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本帖{zh1}由 towersimper 于 2010-4-24 00:06 编辑
Magnesium power
镁能
White-hot energy
白热的能量
New power sources could be made using magnesium
用镁能制造新的能源
Apr 19th 2010 | From The Economist online
STORING energy is one of the biggest obstacles to the widespread adoption of alternative sources of power. Batteries can be bulky and slow to charge. Hydrogen, which can be made electrolytically from water and used to power fuel cells, is difficult to handle. But there may be an alternative: magnesium. As school chemistry lessons show, metallic magnesium is highly reactive and stores a lot of energy. Even a small amount of magnesium ribbon burns in a flame with a satisfying white heat. Researchers are now devising ways to extract energy from magnesium in a more controlled fashion.
广泛采用替代性能源的{zd0}障碍之一就是怎样将能量储存起来。电池体积大而且充电缓慢。氢气，可以通过对水进行电解制造出来，也可以用来给燃料电池提供能量，但是处理起来困难。不过可能还有另一种选择：镁。正如学校化学课中展示的那样，金属镁化学性质非常活泼，储存着大量能量。即使少量镁条燃烧的火焰就足以释放出令人悦目的白热。研究人员目前正在发明一些方法以便更加可控地从镁中获取能量。
Engineers at MagPower in White Rock, British Columbia, for example, have developed a metal-air cell that uses water and ambient air to react with a magnesium fuel supply, in the form of a metal anode, to generate electricity. Doron Aurbach at Bar-Ilan University, Israel, has created a magnesium-based version of the lithium-ion rechargeable cell, a type of battery known for its long life and stability. It would be ideal for storing electricity from renewable sources, says Dr Aurbach. And Andrew Kindler at the California Institute of Technology in Pasadena is developing a way for cars to generate hydrogen on board by reacting magnesium fuel with steam. The reaction produces a pure form of hydrogen suitable for fuel cells, leaving behind only magnesium oxide, a relatively benign material, as a by-product.
例如，位于不列颠哥伦比亚省白石镇的MagPower公司工程师就已开发出一种金属-空气电池，它使用水和大气与以金属正极形式存在的镁燃料供给源发生反应产生电流。 众所周知，可充电的锂离子电池寿命长，稳定性好，而以色列Bar-Ilan大学的Doron Aurbach创造出该电池的基于镁的版本。Aurbach博士说，将来自可再生源的电流储存起来，这是非常理想的。帕萨迪纳市加利福尼亚理工学院的Andrew Kindler正在针对汽车开发一种方法使得在车上通过镁燃料与蒸汽反应产生氢气。这种反应产生的氢气纯度适合燃料电池使用，此外只产生一种相对无害的物质，即副产物氧化镁。
But there is, of course, a catch. Although magnesium is abundant, its production is neither cheap nor clean, says Takashi Yabe of the Tokyo Institute of Technology. Various industrial methods are used to extract magnesium, ranging from an electrolytic process to a high temperature method called the Pidgeon process, but the energy cost is high. Producing a single kilogram of magnesium requires 10kg of coal, says Dr Yabe.
当然也存在不足之处。东京工业大学的Takashi Yab说，尽管镁元素大量存在，但是制造镁的方法并不便宜也不对环境友好。已经有不少方法用来提取镁，范围涵盖从电解过程到被称为皮金过程的高温方法，但这些方法能量消耗高。Yabe博士说，单单产生1kg镁就需要10kg煤炭。
To change this, he is developing a process using only renewable energy. Dr Yabe’s solution is to use concentrated solar energy to power a laser, which is used to heat and ultimately burn magnesium oxide extracted from seawater—where, he says, there is enough magnesium to meet the world’s energy needs for the next 300,000 years. A solar-pumped laser is necessary, he says, because concentrated solar energy alone would not be enough to generate the 3,700?C temperatures required. Dr Yabe calls his approach the Magnesium Injection Cycle.
