Summer ground re-heating

Since the circulating fluid temperature for equal in and out (from the ground) now looks to be about 5-6 degrees, compared to 8-9 last autumn, there is significant ground cooling as expected. We could hope for this to even out over the summer by conduction or ground water movements, but for the borehole depths this might take centuries!

IVT do normally (in Scandinavia) do re-heating by circulating the fluid through an air heat exchanger (without power except for the pump and air fans), giving free air conditioning and, if most of the outgoing air from the house ventilation passes through (which looks hard) some efficiency gain. But this is a pretty expensive (>>£1k) option. It is also not well-suited to our system in which the GSHP is far from the bulk of the house. On the other hand it should be sufficient just to pump the ground fluid round and through an external (cool) 'radiator' in summer and let it heat up naturally. Any condensation would then just drip outside. Options for this (conventional steel being unsuitable for corrosion reasons) could be commercially-available Aluminium or stainless radiators, adapted compact ground loop grids from Ice Energy (?plastic) or a sufficient length of a grid made up specially of copper pipe (estimated some 15-30m of 38mm pipe might be needed). These could all be bolted to [the outside of] an outside wall near the GSHP and the flow re-directed with valves. The WEL should tell how well this works and we are trying to get power estimates from IVT, but a 'radiator' power of a few kW as normally reckoned (albeit for a larger temperature differential to ambient) looks about right to me.