District heating systems have been around since the Romans used underfloor heating. More recently they have been installed from the 1970s to supply heating to residential estates. Interest in the technology has fluctuated: sometimes they are cheap and effective, then power prices rise and they fall out of favor. Nowadays there is an argument that heating districts with renewables will reduce running costs and cut emissions.
At the center of the district heating philosophy is the concept of improving energy efficiency, reducing CO2 and saving on running costs by having one large heat source running very efficiently, rather than each building having their own separate small ones operating less efficiently.
Scandinavia is leading the way with this form of heating, with 65% of Denmark being serviced by district heating, as opposed to 2% of the UK. Many other countries are looking favorably on the technology.
Traditionally, bio-fuels have been the main alternative to fossil fuels in district heating and cooling. However recent improvements in building insulation and power management software have enabled district energy to use widely accessible, low-temperature renewable inputs: solar power, obviously; wind turbines, waste heat sources, micro hydro, heat pumps. Coupling these technologies with battery storage is looking more and more viable. With the UK and many EU states banning new gas boilers, they will need to be replaced by a different system: heat pumps are a strong candidate for this substitution.
Ground source or water source heat pumps can be used with piping to deliver hot water to a whole network of buildings. Modern plastic pipes are better for this than the previously-used steel pipes, and lower in cost. This way the installation cost will be borne by the developers, and not individual home or premises owners. These systems can be designed into new-build areas easily, but it is also possible to retrofit them to existing buildings, though this is more complex and expensive.
The combined advantages of lower emissions, lower costs, together with the benefits of larger scale systems look to make renewable-based district heating systems a component of the energy future.