Mr Whippy
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| posted on 11/1/10 at 01:50 PM |
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cheap solar water heating
Hi,
Just been discussing this with one of the guys at work and was wondering if anyone had used one of these as an outside solar water heater, you know
painted matt black and mounted on the roof. I think it would work very well, especially if the side not facing the sun was insulated with foam.
That you think, would two this size give enough heat for normal hot water in a house?
For the winter when its not doing any heating anyway, I suppose it could be isolated and then drained dry to protect it from icing up inside.
You could even have an inline thermostat that only let water flow once it was at a certain temp so that at night the hot water stored would not be
lost.
[Edited on 11/1/10 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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r1_pete
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| posted on 11/1/10 at 01:58 PM |
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Didn't Dick Strawbridge do something with a rad and solar heating, on one of those "Its Not Easy Being Green" programmes he did?
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Bluemoon
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| posted on 11/1/10 at 02:00 PM |
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You should put it in a box with a "window" to stop convection.. (rad's are rather good at this)..
I'd get a scrap rad and make a test one to see how well it might work before going to to much hassle..
Dan
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Wadders
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| posted on 11/1/10 at 02:02 PM |
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I know someone that has done it, and it has provided trouble free hot water for them for the last 25 years, they live in Scarborough.
They have two on a south facing roof, inside a picture frame affair with perspex covers. the rads are painted black,with insulated silver reflectors
to the rear.
I suppose it depends on your location, and how much hot water you use. Although an immersion heater back up could be fitted.
Antifreeze would stop it freezing in winter.
The only problem they have is if they go away in the summer, the neighbours have to come in and run off the hot water now and again.
Al.
Originally posted by Mr Whippy
Hi,
Just been discussing this with one of the guys at work and was wondering if anyone had used one of these as an outside solar water heater, you know
painted matt black and mounted on the roof. I think it would work very well, especially if the side not facing the sun was insulated with foam.
That you think, would two this size give enough heat for normal hot water in a house?
For the winter when its not doing any heating anyway, I suppose it could be isolated and then drained dry to protect it from icing up inside.
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Mr Whippy
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| posted on 11/1/10 at 02:24 PM |
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Tbh I had thought of just putting them in the back garden (like you suggest in a box with a Perspex window) and running two buried insulated 22mm
plastic pipes into the house and into the hot water tank under the stairs. There's an embankment at the back that faces south and with the
panels on the ground they'd be able to use convection for circulation rather than a pump.
Fame is when your old car is plastered all over the internet
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smart51
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| posted on 11/1/10 at 02:31 PM |
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black panel collectors are the cheap but less effective option but they still work. They need to be kept in a sealed glazed box to keep the warm air
next to the collector from mixing with the cold air outside. Most systems work by having a dual coil hot water tank and circulating antifreeze
through the collector and one of the coils. That way, the hot water never goes through the collector.
The cheap way is to let the antifreeze thermo syphon round the loop. It is not as effective as a pumped system. Pumped systems have a temperature
sensor on the outlet of the collector and in the hot water tank. When the collector temperature is more than the tank, the pump is switched on. If
the collector cools, the pump is switched off.
They work on sunlight not heat so will work in the winter when it is cold. Except there is less sunlight in the winter. Make the collector big
enough and you should have all the hot water you need for large parts of the year.
If you size your system right, on a sunny summer day, you'll have a full tank of piping hot water by mid afternoon. In the winter, you'll
get a small rise in the temperature of your water tank during the day then when your boiler switches on in the evening, it has less work to do than if
you didn't have solar heating. On a snowy day when no light hits the panel, your boiler will have to heat the water from cold.
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Mr Whippy
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| posted on 11/1/10 at 02:53 PM |
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thanks for that, looks very simple and cheap to setup  unlike most of the green ideas this looks like it would quickly pay for itself
Fame is when your old car is plastered all over the internet
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liam.mccaffrey
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| posted on 11/1/10 at 03:27 PM |
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I'm currently building some DIY, very locost, evacuated tube phase change heat exchangers for this very purpose.
I even have a parabolic mirrored trough to focus the light, locost of course
Watch this space. I'll do a write up when I'm done.
[Edited on 11/1/10 by liam.mccaffrey]
Build Blog
Build Photo Album
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scootz
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| posted on 11/1/10 at 04:19 PM |
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We have a double solar-panel approximately 2-3 times the size of the radiator shown in the pic. Works in conjunction with a special dual-cylinder.
A good sunny day (we face Due-South) just about provides enough hot water to keep me and Mrs Scootz happy!
[img][/img]
It's Evolution Baby!
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scootz
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| posted on 11/1/10 at 05:42 PM |
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Lol... that lump of snow in the pic just came crashing down and scared the hell out of the neighbours cat!
It's Evolution Baby!
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Ninehigh
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| posted on 11/1/10 at 08:11 PM |
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Solartwin keep pestering me about this (cos I inquired about it once) and their systems works with the normal system you have. In the winter it still
works but the pump slows down so you still have hot water you'd just be relying on the gas a little more. If you get it working well post the
plans on here 
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MikeRJ
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| posted on 11/1/10 at 08:26 PM |
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quote:
Originally posted by smart51
Pumped systems have a temperature sensor on the outlet of the collector and in the hot water tank. When the collector temperature is more than the
tank, the pump is switched on. If the collector cools, the pump is switched off.
A guy here at work had a solar water heater fitted and the pump was just powered directly from a small electric solar panel with some ballast
resistors to ensure the pump only started up when it was sunny enough. It didn't work very well at all, so we designed a pump controller using
a couple of "one wire" temperature sensors. Works a treat now; it doesn't cool his tank down on bright cold days like it used to!
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Ian D
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| posted on 11/1/10 at 09:52 PM |
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Looks interesting, Id like to see the ROI timeframe?
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Ninehigh
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| posted on 11/1/10 at 11:19 PM |
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I saw on one of those scam builders programs that the ROI could be about 50 years or something stupid...
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MikeRJ
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| posted on 11/1/10 at 11:51 PM |
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quote:
Originally posted by liam.mccaffrey
I'm currently building some DIY, very locost, evacuated tube phase change heat exchangers for this very purpose.
That sounds very interesting...how on earth do you build evacuated phase change collectors at home? Or are you buying Chinese tubes and building your
own system from them?
[Edited on 11/1/10 by MikeRJ]
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