[2008.06.14] Consumer fuel cells 寻找永恒

 Consumer fuel cells
消费者燃料电池

In search of forever
寻找永恒

Jun 12th 2008
From The Economist print edition

As a source of power for cars, fuel cells have been a disappointment. For laptops and mobile phones, they are just about to take off
作为给汽车提供动力的一种能源，燃料电池令人失望。对笔记本电脑和移动电话来说，他们还刚刚开始起步。

METHANOL is nasty stuff. Careless distillation in many a backwoods still has caused it to blind the imbibers of “alternative” alcoholic drinks. Yet it has its uses, and one of them may be to restore fuel cells to their oft-vaunted role as the power packs of the future-but with a twist. The main role that has been discussed for fuel cells over the past few decades is as replacements for the internal-combustion engine. Their actual use may turn out to be to provide power for portable electronic devices.

甲醇是一种危险物质。在一些偏远地区，蒸馏时不小心残留下的甲醇仍在导致饮用”替代”酒精饮料的贪杯者失明。然而它自有其用途，其中一个可能是使燃料电池重新恢复其常被过分吹捧的未来能源组的角色–但是有点变化。过去几十年来一直在讨论将燃料电池作为内燃机的替代者。但它的实际用途可能是为便携式电子设备提供能源。

A fuel cell is a device that combines hydrogen with oxygen to generate electricity. The traditional approach has been to use the gas itself in the cell-and that is the approach taken by the world’s carmakers in their so-far not very successful attempts to make a commercial fuel-cell-driven car. Since gaseous hydrogen is hard to store and handle, an alternative that some people have considered is to lock the hydrogen up in methanol, a liquid whose molecules are made of a carbon atom, an oxygen atom and four hydrogen atoms. Methanol will react with water in the form of steam to make hydrogen and carbon dioxide-a process known as steam reformation. Put a steam reformer in a car along with the fuel cell and you can fill the tank with methanol instead of hydrogen.

燃料电池是一种将氢和氧混合起来以产生电力的设备。传统的方法是在电池中使用气体–这也是全球汽车制造商在至今为止不太成功的商用燃料电池驱动汽车制造过程中采用的方法。由于气态的氢很难储存和处理，一些人已考虑另一种方法：将将氢锁定在甲醇里。甲醇是一种液体，它的分子构成是一个炭原子，一个氧原子和四个氢原子。甲醇遇水就会反应，产生氢气和二氧化碳气体–这一过程被成为”蒸汽转化”（或”蒸汽重整”）。将一个蒸汽转化器放在汽车里，和燃料电池一起，你就可以往油箱加满甲醇而不是氢气。

That idea has not gone very far, either. But it has provoked another thought. What if it were possible to decompose the methanol without steam, and within the fuel cell itself? And that has, indeed, turned out to be possible. The resulting cells are nowhere near powerful enough to run cars, but they are plenty powerful enough to stand in for small batteries. What is more, they last far longer than batteries and when they do need recharging, it is the work of a moment.

这个想法也没有发展得很成熟。但是它引发了另一种思考。如果分解甲醇时能不产生气体，并且将这一过程放到燃料电池内部，会怎么样呢？事实上这已经被证明是可能的。按照这个办法生产出来的电池还达不到驱动汽车的电力要求，但其电力已强到足够替代小型电池。更棒的是，它比电池更持久，并且，当需要重新充电时，只要一下就弄好了。

Proton power
质子能

In a direct-methanol fuel cell (DMFC) the methanol is oxidised at the anode in the presence of liquid water. The reaction, which requires a catalyst, turns the methanol and water into protons and electrons (in other words, dissociated hydrogen atoms) and carbon dioxide. While the electrons pass along an external circuit as an electric current, the protons diffuse through a membrane to the cathode, where they recombine with the incoming electrons to form hydrogen atoms that react instantly with oxygen to make water. With pleasing symmetry the water is then channelled back to mix with the incoming methanol. Even though DMFCs produce carbon dioxide, the amount is small enough for the cells to count as a much greener technology than batteries. Some companies also think the new cells could be safer than batteries, which can burst into flame if short-circuited.

在直接甲醇燃料电池（DMFC）中，甲醇在阳极上遇到液态水而氧化。这种反应，需要催化剂，将甲醇和水变成质子和电子（换句话说，就是游离的氢原子）以及二氧化碳。当电子作为一种电流通过外部电路，质子则渗透一层膜到达阴极，在那里它们与进来的电子又重新结合形成氢原子，这些氢原子立即与氧反应，产生水。由于令人愉悦的对称性，这些水随后被导回去，与进来的甲醇混合。尽管DMFC产生二氧化碳，其量也是非常小的，足以使人将DMFC看作一种比传统电池环保得多的技术。一些公司同时认为，这种新的电池也能比传统电池更安全–传统电池在短路的时候可能会燃烧。

The efficiency of a DMFC is determined by its membrane. One of the most commonly used sorts is made of Nafion, a polymer developed by DuPont from a variation of Teflon. Nafion, however, can be expensive and it allows some methanol to seep through, which wastes fuel. Researchers are therefore trying to come up with more efficient membranes-and one group, led by Paula Hammond of the Massachusetts Institute of Technology (MIT), appears to have done so.

