Narrator: Listen to part of a lecture in an environmental science class.

旁白：听一段关于环境科学课的讲座。

Professor: All right, folks, let's continue our discussion of alternative energy sources and move on to what's probably the most well-known alternative energy source, uh, solar energy.

教授：好了，我们继续讨论可再生能源，这次来讲讲大概是最众所周知的再生能源——太阳能。

The Sun basically provides Earth with a virtually unlimited source of energy everyday but the problem has always been how do we tap this source of energy?

太阳能每天都为地球提供实实在在的可再生能源，问题就是我们如何有效地利用它呢？

Can anyone think of why it's so difficult to make use of solar energy?

有人能想到为什么太阳能这么难以利用吗？

Student A: Because it is hard to gather it?

学生1：因为它很难收集？

Professor: That's exactly it!

教授：完全正确！

Solar energy is everywhere but it's also quite diffused.

太阳能到处都是，但同时它很分散。

And the thing is the dream of solar energy is not a new one, humanities have been trying to use the Sun's light as a reliable source of energy for centuries.

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。

And, uh, around the beginning of the twentieth century, there were actually some primitive solar water heaters on the consumer market, but they didn't sell very well.

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。

Any of you want to guess why?

有人想猜猜原因吗？

Student A: Well, there were other energy choices like oil and natural gas, right?

学生1：嗯，因为有类似天然气这种其他的资源可供选择，对吗？

Professor: Yeah! And for better or for worse, we chose to go down that path as a society.

教授：对！而且不论好坏，我们的社会也选择了这条路。

When you consider economic factors, it's easy to see why.

当你考虑经济因素的时候理由就显而易见了。

But then in the 1970s, there was an interest in solar energy again.

但是在20世纪70年代的时候，对太阳能的热情又回来了。

Why do you think that happened?

为什么会发生这样的事呢？

Student B: Because oil and natural gas were...err...became scarce?

学生2：因为石油和天然气，嗯⋯⋯变得稀缺了？

Professor: Well, not exactly.

教授：也不尽然。

The amount of oil and natural gas in the Earth was still plentiful, but there were other reasons.

地球上的石油和天然气资源还很充足，但另有原因。

Uh, it's a political thing really and I'm not gonna get into that now.

这其实是个政治问题，我现在不打算解释。

So what happened in the 1970s was: oil and natural gas became very expensive very quickly.

20世纪70年代的时候，石油和天然气的价格飙升。

And that spurred people to start looking into alternative forms of energy, solar energy probably being the most popular.

使得人们开始寻找别的能源，太阳能是最受推崇的。

But then in the 80s, this trend reversed itself when price of oil and natural gas went down.

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。

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.

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。

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.

最基本的办法很简单，就是往楼里放窗户，这样太阳光就可以被吸收然后转化成热量。

Can anyone think of where this is most commonly used?

有人能想到这在什么地方被广泛应用吗？

Student A: Greenhouses.

学生1：温室。

Professor: Yep, greenhouses where plants are kept warm and provided with sunlight because the walls of the building are made entirely of glass.

教授：对，温室里的植物之所以保持着温度就是因为它的墙壁是玻璃作的。

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.

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。

Passive systems take advantage of the location or design of a house.

被动供热系统主要利用的是房子的位置和设计。

For example, solar energy is gathered through large glass panels facing the Sun.

比如说，太阳能被面对太阳的巨大的玻璃板所吸收。

The heat is then stored in water-filled tanks or concrete.

热量就被存储在了装满水的容器或者混凝土中。

No mechanical devices are used in passive heating systems.

在被动供热系统中，没有机械装置。

They operate with little or no mechanical assistance.

涉及到很少和几乎没有的机械辅助。

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.

然而，对于主动供热系统，你可以先在一个地点收集太阳能，然后利用泵和风扇通过管道系统转移到容器中，它可以（为家庭）提供热水。

Student B: Excuse me, professor, but I've got to ask, “how can solar energy work at night or on cloudy days?”

学生2：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？

Professor: That's, well, that is a really good question.

教授：这是个很好的问题。

As a matter of fact, science is still working on it, uh, trying to find ways in enhancing energy storage techniques, so that the coming of night or cloudy days really wouldn't matter.

事实上，科学家们还在努力解决这个问题，他们试图加强存储的技术，这样夜晚和阴天就不构成影响。

That is the biggest drawback of solar energy, the problem of what do you do in cases where the sun's light is weak or virtually non-present.

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。

So, the storage of solar energy, lots of solar energy is really an important aspect.

所以从这个角度讲，大量的太阳能储蓄是必要的。

Student A: Does that mean that solar energy can only be used on a small scale, like heating a home?

学生1：这是不是意味着太阳能只能小规模使用呢，比如家庭供暖？

Professor: Well, actually, there have been some attempts to build solar energy power plants.

教授：事实上，有些人尝试过建造太阳能发电站。

The world's largest solar power plant is located in Kramer Junction, California.

世界上最大的太阳能发电站坐落在加利福尼亚的克拉默章克申（地名）。

It can generate 194 megawatts of electric power, but that's just a drop in the bucket.

它可以发194兆瓦电力，但这只是沧海一粟。

Right now the utility companies are interested in increasing the capacity of their 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.

现在各公司有兴趣扩大Kremer Junction发电站的规模，但考虑到当地的经济和政治影响，只有时间能告诉我们，太阳能是否会成为当地的主要能源。