sicetaitsimple wrote:A bit of advice though. I believe I understood that your objective was to increase the average COP of your heat pump over a heating season by slightly heating the geothermal fluid which passes through it. If that's the case, take a look at some thermal solar panels connected in series on the circuit, which won't do any miracles in the middle of winter, but which in the fall or spring will improve things. And which will allow you perhaps not to freeze your geothermal field (the ground around your pipes), which is very penalizing for the exchange. And you will leave at the beginning of the heating season with a warmer ground than just heated "naturally", especially if your pipes are 1,5m deep, which I believe I understood.
Absolutely no guarantees from me, but it's free of charge.
And moreover taken up in principle by B. Labrique in his post at 18:21 p.m. on the performance of his heat pump.
Thermal solar panels:
1° not profitable to put at home because the roof is very little in the sun.
2° in the coldest sequences, the temperature of the glycol water drops close to 0° as indicated above but the heat pump retains a COP of 3. Moreover, the reactivity of the ground in the rise in its temperature is remarkable: thus, in December 2017, given the persistent frost, the temperature of the glycol water at the inlet of the geothermal heat pump had fallen to 1°; in January 2018, the ground having warmed up, it reached > 3°, given a slightly milder weather; at the end of January 2018, it reached > 4° (no intense frost in the meantime).
Moreover, I am convinced that in the presence of a thermal wind turbine, adding thermal solar panels will not bring much and the return on investment (not to mention maintenance costs) may never occur. ...