托福听力TPO12分类之环境科学(托福听力tpo13)

托福听力考试贯穿于整个考试中，很多题目都涉及听力，所以建议同学们要重视托福词汇的记忆，下面是小编给同学们带来的托福听力TPO12分类之环境科学，跟着小编的脚步一起来认真分析一下吧!

托福听力TPO12分类之环境科学

Lecture 4 (environmental science)

Narrator

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

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 - 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?

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?

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...er...became scarce?

Professor

Well, not exACTly. The amount of oil and natural gas in the earth was still plentiful, but there were other reasons. It's a political thing really and I'm 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 80s, 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.

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?

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?

Professor

Well ACTually, there have been some attempts to build solar energy power pla …… 此处隐藏：3039字，全部文档内容请下载后查看。喜欢就下载吧 ……