雅思阅读练习题：Sunny Days For Silicon

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　　Sunny Days For Silicon

　　You should spend about 20 minutes on Question 14-26 which are based on Reading Passage below.

　　AThe old saw that "the devil is in the details" characterizes the kind of needling obstacles that prevent an innovative concept from becoming a working technology. It also often describes the type of problems that must be overcome to shave cost from the resulting product so that people will buy it. Emanuel Sachs of theMassachusetts Institute of Technology has struggled with many such little devils m his career-tong endeavor to develop low-cost, high-efficiency solar cells. In his latest effort, Sachs has found incremental ways to boost the amount of electricity that common photovoltaics (PVs) generate from sunlight without increasing the costs. Specifically, he has raised the conversion efficiency of test cells made from multi-crystalline silicon from the typical 15.5 percent to nearly 20 percent—on par with pricier single-crystal silicon cells. Such improvements could bring the cost of PV power down from the current $1.90 to $2.10 per watt to $1.65 per watt. With additional tweaks, Sachs anticipates creating within Four years solar cells that can produce juice at a dollar per watt, a feat that would make electricity (rum the sun competitive with that from coal-burning power plants.

　　BMost PV cells, such as those on home rooftops, rely on silicon to convert sunlight into electric current. Metal interconnects then funnel the electricity out from the silicon to power devices or to feed an electrical grid. Since solar cells became practical and affordable three decades ago, engineers have mostly favored using single-crystal silicon as the active material, says Michael Rogol, managing director of Germany- based Photon Consulting. Wafers of the substance are typically sawed from an ingot consisting of one large crystal that has been pulled like taffy out of a vat of molten silicon. Especially at first, the high-purity ingots were left over from integrated-circuit manufacture, but later the process was used to make PV cells themselves, Rogol recounts. Although single-crystal cells offer high conversion efficiencies, they are expensive to make. The alternatives- multi-crystalline silicon cells, which factories fabricate from lower-purity, cast ingots composed or many smaller crystals—arc cheaper to make, but unfortunately they arc Jess efficient than single-crystal cells.

　　CSachs, who has pioneered several novel ways to make silicon solar cells less costly and more effective, recently turned his focus to the details of multi-crystalline silicon cell manufacture. The first small improvement concerns the little silver fingers that gather electric current from the surface of the bulk silicon," he explains. In conventional fabrication processes, cell manufacturers use screen-printing techniques ("like high-accuracy silk-screening of T-shirts," Sachs notes) and inks containing, silver particles to create these bus wires. The trouble is that standard silver wires come out wide and short, about 120 by 10 microns, and include many nonconductive voids. As a result, they block considerable sunlight and do not carry as much current as they should.

　　DAt his start-up company—Lexington, Mass- based 1366 Technologies (the number refers to the flux of sunlight that strikes the earth's outer atmosphere: 1.366 watts per square meter)—Sachs is employing "a proprietary wet process that can produce thinner and taller" wires that are 20 by 20 microns. The slimmer bus wires use less costly silver und can be placed closer together so they can draw more current from the neighboring active material, through which free electrons can travel only so far. At the same time, the wires block less incoming light than their standard counterparts.

　　EThe second innovation alters the wide, flat interconnect wires that collect current from the silver bus wires and electrically link adjacent cells. Interconnect wires at the top can shade as much as 5 percent of the area of a cell. "We place textured mirror surfaces on the faces of these rolled wires. These little mirrors reflect incoming light at a lower angle--around 30 degrees-—so that when the reflected rays hit the glass layer at Lire top, they stay within the silicon wafer by way of total internal reflection,” Sachs explains. (Divers and snorkelers commonly see this optical effect when they view water surfaces from below.) The longer that light remains inside, the more chance it has to be absorbed and transformed into electricity.

　　FSachs expects that new antireflection coatings will further raise multi-crystal line cell efficiencies. One of his firm's future goals will be a switch from expensive silver bus wires to cheaper copper ones. And he has a few ideas regarding how to successfully make the substitution. "Unlike silver, copper poisons the performance of silicon PVs," Sachs says, "so it will be crucial to include a low-cost diffusion barrier that stops direct contact between copper and the silicon." In this business, it's always the little devilish details that count.

　　GThe cost of silicon solar cells is likely to fall as bulk silicon prices drop, according to the U.S. Energy Information Administration and the industry tracking firm Solarbuzz. A steep rise in solar panel sales in recent years had led to a global shortage of silicon because production capacity for the active material lagged behind, but now new silicon manufacturing plants are coming online. The reduced materials costs and resulting lower system prices will greatly boost demand for solar-electric technology, according to market watcher Michael Rogol of Photon Consulting.

　　Questions 14- 18

　　Use the information in the passage to match the people or companies (listed A-C) with opinions or deeds below. Write the appropriate letters A-C in boxes 14-18 on your answer sheet.

　　NB you may use any letter more than once

　　A. Emanuel Sach

　　B. Michael Rogol

　　C. Solarbuzz

　　14. Gives a brief account of the history of the common practice to manufacture silicon batteries for a long time.

　　15. Made a joint prediction with another national agency.

　　16. Established an enterprise with a meaningful name.

　　17. Led forward in the solar-electric field by reducing the cost while raising the efficiency.

　　18. Expects to lower the cost of solar cells to a level that they could contend with the traditional way to generate electricity.

　　Questions 19-22

　　Do the following statements agree with the information given in Reading Passage 2?

