Where a sufficiently large body of water is within easy reach of the house, a lake collector which is a pipework system can be used to collect heat energy from the water and deliver it to the heat pump. The lake collector is a 'closed loop' system weighted at regular intervals, floated out on the surface and then once filled with the non-freezing solution it sinks to the bottom off the lake or pond. where the weights hold it in position. Stored solar energy is again collected. The piping is buried 1 metre underground between the lake and the house. The water should be deep enough that it never freezes at the bottom where the piping is laid.
Because no drilling is required and limited ground works, the lake collector can be an economical solution for delivering heat energy to the heat pump where access to a pond exists. Permissions may be required.