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 10 Solar Water Heating (Read 20548 times)
rayo
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Solar Water Heating
Sep 30th, 2013 at 1:06pm
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Hi all. Recently bought a townhouse in Mora and thinking that simple gravity fed Solar Water Heating from a rooftop unit might be practical. Has anyone any experience or recommendations in this respect?
P.S. Most impressed with the forum setup and content.
Cheers, Ray.
  
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David
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Re: Solar Water Heating
Reply #1 - Sep 30th, 2013 at 8:28pm
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Hello Ray.
We have had solar hot water for 7 years. The make is SolaHart.
It is made in Australia. I suppose there are spanish equivalents.
The panel and tank sit on the roof. The water is gravity fed.
It provides all the hot water we need most of the year. Perhaps a few times in winter after a sequence of dull days, we need to use the immersion heater which is built into the tank.
I believe it is now a law in spain that all new builds must have solar hot water heating.
It has saved me a lot of money. I think the pay back is in the order of 5 years but that depends on how much you use it etc. Money well spent in my view.
  
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Nigel
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Re: Solar Water Heating
Reply #2 - Sep 30th, 2013 at 10:50pm
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I have solar hot water (a self built system) and have installed a few systems. All work extremely well, the best solar investment you can make!

One customer of mine has a system he also uses to heat his house - I only installed it this spring so as yet we don't know the results.

I'm currently working on a project to install a hybrid solar/heat pump heating system for my house, again a home made system hopefully I'll have it installed soon and will know how well it works this winter. I had the heat pump working last winter and saved in the order of 1500 euros in heating oil by running it.

I must admit to not being a fan of the gravity fed systems as I've seen problems such as boiling/calcium build up etc. with them. The system I prefer is a closed solar circuit with circulating pump and an indirect heated tank.

Mine, for example, is a single panel (about 2.4m x 1.2m) and a 160 litre water tank. We have hot water from this pretty much from late February to November. Outside of this I use a combination of a heat pump or immersion heater to heat the water, the former being the most efficient. The pump and control runs from solar so effectively costs nothing to run.

  
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philmountains
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Re: Solar Water Heating
Reply #3 - Oct 1st, 2013 at 9:32am
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Nigel did you make the panel yourself -15mm -22mm tube or is it a bought evacuated tube type, and is the cylinder a single coil or a dual coil,  these are dear !!!!! been looking for a while now for one of these to work with a wood burner.
I have just won 2 x ultra violet filters from work this week, and will hope in time Grin to be using 1 of these in a collected rainwater system,I have a bit of a query that might be in your line, as I have also collected a few 24dc shurflow pumps which I was going to incorporate in this system.
, but not sure about flow rate going through filters ? I know there is a max but cannot find info on minimum? any advise appreciated.
Thanks Phil
  
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Smidge
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Re: Solar Water Heating
Reply #4 - Oct 1st, 2013 at 11:57am
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Hi Nigel, could you provide a plan for your 160l system? Smiley
  
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Nigel
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Re: Solar Water Heating
Reply #5 - Oct 1st, 2013 at 8:28pm
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The panel(s) are repaired solar water panels I have been lucky to obtain. All 3 that I have had suffered bursts (probably from freezing) and needed brazing. One had shattered glass and the others were repaired from behind, cutting out the aluminium panel and then repaired with aluminium strips pop-riveted down the cuts.

The 160L tank is a conventional indirect heated tank (Roca) but used with solar instead of from a boiler.

You can read all about the system and how it works with a combination of solar and heat pump here:
http://ecorenovator.org/forum/solar-heating/3123-combined-solar-heat-pump-water-...
  
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philmountains
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Re: Solar Water Heating
Reply #6 - Oct 2nd, 2013 at 9:11am
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Wow they were a good find Nigel, never seen any of them in a skip Grin
And thanks for the link, bookmarked them, useful site for us with an eye for cutting costs.
  
