Level 5 Reading 5B

Reading 5B

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PLUGGING INTO THE SUN Early on a clear November morning in the Mojave Desert, a full moon is sinking over the gigawatt glare of Las Vegas. Nevada Solar One is sleeping. But the day's work is about to begin. It is hard to imagine that a power plant could be so beautiful: 400 hectares of gently curved mirrors lined up like canals of light. Parked facing the ground overnight, they are starting to awaken— more than 182,000 of them—and follow the sun. "Looks like this will be a 700-degree day," says one of the operators in the control room. His job is to monitor the rows of mirrors as they concentrate sunlight on long steel pipes filled with circulating oil, heating it as high as 400 degrees Celsius. The heat produces steam, driving a turbine and dynamo, pushing as much as 64 megawatts onto the grid— enough to electrify 14,000 households, or a few Las Vegas casinos. When Nevada Solar One came online in 2007, it was the first large solar plant to be built in the United States in more than 17 years. During that time, solar technology blossomed elsewhere. The owner of Nevada Solar One, Acciona, is a Spanish company, and the mirrors were made in Germany. Putting on hard hats and dark glasses, plant manager Robert Cable and I drive out to take a closer look at the mirrors. Men with a water truck are hosing some down. "Any kind of dust affects them," Cable says. On a clear summer day with the sun directly overhead, Nevada Solar One can convert about 20 percent of the sun's rays into electricity. Gas plants are more efficient, but this fuel is free. "If we talk about geothermal or wind, all these other sources of renewable energy are limited in their quantity," says Eicke Weber, director of the Fraunhofer Institute for Solar Energy Systems, in Freiburg, Germany. "The total power needs of the humans on Earth is approximately 16 terawatts," he adds. (A terawatt is a trillion—1,000,000,000,000—watts.) In a few years, that number is expected to grow to 20 terawatts. "The sunshine on the solid part of the Earth is 120,000 terawatts," says Weber. "From this perspective, energy from the sun is virtually unlimited." Tapping the Sun Solar energy may be unlimited, but its potential is barely tapped. Today, solar power accounts for a tiny fraction of U.S. electricity production—just over 2 percent. "But," said Robert Hawsey, an associate director of the National Renewable Energy Laboratory (NREL) in Golden, Colorado, "that's expected to grow. Ten to 20 percent of the nation's peak electricity demand could be provided by solar energy by 2030." Achieving that level will require government help. Nevada Solar One was built because the state had set a deadline requiring utilities to generate 20 percent of their power from renewable sources by 2015. During peak demand, the solar plant's electricity is almost as cheap as that of its gas-fired neighbor— but that's only because a 30 percent federal tax credit helped offset its construction costs. The aim now is to bring down costs and reduce the need for subsidies and incentives. To achieve this, NREL's engineers are studying mirrors made from lightweight polymers instead of glass, and tubes that will absorb more sunlight and lose less heat. They're also working on solar power's biggest problem: how to store some of the heat produced during daylight hours for release later on. Nevada Solar One use solar thermal energy (STE) technology, which collects the sun's rays via mirrors to produce thermal energy (heat). Another method is to convert sunlight directly into electricity with photovoltaic (PV) panels made of semiconductors such as silicon. Back in the 1980s, an engineer named Roland Hulstrom calculated that if PV panels covered just three-tenths of a percent of the United States, they could electrify the entire country. Years later, PV panels contribute a small—but growing—amount to the nation's electricity supply. On rooftops in California, Nevada, and other states with good sunshine and tax incentives, they are increasingly common—almost as familiar as air conditioners. For years, PV power was not as developed as solar thermal, but today it is the dominant solar power technology. Massive investment, government incentives, and technological breakthroughs have caused prices for PV panels to fall dramatically. In 2009, the U.S. company First Solar became the first to manufacture thin-film solar cells at a cost of under a dollar a watt—close to what's needed to compete with fossil fuels.

