You will never produce the electricity you require to run the grid with 100% solar/wind/biomass.  It just isn't possible.  

And don't start talking about how Germany did it.  Their installed solar provided an electricity bump for little more than a few minutes on two occasions and on both it caused chaos with their grid.

GSHP systems are incredibly expensive to install, operate and maintain.  It is significantly cheaper and easier to heat with Gas.