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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 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?

Student A

Because it is hard to 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?

Student A

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?

Student B

Because oil and natural gas were...err...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.

Alright 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 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?

Student A

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.

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