Heat recovery opportunities from electrical substation transformers

Abstract

The transformation of voltages in electrical substations leads to energy losses in the form of waste heat; the quantity of which depends on transformer size and electrical loading. This paper investigates how a novel waste heat source, namely transformer waste heat could be harvested and distributed via district heating networks. Firstly, the investigation considered nameplate heat loss factors to quantify the theoretical waste heat potential from electrical substation transformers in England, Wales and Northern Ireland, which varied from 3.0 to 5.4 TWh a−1, equivalent to between 0.7 and 1.25% of annual heat demand for these countries, depending on loading assumptions. A number of heat recovery approaches which could be integrated with existing transformer cooling systems were then proposed. A spreadsheet model was then developed to simulate heat recovery from a transformer, together with the upgrade of the recovered heat using a heat pump prior to delivery via district heating. The model was used to evaluate the merits of capturing transformer waste heat losses, estimated using industry supplied electrical loading data, to meet different heat network demands based on an existing network, compared to conventional heating technologies. Findings suggest that the system proposed can achieve levelised costs that are up to 17% lower than the running costs of air-source heat pumps, whilst reducing emissions by almost 80% when displacing gas boilers. The methodology hereby described can also be used to evaluate the feasibility of recovering transformer waste heat in other countries.