DIY solar thermal?

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DIY solar thermal?
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Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Wed Jan 28, 15 10:24 am Post subject: DIY solar thermal?
I've been told that a suitably insulated, black painted radiator is fairly effective as a solar thermal collector, but I've also heard people say it is not worth the effort. Anyone here tried it? What's the verdict?

gz

Joined: 23 Jan 2009
Posts: 8916
Location: Ayrshire, Scotland

Posted: Wed Jan 28, 15 11:49 am Post subject:
Friend in N Wales did that in the early 1980s when we lived there. Worked ok, definitely use it indirectly,ie fill system with fluid including antifreeze. The Winter "take the chilly off" pre-heating cut bills massively. If you are practically capable and have the components to hand, go for it

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Wed Jan 28, 15 12:03 pm Post subject:
if you can put it in a "cold frame"type thing it will work better. i would think sourcing some recycled double glazing panels and a few old radiators ,a tank with a coil ,pump and pipe would not be beyond a man with a van the rcd for the pump and wiring might be best as new items but the rest could be from a scrapper or plumber chum.

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Wed Jan 28, 15 12:08 pm Post subject:
ps the ch water goes through the coil and the solartherm water goes in the cylinder tank /black rads it needs a header tank like an open ch system cos in summer the thermal expansion can be considerable a similar thing can pre heat water for baths washing up etc pps plenty of insulation to pipes and tank is good to avoid losing what you gain

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Wed Jan 28, 15 12:11 pm Post subject:
It's not very efficient but if you have a surfeit of radiators and Perspex or glass then it might be worth the effort. Your call.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Wed Jan 28, 15 2:01 pm Post subject:

vegplot wrote:

It's not very efficient but if you have a surfeit of radiators and Perspex or glass then it might be worth the effort. Your call.

Where does it lose efficiency?

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Wed Jan 28, 15 2:17 pm Post subject:

Hairyloon wrote:

vegplot wrote:

It's not very efficient but if you have a surfeit of radiators and Perspex or glass then it might be worth the effort. Your call.

Where does it lose efficiency?

You can't lose what you haven't got.

Google it.

perlogalism

Joined: 27 Nov 2009
Posts: 440
Location: Near Welshpool

Posted: Wed Jan 28, 15 3:16 pm Post subject:

vegplot wrote:

Hairyloon wrote:

vegplot wrote:

It's not very efficient but if you have a surfeit of radiators and Perspex or glass then it might be worth the effort. Your call.

Where does it lose efficiency?

You can't lose what you haven't got.

Indeed. If I was going to the trouble of plumbing into a solar coil in a thermal store I wouldn't be wasting my time with some old rads. Buy a 30 tube evacuated array from Navitron and produce nearly all the hot water you want!

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Wed Jan 28, 15 7:01 pm Post subject:
having had a look at the vac panels dont bother with rads/dg /box etc made for the job seems like it is easier and will cover the cost quite quickly

RichardW

Joined: 24 Aug 2006
Posts: 8443
Location: Llyn Peninsular North Wales

Posted: Wed Jan 28, 15 9:39 pm Post subject:
If you have all the bits FOC, want a summer only system that has a back up then go ahead & have a play. You can even make quite a good system just using a long hose. If you want a system that will work for more of the year then get vac tubes.

Mistress Rose

Joined: 21 Jul 2011
Posts: 15966

Posted: Thu Jan 29, 15 7:30 am Post subject:
We built a prototype back in the 1970s when all this stuff raised its head and before all the modern stuff had been developed. It will work after a fashion, although a coil of copper pipe fastened to a black collector in a double glazed frame will be better perhaps. Not very good, but using scrap you at least gain a little.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Thu Jan 29, 15 10:21 am Post subject:

Mistress Rose wrote:

We built a prototype back in the 1970s when all this stuff raised its head and before all the modern stuff had been developed. It will work after a fashion, although a coil of copper pipe fastened to a black collector in a double glazed frame will be better perhaps.

What is it that would make it better?

mark

Joined: 14 Jul 2005
Posts: 2191
Location: Leeds

Posted: Thu Jan 29, 15 12:20 pm Post subject:

essentially efficiency in solar collection is

1) maximising solar heat absorbtion - you need to absorb the heat not reflect it
2) avoiding any head less by convection or conduction or re-radiation in the collector.

stopping air movement or using vacuum stops convection losing heat by convection (no use your radiators getting hot then losing all that heat to the cold icy wind blowing over them)

likewise with conductive losses - you need insulation.

But you don't want you insulation to stop conduction and convection to block any of the nice warming ways.. (the bubble wrap in a greenhouse problem)

Your basic radiator painted black is not efficient. Putting it in a greenhouse under glass makes it better. Putting it in a vacuum more so etc etc.

Also your piping conducting heat to the air (very well if its copper) so you need to insulate.

And so I could go on .. but I'm sure you are getting the plot by now !

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Thu Jan 29, 15 1:09 pm Post subject:

Hairyloon wrote:

Mistress Rose wrote:

What is it that would make it better?

Material
Manufacturing processes
Research and development
Quality
Science
...
...

This list look familiar.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Thu Jan 29, 15 1:19 pm Post subject:
Mark's answer was infinitely superior.

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