In the previous module we discussed converting the sun's solar energy into electricity. It can also be converted directly into heat. In the more northerm climates, solar heat is used for warming homes and indoor gardens. Here in the warm Caribbean Islands, most use it for heating water.
Solar Heat
It is easy to sense photon energy being converted into heat energy. When the sun is shining, even on a cold winter's day, absorption of the photons streaming from the sun will warm a face, a rock or any other dark absorbing surface. (Even white snow absorbs some energy.) Cloudy and hazy days notwithstanding, the energy reaching the earth's surface depends upon where on the earth you live and the time of day. Here in St. Thomas (latitude 18.3o from the equator), the sun is relatively "high in the sky" and a lot of solar radiation reaches the ground. The amount of radiation depends upon the angle between the horizon and the sun. This angle is called the altitude (it is an angle, not a height!). You can learn about the sun's altitude as well as other important angles from a very nice tutorial by Heather B. Potucek, a senior meteorology major at Plymouth State College. The maximum solar radiation occurs when the sun is directly overhead, when about 1000 watts (joules/sec) of energy strikes every square meter. Think of the heat energy from ten 100-watt light bulbs spread over a square meter. We should be able to use all that energy, and we can!
Homemade examples of the simplest method can be seen all over St. Thomas. Get a 50 gallon drum and paint it black. Fill it full of water and let the sun do the heating. Of course, it takes a bit more engineering to construct a solar water heater which provides continuous hot water to your faucets. You can see a good example on top of many of the buildings at the Pearson Gardens complex. Inside the flat rectangular box is a continuous pipe which takes water from the cylindrical tank just above it. The scale of such systems is limited only by the imagination. The systems at the Pearsons Gardens serve a single individual unit.
The Soltice/Crest organization is good starting place for your investigation into these systems. Among the things you may wish to include your report are:
Standard search engines for your own search.
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