Any ideas for solar hot water to main h/w tank?

[PopeyeGordon]

I plan to live aboard a 30 footer in Florida, first choice being a catamaran. I am a big fan of solar technology including solar powered propulsion. Also want to form ideas for using the typical engine heat exchanger in the boat's hot water tank to transfer solar heat from some sort of deck installed solar collector. I would also have the simple solar bladder on the stern for post swim rinsing but since I want to live aboard and anchor out a lot I think there is opportunity to have hot water for the galley and head, saving the reliance for regular engine running to give hot water.
Am I overthinking this, is it enough to just keep a solar bladder on deck over the galley area and use a gravity feed to the sink? Or have you seen a system that takes advantage of the boat's insulated h/w tank and main water system pump to patch in water heated on deck?
Some solar collection panels I have seen look too fragile for topside mounting. How about a 3 gallon aluminum or galvanized tank on deck in the sun, painted flat black, to collect and transfer to the h/w tank below? Or a loop of black tubing around the top of the Bimini cover that circulates to the h/w exchanger coil? It could use a small pump to circulate through the heat exchanger coils, tapped in at the intake side of the tank with a Y-valve that would shut off the engine coolant loop.

[sailingdog]

Why make things more complicated than necessary. Keep a solar shower or similar setup on deck...use as needed. Duckworks sells a pressurized bug sprayer with a handheld thumb-trigger shower head that is a nice setup for just this purpose.

[PopeyeGordon]

As I originally stated, I will use a simple solar shower on the stern. My post is wondering how to take advantage of the sun to have hot water in the galley and head without relying on the engine or heating water with fuel on the cook stove. Do boaters in the tropics not use hot water? It seems to be useful for washing dishes, scrubbing greasy hands and shaving.

[sailingdog]

Originally Posted by PopeyeGordon

As I originally stated, I will use a simple solar shower on the stern. My post is wondering how to take advantage of the sun to have hot water in the galley and head without relying on the engine or heating water with fuel on the cook stove. Do boaters in the tropics not use hot water? It seems to be useful for washing dishes, scrubbing greasy hands and shaving.

The bug sprayer setup I mentioned would allow you to use hot water wherever you need it... Just leave the sprayer sitting in the sun during the day... the water can be surprisingly hot by the end of the day.

[PBzeer]

I keep my solar shower full at all times and exposed to the sun.

[arf145]

I wouldn't want to mess with, and possibly jeopardize, my engine cooling loop. But how about putting in another 5 or 6 gal tank to serve as your "pre-heater"? Have the output of the solar tank feed the input from your regular hot tank. If you got your solar tank with a heat exchanger in it, you could set up a closed loop system. That pump is going to be using some power though.

Don't know about the collectors. I don't think just tubing, black or otherwise, would do it. Need a plate, even if it's just copper foil, and a cover to capture the heat. I wonder if this small collector would be enough?

[mitiempo]

I live aboard year round - not in the tropics unfortunately. I have pressure water but cold only. I heat up some in the kettle for washing dishes etc.

Shaving? Good time to cultivate a beard like Joshua Slocum.

[PopeyeGordon]

Although there may be an efficient pump made for such use that could be switched only when the water warms, I like the idea of the preheater tank on deck - and perhaps the simplest possible arrangement is to have a bypass valve that routes demand past the main hot water heater, through the on deck tank, and to the cabin sinks. Home systems with heat exchangers rely on large tanks, 40 to 60 gallons, that can build up a thermal reserve for the night. Our boat tanks average 10 gallons which means an elaborate system could be of dubious value.

A bypass to the small deck tank would do two things - keep the tank always full, and make use of the convenient on-demand water pump system. Most of the year, the deck tank could be left on since it won't cool excessively at night. The shower bladder could still be used if more water was needed but I like the idea of not lugging a heavy jug in and out of the cabin.

[PopeyeGordon]

Thanks to Brian for that great Slocum photo!

I have done the camping thing many months aboard and am not too lazy to heat water on the stove. My reason for the thread was to form a plan to take full advantage of solar power and save fuel. I will be on an extreme budget most of time. Hot water is easy to come by with marina power. Solar showers are the most popular choice on the hook but we live in a creative time so let's think of more ways to enjoy the convenience of hot water.

[Mark F]

Hi PopeyeGordon,

How about a large, black, sealed spinnaker pole? Or two.