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Solar Water Heating


Alex H
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Hi Alex,

We installed solar heating for water two years ago and it's working really well. We've got a DeDietrich system with three panels and a 500l tank. The tank will be heated by the oil burner if there isn't enough solar power, but only for the top 30% of the water in the tank. I understand that the DeDietrich is probably one of the most expensive on the market, but it's also of the highest quality and as we do have two gites with the house we didn't want to gamble. We also got a subsidy of about 20% from ADEME.

Kind regards,

Christiane
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[quote]Hi Alex,We installed solar heating for water two years ago and it's working really well. We've got a DeDietrich system with three panels and a 500l tank. The tank will be heated by the oil burner if t...[/quote]

What is the procedure to get the subsidy - our heating engineer is advertising this at 30%, but as my French is not too clever, I'd like to know before get myself in deep water !

We do not live in France as yet. Our heating will be the same as yours as we have an oil fired boiler at the moment

Alex

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We use solar for heating the swimming pool. An experimental shallow concrete open trough painted on the inside with resin having had black colouring agent added. Being about 10 square metres, a bit too small for the 5m x 10m pool it serves but having said that gives a three degree (Celsius) rise (in full sun) on each pass at 6 galls/minute. With a small temperature differential it is not worth glazing this type of panel unlike those which you describe for heating water for the house. As you can tell I am a bit of a DIY nut and would like, when I have time, to make up some panels for water heating for the house. In summer a simple batch heater might be all that is needed but in Spring and Autumn the higher technology plastic panel or better still the glass tube half mirror type (expensive) would be better though I prefer simple low tec approaches myself. When I get around to it, it will be the sort of installation where the panel pre-heats the supply to a standard electrically heated tank. Good luck with your project, "free" energy is an exciting concept. ...............................John not Jackie
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Our heating engineer showed us the setup in his house - 4 squ. m. of panels heating a 300l tank - the tank water was at 75 degrees and this was 2 weeks ago and it is only heated by the panels. He ran a tap for us to demonstrated how hot the water is and 75 is HOT!!!!

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When I was building our current house we had a period when we had a working(ish) foss but no HW in the house. I was living in a caravan at the time and decided I couldn't face starting each day with a cold-water wash (or finishing after a day of installing insulation in the roof) and resolved to get a hot shower one way or another.

I bought a cheap 200L chauffeau,  8' x 4' sheet of osb, some plastic sheeting, and a cheap shower mixer. With a couple of bits of 2"x3" I made a shower cubicle and set it up in the caravan awning (the 'sheltered' side!) and with the remaining piece I made a solar panel, so it would be about 3' x 5' roughly. The size was dictated by an off-cut of polystyrene I had to hand to insulate it. Some 15mm copper pipe, a bag of 'T's, a few elbows and an hour's worth of soldering and it was done. The only things I bought specially were a panel of clear plastic for the front, a roll of the flashing repair stuff to weather-proof it, and a can of black spray paint to black the alu foil between the pipes.

On a decent day it would heat a full tank to 65-70 0 and certainly it more than recovered a shower or two. Eventually, I connected it to the electricity after a week of really miserable weather, (to top up during the night) but it certainly proved it would make a sizable impression on an electricity bill over the course of a year, and I shall definately make a few solar panels to fit permanently on the next house.

I can confirm that a front glazing panel isn't needed for a pool heater, the low gain means that there is no heat lost by radiation from the collector pipes.

paul

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This is something that intrigues me as well, we are in a small vilage in the Haute-Vienne, but have the Chateau problem opposite. However, I would love to know whether we could install solar panels on the rear of our roof, away from the Chateau. Anyone out there in the Piegut area might know about a guy who attends the Wednesday market - he carries all the info etc., and as the local guy (a bit like double glazing I suppose), he has all the leaflets on installation with grants etc. Does anyone know whether we could get away with this idea at the rear of the property?
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Keni

As long as the panel face South (or near that) then they will work to an extent.

The optimum is facing directly south with an inclination which is equal to the latitude plus 10 degrees (I think) to the horizontal, but I'll have to look it up to be sure.

Low tech is good, you just need more area of panel to heat the water, if your space challenged you'll need high tech to get the same energy absorbtion. At any rate, however you get there its the way forward because its free...... No nukes.

Andrew

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We were the first people to install solar heating in the south of Indre, the DDE were very keen to rubberstamp our permissions for that and various alterations and from start to finish only took a week. We didn't bother with the grants as we installed the system ourselves and it was much cheaper to source from the UK. We use electric back up for our heating/hot water which being underfloor means it's not so bad although on wet cloudy days like today we don't get much solar efficiency. The annoying thing is when its hot and sunny outside you don't need the heating or amount of hot water that you do in the winter so we often have hot water we need to get shot of as the tank heats up very quickly. Our tank is 350l's which was the largest we could get in our loft space. I'd advise anyone to buy the biggest water tank possible and think about using the system to heat a swimming pool, it will easily do this with the excess hot water in spring/summer.
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Hi Alex, about the subsidy. It was actually our plumber who sorted most of it out for us. Your plumber should send a proposal off to the subsidy giver, in our case it was ADEME, and they will approve it before he goes ahead with the work. After that you have to send the original invoice off in order to receive the subsidy directly. Whether it is 20 or 30% does depend on the price of your instalation. There are different amounts for different size systems. The subsidy we got was about €1700, however, our system is big and quite expensive. It would make sense to look at different systems and calculate exactly what you need. Our boiler has a capacity of 1200l of hot water per hour on a warm summer day, which we need because of the gites. I can also tell you that on a hot summer day the water temperature can easily go up to 75C, ours has been up to 90C during the Canicule 2 years ago.

Christiane
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On the subject of pool heating I would not pump pool water through a copper pipe system as the pool chemicals might well attack the copper and turn the water green. This must be especially true for saline pools but I am not enough of a chemist to know if added chlorine type pool water would have a similar effect. Maybe a stainless steel heat exchanger could be used but the commercial kits all seem to be made of black plastic pipe. Just a thought...........................John not Jackie
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