I guess you could say that the first solar powered water heater was invented by the first outdoorsman to pour some water into a black garbage bag, leave it in the sun all afternoon, and use it to take a shower. But let’s be serious, that’s not exactly practical if you’re hoping to heat water for indoor plumbing.
For practical home use, a more complex kind of solar hot water heater is employed, but the basic principal stays the same. The sun is used, directly, to heat water. More than just water, though, solar water heaters plus space heating solar combisystems are actually used to provide around twenty percent of all home heating energy in many European countries.
The way it works is basically like this…
A solar heating system is comprised of solar thermal collectors and a fluid system. The fluid system pumps water into and out of the collector. The heat collectors really do work on about the same principle as the black garbage bag. Water is stored in the collector until it is the appropriate heat, and then it’s placed into a reservoir. Once the water in the reservoir drops below a certain temperature, it goes back into the collector. Simple as that.
The collectors come in a few different types…
Formed Plastic Collector
Formed plastic collectors usually consist of either tubes, or formed panels. The problem with this type is its lack of insulation. When the ambient temperature drops to a certain level, formed plastic collectors do a poor job of retaining heat.
Flat Plate Collector
When you see those big black panels at the swimming pool, that’s what a flat plate collector looks like. On the other side of those panels, you’ll find coiled tubing running from one end to the other. The water runs through this tubing and back into the insulated reservoir. The panelling is usually made of either thermally stable polymer, or sheet metal like aluminium or copper, covered in a layer of black coating to better absorb solar heat.
Evacuated Tube Collector
An evacuated tube collector is made up of a series of modular tubes, mounted in parallel to one another. The tubes are made of glass, and each of those tubes contains an absorber tube. The absorber tube will absorb the heat from the sun as the light passes through the glass tube. The best of these systems utilize foam insulation to maintain heat even after the temperature outside has dropped.
In many parts of the world, solar water heating is catching on fast, however, don’t expect to be able to buy a full solar water heater for less than $7000. Although, you can actually get ahold of a compact heater or a do it yourself kit for considerably less.
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yes, they are catching on alright. israel are massive on solar water heaters. also, i’ve just read that the state of hawaii has just made it law to have one in your house. way to go hawaii!