What role can district heating play in the energy transition?
District heating is just pipes and water - whether it is good for the climate depends on what you put into it. If you are filling it with coal, there is an energy efficiency gain (compared with home boilers) I suppose, but even that presumes the network is properly designed and maintained.
Please note that this article was originally published by Energy Monitor, here.
When Paul Voss, managing director at industry association Euroheat and Power, was first approached about working in district heating for Danish industrial company Danfoss, he said no.
“I had seen a couple of big systems in China and I thought, ‘that is just making heat from coal’,” he recalls. “But then I talked to my brother, and he said, ‘aren’t you aware of what they are doing in Denmark?’ I went to Denmark, and I noticed there were no chimneys in Copenhagen because there is no combustion for heat. I took the job, and ended up falling in love with the technology.”
This is the dichotomy at the heart of district heating’s role in the energy transition. On the one hand, it is a no-brainer that pumping excess heat generated by a power plant or industrial facility around a city to heat people’s homes is good for climate change. On the other hand, these large systems, which were especially popular in Communist countries, were historically mostly fed with coal.
In the age of climate action, cities with these old systems can, in theory at least, boast of lower heating emissions. This is important, given that 50% of global final energy consumption – and 40% of the world’s CO2 emissions – comes from heat. Heating buildings with individual boilers or furnaces is the least efficient way of keeping them warm. One of the most efficient ways is using the excess heat generated by power plants or other sources that would otherwise be wasted.
A combined heat and power (CHP) plant typically has site efficiency (usable energy out divided by energy in) of around 75%. A normal power plant has less than 33%. However, the situation becomes more complicated when thinking about setting up a new system.
Anyone who has lived in an apartment using one of these older systems may be sceptical of considering district heating as a cutting-edge solution to climate change. Often, residents are unable to control the temperature in their own home and when it gets too hot the only solution is to open a window.
Despite these negative connotations, Voss insists district heating can be green and forward-looking. “District heating is just pipes and water – whether it is good for the climate depends what you put into it,” he says. “If you are filling it with coal, there is an energy efficiency gain [compared with home boilers] I suppose, but even that presumes the network is properly designed and maintained.”
The key question, therefore, is whether district heating systems can be fed with renewably generated heat rather than by fossil fuels. The Nordic countries, which get 65% of their heat from district heating, have led the way on this. Sweden, blessed with plentiful hydropower, sources over 70% of its district heating from renewables. Iceland is close to 100%, thanks to its geothermal resources. A total of 70% of the district heating in windy Denmark is from renewables or waste heat. So far, Denmark is the only country with a significant amount of district heating coming from wind and solar installations rather than hydro, geothermal or biomass. The country accounts for a whopping three-quarters of the installed capacity of solar thermal energy in district heating worldwide, according to the International Energy Agency (IEA).