This is the biggie; this is the project I've been meaning to do for the last three years or so but haven't actually quite got down to doing. This was always part of the heating project grand plan and the thermal store (big water tank) was made with an extra coil to take the water from the solar panels when they were in place. We've probably had our heating operating below its capacity for the last three winters due to that empty coil.
Being me, we're not talking about a simple matter of buying solar panels and getting them installed, or even installing them myself. Oh no, I'm proposing to make them. Household radiators are usually filled with hot water and radiate the heat out into a room, but they'll work pretty well the other way round too. If filled with cold water and placed in sunlight, the water will heat up. This isn't a new idea, it made it into the Telegraph over a decade ago*. They obviously won't be as efficient as manufactured panels but they are a great deal cheaper, and the efficiency difference isn't as huge as you might expect.
I dithered over the project for some time because I was worried about constructing a roof that would support it. We have a south-facing gable end to this house, and I thought the obvious place for solar panels would be a lean-to roof against this wall, under which we'd store wood. However, a full radiator is very heavy and I doubted my ability to build a structure that would support several of them. Then one day my friend Gill asked if we had any plans for using the area above the conservatory.
I can't remember whether Gill suggested it or whether I thought of it myself, but that's a potential site for solar panels. It's east facing, not south, but that's not such a drawback as it might be. We have hillside and trees to the west of this property, so even the south facing wall gets shaded by about 4pm, and this spot gets shaded only about an hour earlier in the day. On the other hand, it gets the morning sun much earlier, even with the roof to the east. It's higher than the tank, so I wouldn't be able to use the thermosyphon system I'd been thinking of, but between this spot and the tank there's only one wall of the extension, as opposed to the three two foot thick walls I'd have to drill through to get to the other site. Also, being on the ground, this is much more accessible. On balance, this seems like a much better site than the other one, and avoids the danger of the whole construction collapsing due to my inadequate construction skills.
OK, so... DIY solar panels... what do I need? Radiators, obviously.
A sheet of glass over the top will improve the effectiveness considerably - the original greenhouse effect. I have acquired a selection of windows, from Gill's old house...
... and from Jasper's old caravan.
They'll need some kind of box to contain them. Um, what have I got? I have some floorboards...
... and a sheet of plywood that used to be the back of a wardrobe.
Insulation behind the radiator would be a good idea, too, so the heat doesn't radiate straight into the ground.
I'll obviously need pipes to plumb this all in, and I have some of those left over from the old central heating, too.
And then because this won't be the thermosyphon system I originally wanted, I'll need a pump. Ah, hm, yes. I'll tell you about the pump in another post.---
* I don't know whether the author has revised his views on global warming in the last ten years.