查看听力原文
NARRATOR:Listen to part of a lecture in an environmental science class.
MALE PROFESSOR:Alright folks, let's continue our discussion of alternative energy sources, and move on to what's probably the most well-known alternative energy source, umm, solar energy.The sun basically provides earth with a virtually unlimited source of energy every day, but the problem has always been how do we tap this source of energy.Can anyone think of why it's so difficult to make use of solar energy?
FEMALE STUDENT:Because it's hard to... um... gather it?
MALE PROFESSOR:That's exactly it.Solar energy is everywhere, but it's also quite diffused.And the thing is, the dream of solar energy is not a new one.Humanity has been trying to use the sun's light as a reliable source of energy for centuries.And around the beginning of the 20th century there were actually some primitive solar water heaters on the consumer market, but they didn’t sell very well.Any of you wanna guess why?
FEMALE STUDENT:Well, there were other energy choices like oil and natural gas, right?
MALE PROFESSOR:Yeah, and for better or for worse, we chose to go down that path as a society.When you consider economic factors, it's easy to see why.But then in the 1970s, there was an interest in solar energy again. Why do you think that happened?
MALE STUDENT:Because oil and natural gas were... err... became scarce?
MALE PROFESSOR:Well, not exactly.The amount of oil and natural gas in the earth was still plentiful, but there were other reasons, uhh, it’s a political thing really, and I’m not gonna get into that now.So what happened in the 1970s was, oil and natural gas became very expensive very quickly, and that spurred people to start looking into alternative forms of energy—solar energy probably being the most popular.But then in the 80’s, this trend reversed itself when the price of oil and natural gas went down.
All right. Let's shift our focus now to some of the technologies that have been invented to overcome the problem of gathering diffused solar energy.The most basic solution is simply to carefully place windows in a building so that the sun shines into the building and then it's absorbed and converted into heat.Can anyone think of where this is most commonly used?
FEMALE STUDENT:Greenhouses.
MALE PROFESSOR:Yep, greenhouses, where plants are kept warm and provided with sunlight because the walls of the building are made entirely of glass.But we do also have more complex systems that are used for space heating and they fall into two categories: passive and active heating systems.
Passive systems take advantage of the location or design of a house—for example, solar energy is gathered through large glass panels facing the Sun.The heat is then stored in water-filled tanks or concrete. No mechanical devices are used in passive heating systems.They operate with little or no mechanical assistance.
With active systems, on the other hand, you collect the solar energy at one location, and then you use pumps and fans to move heat from the collectors through a plumbing system to a tank, where it can be used to heat a home or to just provide hot water.
MALE STUDENT:Excuse me professor, but I've got to ask. How can solar energy work at night or on cloudy days?
MALE PROFESSOR:That's... well... that is a really good question.As a matter of fact, science is still working on it, trying to find ways of enhancing energy storage techniques so that the coming of night or cloudy days really wouldn't matter.That is the biggest drawback to solar energy, the problem of what do you do in cases where the sun's light is weak or virtually non-present.So the storage of solar energy—lots of solar energy—is a really important aspect.
FEMALE STUDENT:Does that mean that solar energy can only be used on a small scale, like heating a home?
MALE PROFESSOR:Well actually, there have been some attempts to build solar energy power plants.The world's largest solar power plant is located in Kramer Junction California. It can generate 194 megawatts of electric power, but that's just a drop in the bucket.Right now, the utility companies are interested in increasing the capacity of the Kramer Junction Plant.But only time will tell if it will ever develop into a major source of power for that region, considering the economic and political factors involved.
旁白：听一段关于环境科学课的讲座。
教授：好了，我们继续讨论可再生能源。这次来讲讲众所周知的再生能源——太阳能。太阳基本每天都为地球提供了无限的能量来源，问题就是我们如何有效地利用它。有人能想到为什么太阳能这么难以利用吗？
学生：因为它很难收集？
教授：完全正确。太阳能到处都是，但同时它很分散。而且利用太阳能的梦想并不是新鲜事。人类试图利用太阳能作为可信赖的能源已经好几个世纪了。而且在20 世纪初期，市面上出现了一些太阳能热水器，但销量不好。有人想猜猜原因吗？
学生：嗯，因为有类似石油和天然气这种其他的资源可供选择，对吗？
教授：对。而且不论好坏，我们的社会也选择了这条路。当你考虑经济因素的时候，理由就显而易见了。但是在20 世纪70 年代的时候，对太阳能的热情又回来了。为什么会发生这样的事呢？
学生：因为石油和天然气，嗯⋯⋯变得稀缺了？
教授：也不尽然。地球上的石油和天然气资源还很充足，但另有原因。这其实是个政治问题，我现在不打算讲这个。20 世纪70 年代的时候，石油和天然气的价格飙升，使得人们开始寻找别的能源，太阳能是最受推崇的。但在80 年代，这股潮流被逆转了，因为石油和天然气的价格回落了。
好了，现在我们转而看看为了克服收集分散太阳能这个困难而发明的一些技术。最基本的解决办法就是在建筑中放置窗户，这样太阳光可以照射到建筑物里，然后就可以被吸收转化成热量。有人能想到这在什么地方被广泛应用吗？
学生：温室。
教授：对。温室里的植物之所以保持着温度，并提供着阳光，就是因为它的墙壁全部是玻璃做的。但我们也有更加复杂的供热系统，它们分为被动和主动供热系统。
被动供热系统主要利用的是房子的位置和设计，比如说，太阳能被面对太阳的巨大的玻璃板所吸收。热量就被存储在了装满水的容器或者混凝土中。在被动供热系统中，没有机械装置它们很少或基本没有机械辅助。
然而，对于主动供热系统，你可以先在一个地点收集太阳能，然后利用泵和风扇将收集到的热量通过管道系统转移到水槽中，为家庭供暖或提供热水。
学生：不好意思，教授，但是我想问一下，太阳能如何在晚上和阴天工作呢？
教授：这是个很好的问题。事实上，科学家们还在努力解决这个问题。他们试图加强能量存储的技术，这样夜晚和阴天就不构成影响。这是太阳能的最大缺陷，当太阳光变弱或者不存在时，人们该何去何从。所以从这个角度讲，大量的太阳能存储是必要的。
学生：这是不是意味着太阳能只能在小范围内使用呢，比如家庭供暖？
教授：事实上，有些人尝试过建造太阳能发电站。世界上最大的太阳能发电站坐落在加利福尼亚的Cremer它可以发194 兆瓦电力，但这只是沧海一粟。现在，电力公司有兴趣扩大CremerJunction 发电站的产能。但考虑到当地的经济和政治因素，只有时间能告诉我们，太阳能是否会成为当地的主要能源来源。
题型分类：主旨题
原文定位：
The sun basically provides earth with a virtually unlimited source of energy every day, but the problem has always been how do we tap this source of energy. Can anyone think of why it's so difficult to make use of solar energy?
选项分析：
讲座介绍了太阳能利用的历史和现状，说明了太阳能的缺点，并由此阐述了太阳能不 能广泛使用的原因。因此选项C正确。
如果对题目有疑问，欢迎来提出你的问题，热心的小伙伴会帮你解答。