District heating has reentered the conversation as a low-carbon, low-cost heat solution for large groups of people.
These heat networks take heat from a central source, often as a waste byproduct of manufacturing, power generation or waste destruction, and channel it through a series of insulated pipes into a group of different buildings, with heat pumps allowing for cold and hot air to be transmitted on request.
Whilst the concept is simple and dates back to the Roman Empire, its scalability and adaptability makes it far more effective for heating homes than an individual boiler in each home, especially if you take advantage of heat sources that already exist.
The most common example that has been explored is the combined heat-and-energy plant, where a power plant that would have heat as a waste byproduct instead distributes it to homes that need it.
Whilst this, and natural geothermal sites such as those in places like Bath are well known, there are other district heat sources that are not as well known but could be a major part of the heat network ecosystem in the future.
Here are some examples of unique district heating sources.
Flooded Coal Mines
Whilst much of the UK’s historic coal mining industry has long been closed, the mines themselves may have the potential to provide affordable low-carbon heat.
The UK Coal Authority published a report in December 2020 that suggested that flooded mines would have heated water thanks to geothermal processes underground, which would be between 12 and 20 degrees Celcius.
This temperature is only just under the optimum temperature for central heating systems and low carbon heat pumps would work to efficiently heat the water the rest of the way.
The temperatures that were challenging to miners decades ago would help to provide a sustainable source of heat and energy long beyond the mine’s viability for coal.
Nuclear power produces huge amounts of energy but as a consequence also generates intense levels of heat, requiring huge cooling towers to remain viable. This heat is wasted when it could be potentially be used in district heating schemes.
The government has opened a consultation to demonstrate the potential in using advanced nuclear power stations to help decarbonised heavy industry and pave the way for net-zero carbon.
Computer systems generate large amounts of heat, and server rooms have utilised increasingly creative means to keep large racks of computers cool to avoid malfunctioning systems and a potentially catastrophic loss of data or access.
However, a potential solution may be taking advantage of district heating systems by utilising waste heat from server farms and using this heat as part of heat network systems.
A study undertaken in Finland suggested that not only could it save energy for heat generation but could also save up to 7 per cent for the business managing the server farm.
Given that the past year has seen an increasing number of people use remote access servers and systems rather than work in offices, this could be an increasingly viable method of gathering and distributing heat in cities.