Thermal Energy Storage (TES) application in an Italian District Heating (DH) network: A Computational Fluid Dynamic (CFD) analysis to assess the operating efficiency

To date, Thermal Energy Storage (TES) systems have been recognized as a crucial energy technology in both civil and industrial sectors since they improve the effectiveness of thermal plants from both technical and economic points of view. In particular, a TES installed downstream a Combined Heat and Power (CHP) unit overcomes the problem of the mismatch between energy supply and demand, satisfying the end-users' needs throughout the year and extending the operating hours of the CHP unit. In this work, a real installation of a water-based TES has been considered: as previously said, it is installed downstream a 1.3 MWth CHP unit, Internal Combustion Engine (ICE) based, that is connected to a District Heating (DH) network in a town located in the center of Italy. The CHP unit provides heat to the end-users throughout the year, whereas the produced electricity is directly injected into the national grid. The purpose of the present study is to assess the viability and the advantages coming from the use of the TES that provides further flexibility to the CHP unit. A Computational Fluid Dynamic (CFD) analysis on the water-based TES has been performed to study both charging/discharging phases according to different flow rate values within the TES circuit, which depend on the end-users' thermal energy demand. Indeed, experimental data showed how the TES has effectively increased the flexibility of the CHP unit, which can then operate longer and allows the DH management to get more Energy Efficiency Titles (EETs) and also higher economic revenue.