　　In boxes 19-22 on your answer sheet, write

　　TRUE if the statement is true

　　FALSE if the statement is false

　　NOT GIVEN if the information is not given in the passage

　　19. The Achille’s heel of single-crystal cells is the high cost.

　　20. The multi-crystalline silicon cells are ideal substitutions for single-crystal cells.

　　21. Emanuel Sachs has some determining dues about the way to block the immediate contact between an alternative metal for silver and the silicon.

　　22. In the last few years, there is a sharp increase in the demand for solar panels.

　　Questions 23-27

　　Summary

　　Complete the following summary of the paragraphs of Reading Passage, using No More than Three words from the Reading Passage for each answer. Write your answers in boxes 23-27 on your answer sheet.

　　Emanuel Sachs made two major changes to the particulars of the manufacture 23. One is to take a 24 in the production of finer wires which means more current could be attracted from the 25 . The other one is to set 26 above the interconnect silver bus wires to keep the incoming sunlight by 27 .

　　参考译文：

　　太阳能硅电池

　　A

　　古语“细节决定成败”形象地刻画出了了那种针尖大小的障碍足以阻止一个创新的概念转化成一项实用的技术。它往往也描述出了这样一类问题：通过降低产品的成本来吸引消费者来购买。麻省理工学院的Emanuel Sachs在他的职业生涯中一直在努力通过许多这样的小细节开发低成本且高效率的太阳能电池。在他最新的研究中，Emanuel Sachs己经发现许多在不增加成本的前提下提高普通光伏(PV)从太阳光中产生的电量。具体来说，他将由多结晶硅制成的测试电池的转换效率从典型的15.5%提高至近20%——达到了比其价格更高的单晶硅电池的转换效率。这种改进可能将光伏发电的成本由现在的$1.90到$2.10每瓦下跌到$1.65每瓦。随着更多的调整，Sachs预计在四年内发明出太阳能电池，他可以讲成本降到$1每瓦，这将使转化自太阳能的电力由燃煤电厂生产的电力形成竞争关系。

　　B

　　大多数光伏电池，比如那些在家里的屋顶，是依靠硅材料将太阳光转换成电流。金属互相连接将电流从硅中导出来向电网输电。德国Photon Consulting公司常务董事Michael Rogol，认为自太阳能电池在30年前被普遍推广使用起，工程师们大多是釆用单晶硅作为活性物质的。该物质的晶片通常是从由一大块晶体组成的锭上锯下来的，而该晶体是从一大桶熔化了的硅中像太妃糖似得被拔出来的。Rogol补充说，特别是在刚开始的时候，髙纯度硅锭被废弃在集成电路制造厂，但之后就被用来制造太阳能电池。虽然单晶电池能提供商的转换效率，但它们的生产成本很高。其替代品——多晶硅电池，是工厂用低纯度的由许多小的晶体组成的铸造锭中制造的，生产成本低廉，但不幸的是他们比单晶电池的转换效率要低。

　　C

　　Sachs率先推出了一些新的方法使得太阳能硅电池更便宜更有效，最近他又将重点放在多晶硅电池制造的细节上。他解释说，第一个需要小幅改进的问题是关于“收集电流从硅表面上汇集电流的小的银制线路”。在传统的制造工艺中，电池制造商使用丝网印刷技术(“就像像高精度丝网印刷T恤一样，”Sachs注)和含有银粒子的油墨来创建线路。麻烦的是，标准的银制电线一般宽而且短，大约120微米长10微米宽，并包含许多不导电的空隙，因此阻挡了大量的阳光的吸收从而减少了本该传输的电流星。

　　D

　　在他创办的第一家位于马萨诸塞州Lexington的Technologies公司(该数字意指太阳光撞击地球外层大气的流量是：每平方米1366瓦特)——Sachs采用一项专有技术来制造更薄更高的电线：20*20微米。这种更细的电线使用成本较低的银，并且可以放置得更近，使它们能够从邻近的活性物质吸引更多的电流，在这些活性物质中，自由电子只可以在有限的范围内移动。与此同时，该电线比其它对应电线阻挡较少的入射光。

　　E

　　他的第二项创新改变了用来收集从银制电线以及电气连接的相邻的电池中的电流的扁平较宽的互相交错的电线。位于顶部的互相交错的电线可遮挡一个电池多达5%的区域。Sachs解释道，“我们在这些轧线的表面放上质感的镜面。这些小反射镜在一个较低的角度——大约30度左右反射入射光。因此，当反射光线击中顶部的玻璃层时，它们将会通过全内反射的方式留在硅晶片内。” (当潜水和浮潜的人从水下面看水的表而时，通常会看到这种光学效应。)该光线在硅晶片中停留的时间越长，它越有机会被吸收且被转化成电能。

　　F

　　Sachs预计新的抗反射涂层将进一步提高多晶电池的效率。他公司的未来目标之一是用较便宜的铜制电线替代目前使用的价格昂贵的银制电线。他对于如何成功地完成这项转换已经有了一些想法。Sachs说“铜不像银，它会削弱硅光伏电池的性能，所以使用阻断铜与硅之间的直接接触的材料将是至关重要的。”在这个行业，往往是细节决定成败。”

　　G

　　美国能源信息署和行业跟踪公司Solarbuzz认为，太阳能硅电池的成本很可能会随着硅价格的下降而走低。最近几年太阳能电池板销售的陡然上升己经导致硅的全球性短缺，因为活性物质的产能落后，但是现在新的硅制造工厂即将上线。Photon Consulting公司的市场观察员Michael Rogol认为，降低的材料成本以及随之降低的价格大大提高提振太阳能光电技术的需求。