How does a heat pump work?

I am not aware of a way that you do this cheaply. Heat pumps that use underground sources, work in the same way as a domestic fridge. They pump refrigerant through a pipe and it converts into heat in a boiler, this is then pumped through the ground to cool, and the whole thing starts again. Apart from the cost of electricity to run the pump, the whole operation is zero carbon. The cost of the heat exchanger is very expensive. The water produced all year round is hot enough to shower in and produce heating for a well insulted dwelling..