Solar water heating

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Solar water heating

Postby qwerty » Mon Jul 31, 2017 10:56 am

As a newbie to this forum, I’ve tried searching for threads about solar water heating without too much success. Perhaps I’m not searching very well at the moment.

As a small project, I’d like to have hot (well warmish) water to wash the plates in the kitchen sink.
I’ve looked at a few youtube videos about this. The main thing I can remember was some discussion about whether the reflecting surface behind the pipework enclosure on the roof should be black, white or silver.

Like I said, I envisage this just as a small project to begin with, more out of interest really, unless someone may suggest otherwise.
If there is a member who has undertaken this already, then perhaps some details may be on the forum already?

Bearing in mind I’m looking to do this on the cheap. So for example, the construction of a suitable enclosure, is there something off-the-shelf that might be suitable?
Is it practical to use the standard blue plastic pipe, painted appropriately? What diameter size pipe should I use for a half-inch tap feed? What length & number of pipe runs within the enclosure?

My water installation is a city water supply that fills two 1,000 litre plastic storage tanks. From the tanks it is pumped into the house.
I’m guessing I’d fit a second tap in the kitchen sink, rather than a mixer tap, so the feed to that would the the usual half-inch fitting & pipework equivalent?

Thanks for any ideas, negative or otherwise.
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Re: Solar water heating

Postby schuimpge » Mon Jul 31, 2017 3:09 pm

viewtopic.php?f=3&t=5192&start=180

Tertim has built a solar heater.
See the link above. Quite sure he'll be happy to respond to any queries you might have.

Sometimewoodworker is in the planning stages to build something similar also

Cheers,
Luc
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Re: Solar water heating

Postby Sometimewoodworker » Mon Jul 31, 2017 3:59 pm

qwerty wrote:As a newbie to this forum, I’ve tried searching for threads about solar water heating without too much success. Perhaps I’m not searching very well at the moment.

As a small project, I’d like to have hot (well warmish) water to wash the plates in the kitchen sink.
I’ve looked at a few youtube videos about this. The main thing I can remember was some discussion about whether the reflecting surface behind the pipework enclosure on the roof should be black, white or silver.

You've probably been reading/watching information for countries where it isn't as hot as Thailand, I don't think you need a reflecting surface.
Like I said, I envisage this just as a small project to begin with, more out of interest really, unless someone may suggest otherwise.
If there is a member who has undertaken this already, then perhaps some details may be on the forum already?

Bearing in mind I’m looking to do this on the cheap. So for example, the construction of a suitable enclosure, is there something off-the-shelf that might be suitable?


I'm probably not going to bother with an enclosure at first just the pipe, maybe on expanded polystyrene.

Is it practical to use the standard blue plastic pipe, painted appropriately?


No, it will degrade in sunlight and be too expensive to paint. Use HDPE/ LDPE, it's already black

What diameter size pipe should I use for a half-inch tap feed? What length & number of pipe runs within the enclosure?


If you are trying for a thermosiphon then the bigger the better with a minimum of 1 ½ inch. You will need a tank for hot water. 50 to 100 metres.

If you are going to pump the water through the collect you can get to 60 degrees

My water installation is a city water supply that fills two 1,000 litre plastic storage tanks. From the tanks it is pumped into the house.
I’m guessing I’d fit a second tap in the kitchen sink, rather than a mixer tap,

Unless you are going to pump the hot water from its storage tank you will have to do that.
so the feed to that would the the usual half-inch fitting & pipework equivalent?.

For short distance pumped supply yes.

Tertim has a pumped collection system in 1"
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Re: Solar water heating

Postby qwerty » Mon Jul 31, 2017 6:53 pm

Thanks for all the replies.

Sometimewoodworker, I see you’re apparently planning a similar project too. I appreciate you having taken the time to answer my queries in detail.

