District heating (also known as a heat network) takes heat produced from a variety of sources and connects it to homes or public and commercial buildings via insulated pipes. Instead of each building generating its own heat, with for example a gas boiler, a heat exchanger allows each building to take the heat it needs from hot water flowing through a heat network.
A heat network will typically comprise:
- An energy centre where heat is generated. This can be done in many ways, and there may be multiple energy centres on a single network.
- Buried pipes. Insulated pipes carry hot water around the network
- Heat Interface Units in each building. These control how much heat and when each building takes heat off the network.
District heating is not a new concept. There have been district heating schemes in the UK since the 1960s and in some places it is very common – in Denmark 62 percent of the population heat their homes using district heat networks. Only a relatively small number of district heat networks currently exist in Scotland.
The beauty of heat networks is their versatility. They aren’t static entities, but can be shaped and grown according to shifting needs and capabilities. Large, city wide heat networks are efficient and can take advantage of a range heat sources, including waste heat from industry. New technologies for creating low carbon heat can easily be added. Homes and businesses benefit from no longer needing to find space for and pay to maintain and replace individual heating equipment.
District heating has a crucial role in achieving the Scottish Government’s ambition for net-zero carbon emissions by 2045. Heating buildings is Scotland’s second biggest source of carbon emission and heat networks help tackle this as they are more efficient and can take advantage of new technologies and opportunities more easily.
There are many technologies and sources of energy for use in heat networks. Heat pump technology can harness heat energy from air, ground or water sources (including waste water and water in disused mines). Solar thermal panels can be used to capture energy from the sun. Combined heat and power (CHP) systems can generate heat and electricity highly efficiently. Heat recovery technology can capture waste heat from industrial processes and pipe it into a heat network supplying nearby buildings. A biomass plant can burn sustainably sourced wood or other energy crops and bio waste to produce heat energy. Boreholes drilled deep into the earth can capture geothermal heat.
Establishing district heating in Scotland’s cities is not a small challenge and requires planning and regulation. To ensure they operated efficiently they require large ‘anchor loads’ that require a steady supply of heat (for example hospitals or swimming pools) and new developments should be planned around the network.