Thermochemical storage networks for integration of renewable energy sources through seasonal load shifting

Abstract

Thermochemical networks are a rather new subject in research and support our goal to lower winter electricity demand and foster the integration of renewable energy sources. This paper takes a first step towards a performance analysis of thermochemical networks and a comparison to a classical district heating network for a virtually defined network of 1.3 km length, assuming a space heating load of 204.7 MWh represented by 33 residential buildings. The performance comparison is done for winter operation when space heating demand is present. The simulation results clearly revealed that for the classical district heating system, thermal and pressure losses lead to a significant increase in the loads, further increasing the electricity demand for the heat pump and the circulation pump. Conversely, for the thermochemical network, no compressor is needed to extract the heat from the boreholes and the circulation of the sorbent solution was found to be minute, leading to a negligible electricity demand for space heating supply. This resulted in a very high electric COP as well as a high exergy efficiency compared to a classical district heating system. Further, the volumetric energy storage density was compared, recording a 2 to 22.3 times higher value for the thermochemical network.