Options for low-carbon space and water heating include:
• Low-carbon Hydrogen replacing natural gas in the gas network.
• Individual Electric Heat Pumps using renewable electricity.
• District Heating (DH) with large Combined Heat and Power (CHP) plants and renewable heat.
Low-carbon Hydrogen and Electricity even for Heat Pumps are still poor exergy matches for space and water heating.
Modern District Heating networks have an annual average water flow temperature of about 70o C.
So by the Second Law of Thermodynamics, they give the best possible exergy match to space and water heat loads.
Compared with current gas boilers, large CHP plants give large savings in fuel consumption and CO2 emissions for heat.
They can be Combined Cycle, fuelled with gas or biomethane, or Steam Cycle, fuelled with Municipal Waste or Biomass.
Only District Heating can harness low-carbon renewable heat sources, such as solar and deep geothermal heat, as well as excess renewable electricity.
Unlike gas boilers and electric heat pumps, District Heating enables the central CHP and renewable heat plant to be halved in size, due to the Diversity of the individual heat loads.
Copenhagen, using District Heating with heat from large Combined Heat and Power plants and renewable sources, is on track to be zero-carbon by 2025.