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Smidge
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Re: Solar Water Heating
Reply #7 - Oct 2nd, 2013 at 11:33am
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Nigel, thanks for the link. Smiley
  
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rayo
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Re: Solar Water Heating
Reply #8 - Oct 2nd, 2013 at 12:43pm
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Thanks all for input. Gravity system still looks simplest (and probably cheapest) to me..acknowledged that I'm only going on reading stuff and that there might be some longer term issues. Seems difficult to find a spanish supplier quoting prices, but I have found some in Malaga via ebay uk site if anyone is interested.
Cheers, Ray.
  
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Re: Solar Water Heating
Reply #9 - Oct 2nd, 2013 at 8:29pm
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I might be talking carp here but if the water from my green hose pipe is anything to go by, would it not be feasible to just lay out a coil of about 100m of 32mm black irrigation pipe ?  Either on a flat roof or the deck (if you could fit it into the typically tiny "gardens" here)  Cheesy
If one end was fed from the cold supply and the other to a typical butane water heater via a thermostatically controlled mixer valve, the heater should only cut in if it's input drops below 65C ?
  

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Nigel
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Re: Solar Water Heating
Reply #10 - Oct 3rd, 2013 at 9:59am
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I see lots of this type of system around - it seems an obvious solution but does have limits, some of which are below:

  1. The pipe radiates heat and as it is not enclosed in a panel the heat escapes so reducing the efficiency. Also wind will cool the pipe if not enclosed in some form of panel.
  2. The quantity of water is limited to the amount that will fit in the pipe.
  3. The surface area of the pipe in contact with the water is small. The bigger the pipe the less contact.
  4. The surface area of the pipe exposed to the sun is small as large parts of the pipe are in the shade.
  5. Plastic pipe is not a good conductor of heat.
  6. At night the heat will be lost due to lack of insulation.


  
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cactus jack
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Re: Solar Water Heating
Reply #11 - Oct 3rd, 2013 at 10:15am
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When I first came over and had no bathroom in my chicken shed, I used a black plastic expansion tank with a hose out of it. Worked brilliantly so long as I had my shower before the sun went down. Sometimes it was too hot.
I am thinking of putting a hose back up on the roof and preheating the water for the gas heater.
If it goes cold at night it doesn't make any difference as the current feed is cold anyway. If it freezes then I'll have ice for my G&T Smiley
  

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Re: Solar Water Heating
Reply #12 - Oct 3rd, 2013 at 1:41pm
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Hi Nigel,
I hear what you say but :-
1.  I'm thinking that if a 30m green hose pipe gives me about 10 litres of water hot enough for washing up (and too hot for showering) then 100m of black 32mm pipe would give a lot more (i.e about 300 litres).  More than enough for general houshold use at any one time as once you've done the washing up or showered (or whatever) the residue in the pipe would carry on heating up.  It wouldn't be difficult to locate the pipe in the lee of the wind ?
2.  See above.
3.  Don't get that ?
4.  Ratio mentioned in 1. still applies.
5.  Ratio mentioned in 1. still applies.
6.  How much washing up etc. do you do at night ?
I'm not trying to deliberately contradict you and your laws of physics are correct but it seems to me that it would be very cheap and simple to construct.  I'd give it a try if I had nowt else to do and a 15 bottle of gas lasts about three months on the water heater.
Could an insulated storage tank not be included in the circuit so that there was a resevoir of pre-heated water to feed the boiler in the morning ?
  

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Re: Solar Water Heating
Reply #13 - Oct 3rd, 2013 at 4:43pm
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I got through two insulated hot water copper tanks in four years. The water I have from a well at the bottom of the mountain is very corrosive. I gave up on the tanks and just use a gas water heater.
I also used to use a vacuum tubes  system but the pumps used to fail on a regular basis Sad
Where can you buy gas at 15 a bottle? I paid 17.50 last week
  

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Smidge
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Re: Solar Water Heating
Reply #14 - Oct 3rd, 2013 at 5:26pm
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Nigel what is your opinion on 3/400 ft. of 32mm black pipe coiled flat on 8x4 ply base painted black enclosed on top with uv grade polycarbonate. placed on a frame on the ground facing the sun. The hot water from the coil thermosyphons up through insulated pipe to a heavly insulated 1000l tank on the roof with either a second coil or just direct feed from the tank back to the coil gaining heat during each cycle.  Smiley
A DC pump with panel could be used for circulation if the thermosyphon is not enough.
  
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