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Solar thermal on a boat

I know the panels would be ugly, but has anyone tried solar thermal for hot water heating on a boat?
It might be good for liveaboards who are not moving much/don't want to use engine to heat water up.
Also it should save on gas/diesel over traditional hot water systems.
On domestic houses they are very efficient and can produce piping hot water all year round.
The basic set up would be:
- 1-2 panels on the roof (I did check online and it appears there are panels of the right size for the top of a narrowboat).
- pipes from panels through roof to water cylinder.
- small 12v pump to pump the fluid to the panels. This fluid circulates in the panels, absorbs the heat from the sun and takes the heat back to the water cylinder.

Asked by: Paul McMahon  | 4.01pm, Monday 8 October


WW says:

The Canal Shop at Whilton did, a few years ago, sell an off-the-shelf solar water heater for boats. ALthough, as you say, not exactly pretty, they can be effective. I have always been surprised that they are not used as much- they are quite rare on any boat, not just inland ones.
One of the reasons that i think they may not have taken off is, as well as the bulk, finding one that didn't look out of place was difficult. Also, if you currently have a calorifier heated by the engine and/or a wet central heating system, you would need a spare "coil" in the calorifier. This would often mean buying an additional calorifier, or isolating and removing one of the heating feeds.
Designed from new, it would be quite feasible to run a solar water heater, through a coil in the calorifier, and use a pump, possibly powered (almost dirrectly) by a suitable photovoltaic solar as it would be a low power pump.
The only reservation is that, as in domestic systems, they need regular purging to achieve 70C or higher, to avoid bacterial contamination- especially legionaires disease. However, if the calorifiers second coil was fitted to the engine, when cruising, this would be easily achieved if the solar heating didn't reach this level.
It is certainly worth trying- and you can get three-coil calorifiers as well, which would enable this to be fitted quite simply!

Mark Langley  | 7.58PM, Monday 8 October

In the January 2013 issue (p 78-79) we ran a short piece about a new company, Solar Powered Air Heaters Ltd, which was producing solar-powered air heating. Their panels included a small PV panel to drive the air circulating fans.
At the time they were only doing houses, but the company was looking for a boatbuilder who wanted to fit the technology and were offering big discounts to the first few boaters to have it fitted.
One year on, the MD says they are constantly refining the technology, adds that it can now provide heating even on overcast days, and he might be ready to try it with hot water too. I'm waiting to hear from him on the first case studies.
You can find them at solarpoweredairheaters.com
If you are a subscriber you can read the original piece in WW on http://reader.waterwaysworld.com/reader.cgi?issue=2013-01&page=78-79

Andrew Denny  | 11.48AM, Wednesday 13 November


Readers say:

Thanks for the response.
It would be for a new build, but I guess could be retrofitted to an existing boat (with more difficulty of course).
Yes I was already thinking along the lines of a twin calorifier with 2nd loop to engine. Seems a shame not to use the heat from the engine when available.
Glad to see that an expert thinks it's feasible!
I'll let the forum know if I actually do it. My boat is in the planning stage at the moment and it may well be a few years before it actually gets built.
I think there are some nicer looking panels on the market now by companies like Schuco.

Paul McMahon  | 11.48AM, Tuesday 9 October

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