Nobody has mentioned it yet, but i have a connection on my 3 panel solar hot water system cut in before the temper valve and run to my brew shed.
When i go to heat strike/sparge water i start with water that is tween 60 and 80C. It's heated for next to nothing and is a considerable time/money saver.
For a system like you are proposing i would investigate a custom designed solar heater.
Also, when i was looking into commercial production of my beef jerky, foodsafe advised me that while it was legal to have a food system in my home (or seperate to it) if i met the right conditions....they would never approve it as they had no legal right to inspection on a private dwelling unless they obtained a warrant.
This information is 12-18 months old, so things may have changed, but i doubt it.