DIY Solar Panel September 6, 2007
Posted by Graham in : Green Building, Renewable Energy , trackbackI have recently installed a DIY solar panel on the Permacabin (Timber framed cabin with all perma-cons):
This has been constructed using clip-fins from CAT and following instructions in their booklet Solar Water Heating- A DIY Guide by Paul Trimby.
The basic principle is straightforward: an insulated box is constructed-
we used warmcell which is then covered in aluminum reflective foil on top of which the clip fins (painted black to absorb more heat) are placed with the pipes clipped onto them:
A sheet of toughened glass is fixed on top of the box which is then ready for installation. My panel is located immediately below the water tank which allows thermo-siphoning an therefore avoids the need for a pump. This week has seen some of the best weather in living memory and certainly the best of the summer, giving the perfect time to check the panels’ performance.
A single good day of sunshine heats the water to 40 degrees Celsius, which is not really warm enough for a comfortable shower, but two successive days have heated the tank to 50 degrees which is just right. It may be that the 200litre tank is too large for the panel in which case I may have to ultimately make a second panel; or I may still be able to improve performance with extra insulation. Solar panels like this wont do much on cloudy days or through most of the winter so I will also have a wood-burning stove with a back-boiler to heat water for these periods. Total cost of the panel (excluding all the plumbing) is about 150 euros. You could certainly make one for less if you use an old radiator- instructions for this design are also to be found in the CAT booklet.
Comments»
From our own experience, termo-siphoning is by far the best option, eliminating the need for pumps (which aways prove to be troublesome :).
200 litres of tank capacity for a single panel is fairly big (we have around 150 litres / panel), but I think it is better to err on the side of too big a tank, as a smaller tank means that on a fine day, the water gets very hot (can easily be above 60 degrees), and then, the heat just gets lost. Sure, if you are getting 40 degree after a day of full sun in September, you probably got it about right anyway, no? It is worth insulating the tank as well as possible, a well large, well insulated tank will get your through a day with no sun.
Thanks for that Cristophe
Like you I didnt want to use a pump and the roof design planned for the addition of solar panels below the eves at the same angle.
One possibility is that we have currently plumbed the panel into the lower coil- the top coil in the tank is for the wood-burning stove (yet to be installed); I think we will try it the other way around which might help a good bit.