A general approach to integrating compression heat pumps into biomass heating networks for heat recovery

Abstract

Over the past few years, studies have shown that the efficiency issue of biomass heating has become increasingly important to enhance their competitiveness. The integration of a compression heat pump into the system to recover heat from exhaust gases could be a promising solution. However, the different ways of integrating heat pumps lead to highly variable techno-economic results over their lifetime. To find out how to integrate compression heat pumps into a biomass heating network more effectively, a general approach for the integration is presented in this paper, where the heat pumps can be integrated either into the flue gas condenser or into the network return flow. A detailed model for implementing the integration approach is proposed and validated against the measured data from two real biomass heating networks. The evaluation results show that both integration variants improved system efficiency by more than 17% in practice. For a techno-economic comparison and analysis of both variants, the proposed integration approach is also applied to a use case in Germany. In the studied case, the flue gas-side integration is more cost-effective than the network-side integration, and both concepts improve system efficiency by 12.6%. By analyzing the technical parameters, it is noticed that both integration concepts can be achieved cost-effectively in practice by finding the optimal setpoint of exhaust gas temperature under certain conditions. The analysis of electricity and fuel prices shows that the integration concepts are sensitive to the ratio of electricity price and biomass fuel price. If the fuel prices increase sharply in the future, both concepts will take on greater significance.