> I have built a 30 kWp PV at home 2 years ago - you would think this is quite big, for a private plant. It is not enough. If I want to power a heat pump (with

> I have built a 30 kWp PV at home 2 years ago - you would think this is quite big, for a private plant. It is not enough. If I want to power a heat pump (with drilled holes), e.g. to cover the heating for the house from November - February, I calculated I would need about 70 to 80 kWp (optimized for winter sun angle, e.g. pretty steep modules at 60° or 70° that relatively produce less in summer, but more in winter). Have you considered a thermal battery? A cubic meter or ten of NaOH solution can store a surprising amount of energy, and can be charged during summer/spring/autumn with simple solar modules consisting of black pipes in glass. Even if you only store half the energy needed for some of December and January, it halves the needed size of modules. Hydrogen electrolysis is also shockingly cheap, if there were some safe, small scale storage this issue would be solved.