Firstly, having looked at more youtube videos, I can see I was naive in thinking I could use a multiple pipework array in a back and forth layout (I don’t know what the proper term for it is?) As it seemed it would be a reasonably low-usage system, I thought it would be pumped from the main water tank, through the collector (I think I’ve got that term sussed now?) and out to the kitchen sink tap, although I realised there wouldn’t be too much hot water that way.
It didn’t occur to me that I would need a hot water storage tank. If I need that, then it makes me think that if I do go ahead with the project. then it might be practical to supply the showers in the two bathrooms.

Already it’s getting pretty ambitious and I haven’t even got off my backside yet!

You said I will need a tank ‘50 to 100 metres’ Did you mean litres, or is that a maximum distance for a total pipe run?

The control system Tertim has installed seems quite complicated and I’d imagine needs some cash spending to get to that stage.

Regarding the use of HDPE/LDPE pipe. I had to google it, as I hadn’t heard of it before. Is it readily available here - Global House and the likes? Is it more expensive than the blue PVC pipe? If it is available, is it just referred to as HDPE, or is there a Thai colloquialism for it?

Thanks again for the help.
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Re: Solar water heating

Postby Klondyke » Mon Jul 31, 2017 9:57 pm

One of simple solutions - not overly hot water but for dish washing enough (during the day):
If your house has a heavy ceramic roofing, you can try to lead the pipes - in a proper length, - to the kitchen tightly under the roof covering, with some simple insulation underneath (e.g. a gypsum desk with alu foil). You can check that already early in the morning the tiles are very warm.

The usual blue PVC pipes 1/2" - 3/4" should serve OK.
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Re: Solar water heating

Postby Sometimewoodworker » Tue Aug 01, 2017 7:06 am

qwerty wrote:Firstly, having looked at more youtube videos, I can see I was naive in thinking I could use a multiple pipework array in a back and forth layout (I don’t know what the proper term for it is?) As it seemed it would be a reasonably low-usage system, I thought it would be pumped from the main water tank, through the collector (I think I’ve got that term sussed now?) and out to the kitchen sink tap, although I realised there wouldn’t be too much hot water that way.

That could work, you could add a storage tank later, don't underestimate the volume of water in the pipe work.
It didn’t occur to me that I would need a hot water storage tank. If I need that, then it makes me think that if I do go ahead with the project. then it might be practical to supply the showers in the two bathrooms.

That's what I'm intending
Already it’s getting pretty ambitious and I haven’t even got off my backside yet!

You said I will need a tank ‘50 to 100 metres’ Did you mean litres, or is that a maximum distance for a total pipe run?


Not quite. I said you probably need a tank. The 50 to 100 metres applies to the length of pipe needed for the collector

The control system Tertim has installed seems quite complicated and I’d imagine needs some cash spending to get to that stage.

That could be because he started with a small diameter pipe.
Regarding the use of HDPE/LDPE pipe. I had to google it, as I hadn’t heard of it before. Is it readily available here - Global House

Yes, my local Global House has it stacked outside in either 50 or 100 meter coils, the others may also have it, I didn't look.

and the likes? Is it more expensive than the blue PVC pipe? If it is available, is it just referred to as HDPE, or is there a Thai colloquialism for it?

Much cheaper than blue PVC, I don't know what it's called but it has the letters HDPE or LDPE on the price label
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Re: Solar water heating

Postby qwerty » Tue Aug 01, 2017 2:08 pm

Sometimewoodworker, thanks once again for all the info.

Even if I didn't go ahead with this, I am learning a lot more about the details here, better than the youtube videos I've seen so far.

Yes, I had underestimated the amount of water in the collector. I initially guessed at 20 metres (working on 10 rows of 2 metres per row), but from what you’ve told me I’d need three to five times that amount. Do you know what diameter collector I’d likely to need for 50 or maybe 100 metres of pipe, if it’s laying in a flat spiral?

