Flexibility in thermal grids: a review of short-term storage in district heating distribution networks

Future energy systems need to be more flexible. The use of cross-sector coupling in combination with thermal storage in thermal grids has been shown to provide such flexibility. The presented study reviews how short-term storage in district heating distribution networks is used or modelled for flexibility, what are the most important parameters, and where the knowledge gaps remain The results show that the potential for flexibility from district heating has not been fully exploited. Sensible thermal storage tanks are 50-100 times cheaper than electrical storage and storage in the distribution network requires little additional investment in infrastructure. In some countries, the majority of district heating systems have sensible thermal storage tanks, with as much as 64 % of their capacity available for flexibility services. Initial results suggest that only smaller networks are prevented from using the distribution network for storage, but the impacts of this type of use on the physical components and the capacity limitations remain unclear and show a need for standardised methods for analysis. There is a growing interest, both in Europe and China, in the use of short-term storage in district heating to provide flexibility, particularly in the form of ancillary services to the electricity grid, but implementations of these techniques are rare. The presented study identifies a number of remaining knowledge gaps that should be addressed in order to harness available flexibility in district heating. (C) 2019 The Authors. Published by Elsevier Ltd.