第4部分 阅读理解
Better Solar Energy Systems: More Heat,More Light
Solar photovoltaic thermal energy systems,or PVTs, generate both heat and electricity, but until now they haven’t been very good at the heat-generating part compared to a stand-alone solar thermal collector. That’s because they operate at low temperatures to cool crystalline silicon solar cells, which lets the silicon generate more electricity but isn’ta very efficient way to gather heat.
That’s a problem of economics. Good solar hot-water systems can harvest much more energy than a solar-electric system at a substantially lower cost. And it’s also a space problem: photovoltaic cells can take up all the space on the roof, leaving little room for thermal applications.
In a pair of studies, Joshua Pearce, anassociate professor of materials science and engineering, has devised a solution in the form of a better PVT made with a different kind of silicon. His research collaborators are Kunal Girotra from Thin Silicon in California and Michael Pathak and Stephen Harrison from Queen’s University, Canada.
Most solar panels are made with crystalline silicon, but you can also make solar cells out of amorphous silicon, commonly known as thin-film silicon. They don’t create as much electricity, but they are lighter, flexible, and cheaper. And, because they require much less silicon,they have a greener footprint. Unfortunately, thin-film silicon solar cells are vulnerable to some bad-news physics in the form of the Staebler-Wronski effect.
“That means that their efficiency drops when you expose them to light— pretty much the worst possible effect for a solar cell,” Pearce explains,which is one of the reasons thin-film solar panels make up only a small fraction of the market.
However, Pearce and his team found a way to engineer around the Staebler-Wronski effect by incorporating thin-film siliconin a new type of PVT. You don’t have to cool down thin-film silicon to make it work. In fact, Pearce’s group discovered that by heating it to solar-thermal operating temperatures, near the boiling point of water, they could make thicker cells that largely overcame the Staebler-Wronski effect. When they applied the thin-film silicon directly to a solar thermal energy collector,they also found that by baking the cell once a day, they boosted the solar cell’s electrical efficiency by over 10 percent.
31. PVTs are not efficient in
A. creating electricity.
B. cooling silicon solar cells.
C. generating heat.
D. powering solar thermal collectors.
32. One of the problems PVTs have is that
A. their thermala pplications are costly.
B. they are too expensive to afford.
C. it is hard to fix them on the roof.
D. they occupy too much space.
33. Which of the following is NOT mentioned as an advantage of thin-film silicon solar cells?
A. They are flexible.
B. They are less expensive.
C. They are electrically efficient.
D. They are environment friendly.
34. Thin-film solar panels do not sell well on market because
A. they do not work well if exposed to light.
B. their advantages are not well-recognized.
C. they need improving in appearance.
D. they are not advertised.
35 Which of the following statements is true?
A. New techniques have been developed to produce thin-film silicon.
B Thin-film silicon works efficiently at low temperature.
C Thin-film silicon's electrical efficiency improves when heated up.
D Anew material enlarging the Staebler-WronsKi effect has been created.
译文：
第十三篇 更有效的太阳能系统：更多热量，更强灯光
太阳能光伏热能系统，也叫PVT，能够生成热量和电能。与太阳热能单机收集器相比，传统太阳能光伏热能系统在转换热能方面效率不是很高。原因是，为了使晶体硅太阳能电池冷却，该系统在低温下工作。因此，硅体能产出更多的电能，却不能有效地产生热量。
第一，经济问题。好的太阳能热水系统比太阳能电力系统收集的能量更多，而且成本低得多。第二，空间问题。光电管占去屋顶的所有的空间，几乎没有空间留给热能的产出。
在一项研究中，材料科学与工程副教授Joshua Pearce找到了一个解决方案：用另外一种硅制成PVT来解决效能问题。他的合作者有：来自加利福尼亚ThinSilicon的Kunal Girotra和加拿大皇后大学的Michael Pathak和Stephen Harrison。
大部分太阳能电池板是由晶体硅制成，但是，你也可以用非晶硅制成太阳能电池，这种非晶体硅通常被叫作薄膜硅。它们不能产生那么多的电能，但是更亮、更灵巧、成本更低。而且，由于它们需要的硅较少，它们更环保。不幸的是，薄膜硅太阳能电池易受SWE效应攻击(在光的照射下，非晶硅氢的导电性短时间内显著衰退，这种特性被称为SWE效应)。
“当被暴露在光线下，那就意味着它们的能效会降低——这几乎是太阳能电池最可能糟糕的效应。”Pearce解释道。这就是薄型太阳能板只占有一少部分市场的原因。
然而，Pearce和他的团队把薄膜硅合成为一种新型的PVT，可以克服或绕过SWE效应。这种方法可以不用冷却薄膜硅而让它们产生效能。事实上，Pearce团队发现，通过把薄膜硅加热到太阳热能操作温度，即临近水的沸点，可以把它制成较厚的电池，从而可以遏制SWE效应。当把薄膜硅直接应用到太阳热能集热器时，他们也发现，如果一天把太阳能电池加热一次，那么太阳能的电力效能会增加10%。