ATES systems use ground water itself, which is stored in aquifers, to inject or extract thermal energy. ATES systems typically have a cold and a hot well. In the summer the heat is extracted from the hot well, cooled down when the heat is delivered to the system and the cold is injected in the cold well. In the winter it’s the other way around.
In the Hysopt library there are different ATES Base Circuits available.