Thanks for suggesting a larger collector pipe size too – 1½ inch, that’s about 40mm. I was imagining using ½” or ¾”.
Perhaps I'm getting too carried away now - 2" would be even better, but would need an even larger collector. I imagine even with pumping the water through it, would still give a better overall result?

This is beginning to smack of forward planning now, ha ha! Seriously though, I’m all for that. If I did go for a tank, is there a standard one that’s best/easiest to use, do you know? I saw in that Nepal video they had to drill and fit pipe adaptors into a pretty ropey looking plastic tank.

I guess Global House will sell the HDPE/LDPE pipe in metric diameter, but you never know. Is there any important difference between HDPE and LDPE I’d need to know about for this project, as long as it’s black? I take it Global House sell the fittings and also adaptors from blue PVC to HDPE/LDPE?

I have to go to Global House in the next couple of days anyway, so I’ll have a look. I have looked at their website already, but it’s entirely in Thai with no search facility. Looks like the pages are scanned from their catalogue.
I’m in Udon, not a million miles from you I gather. My nearest branch is on the Udon ring road.
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Re: Solar water heating

Postby Klondyke » Wed Aug 02, 2017 11:11 am

I saw the black pipes at GH in 100 m rolls, seems that the smallest is 20mm (3/4"). Smaller diameters In smaller rolls are available at Thai Wasadu and HomePro with the suitable fittings - no glue needed.

For a dish washing - as you wrote - some 20 - 30 l should be enough (length 100 m of 1/2" gives 11 l of water, 3/4" = 28 l), once you do not have a Laan Ahaan for people around. The larger diameters (1.5") will contain more water storage, however, the heat transfer for that water volume is slower than at smaller diameters - tube surface grows with power 2, the volume with power 3. Also the bending of such large diameter is not so easy.

Water storage volume can be increased by a smaller tank (50 - 100 l) - properly insulated - where the warm(ed) water inlet is at the bottom, outlet at the top.

With a pipe register placed on the roof a problem of covering by leaves and other dirt is to be regarded (in Thailand - unless it is not under a glass), also a faster deterioration of the plastic material. And I think that the heat transfer is cooled down by ambient air. Unlike when the pipes are led under the roof (if the roof is by clay shingles). This kind of roofing absorbs the solar radiation and gives it down away in form of infrared radiation. So I think that in a long term the warming result (and the lifetime) under the roof is better.
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Re: Solar water heating

Postby qwerty » Wed Aug 02, 2017 4:24 pm

This is just FYI for anyone who might just be interested, regarding the black LDPE pipe.
I went to Global House this morning. These are the prices I was quoted per length:

2” x 50m 1,970 Baht
1½” x 100m 2,430 Baht
1” x 200m 1,890 Baht
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Re: Solar water heating

Postby qwerty » Tue Aug 08, 2017 7:35 pm

The more I think about the solar water heating idea, the more I feel it would be good to be able to use for showering too.

I have been doing some basic investigation into the volume of water required for showering. There are three of us in the house. I have checked our average time having a shower and measured how much water per minute the shower pushes out. For three of us to have one shower each, it would use about 100 litres of water. Plus there is Klondyke’s estimate of about 30 litres for dish-washing.

It seems lucky that Global House sell LDPE. Reading about HDPE and LDPE, the LDPE is more flexible.
These are the pipe diameters and coil lengths on sale in Global House again: 2”x 50m, 1½”x 100m, 1”x 200m.
I found a website listing volume per metre of pipe, by various diameters. All these three have a capacity of 100-110 litres.

Needless to say, without using a water storage tank I can’t imagine making a collector with 200 metres in a flat spiral. That would cover the entire garden.
Bearing in mind Klondyke’s comment that the larger the collector pipe diameter, the slower the solar heat transfer, I read that one project increased the pipe diameter dramatically, as there wasn’t enough heat (or was it just flow?) produced in a smaller pipe (was it ½” initially?)

What pipe length & diameter, along with collector overall diameter have others used successfully?
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