Hi folks, I've been thinking about a simplified ground source heating setup for DIY and would value constructive and educated input.
You hopefully already know how ground-source heating works: Water is pumped through buried pipes and fed through a heatpump to concentrate the collected heat.
My simplified method would be to do away with the heatpump and water systems and suck (not blow!) air through slightly larger diameter buried pipes directly , with a constriction at the intake end. Since the air would be at a lower pressure inside the tube it would heat up as it regains ambient pressure indoors (similar to how heat pumps work). The air would obviously be fed over the pump/fan motor to salvage heat from that too.
(At daytime the air could be sucked through solar boxes which are warmer than the ground would be, but my main concern is night time heating.)
My rough calculations say that the low pressures achieved by a high powered vacuum cleaner are adequate (remembering that degrees Kelvin must be used for the maths). Obviously I don't plan to use a vacuum cleaner for anything other than tests but a purpose built vacuum pump.
So the big question is: Could this setup approach the energy efficiency of an air conditioning unit or existing ground source heating system? Mechanically it would be a much simpler system to build and maintain.
The second idea is for a refinement to above: Instead of sucking air through a constriction, how about recouping that energy by powering a smaller air motor from it and mechanically returning some energy to the vacuum pump? In practice, the unit would be designed to do both, running on a single shaft with the air motor being a slightly smaller capacity version of the vacuum pump doing the suction work.