Hybrid 3 in 1 thermal energy storage system – Outlook for a novel storage strategy

Abstract

Thermal energy storage (TES) technologies have been traditionally classified into sensible, latent and thermochemical categories. TES needs significant research efforts to address some fundamental challenges to reach its full potential. The hybridisation of TES technologies provides potentially a highly effective solution to the challenges. We present here a new concept, the 3 in 1 system, examining the feasibility, and the applied aspects of the newly proposed technology. The 3 in 1 system integrates the three known thermal storage methods of sensible heat, latent heat and thermochemical based TES into one system, providing three different operational configurations with cascading, charging integrated and discharging integrated working conditions. These different configurations offer controllability of TES charge/discharge processes while enhancing system-level efficiency. The proof of concept consists of a co-working matrix of a polymer as the phase change material (PCM), high-density polyethylene, and one of the most studied thermochemical material (TCM), MgSO4·7H2O. The feasibility of the composite containing 80–90 wt% of TCM was studied, over 15 cycles, for mechanical integrity, stability, energy stored and reaction kinetics. The results show that the system has a great potential for storing heat, up to 2 GJ∙m−3 and offers a wide working temperature range, from 30 °C to ∼150 °C. The combination of the PCM/TCM pairs give the composites mechanical integrity while accommodating the volume change and maintaining the structural stability during thermal cycling. This novel idea addresses some key technology gaps in TES particularly degradation and hence short life-span of TCM, cost-effectiveness and flexibility of the TCM based technology, thus offers potential paradigm shift to the thermal energy storage technology.