Solar water heater advice wanted

Pugwash69

Full Member
I've seen some solar water heater ideas on Youtube that involve feeding your cold water through a series of black pipes on the roof to warm it up. The alternative idea is to fill a larger black pipe with water, let it warm up and inflate it to force it out hot.

I realise there's some drawbacks, like lack of sunshine and holding water on the roof!

What I'm curious to know is if anyone has fitted one to a motorhome and uses it?
 

wildebus

Full Member
I'm not sure if we get enough sun that is hot enough to make it worthwhile, sadly?
What can be worth it is getting a water container, painting it black and leaving it in the sun when camped up. That can be handy :)
 

wildebus

Full Member
The general principle of using solar energy to heat water is a good one. This is the installation I had installed on my house in Devon:
1571300525287.png

But that is on the south coast, facing near enough due south and at an optimum angle. You won't get that on a vehicle.

You can see how much the fluid got warmed up each day from this graph
1571300749060.png

In the summer, had loads of hot water and never used the boiler (it got bypassed automatically). In the winter, had a typical 20C increase in the water temp going into the boiler.

However ... this was fitted at the time PV panels were much more expensive than they are now. I believe a better way than water pipes would be to have an low-power (300W-500W) immersion element into your hot water supply container and use PV (solar) panels to generate the electricity to heat the water. There is very little energy loss this way and you have a system that is more useful than just heating water - plus you can use the 'free' power from the alternator when driving to also heat the water via your split-charge system - so again more useful then a setup that would be little use in winter in reality.
I have my Water Heater set to turn on automatically when the battery level hits 99% of full charge and stays on until down to 95%. This way in the summer, once the solar energy (or split charge) has filled the battery, any excess will go to heating the water until that is hot as well. I can also bypass the Auto switch and either have it come on regardless (maybe I know I am going on a long drive and will get a good charge?) or have it off regardless (not using van for a while).

Use the real estate on the roof for extra PV instead of Pipes :)
 

Millie Master

Full Member
When living in France I fitted solar panels (Navitron) to both of my properties as well as the shower blocks on the caravan sites I built, they worked superbly, even in winter!

As for having something on the roof of your van @Pugwash69 then I would do as Dave has suggested and only when on site, put some kind of black painted container on the roof that has a breather at the top and a tube welded into the bottom........... That is if you must, as personally speaking I might get more excitement out of watching paint dry ;)

Phil
 

RAW

Full Member
Only useful outside of the UK apart from maybe 6 weeks a year perhaps
I've seen some solar water heater ideas on Youtube that involve feeding your cold water through a series of black pipes on the roof to warm it up. The alternative idea is to fill a larger black pipe with water, let it warm up and inflate it to force it out hot.

I realise there's some drawbacks, like lack of sunshine and holding water on the roof!

What I'm curious to know is if anyone has fitted one to a motorhome and uses it?
 

trevskoda

Full Member
Doing it right will require lots of thin flat pipes in a grid so small amount of water passes through the biggest surface aria.
 

mistericeman

Full Member
You could stick one of these on the roof and roll it up when not needed....

Surface area is the important bit for efficiency I think.

 

Sprinter 1 cup

Full Member
You could stick one of these on the roof and roll it up when not needed....

Surface area is the important bit for efficiency I think.

.

And you could fit it under solar panels! lovley looks like a good fifteen mins save on every warm up.
YouTube put a waste pipe 4in, the length of roof. But I can't calculate the LTRs held .5mx100mm= not enough.may be two pipes.
Good idea! Better than heating from cold.
 

RAW

Full Member
Were at £49.99 and now £120.99 - £80 price hike in under two months, I would not buy from that seller and look elsewhere. Nonethless an interesting way of creating hot-water via solar that could be mobile so thanks for sharing @Sprinter 1 cup :)

1596126173503.png
 

Pugwash69

Full Member
I did abandoned the idea of solar heating. I can't remember if I mentioned this on here, but I picked up a second hand Carver 2 in good condition.
 

Tookey

Full Member
My first thought was frozen pipes but you could drain down. What material were you thinking with reference to longevity due to weathering? I appreciate that it's not ideal for when you are static for a long period but if you are up for a project maybe using hot water from the engine to heat a well insulated calorifier might be more suitable for the UK. Hot shower every few days might be more appealing than regular tepid showers and no shower in winter unless you are 'hard as nails'. I have assumed it's to wash with as it's a lot of work for just washing up

Keep us posted
 
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Tookey

Full Member
I'm not trying to put you off a solar project but unless you travel further south frequently I'm not convinced in the UK it's worth your time and money. Engine air or water would be an interesting and rewarding project
 
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mistericeman

Full Member
I was going to fit a multi plate heat exchanger in the heater circuit (enables temp control via the dashboard heater valve) and calorifier

And a eberspacher hydronic to warm the engine water when the engines off....

Never got round to it so must stick the heat exchanger on ebay when I find it lol.
 
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SquirrellCook

Full Member
We use a calorifier connected to the engine coolant. So when we stop we have a tank of hot water. if untouched it's still hot after 24 hours.
Of grid we can heat the water with an eberspacher. I like Wildbus's idea of using surplus solar to heat the water, but you'd need a big inverter or low wattage element for the calorifier.
 
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wildebus

Full Member
as far as Solar Heated Hot Water goes (as distinct from using solar to generate electricity to heat water), for the UK I would be inclined to use a portable water container, either made from black plastic or painted black, and just leave it in the sun. Depending on the sun it could be hot enough to use, or even if 'pre-warmed' a bit could save some power to warm up further.
If you have a roof rack, secure it on there when driving; and/or leave in the sun on the ground when parked up.
I do like the "solar shower" setups with the tubes that you see some US 'Vanlifers' use, and I bet they are good in places like Arizona, but in the UK, for a lot of the year I bet you would loose more heat over night then you would ever gain in the daytime.

On the Sprinter Source forum, there is a lot of discussion on a "sous vide" type solution for water heater (adapting a cooking system for heating water). I looked at this but for myself decided there was too much faffing around and wanted a permenant installed system, but it may well suit others (there are a few people on that forum who love it!)
Here is a link (you may need to register/login to the forum to see all the results? I am not sure) - https://sprinter-source.com/forums/index.php?search/48451/&q=sous+vide&o=relevance

As an aside, I tried a similar thing to one of those sous vide setups using a 300W 12V immersion element and a 5L black plastic fuel can, modifying the cap so I could drop in the element..... In one aspect, the principle worked, but the when I left the heater element on for a time, the cap essentially welded itself to the can and I cannot remove it! Clearly not a good solution with THAT container :(
 
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mistericeman

Full Member
Black British army water Jerry cans are tough and cheap (and in the roof rack of the landrover got bloody warm in the sun after a while of being jiggled around.....)

However the larger the surface area you can circulate the water through the better...
Hence the flexible mat types being pretty efficient...
Especially IF you were to circulate the water from a tank through them...
 

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