Numerical modelling of high temperature latent heat thermal storage for solar application combining with double-effect H2O/LiBr absorption refrigeration system

Abstract

Latent Heat Thermal Storage (LHTS) systems can be applied to minimize the discrepancy between energy supply and demand in solar applications. Combining this system with a double-effect H2O/LiBr absorption system could reduce the investment costs for cooling purposes. These systems require generation temperatures higher than 150°C. Phase Change Materials (PCMs) in the desired temperature range have previously not been thoroughly studied and the integration of an LHTS system into this absorption system has not previously been reported. In this paper a numerical investigation was carried out for a shell-and-tube LHTS system, combined with a solar driven H2O/LiBr double-effect absorption system. The numerical model of the LHTS system was coupled with a mathematical model of the absorption system, and the estimation of the cooling demand and the solar energy. The phase change process was numerically solved using the enthalpy method. Hydroquinone was identified as a suitable PCM. Results indicated that for this configuration of the LHTS system, natural convection cannot be neglected in the modelling of the solidification process. With a LHTS system of 12.55m3, it was possible to fulfil the considered 100kW peak cooling demand for the 2400m2 office building without external energy input. The presented work provides guidelines for the thermal performance and design optimization of a hydroquinone based LHTS system for a solar driven H2O/LiBr double-effect absorption system.