Flat Plate Solar Hot Water Systems
These are the most widely used used type of collector for domestic solar water heating. Flat plate collectors are shallow rectangular boxes with glass lids and usually aluminium for the body. Typically 1-1.5 meters wide by 2-2.5 metres long.
OK, so we've got a shallow aluminium box, on top of which will go a glass lid. Directly underneath the glass are placed copper pipes. These copper pipes carry the water through the collector and absorb the sun's heat. A typical pattern of piping is shown here:
Now if we put these pipes in the box as they are, they will get our water hot, but they won't be very efficient. In order to capture as much sun as possible, we want to maximise the surface area of the pipes that is exposed to the sun.
We do this by welding horizontal fins between the pipes.
Then we put some insulation in the bottom of the box to make sure the heat goes into the water, not through the panel and into our roof, and lay the copper assembly onto the insulation. We might paint the copper black so it absorbs even more heat, then pop the toughened glass on top and voila, there's out flat panel solar hot water collector.
Here's a cutaway of the finished panel:
And here's the finished thing in all it's glory:
As you can see, these are fairly simple devices which means that they are relatively cheap to manufacture and very reliable. They are also incredibly tough. A good flat plate collector would probably withstand a thermonuclear war (so at least the cockroaches could have a hot bath).
This (apart from the cockroach bit) probably explains their popularity in Australia.
The alternative to a flat plate collector is the evacuated glass tube collector. If you thought the Holden / Ford rivalry was bad – you want to see the evac tube / flat plate fans argue about which is best! I'll just present the facts and let you decide, dear reader!