Compressor-assisted heat transformer for waste-heat powered district heating applications

The recovery of low-temperature waste heat can be promoted by upgrading its temperature. Heat transformers are capable to increase the temperature of a heat stream with a minor contribution of electrical energy. However, the lifting capability of heat transformers are limited by the operating conditions and often insufficient to meet the temperature required by many applications. To overcome this limitation, in this paper a compressor assisted heat transformer is numerically investigated, targeting the application in medium and high temperature district heating networks. Using waste heat at 50 and 60 °C and heat rejection temperature at 0 °C and -10 °C, it is possible to upgrade heat up to 120 °C with an electrical COP always above 4, a thermal COP of about 0.5 and an upper pressure below 40 bar.