This is all backwards, because I've done some plumbing that I haven't yet told you about, but, fascinating though pumps and pipework may be(!), this is far more exciting. Just to bring you up to speed, the situation this morning was household pipework in place, with hardly any leaks and a working pump. One black-painted radiator is outside, more or less in position, connected to the pipework with temporary connections (for the purpose of testing the household plumbing) that proved surprisingly leak-free.
This morning, sitting on the terrace eating my breakfast in the blazing sunshine, I thought,
This is ridiculous. I have a complete, if rather basic, solar panel connected up to my household plumbing. Why am I not using it yet? I upgraded the panel slightly by bringing the largest caravan window up and laying it over the radiator.
A little later in the day I upgraded slightly further by stuffing a blanket along the top edge, blocking the gaps where the radiator fins waft hot air up and away from the radiator. Before that, though, I filled the header tank in the loft, which involves running a hosepipe from the outside tap downstairs, up through the loft hatch and into the tank, then going back downstairs to turn the tap on, hoping that the top end of the pipe stays put, then when it's full, removing the hosepipe so it doesn't siphon all the water back out again.
Switching on the pump - initially just to fill the panel - requires an extension lead.
Once I had the system filled, I waited a bit then went to check the temperature of the panel, by which I mean, stuck my hand under the glass to feel whether the radiator was hot yet. It heated up quite quickly - half an hour to
hand hot, at which point I turned the pump on. Actual hot water flowed through the pipes and into the coil in the tank! I got terribly excited about this.
I can't say the impact on the temperature of the tank was very dramatic - maybe one degree Celcius increase each time I pumped the hot water round, but as Ian said, we need to bear in mind how long it takes for the wood-burner to heat the water in that tank, and that's a great deal hotter than
hand hot! This experiment also highlighted the importance of an automatic controller. I'm going up the stairs to check the temperature of the panel maybe four times an hour, and when it's hot enough, running the pump until the pipes are cool again, which takes about ten minutes, and much monitoring.
Although this is only a partial system, it does actually work. This is a hugely encouraging as I face the next challenge, which is making the box part of the panel (There will be more than one panel, eventually). In the meantime, this even-more-basic solar water heater is proving quite effective at heating water to do the dishes: