Controllers for multiple heat sources

I am planning a thermal storage tank system a la builditsolar http://www.builditsolar.com/Experimental/OffShelfDHW/OffShelfSolarDHWV2.htm plus a water loop in my woodstove and a geyser heat pump water heater to maintain a minimum tank temp.

I can figure out a few simple ways to set up the multiple heat sources with independent controllers, but I am not sure how to set up for three. Any tips or pitfalls to avoid?

I like heat pump hot water heaters as "turn the problem into the solution" kind of thing--it heat pumps the heat from the home into the water but purely controlled based on water heat needs, not AC needs. Any ideas how to make a smart controller that would adjust for both air and water temps?

I am reluctant to use plastic collectors for domestic water heating, From the plastic collector mfg. web sites they claim that these heaters will only heat the water to 15 degrees above ambient, therefore it is difficult to get the temperature of the water very hot most of the year. I prefer flat plate collectors in almost every case. they do not cost that mush, last a generation and get the water hot, but not boiling in most situations. Also, I have little experience with what you are asking for, so I must defer on this one.

Bob

Thanks. After more research, you have convinced me on the flat plate collectors.