853 wrote: ↑30 Sep 2022, 6:23pm
You are, of course, correct. I did say it was a first experiment and "a quick lash together".
I have discovered, from experience, that when you try something completely new your first attempt is something of a failure. Except it's not a failure, because if you analyse it properly you can see were it went wrong and get a better appreciation of the whole project and learn from it. I expect my second experiment to be better.
I believe that a large, properly built (I know who to ask now!), cold-frame could possibly heat enough bricks to a hot enough temperature to be viable. I am a bit reluctant to spend, what could turn out to be over £100, until I've proven to myself I will get some benefit back.
The forecast is for sun here tomorrow, so I will try the same arrangement as experiment 1 but try and stop the drafts. I'll let you know how I get on, as it will be a change from reading
Woodburners Weekly
Experimentation is my way with most things too, as you say, everything is better understood and the rate of learning is high. It's great to be able to browse the Internet and look at other approaches, depending on space, country and cost. As axel_knutt says above, a lot of mass is needed for a modest amount of heat, it's never going to be hotter than what liquid or solid fuels can provide unless it's enormous in relation to the space heated, although the solar wall inside an insulated box which is itself within a glasshouse does work well in the case I described.
They sourced the bricks for the cost of collecting them, I think the same for the other materials apart from the black paint and fan. I did some rudimentary sums but there are some really quite complex calculations needed to give even a vaguely definitive answer, so I suggested a single thickness wall 18' x 4' might well not be sufficient to raise one roughly 15'x18'x8' room's temperature to comfortable. There was the likelihood of building another behind the first, he was even considering mirrors to reflect the sun onto the rear wall.
As it turned out, the heat is modest but makes enough difference to be worthwhile for a well-insulated room when the air is cool and sun is warm. It was decided a second wall behind the first may improve output by a half or more, but not worth the effort. If a room to be warmed is draughty or poorly insulated, then the modest heat from such a setup is unlikely to be effective.