Never mind the EVCPs, what about the boilers.

broadgage:

A modern power station rejects heat at very low temperatures, often less than blood heat. This is too low for domestic or similar heating. The volumes of only slightly warmed water needed would be vast as would be the energy used in pumping this water.

Water at such low temperatures requires either heated floors, or improbably sized radiators to transfer enough heat into the rooms.

Heated floors are of course possible, and somewhat common, and could be incorporated into new-build properties to allow for heating with low temperature water. Forced air heat exchangers are also useful at these temperatures.


Perhaps more practical as a retrofit, consider that it could be used to greatly improve the coefficient of performance of a heat pump. The maximum possible COP for a heat pump from 0 C (outside winter air) to 60 C is 5.6, the maximum for a heat pump from 40 C to 60 C is 16.7 (yes, these are both theoretical maximums, and real-world numbers are inevitably lower, still it demonstrates the benefit of pumping across a smaller differential).


Water has a usefully high heat capacity, 1 tonne of water per minute delivered at 40 C and returned at 25 C would deliver a megawatt, call it 100 domestic properties worth of heating. At that flow rate an 8" pipe would drop 230 mbar per km, it's not sounding silly in a dense urban area. But we knew that anyway because we know other countries, mostly in eastern Europe, do it successfully.


 

broadgage:

A modern power station rejects heat at very low temperatures, often less than blood heat. This is too low for domestic or similar heating. The volumes of only slightly warmed water needed would be vast as would be the energy used in pumping this water.

Water at such low temperatures requires either heated floors, or improbably sized radiators to transfer enough heat into the rooms.

Heated floors are of course possible, and somewhat common, and could be incorporated into new-build properties to allow for heating with low temperature water. Forced air heat exchangers are also useful at these temperatures.


Perhaps more practical as a retrofit, consider that it could be used to greatly improve the coefficient of performance of a heat pump. The maximum possible COP for a heat pump from 0 C (outside winter air) to 60 C is 5.6, the maximum for a heat pump from 40 C to 60 C is 16.7 (yes, these are both theoretical maximums, and real-world numbers are inevitably lower, still it demonstrates the benefit of pumping across a smaller differential).


Water has a usefully high heat capacity, 1 tonne of water per minute delivered at 40 C and returned at 25 C would deliver a megawatt, call it 100 domestic properties worth of heating. At that flow rate an 8" pipe would drop 230 mbar per km, it's not sounding silly in a dense urban area. But we knew that anyway because we know other countries, mostly in eastern Europe, do it successfully.