接通太阳 11月一个晴朗的清晨，在莫哈韦沙漠， 一轮满月正笼罩在拉斯维加斯的千兆瓦眩光之上。 内华达太阳能一号正在睡觉。 但一天的工作即将开始。 很难想象一座发电厂会如此美丽： 400公顷的平缓弯曲的镜子像光线的运河一样排列。 他们面朝地面停了一夜，开始苏醒-- 超过18.2万只，追随太阳。 “看起来这将是700华氏度的一天，” 控制室的一名操作员说。 他的工作是监控成排的镜子，因为它们将阳光集中在长钢管上 充满循环油，将其加热至400摄氏度。 热量产生蒸汽，驱动涡轮机和发电机， 向电网输送高达64兆瓦的电力-- 足以为14000户家庭或拉斯维加斯的几家赌场供电。 当内华达太阳能一号于2007年上线时， 这是17年多来美国建造的第一座大型太阳能发电厂。 在那段时间里，太阳能技术在其他地方蓬勃发展。 内华达太阳能一号公司Acciona的所有者是一家西班牙公司， 镜子是德国制造的。 戴上安全帽和墨镜， 工厂经理罗伯特·凯布尔和我开车出去仔细看看镜子。 一辆运水车的男人正在冲洗一些水。 凯布尔说：“任何灰尘都会影响它们。”。 在一个晴朗的夏日，阳光直射头顶， 内华达太阳能一号可以将大约20%的太阳光转化为电能。 天然气厂效率更高，但这种燃料是免费的。 “如果我们谈论地热或风能， 所有这些其他可再生能源的数量都是有限的，” 德国弗莱堡弗劳恩霍夫太阳能系统研究所所长Eicke-Weber说。 他补充道：“地球上人类的总电力需求约为16太瓦。”。 （一太瓦等于一万亿瓦。） 几年后，这一数字预计将增长到20太瓦。 韦伯说：“地球固体部分的阳光是12万太瓦。”。 “从这个角度来看，太阳的能量几乎是无限的。” 轻敲太阳 太阳能可能是无限的，但它的潜力几乎没有被挖掘出来。 如今，太阳能在美国电力生产中只占很小一部分，仅略高于2%。 “但是，”罗伯特·霍西说， 科罗拉多州戈尔登的国家可再生能源实验室（NREL）副主任， “预计会增长。全国峰值电力需求的10%至20% 到2030年，太阳能可以提供。” 达到这一水平需要政府的帮助。 内华达太阳能一号的建造是因为该州设定了最后期限 要求公用事业公司到2015年将20%的电力来自可再生能源。 在需求高峰期，太阳能发电厂的电力几乎 和它的燃气邻居一样便宜-- 但这只是因为30%的联邦税收抵免 帮助抵消了其建筑成本。 现在的目标是降低成本，减少对补贴和激励措施的需求。 为了实现这一目标，NREL的工程师 正在研究由轻质聚合物而不是玻璃制成的镜子， 以及吸收更多阳光、损失更少热量的管子。 他们也在研究太阳能最大的问题： 如何储存白天产生的一些热量，以便稍后释放。 内华达太阳能一号使用太阳能热能（STE）技术， 其通过镜子收集太阳光线以产生热能（热）。 另一种方法是将阳光直接转化为电能 使用由硅等半导体制成的光伏（PV）面板。 早在20世纪80年代，一位名叫Roland Hulstrom的工程师 经计算，如果光伏电池板仅覆盖美国十分之三的面积， 他们可以给整个国家通电。 几年后，光伏电池板对国家电力供应的贡献虽然很小，但还在不断增长。 在加利福尼亚州、内华达州和其他阳光充足、税收优惠的州的屋顶上， 它们越来越常见，几乎和空调一样熟悉。 多年来光伏发电不如太阳能热发电发达， 但如今，它是占主导地位的太阳能技术。 大规模投资、政府激励和技术突破 导致光伏电池板价格大幅下跌。 2009年，美国公司First Solar成为第一家生产薄膜太阳能电池的公司 每瓦的成本不到一美元，接近与化石燃料竞争所需的成本。

