I am new to the forum, alternative energy systems are just a hobby for me. My largest install is for a friend lwho ives off grid in 3 bedroom 2 bath mobile home with 3 window 5000 BTU AC units, 220 VAC water pump and all comforts of modern home living. They are now building a 2800 sq ft home. I am installing a thrid SW4024 inverter and a total of 4500 amp hour batteries. The new home will have geothermal HVAC system which will reduce the electrical demand for AC power by 50%. Also installing a solar water heater system and using the generator wasted heat energy to heat the water as well. I am building aheat exchanger using the hot exhaust gases to heat up a phase change thermal storage mass. The phase change material will be tin lead (plumbers solder) in a tank the will store the heat from the exhuast (800 to 1200 degrees) then a second coil in the tank will transfer the heat energy by pump to the hot water heater. I will also be using the engine oil heat by using another heat exchanger to extract that wasted energy as well. Still working on all the safety issues like temp control valves to prevent overheating. These micro and mini congeneration system are becoming more and more popular. Hope to learn from others on this forum as well. This is a great way to learn for other peoples experiances. I am looking for other peoples help with information on solar water heating, using glycol or some other means of heat transfer, all input would be welcome. arcandspark