DMFC的性能取决于它的膜。最常使用的一种膜是用Nafion制造的，这种大分子聚合物是杜邦公司从Teflon的一个变种开发出来的。然而，Nafion很昂贵而且能渗透过去一些甲醇，造成燃料的浪费。研究者们因此正尝试制造更高效的膜–其中一个组织，由麻省理工学院（MIT）的 Paula Hammond领导，看来已经做到了。

Dr Hammond and her colleagues used a newish thin-film fabrication technique known as “layer-by-layer”. This repeatedly dips a material into a solution, to build it up one layer at a time, while the properties of the liquid are gradually changed. That enables the structure of the resulting film to be fine tuned. When Dr Hammond coated a Nafion membrane in this way it became less permeable to methanol but kept its ability to transport protons. The effect, which the group reported in a recent issue of Advanced Materials, was to boost the cell’s electrical output by more than 50%. The next stage, which the team has now embarked on, is to build complete membranes rather than mere coatings. The researchers think these may be able to work as proton-exchange membranes in their own right.

Hammond博士和她的同事们使用一种新的薄膜制造技术，叫做”分层技术”。它将材料反复浸入某种溶液中，每次产生出一个涂层，而溶液的属性则慢慢地被改变。这使得最后得到的薄膜其结构能被精确调整。当Hammond博士用这种方法给Nafion膜做涂层，它对甲醇的渗透性降低了但保持了输送质子的能力。其效果，该小组在最近的《高级材料》上所做的报道说，是将燃料电池的电量输出提高了50％。下一步，该小组已经在着手进行了，是建造完全的膜而不仅仅是涂层。研究者们认为这些”完全的膜”其本身就具有交换质子的功能。

Squeeze me, please me
榨干我吧，让我高兴吧

Toshiba, a large Japanese electronics firm, reckons that DMFCs can be used to produce mobile devices that have no need for batteries at all. In its latest investment plan, it says it will begin making such cells within a year for mobile phones and laptops. Sharp, one of its rivals, recently said that it had developed new microfabrication techniques to build DMFCs with the highest power densities yet achieved. Sharp reckons this will enable it to produce cells that are the same size as the lithium-ion batteries used in mobile devices, but which can run those devices for much longer. Some in the industry talk of mobile phones capable of operating continuously for several weeks before their fuel cells need topping up.

东芝，日本一家很大的电子产品公司，认为DMFC能被用来制造根本无需电池的移动设备。在最近的投资计划中，它说将在一年内开始制造给移动电话和笔记本电脑使用的燃料电池。夏普，它的一个竞争对手，最近说已开发出了新的微制造技术，用来制造迄今为止功率密度最高的DMFC。夏普认为这将使它能够生产在移动设备中使用的锂离子电池那样大小的燃料电池，但是其续航时间要长得多。该行业的一些人谈到够连续工作几周的移动电话–在其燃料电池需要充电之前。

The most likely way that topping up will be done is with a cartridge of methanol that is inserted into the device and replaced when it is running low. As portable devices become more sophisticated, with added functions and large colour screens, they are draining batteries faster. MTI Micro, an American company, has put its version of a DMFC into satellite-navigation devices, which are often used for long periods. The company says it can run even a power-hungry model for up to 60 hours before the gadget needs refuelling.

最有可能的充电方法是将一个装有甲醇的盒子插入设备中，当它电力不足时就替换它。当便携式设备变得更加成熟，随着功能的增加和大彩色屏幕的出现，它们正在更快地耗尽电池。MTI Micro，一家美国公司，已将它的一种DMFC放到卫星导航设备中，这些设备通常要使用很长一段时期。公司说在需要重新充电之前它能在高耗电量的情况下运行长达60小时。

Longer life is a big appeal; some people would like to run their laptops continuously on a 12-hour flight. Hence, new rules are being drawn up for aircraft. America’s Department of Transportation is planning a rule change from October 1st to allow passengers and crew to bring fuel-cell-powered electronic devices and one or two fuel cartridges on board in their carry-on baggage. To qualify, the devices will have to meet certain safety standards. It is proposed that each passenger would be limited to about 200ml of fuel.

寿命更长是个巨大的吸引力；一些人喜欢在12小时的飞行中连续运行他们笔记本电脑。因此，航空业正在制定新的规定。美国交通部正计划从10月1日开始允许乘客和机组成员携带以燃料电池做能源的电子设备以及在他们的随身行李中携带一到两个燃料电池盒子。为了安全，这些设备将不得不符合特定的安全标准。有提议说每个乘客将限制在大约200ml燃料。

Successful work like that at MIT will help to make DMFCs cheaper and more efficient, which will, in turn, make them even more attractive as power sources for portable devices. Already, some companies are predicting that sales of refuelling cartridges could run into the billions within a few years of them coming into the market. Forget, then, the familiar cry: “Has anyone got a charger I can borrow?” It will be replaced by: “Can you spare me a squirt of methanol?”-and that won’t mean in your hooch.

MIT所取得这类成功将有助于制造出更廉价、更高效的DMFC，而这又反过来使得它作为便携式设备的能源更具吸引力。已经有一些公司在预测，一旦可反复添加燃料盒上市，其销售额在几年内就能到达几十亿个。那么，忘记这种熟悉的哭喊吧：”哪位有充电器可以借我？”它将被换成：”你能借我一滴甲醇吗？”–而这并不是指你的酒。

译者: 7colorwolf  http://www.ecocn.org/forum/viewthread.php?tid=12133&extra=page%3D1