks, planes and ships can’t be plugged into the grid while on the go). There are also a number of start-ups dedicated to transforming light energy into a storable, chemical alter ego; MIT Technology Review lists Opus12, Liquid Light, Joule Unlimited and LanzaTech. One challenge, among many, is to find cheap and plentiful catalysts; some techniques use platinum.

該中心的任務(wù)是開(kāi)發(fā)一項(xiàng)可以大規(guī)模應(yīng)用的技術(shù)，將二氧化碳、水和陽(yáng)光轉(zhuǎn)化為可再生的運(yùn)輸用燃料(即使在一個(gè)綠色未來(lái)，卡車(chē)、飛機(jī)和船舶也不可能插著電線運(yùn)行)。還有多家初創(chuàng)公司致力于將光能轉(zhuǎn)化為可儲(chǔ)存的化學(xué)能;《麻省理工科技評(píng)論》(MIT Technology Review)列舉了Opus12、Liquid Light、Joule Unlimited和LanzaTech。其中一個(gè)挑戰(zhàn)是，找到廉價(jià)和取之不盡的催化劑;目前一些技術(shù)使用鉑作為催化劑。

The excitement over artificial photosynthesis stems from its potential to create “dispatchable” renewable fuels, which can be stored and used when needed. In contrast, wind turbines and solar panels generate energy intermittently. That hurdle has hampered the bid to put renewables more firmly into the energy mix: one estimate, from the Cambridge University Science and Policy Exchange, contends that replacing the power supply of one coal-fired power station requires solar or wind substitutes to produce four times the output.

人工光合作用之所以令人振奮，是因?yàn)樗锌赡苤圃斐瞿軌騼?chǔ)存并在需要時(shí)使用的“可調(diào)遣的”可再生能源。與此形成反差的是，風(fēng)力發(fā)電機(jī)和太陽(yáng)能電池板只能斷斷續(xù)續(xù)地產(chǎn)生能量。這個(gè)問(wèn)題阻礙了使可再生能源成為能源結(jié)構(gòu)中更可靠組成部分的努力：劍橋大學(xué)科學(xué)和政策交流中心(Cambridge University Science and Policy Exchange)進(jìn)行的估測(cè)認(rèn)為，如果要用太陽(yáng)能或風(fēng)力發(fā)電來(lái)代替一座燃煤電廠的電力供應(yīng)，前者的裝機(jī)容量要達(dá)到后者的4倍。

There is another bonus to solar fuels: they need no infrastructure. They can be whisked to even the remotest rural locations, with obvious implications for the developing world. Those advocating more public support of the technology point out it can be deployed quickly in places such as refugee camps and isolated villages undergoing disease outbreaks. For those reasons, Bill Gates declared himself an aficionado of the concept earlier this year. In March, he blogged: “I’ve written before about the need for an energy miracle to halt climate change and provide access to electricity to millions of the poorest families who live without it. Making solar fuel would be one of those miracles.” Mr Gates, among others, founded breakthrough energy ventures to invest $1bn in clean energy.

太陽(yáng)能燃料還有一個(gè)好處：不需要基礎(chǔ)設(shè)施。它們可以被迅速送往最偏遠(yuǎn)的農(nóng)村地區(qū)，這對(duì)發(fā)展中國(guó)家來(lái)說(shuō)顯然意義重大。呼吁公眾加大支持這種技術(shù)的人士指出，這種技術(shù)可以快速部署在難民營(yíng)、疫情爆發(fā)的孤村等地方。出于這些理由，比爾•蓋茨(Bill Gates)在今年早些時(shí)候宣稱(chēng)，他本人對(duì)這個(gè)概念心向神往。他在3月發(fā)布博文稱(chēng)：“我之前曾撰文說(shuō)過(guò)，我們需要一個(gè)能源奇跡來(lái)遏止氣候變化，同時(shí)讓數(shù)以百萬(wàn)計(jì)目前尚未通電的最貧困家庭用上電。生產(chǎn)太陽(yáng)能燃料將是這樣的奇跡之一。”蓋茨和其他人創(chuàng)立了突破性能源風(fēng)投基金，對(duì)清潔能源投資10億美元。

Artificial photosynthesis will also appeal to another class of consumer: those living off-grid. By 2035, Accenture estimates, 12 per cent of people in North America and 11 per cent in Europe will be energy self-sufficient and potentially living off-grid.

人工光合作用還將吸引另一個(gè)消費(fèi)者群體：過(guò)著“脫網(wǎng)”生活的人。埃森哲(Accenture)估計(jì)，到2035年，北美12%的人和歐洲11%的人將實(shí)現(xiàn)能源自足，可能會(huì)脫離電網(wǎng)。

Tesla has already anticipated the trend: the company’s Powerwall battery is designed to store solar power generated during the day so that it can be used at night, and is targeted at the same market. Indeed, a whole movement has sprung up around eco-living, with multiple books and websites offering blueprints for off-grid utopias, often powered by wood-chopping.

特斯拉(Tesla)已經(jīng)預(yù)測(cè)到了這種趨勢(shì)：該公司的Powerwall電池能夠在白天儲(chǔ)存太陽(yáng)能電力，以便在夜間使用，該產(chǎn)品瞄準(zhǔn)同一個(gè)市場(chǎng)。實(shí)際上，圍繞著生態(tài)生活掀起了一陣?yán)顺保S多書(shū)籍和網(wǎng)站描繪了脫網(wǎng)生活的烏托邦藍(lán)圖，方法往往是砍柴。

This has inspired talk of a “death spiral” in the utilities industry: as renewables become cheaper, and with a huge infrastructure being serviced by a decreasing pool of customers, more will go off-grid. Enthusiasm for artificial photosynthesis, as with other renewables, is fuelled by green concerns too — and how fabulously post-modern that the cleanest way of going back to nature might be to fake it.

這引發(fā)了有關(guān)公用事業(yè)“死亡螺旋”的討論：隨著可再生能源變得更廉價(jià)，隨著越來(lái)越小的客戶(hù)群要支撐起龐大的基礎(chǔ)設(shè)施，更多人將選擇“脫網(wǎng)”。對(duì)人工光合作用乃至其他可再生能源的熱情，還受到人們對(duì)環(huán)境憂(yōu)慮的推波助瀾——要回歸自然，最清潔的方式可能是模仿自然，這是多么詩(shī)意的后現(xiàn)代啊。

The writer is a science commentator

本文作者是科學(xué)評(píng)論員