Comparative analysis of insulated floating cover of water pit thermal energy storage

Water pit thermal energy storage (PTES) as a sensible heat storage technology has been applied in many places with significant success. The insulated floating cover (IFC) of water pit is the key component of the PTES thermal storage efficiency and accounts for more than half of the total cost of the entire water pit. In this paper, a one-dimensional finite element model (1D FEM) and a zero-dimensional lumped thermal system model (0D LTSM) are established for the composite IFC of PTES, and their respective results are compared with experiments respectively. LTSM results match the FEM resolution results if the LTSM is sufficiently refined by discretized each layer into several sub-systems with their own mass and thermal resistance. In this LTSM, 5 sub-systems are used in the thermal insulation layer, and 2 sub-systems are used in the upper and lower impervious barrier respectively. The results show that the LTSM can accurately describe the transient heat transfer process of the composite IFC. The results of LTSM and FEM are in good agreement with 99.2%, which is about 2.6% different from the experimental results.