So been sat around thinking today about how to power a school bus RV project, been running some numbers to try and make everything balance out. if this wild project does ever get off the ground i would like to explore pretty much the whole country hot cold and in-between. i also like the idea of not been tied to camp sites especially when out in the boon docks. So it was apparent pretty quickly that solar and batteries is quite economical especially the last few months the prices of panels seems to have been dropping i'm seeing 300w for $200. so 1200w installations are not out of this world expensive (any more). also 12v and 120v split AC options are totally doable. however try and store enough energy during the day in batteries to heat at night and the wheels fall off pretty quickly. the cost, volume and weight in batteries is unfeasible. however...
55g of water in a insulated tank with coils (heat exchanger) on a circuit that includes a fossil fuel heater, engine heater circuit, and the coach heater. this same circuit could also include the domestic hot water (with a backup heating coil of course).
on a circuit separate from the engine coolant / coach heaters would be a roof mounted solar panel that would heat the mass directly. from what i have read on the net a single panel (forgot the dims right now) would be plenty for a 40' bus.
something like this... black hose pipe...
https://www.amazon.com/dp/B00ULYKO9W...a-313605881933
you would probably want to isolate the engine when you were parked for any length of time to stop the system trying to keep it warm for no reason.
i also like this system because if plain water was used it could be dumped when not needed.
i mentioned this in another thread but its still border line not worth it with the cheap price of diesel and propane.
anyway i would be interested to hear constructive thoughts on the subject, positive or negative.