为了改变这种情况，他正在开发一种只使用再生能源的过程。Yabe博士的解决方法就是使用集光型太阳能给激光提供能量，而激光用来加热和最终灼烧从海水中提取的氧化镁。他说，海水里有足够的镁来满足这个世界未来30万年的能量需求。他说，这个太阳光泵浦激光是必须的，因为集光型太阳能单独并不足以产生所需的3700?C高温。Yabe博士将这个过程称为镁注入循环法。
The pure magnesium can then be used as a fuel (its energy density is about ten times that of hydrogen). When the magnesium is mixed with water, it produces heat, boiling the water to produce steam, which can then drive a turbine and do useful work. The reaction also produces hydrogen, which can be burned to produce even more energy. The byproducts are water and magnesium oxide, which can then be converted back into magnesium using the solar laser.
该方法产生高纯度的镁随后就可作为燃料(它的能量密度大约为氢气的10倍)。当镁与水混合在一起时，它就会产生热量，让水沸腾产生蒸汽，而产生的蒸汽然后就可以驱动涡轮机，而且也可用来做些有用的工作。这个反应也产生氢气，而氢气燃烧后能产生更加多的能量。反应副产物是水和氧化镁，而氧化镁然后又可通过使用太阳能激光法转换成镁。
The trouble is that concentrated solar collectors tend to be huge and costly, and solar-pumped lasers are normally very low powered. Dr Yabe’s trick is to use relatively small Fresnel lenses—transparent and relatively thin planar lenses made up of concentric rings of prisms. These are commonly found in lighthouses to magnify light in a way that would normally require a much larger, thicker lens. His other trick is to boost the output power of the lasing material, neodymium-doped yttrium aluminium garnet. It normally only absorbs about 7% of the energy from sunlight, but when doped with chromium this figure increases to more than 67%.
该方法的缺点在于集光型太阳能收集器往往体积比较庞大且造价昂贵，以及太阳光泵浦激光正常情况下功率太低。Yabe博士所采用的方法诀窍就是使用菲涅耳透镜----透明和相对薄的由同心环棱镜制成的平面透镜。人们经常会在灯塔上发现这些透镜，灯塔以某种方法将光放大，而正常条件下做到这点则需要非常大且厚的透镜。他所采用的另一个诀窍就是提高激光物质，掺钕的钇铝石榴石的输出功率。这个激光物质正常条件下只吸收大约7%的来自太阳光的能量，但是当掺杂铬时，这个数字可以增加到67%以上。
Dr Yabe has built a demonstration plant at Chitose, Japan, in partnership with Mitsubishi. It is capable of producing 80 watts of power from the laser, enough to cut steel and extract 70% of the magnesium in seawater. The process will, says Dr Yabe, become commercially viable when the laser power reaches 400 watts, which could happen later this year. “As a starting point we are planning to use 300 lasers to produce 50 tonnes of magnesium per year,” he says. After that, it is just a small matter of convincing the world to start thinking about a magnesium economy instead of hydrogen one, he adds.
Yabe博士与三菱合作，已经在日本千岁建立了一座实验厂。该厂能产生80瓦功率的激光，足以用来切割钢铁和提取海水里70%的镁。Yabe博士说，当激光功率达到400瓦时，这种过程在商业上就能切实可行，而这要到今年晚些时候方可实现。他说，“起点就是我们正在计划使用300束激光每年生产50吨镁”。他补充道，在此之后，仅需要做点小小的工作来说服整个世界开始思考用镁经济来代替氢经济。
【注释】
solar-pumped laser：中文意思就是太阳光泵浦激光。它跟常规激光一样有着相同的光学性质，比如产生的激光束是由相干性的电磁辐射组成，且电磁辐射能达到很高的功率，不同的是它使用太阳光辐射来驱动激光物质产生激光，而常规的激光则使用人工做的能源来驱动。就太阳光泵浦激光而言，研究得最多的两种激光物质是碘，产生的激光波长为1.31微米，和钕钇铝柘榴石(NdCrYAG)，产生激光波长为1.06微米。 |
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