Waste heat recovery from urban electrical cable tunnels

Electrical power distribution within cities is most often distributed through underground cables located just below the road surface. Due to steadily increasing electricity demands, many power suppliers are making large investments in housing these cables in underground tunnels. These urban cable tunnels often extend to many kilometres in length. Through the electrical loading of the cables a significant amount of heat is generated. Often this heat has to be removed through ventilation in order to avoid overheating the cables and to provide safe conditions for access. As opposed to rejecting the heat to the atmosphere, this low grade energy could potentially be recovered, upgraded if necessary, and distributed to nearby heat users above ground. This paper discusses possible heat recovery methods applicable for urban electricity distribution networks, i.e. transformers and cable tunnels. It also presents results from a modelling-based preliminary feasibility study which used cable tunnels in London as a case study.