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DIY solar thermal?
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perlogalism



Joined: 27 Nov 2009
Posts: 440
Location: Near Welshpool
PostPosted: Wed Jan 28, 15 3:16 pm    Post subject:  Reply with quote    

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: 35096
Location: yes
PostPosted: Wed Jan 28, 15 7:01 pm    Post subject: Reply with quote    

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: 8432
Location: Llyn Peninsular North Wales
PostPosted: Wed Jan 28, 15 9:39 pm    Post subject: Reply with quote    

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: 10535

PostPosted: Thu Jan 29, 15 7:30 am    Post subject: Reply with quote    

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: 15216
Location: Today I are mostly being in Yorkshire.
PostPosted: Thu Jan 29, 15 10:21 am    Post subject: Reply with quote    

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: 2186
Location: Leeds
PostPosted: Thu Jan 29, 15 12:20 pm    Post subject: Reply with quote    

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: 21298
Location: Ynys Môn
PostPosted: Thu Jan 29, 15 1:09 pm    Post subject: Reply with quote    

Hairyloon wrote:
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?


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

This list look familiar.

Hairyloon



Joined: 20 Nov 2008
Posts: 15216
Location: Today I are mostly being in Yorkshire.
PostPosted: Thu Jan 29, 15 1:19 pm    Post subject: Reply with quote    

Mark's answer was infinitely superior.

vegplot



Joined: 19 Apr 2007
Posts: 21298
Location: Ynys Môn
PostPosted: Thu Jan 29, 15 3:01 pm    Post subject: Reply with quote    

Hairyloon wrote:
Mark's answer was infinitely superior.


What is it that makes Mark's answer better?

Hairyloon



Joined: 20 Nov 2008
Posts: 15216
Location: Today I are mostly being in Yorkshire.
PostPosted: Thu Jan 29, 15 3:06 pm    Post subject: Reply with quote    

vegplot wrote:
Hairyloon wrote:
Mark's answer was infinitely superior.


What is it that makes Mark's answer better?

It contains actual answers.
Yours just says "the professionals do it better. Nyah nyah."

vegplot



Joined: 19 Apr 2007
Posts: 21298
Location: Ynys Môn
PostPosted: Thu Jan 29, 15 3:09 pm    Post subject: Reply with quote    

Hairyloon wrote:
vegplot wrote:
Hairyloon wrote:
Mark's answer was infinitely superior.


What is it that makes Mark's answer better?

It contains actual answers.
Yours just says "the professionals do it better. Nyah nyah."


I wasn't expecting a reply as the question was tongue in cheek.

But thanks.

Mutton



Joined: 09 May 2009
Posts: 1508

PostPosted: Sun Feb 01, 15 9:51 pm    Post subject: Reply with quote    

Go look at www.builditsolar.com.

All sorts of self-build designs and data on how well they work. Some include costs to build as well.

I've always had a fancy for a solar shed.......

Tavascarow



Joined: 06 Aug 2006
Posts: 8407
Location: South Cornwall
PostPosted: Mon Feb 02, 15 8:45 am    Post subject: Reply with quote    

A lot of the professional instalers are going away from the Chinese evacuated tubes (Navitron) back to flat plates. Problems with maintaining vacuum.
If you can instal your panel below the tank so it works on gravity & fit a non return, so when the panels colder than the tank it doesn't suck the heat back, fairly cheap & easy IMHO.

vegplot



Joined: 19 Apr 2007
Posts: 21298
Location: Ynys Môn
PostPosted: Mon Feb 02, 15 9:39 am    Post subject: Reply with quote    

Tavascarow wrote:
A lot of the professional instalers are going away from the Chinese evacuated tubes (Navitron) back to flat plates. Problems with maintaining vacuum.
If you can instal your panel below the tank so it works on gravity & fit a non return, so when the panels colder than the tank it doesn't suck the heat back, fairly cheap & easy IMHO.


Or perhaps installers breaking too many tubes?

I prefer the flat plate collectors. The may be less efficient but are more reliable and tougher they also look better IMHO.

Mutton



Joined: 09 May 2009
Posts: 1508

PostPosted: Mon Feb 02, 15 11:46 am    Post subject: Reply with quote    

I worked with glass vacuum equipment a lot of years ago - not glass solar hot water tubes - but I spent a lot of my life leak hunting.....

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