Join Date: Jun 2006
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Why is the engine running temperature so low? Mine is 160 F, and that is plenty to heat hot water for sinks/showers (I keep it at 145 F at home, for instance).
I only point this out because the engine-heated water is free, from a systems point of view, whereas the "kettle" approach in the hot water heater is electrically intensive and more apropos to dock power.
Have you considered converting your diesel to fresh water cooling with a heat exchanger? That way, the heat from the engine raises the temperature of the coolant to 160F-190F, and the raw water is moderated via the thermostat to cool that coolant in the closed circuit. You can plumb the heat exchanger coolant circuit into the hot water tank, and the engine heat is thus transferred to the tank, which gets 12 gallons of hot water in it in a matter of minutes.
My grasp of thermodynamics is not Newtonian, but that seems more feasible than the kind of inverter and battery capacity you'd need to put 12 gallons of water on the boil using a 12 VDC-120 VAC conversion.