This type of system is simple and only requires the energy of the PV module to operate. Systems that rely on AC electricity will shut down if the grid or an inverter fails, causing the collector loop to stagnate. Stagnation may cause excessive heating of the glycol, destroying its ability to protect the system from freezing. I am planning to have a backup pump operated by a second Aquastat and a second PV module to protect the system against this worst-case scenario.
It has been a lot of work and a lot of trial and error, but we sure do like having this system. Our current goal is to get as much of our required energy from our 0.7 acre as possible. We have quite a number of trees on our property and have planted more. It is tricky having the trees and the wind generators and PVs together on such a small piece of property. The type of tree and placement has been critical.
By relying mostly on the wind and sun for our electrical and heating needs, we use relatively little wood for heating. As the price of energy increases and availability decreases, we will likely see more people doing this. The town of Didsbury has expressed interest in putting up a system as well. While we started out simply trying to cover our modest load, I definitely caught the RE bug, and have built a large and complicated system that makes more energy than we need most of the time. But having a showcase system has really helped us to open others’ minds to the possibilities of renewable energy sources.