What Are Focusing Solar Collectors

The Greek word for sun is Helios. As we all know, much of our English language has evolved from the ancient Greek, and many English words have Greek parts. So any word that has the prefix helio- probably has something to do with the sun.

A helioelectrical process is a way of converting sunlight to electricity — something we're just learning to do efficiently. Photosynthesis, mentioned in the last chapter, is an example of a

Focusing collectors — or solar concentrators as they're sometimes called — redirect the sun's parallel rays to a specific focal point or "target."

Figure 18. A focusing — or concentrating — collector changes the direction of parallel solar rays so they zero in on a given focal point. Double convex lenses, such as those in magnifying glasses, do this directly. A parabolic mirror, on the other hand, reflects concentrated rays back to a target in front of the reflector. Either way sunlight is intensified tremendously.

Figure 18. A focusing — or concentrating — collector changes the direction of parallel solar rays so they zero in on a given focal point. Double convex lenses, such as those in magnifying glasses, do this directly. A parabolic mirror, on the other hand, reflects concentrated rays back to a target in front of the reflector. Either way sunlight is intensified tremendously.

Magnifying Glass Heater

Anybody who has ever lit a fire with a magnifying glass has used a solar concentrator. A magnifying glass is actually a double convex lens, which bends parallel rays and makes them converge on a central point. The bead of light thrown by the glass can be made hot enough — by adjusting the height of the glass — to ignite paper or even light kindling (Figure 18).

Another common type of focusing collector is a parabolic mirror, a bowl-shaped reflector that directs solar rays to a central target right in front of the mirror itself. A good silvered-glass mirror or polished metal surface shaped like the inside of a car's sealed beam headlight should reflect about 92% of the light that hits it and shoot it all to one spot. The advantage of any focusing collector is that it can generate tremendous temperature — as high as several thousand degrees — because it intensifies radiation hundreds of times (Figure 18A).

But there are serious disadvantages to focusing collectors. First, they must point exactly toward the sun or they won't work at all. This means that they either have to be moved by hand or be hooked up to a device called a heliostatic mount that tracks the sun all day long. Second, most solar concentrators can't focus diffuse light, making them almost worthless when there is

Figure 18A. The problem with focusing collectors is that they rely on direct radiation. They also must always face the sun. When they don't, this is the result. Unless the orientation of the collector is perfect, rays bounce everywhere except against the target.

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Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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Responses

  • rose bolger
    What Are Focusing Solar Collectors?
    8 years ago
  • gringamor
    How a magnifying glass intensifies light?
    8 years ago
  • bladud
    How do you focus heat with a magnifying glass?
    8 years ago
  • Lisa Bumgarner
    How parabolic heater works?
    8 years ago
  • Pandora Grubb
    Is there a heater that reflects the suns rays indoors?
    6 years ago
  • sonja
    What is focusing collector?
    4 years ago

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