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Running Cars on Hydrogen Made from Starch/用淀粉中提取的氢燃料驱动汽车

(2007-05-27 13:05:31)

Running <wbr>Cars <wbr>on <wbr>Hydrogen <wbr>Made <wbr>from <wbr>Starch/用淀粉中提取的氢燃料驱动汽车

Running Cars on Hydrogen Made from Starch
A new way to make hydrogen from corn or potatoes could make fuel-cell vehicles more practical.




Using a stew of enzymes culled from several organisms, researchers have developed a way to convert starch, available from numerous sources including corn and potatoes, into hydrogen gas at low temperatures and pressures. The method produces three times more hydrogen than an older enzymatic method does, suggesting that it might be practical to use such enzymes to produce hydrogen for fuel-cell vehicles.


While fuel-cell vehicles are appealing because they emit no pollutants, it's been a challenge to find clean and affordable ways to produce, transport, and store hydrogen to fuel them. Most commonly, hydrogen is extracted from fossil fuels. Making hydrogen by electrolyzing water is energy intensive and can be expensive. The new system improves on other experimental methods for creating hydrogen from biomass by using low temperatures, making it potentially more convenient and energy efficient.

The researchers--from Virginia Tech, in Blacksburg, VA; Oak Ridge National Laboratory; and the University of Georgia, in Athens--combined 13 commercially available enzymes isolated from yeast, bacteria, spinach, and rabbit muscle. The work is available online in PLoS ONE, a journal published by the Public Library of Science. The hydrogen comes from two sources: the starch and the water used to oxidize the starch. The enzymes facilitate chemical reactions in which the water and starch can be completely converted into hydrogen and carbon dioxide, says Y. Percival Zhang, professor of biological systems at Virginia Tech. (The carbon dioxide released is offset by the carbon dioxide captured by plants that provide the starch.)
来自于弗吉尼亚理工(位于Blacksburg, VA)、Oak Ridge国家实验室以及佐治亚大学的研究人员在雅典对13种市面上可以获取的商业酶进行合成,这些酶是从酵母、细菌、菠菜以及兔子的肌肉中提取出来的。他们的研究成果可以在PLoS ONE的网站上在线获取,PLoS ONE是由科学公共图书馆公司发行的一本学术期刊。氢可以来源于两种途径:淀粉及氧化生成淀粉所需要的水。Y. Percival Zhang(弗吉尼亚理工生物系统教授)称这些酶可以加速化学反应,并能使水和淀粉充分地转化成氢气和二氧化碳。可以采用植物来吸收所释放的二氧化碳,而这些植物又可以继续产生新的淀粉。


The new system produces a higher yield of hydrogen than previous experimental systems that used enzymes for converting sugars into hydrogen. But while the yield of hydrogen is high, so far the rates at which the gas is produced are extremely low. That's in part because the researchers used off-the-shelf enzymes and have not optimized the system, Zhang says. The scientists' next project will include analyzing each stage of the process in detail to find the rate-limiting steps.

For example, one of the enzymes may be producing a by-product that slows down later steps, says Michael Adams, professor of biochemistry and molecular biology at the University of Georgia. The researchers would then look for other enzymes, or modify current ones, to minimize the by-product. They will also look for enzymes that can operate at higher temperatures. "If you increase the temperature by 10 degrees, most times you can increase the reaction rate twofold," Zhang says.
Michael Adams(佐治亚大学生物化学及蛋白质生物学教授)说,可能其中一种酶会产生一种减缓后续反应步骤的副产物。研究人员将寻找其他的酶,或对现有的酶进行调整,将副产物最小化。同时,他们还将寻找可以在高温条件下工作的酶。Zhang教授指出:通常地,如果你将温度升高10度,那么反应的速度将随之翻倍。


One of the first applications of the system, Zhang says, could be generating hydrogen for fuel cells in portable electronics. The starch could be a safer way of storing energy than using methanol, a current leading option for such small fuel-cell systems. He estimates that it will take about six to eight years to improve the rates enough for such applications. Eventually, he hopes to use his process to solve one of the biggest current problems with hydrogen fuel-cell vehicles: fitting enough hydrogen on board to compete with gasoline-powered vehicles.


But some Department of Energy (DOE) officials doubt that the entire system will be light enough for onboard use. Sunita Satyapal, the hydrogen-storage team leader at DOE, notes that the researchers' estimates do not include the weight of the water or the other equipment needed to produce the hydrogen. These things could more than double the weight of the system, she says, even if water produced by the fuel cell is recycled. The system will probably be too heavy to give the vehicle a

driving range competitive with gasoline engines, suggests Satyapal.
但是一些能源部(DOE)的一些官员怀疑这套系统的重量是否适合车载使用。Sunita Satyapal(DOE氢储存团队领导者)指出:该系统的研究人员没有考虑到水的的重量以及产生氢气所需要的其他设备,这些将成倍增加系统的重量,即使燃料电池所产生的水可以循环使用。Satyapal指出这套系统可能会因过太沉而影响到行驶里程,进而影响它和汽油引擎的竞争力。


She also notes that the rate of hydrogen production is now orders of magnitude lower than it would need to be for use in vehicles, and it will be very difficult, if not impossible, to sufficiently improve the rate.


But even if the new system is not useful as a way of producing hydrogen in a car, it eventually could prove useful for producing hydrogen at fueling stations. One of the challenges with hydrogen production is the cost of compressing and transporting hydrogen from central locations. On-site production using enzymes at filling stations, or even in people's homes, could get around these issues. In such applications, the hydrogen production rate can be lower than it is aboard a vehicle, as the hydrogen can be produced around the clock in relatively large tanks.


Still, some are skeptical of the basic concept of using starch to create fuel. "Making food into hydrogen is not such a great idea," says John Deutch, a chemistry professor at MIT. Indeed, demand for corn to make ethanol is already increasing food prices. Using corn starch to make hydrogen could exacerbate the problem.
即使这样,还是有一些人对采用淀粉制造燃料持怀疑态度。John Deutch(麻省理工学院化学教授)认为将食物转化成氢气并不是一个很好的主意。通过玉米生产乙醇方法已经抬高了食物的价格,而用淀粉生产氢气的做法只会使问题变得更加严峻。

But Zhang notes that employing starch to make hydrogen would be a much better use of the available corn than turning it into ethanol: fuel cells can be three times more efficient than ethanol-burning internal combustion engines. Nevertheless, he sees starch as a temporary solution. Zhang is also developing a version of the process that starts with cellulose, found primarily in the nonfood parts of plants.
但是Zhang 教授指出采用淀粉产生氢气要优于用玉米制造乙醇:燃料电池的效率要3倍于乙醇内燃引擎,甚至更高。然而,他认为淀粉只是一个暂时的解决方案。Zhang 教授同时也在发展另一种处理方法-通过纤维素产生氢气,而纤维素主要存在于植物的非食物部分。


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