The latter. The silo is for source, a thermal capacitor of you will, and the geothermal well for sink. Home is in the middle, and homeostasis is achieved near passively between the two. If the silo is large enough, it will also keep the home warm in the winter, not only dry in the summer.
Discussion
I haven't ever looked into it, but I often wonder how many w/m^2 the ground can absorb in steady state. Almost every system I have seen was under-sized, because eventually the volume of earth your pipes are running through is overwhelmed by the lack of flux into the surrounding environment. At least I think that was the problem. The may have also just skimped on the heat pump.