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Forum Index : Solar : Deciding if I should build this solar heater
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 929
Posted: 02:30pm 12 Aug 2025
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Haha, thanks Mike. I think I'm still a little shellshocked over the whole thing, though it was really nice to see it pumping out the heat this arvo.
Thanks Aaron. Yes, that's the beauty of the prototype too. I couldn't get over how it could be cold, rainy, windy and blustery ... but if there was any sun ... the thing was producing heat.
Something else that always impressed me was that the tubes act like a battery and slowly charge up. It may not be very bright or sunny ... but if it's off for a while (the fan), the temperature slowly rises ... and when you do turn it on it can be quite high ... and take quite some time to go low enough that it needs to be turned off again. Might start off at 50 degrees but take 20 mins to get down to 25 or so.
If you leave it off for a couple hours while the sun is out, it may start off at 100C ... seriously hot.
My first experiments were with collecting the hot air under the tin roof of my shed too ... and feeding it down one of the c-section posts into my workshop. Is still connected too, though was pretty underwhelming in my case. Good to hear yours gets nice and hot.Cheers, Roger
Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1513
Posted: 04:58am 17 Aug 2025
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Well comeon Roger fessup mate just how is this working out and the big question are you in a T-shirt when it's 5C outside
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 929
Posted: 12:26pm 17 Aug 2025
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Haha Bryan. Well the first day was a bit of a disappointment due to the cloud and the second not that fantastic ... but I have had it running every day from about 9am until about 4.45.
I've turned it off a couple times for 15 or 20 mins because the cloud cover was back ... but when turned back on it seemed to have built up a decent amount of heat and really poured it out.
I haven't fitted the differential controller yet because I've still got it running the original heater ... but it seems that is all I'll need to make it operate like the original. The new one is definitely a lot less responsive ... takes longer to build up heat ... but holds on longer too.
Each time I come inside, I can't believe how warm it is ... and have to strip off my jacket straight away ... and if I stay for a while, start to regret wearing long johns, which I need working in the shed. It gets the room temp to 23 or 24° by lunch time.
As far as actual temperatures go, Thurs was a nice sunny day and it was pumping all day. I turned it on about 9.30am and it was only a bit over 30 ... but when I came in for lunch was 47-48° ... and still there at afternoon tea time.
I turned it off at 5pm when it had dropped to 30° again.
Judging from experience with the prototype and the first day with this one starting at lunch time ... it certainly acts like a heat battery and keeps building up heat if the fan's not on to push it out. Perhaps I'll try it out when the sun is good and turn it off for half an hour or an hour ... and see what it gets up to.
Most days once it starts to get warm in the living area, I turn on just the fan in the ducted system and that circulates the warm air all around the house. The output in each room is at a constant 27° at the vents. I dunno what it would be at if I was using the aircon for heat ... and I can't even try it now as the compressor has died.
At nights I've still been lighting the fire as it certainly still cools down by 7 or 8 o'clock (21.5° at 8.30) ... but let it go out in the morning ... so no wood used during the day at all.
So far I'd have to say I'm pretty happy with it. I do have to find a way to get a reflective surface below the tubes like the prototype has. This one just has the grey tiles soaking up the heat that misses the tubes.
I'd like some of that reflective mylar film ... but without fitting it to big sheets of something, it would flap itself to bits in short order. I'm starting to think that I could use some shiny corrugated iron underneath. There's enough space to put several sheets under the tubes on each side ... and if they run at right angles to the tubes, would allow the water to run straight off.|
Does anyone have any other ideas for how I might get a reflective surface below the tubes? Thanks. Cheers, Roger
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 549
Posted: 10:03pm 17 Aug 2025
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Hi Roger, well it sounds like it is doing a great job. Where we live 21 degrees is as hot as we like our place to be, if it gets above that we open windows. I did buy some plastic adhesive mirror material once on ebay. Maybe some of that stuck to a flat board or maybe even better to corrugated roofing, would work well. You may get complaints from passing aircraft about the reflections though. Is the large tunnel the air collects in insulated. If it were well insulated then it may make an even better heat store. nice work pete
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 929
Posted: 10:54am 18 Aug 2025
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Thanks Pete, I'd be happy with 21 degrees too but sadly my wife must have a broken thermostat or something ... and now we're caring for her mum who's from Darwin and she hates the cold too.
I had seen some of the adhesive mirror film ... but wasn't sure what to attach it to as it's a wide expanse without fitting more cross members. I hadn't thought of attaching it to corrugated iron ... that should work.
Most corrugated iron nowadays isn't very shiny, so sticking foil to it wouldn't be a bad idea. Probably the best I found was some mini orb ... but still not all that shiny ... and quite expensive still.
I had wondered about complaints about reflections, but we're on a dead end road, so not that much traffic. The local pilots may start complaining though.
That outer collection duct has about 2 inches of foil board lining it ... so is well insulated. I've resurrected my temperature data loggers and will try them out again to learn more about how it works. Still very happy with the results so far.Cheers, Roger
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 929
Posted: 10:49am 20 Aug 2025
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I resurrected a temperature data logger and have hooked it up at the vent where the heat comes into the living area.
This was yesterday's effort.
And this was todays. I turned it on earlier than yesterday ... but you can see there was already a reasonable heat build up in the tubes ... so the starting temperature was higher.
That store was depleted and then it settled down into what the sun could provide continuously.
This is a shot I took at 4.45pm a few minutes before I shut it off for the day. There's still some sun on the unit but it was running out of steam. Maybe the low angle of the sun causes light to reflect off the outer glass rather than go through and be absorbed.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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just how is this working out and the big question are you in a T-shirt when it's 5C outside 
