Methanol-based thermochemical storage for energy-saving district heating networks

With the increasing volatility in natural gas markets and the need for residential heat, research for alternative fuels is necessary for several regions. This paper presents a high-duration thermochemical energy storage system (TCES) based on methanol, evaluating its integration with district heating networks, offering a renewable solar-based storage solution and low-temperature heat generation from the exothermic discharge reaction heat. The system eliminates greenhouse gas emissions by using concentrated solar thermal energy to decompose methanol into synthesis gas. Applying the optimised operational thermodynamic parameters, it is possible to satisfy the thermal demand of 892 households in Spain through 12 MW of concentrated solar energy supported by 10 hours of energy storage. Storage efficiencies exceeding 30% and chemical conversion efficiencies exceeding 65% have been demonstrated, resulting in a combined efficiency of 55% for the heating network and methanol TCES. The results show a levelized cost of storage (LCOS) highly competitive with other storage systems (<100 €/MWh), given the simplicity and flexibility of the proposed system.