Combined benefits of cooling with heat recovery for electrical cable tunnels in cities

Abstract

Electrical power in cities is typically distributed by means of underground cable tunnels. The cables generate significant heat, and tunnel temperature is generally controlled via ventilation shafts with circulation to prevent overheating. If active cooling of the inlet air is provided, then temperatures can be lowered and electrical distribution losses reduced. This novel study, the first looking at cable tunnels with District Heating, investigates the effect and impact of heat recovery. The work combines technical and economic modelling together with measured data from a case study and shows significant benefits with wide-scale replication potential.A finite element (FE) model, for heat dissipation in a section of cable tunnel together with a spreadsheet model has shown that up to 460 kW of heat can be delivered to the local heating network for a single cooling point. The study indicates savings of 570 kg CO2e and 4000 kWh (of combined heat and electrical energy) per metre of tunnel per annum with reduced operating costs. Given the widespread network of cable and other tunnels in major cities, close to numerous heat users, the application of these techniques has major financial and low-carbon benefits for the UK and globally.