Water heater using solar (not the camping bag)

[Pete7]

[QUOTE=Pete7;2580106]So having poured scorn on Loud Musics suggestion, actually I wonder if it would be better to ignore the solar panels and put a swimming pool flexible tank on top of the sprayhood. Will it work for say a 22L or 6 US Gal tank?

One here for £22, might be worth a punt.

https://www.amazon.co.uk/Intex-Pool-...ng+pool+heater

[Pete7]

Originally Posted by sailorchic34

From a heat exchage standpoint it would work ok connected to the U loop exchanger in the water heater. The issue is working pressure and the pool heater would most likely have too low a working pressure to even work with the engine loop (13 psig)

I have a raw water cooled engine therefore can't tap into the cooling circuit. So a new calorifier is needed, one with twin tubes. As it happens the existing calorifier is on the list of things to be changed anyway so there could be a project here.

Pete

[sailorchic34]

Originally Posted by Pete7

I have a raw water cooled engine therefore can't tap into the cooling circuit. So a new calorifier is needed, one with twin tubes. As it happens the existing calorifier is on the list of things to be changed anyway so there could be a project here.

Pete

Just add a small 20 plate brazed plate heat exchanger for the engine loop. far cheaper then a dual look calorific. Then just add a manual three way valve on the heater side to switch between engine and solar.

https://www.amazon.com/dp/B074PP2WL5/ref=biss_dp_t_asn
BTW it's 3/4" not 1/4" connectings as listed. Pretty sure you can get metric type in UK

[Pete7]

Hmm, this is all starting to get a bit complicated and the one thing I have learnt about boats is the "KISS" principal or it all goes pear shaped at the worst possible moment.

A Honda 10i genny is a lot simpler.

Pete

[Q Xopa]

Originally Posted by sailorchic34

The whole idea of using a PV panel as a heat exchanger to heat water is a very bad idea and a non starter. If the water did not circulate or got too warm it would drop the PV output voltage too low to charge the batteries to 100%. It looks good on paper only to those that don't understand the inverse relationship between PV output voltage and PV cell temperature.

Yes one could use water to cool the PV panel but the use of a small pump to circulate the water would cut any energy savings by maybe 50%. And you would get no useable heating from it.

The issue is the surface area of the PV panels is far larger then what is needed to heat the water in a water heater on the typical boat. What happens is the water continues to get hotter under the pv panesl which would cut PV voltage output during mid day, when it's needed most. So yes You can hot water using a PV panel heat exchanger. But the PV output would be drastically effected in a negative way.

BTW, I am an engineer who thought of this very idea 15 years ago. But it reduces PV panel output too much to be practical.

A dedicated 2x2 solar hot water panel would be a far better idea and is the perfect size for a 6 gallon marine water heater. Add some 3/8" pex, a 1 gpm 12v pump and a DeltaT controller and your mostly in business.

Hi Salorchic,

I have been accused of being gullible and believing in Unicorns before. It sounds like you know a lot more about this stuff than me, just asking. And of course we cant believe everything we hear or particularly see on the internet.

It's not a recent article but these guys claim that they are sucking heat off the back of PV panels for space heating etc- Solar PV and thermal – a marriage made in heaven? - Renewable Energy Focus

[RaymondR]

My new boat has a hot water system with both AC electric and engine heat exchanger heating and it's pure luxury.

However, between 2001 and 2016 I bathed out of a bucket in the cockpit and often pondered schemes for low fuel input water heating.

Two of the more practical were a heat exchanger exhaust on the small petrol engine I used as a 12V battery charger and using the tubular frame around the solar panels as a solar collector.

Most of the time we only need warm water which is fairly easy to achieve using solar or waste heat.

[Captain Puget]

Another approach for cockpit hot water showering:
- 5 gal bucket
- fill 40% full
- heat 1-2 teakettles.. depending, to desired warmth
- submersible battery operated pump w showhead attachment

I heat water on a diesel stove, so no propane on board , no 🔥



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