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  3. Two new studies offer signs that this could be changing quickly. One offers a new way to produce solar cells more cheaply and sa

Two new studies offer signs that this could be changing quickly. One offers a new way to produce solar cells more cheaply and sa

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问题     Two new studies offer signs that this could be changing quickly. One offers a new way to produce solar cells more cheaply and safely than current methods. The other indicates that concentrating solar power, which uses the sun’ s energy to heat up a liquid that drives a turbine, could supply "a substantial amount of current energy demand."
    In a study released Wednesday in journal Nature, University of Liverpool’s Jon Major and several other researchers announced that they had found that magnesium chloride, which is used in making tofu, bath salts and applied to roads in the winter could replace cadmium chloride in the making of second-generation, thin-film solar cells.
    Speaking in a teleconference from Copenhagen, Major said magnesium chloride, which is extracted from seawater, would cost $0,001 per gram compared to $0.3 for cadmium chloride. It would also eliminate the challenges and expense of handling cadmium chloride, a highly toxic compound that requires elaborate safety measures to protect workers during its manufacture and a special disposal process when panels are no longer needed.
    "So what we have done without any loss of efficiency is to replace expensive and highly toxic material with one that is completely benign and much lower in cost in the process," Major said. "This offers a great cost benefit for production of these kinds of solar cells and could help make a step change in the production of them." The solar market is currently dominated by panels made with silicon. In a bid to make solar more competitive, there is growing interest from companies like First Solar in developing solar cells using cadmium telluride, which is more efficient and more flexible so it could be applied many more surfaces including windows. To make these cadmium telluride cells, a thin layer of cadmium chloride is applied to the solar cell, and then heated up in a furnace. This is considered the activation process, Major said, helping to boost a cell’s efficiency from around 1 percent to as much as 20 percent. In a bid to find a safer alternative, Major and his team first looked at sodium chloride, but found the efficiency was about half of cadmium chloride. Another option was difluoro chloromethane but that has been linked to ozone depletion and its use has been restricted by international agreements.
    They then turned to magnesium chloride and found that it was just as efficient as comparable and could be applied without any expensive safety equipment.
    Major said magnesium chloride isn’t being used at the moment, but was hopeful it "would be taken up by research and hopefully by industry once this work is publicized."
    Steve Krum, the director of corporate communications for First Solar, would only say cadmium chloride remains "critical part" of its production process and that it was not a "major cost driver in our manufacturing process."
Which of the following is not the reason why cadmium chloride is replaced by magnesium chloride?
选项 A、Magnesium chloride is cheaper than cadmium chloride.
B、Magnesium chloride has no poison.
C、The efficiency of magnesium chloride is as high as cadmium chloride.
D、Magnesium chloride can produce more efficiency than cadmium chloride.
答案D
解析 细节题。第四段第一句讲到“So what we have done without any loss ofefficiency is to replace expensive and highly toxic material with one that is completelybenign and much lower in cost in the process．”即所以。我们完全可以用一种完全良性而且成本低得多的物质来取代这种昂贵且带有剧毒的原料。而且无需承受任何效率损失。联系上下文可知，此处的one指的是氯化镁，由此可知，氯化镁无毒害、更廉价、效率与氯化镉相当，因而可以取代昂贵而有剧毒的氯化镉。A、B、C都符合文意。D项意为“氯化镁比氯化锅效率更高”，显然错误。因此，不能构成原因。
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