Multi-scale Modelling of a Shell-and-tube Latent Heat Thermal Storage Unit for Building-level Dynamic Simulation

The optimal management of renewable energy systems can be enhanced by energy storage. Especially, selfconsumption of self-produced renewable energy can be maximized. Among the technologies for storing thermal energy, a latent storage system based on Phase Change Materials (PCMs) yields higher energy density compared to a sensible heat storage unit. Thus, Latent Heat Thermal Storage (LHTS) units fit an urban context with building-integrated systems where limited space is generally available. However, the integration of LHTS in an existing or newly developed heating system is hindered by a few technical issues (linked to heat transfer enhancement) and, most importantly, by a scarce knowledge about their dynamic behaviour at system level. Hence, this study presents a multi-scale modelling approach for rapidly simulating the operations of a shell-and-tube LHTS unit. A 1D model for the pipes crossed by the heat transfer fluid (HTF) is coupled with analytical thermal power characteristic curves representing the heat flux exchanged by the PCM domain. In this way, the heat transfer between the PCM and the HTF pipes is decoupled. The adopted thermal power characteristic curves are calibrated on a 2-dimensional model considering different boundary conditions. Summarizing, the proposed model is useful for investigating numerous LHTS building-integrated management strategies thanks to the possibility of varying two relevant input parameters: the HTF mass-flow rate and the HTF inlet temperature