Wow randen, Solar Heating with GSHP Backup.
What a luxury!
Another angle on this setup is that you'll be drawing less heat from your loop field, and the replenishment solar energy falling on the loop filed will bring the temperature up.
BTW, do you have any plans to store the solar energy that you will be gathering, but not needing throughout the summer?
That would raise the ground temp and really increase the efficiency of your heat pump when you do need to use it.
Remember this graph:
It indicated a COP 6 down to COP 4, ultimately depending on the delta T, but most understandably it relates very much to the source temperature (loop field temperature).
Is you house set up to work in that manner? Mostly a matter of plumbing, and some sensors, and a little Arduino magic (hint! hint!).
Best,
-AC