In February 2016, the European Commission (EC) published the EU’s strategy towards sustainable heating and cooling. This strategy includes a number of actions to decarbonise the heating and cooling sectors, which are grouped into four clusters:
- Renovation of building stock
- Increase of renewables’ share
- Recovery of waste energy
- Enhancement of the users’ awareness and involvement
Within the cluster of actions related to the recovery of waste energy, district heating and cooling solutions play a major role, since the amount of waste heat available could be exploited to cover the needs of buildings in urban areas.
Current studies on district heating and cooling expansion have focused on the quantification of available industrial waste heat volumes. It is shown that in the EU the amount of heat wasted by industries in the form of hot water or flue gases is sufficient to cover 100% of the EU’s heating needs. Since industrial sites are often located far from urban areas, only a part of this waste heat is at a reasonable distance from urban centres where it could be recovered in district heating. More easily accessible, and still unexploited opportunities, lie in the recovery and reuse of low temperature waste heat from different urban sources such as: the transport sector, services buildings, sewage water networks, data centres, harbours, rivers, lakes and seawaters, was well as electrical substations.
A large amount of waste heat is available in urban areas from aforementioned sources. This kind of unconventional heat sources are low enthalpy sources (around 20-40°C) and due to the proximity to the end-users, they could effectively provide heating and cooling through individual systems as well as district heating and cooling networks.
The urban dimension of heating and cooling is crucial as it is estimated that 75% of EU citizens will live in urban areas in 2020, a share that will increase to 84% by 2050. Despite the potential of unconventional waste heat sources, only a restricted number of small scale examples of their use are available across the EU today.