Germany's Solar Solution On a cold December morning west of Frankfurt, Germany, fog hangs frozen in the trees, and clouds block the sun. In the town of Morbach, the blades of a 100-meter-high wind turbine appear and disappear in the gloom, while down below, a field of photovoltaic panels struggle for light. Considering its unpredictable weather, who would have thought that Germany would transform itself into one of the top producers of photovoltaic power in the world? A fraction of Germany's five-gigawatt photovoltaic power comes from centralized the plants like the one at Morbach. With land at a premium in Germany, solar panels can be found mounted on rooftops, farmhouses, even on soccer stadiums and along the autobahn. The panels, dispersed across the German countryside, are all connected to the national grid. The solar boom has completely transformed towns like "sunny Freiburg," as the tourist brochures call it. The town sits at the edge of the Black Forest in the southern part of the country. Towering walls of photovoltaics greet visitors as they arrive at Freiburg's train station. Across the street from a school covered with photovoltaic panels is Solarsiedlung (" solar settlement"), one of the town's condominium complexes. "We are being paid for living in this house," said Wolfgang Schnurer, one of Solarsiedlung's residents. The day before, when snow covered the roof, Schnurer's system produced only 5.8 kilowatt-hours, not enough power for a German household. But on a sunny day in May, it yielded more than seven times that much. In Germany, regulations require utility companies to pay even the smallest PV producers a premium of about 50 euro-cents a kilowatt-hour. In 2008, Schnurer's personal power plant yielded over 6,000 kilowatt-hours, more than double the amount the family consumed. When they subtracted their usage from the amount they produced, the family found they were more than 2,500 euros (nearly $3,000) in profit. Anybody who installs a PV system is guaranteed above-market rates for 20 years— the equivalent of an 8 percent annual return on the initial investment. "It is an ingenious mechanism," Eicke Weber said. "I always say the United States addresses the idealists, those who want to save the planet. In Germany, the law addresses anyone who wants to get 8 percent return on his investment for 20 years." In total, Germany now generates over 6.5 percent of its electricity annually from solar energy, whereas the United States generates less than half this amount. The largest photovoltaic installation in the United States— the Solar Star in California—is only the 11th largest in the world. Nearly all the bigger ones are located in either China or India. But in the United States, too, there is a gathering sense that the time for solar energy has arrived— if there is a commitment to jump-start the technology. "Originally it seemed like a pie-in-the-sky idea," said Michelle Price, the energy manager at the Nellis Air Force base outside Las Vegas. "It didn't seem possible." Many things seem possible now.

德国的太阳能解决方案 在德国法兰克福以西一个寒冷的12月早晨， 雾冻在树上，云挡住了太阳。 在莫尔巴赫镇，一台100米高的风力涡轮机的叶片 在黑暗中出现和消失， 而在下面，一片光伏板正在争光。 考虑到其不可预测的天气， 谁会想到德国会改变自己 成为世界上最大的光伏发电商之一？ 德国5吉瓦光伏发电的一小部分 来自集中化的工厂，如莫尔巴赫的工厂。 由于德国的土地价格很高， 太阳能电池板可以安装在屋顶、农舍、屋顶上， 甚至在足球场和高速公路沿线。 这些配电盘分散在德国农村，全部与国家电网相连。 太阳能热潮彻底改变了像“阳光明媚的弗莱堡”这样的城镇 正如旅游手册所说。 该镇位于该国南部黑森林的边缘。 当游客抵达弗莱堡火车站时，高耸的光伏墙迎接他们。 街对面是一所学校，上面覆盖着光伏板 是Solarsiedlung（“太阳能定居点”）， 该镇的一栋共管公寓楼。 “我们住在这所房子里是有报酬的。” Solarsiedlung的居民Wolfgang Schnurer说。 前一天，当雪覆盖了屋顶， Schnurer的系统仅产生5.8千瓦时的电力，不足以满足德国家庭的用电需求。 但在五月的一个阳光明媚的日子里，它的产量是这个数字的七倍多。 在德国，法规要求公用事业公司支付 即使是最小的光伏生产商，每千瓦时也能获得约50欧分的溢价。 2008年，Schnurer的个人发电厂发电量超过6000千瓦时， 是家庭消费量的两倍多。 当他们从生产量中减去使用量时， 这家人发现他们的利润超过2500欧元（近3000美元）。 任何安装光伏系统的人都可以保证在20年内高于市场价格-- 相当于初始投资8%的年回报率。 “这是一个巧妙的机制，”Eicke-Weber说。 “我总是说，美国是针对理想主义者的， 那些想要拯救地球的人。 在德国，法律适用于任何希望在20年内获得8%投资回报的人。" 总的来说，德国现在每年超过6.5%的电力来自太阳能， 而美国的产量不到这一数字的一半。 美国最大的光伏装置-- 加利福尼亚州的太阳星是世界上第11大恒星。 几乎所有较大的公司都位于中国或印度。 但在美国， 人们越来越觉得太阳能时代已经到来-- 如果有人承诺启动这项技术。 米歇尔·普莱斯说：“起初，这似乎是一个不切实际的想法。”， 拉斯维加斯郊外内利斯空军基地的能源经理。 “这似乎不可能。”现在很多事情似乎都是可能的。

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