3E evaluation of a cascade PCM-based solar cooling system for meeting different cooling loads

This research presents a Techno-Economic-Environmental (3E) evaluation of a cascade phase change material (PCM)-based thermal energy storage (TES) integrated into a solar-driven cooling system designed to meet different cooling loads, including freezing, refrigeration, and air-conditioning. The system employs paraffin and salt hydrate PCMs with modified melting points to enable multi-temperature operation through thermal stratification. The configuration combines ammonia-based charging and R134a/water discharging loops, supported by TRNSYS–MATLAB co-simulation, to analyse the dynamic thermal response, phase transition behaviour, and overall system efficiency. Results show that the cascade PCM arrangement provides stable cooling performance across diverse load ranges, with PCM2 (4°C) and PCM3 (15°C) contributing over 90 % of total stored energy. However, the high capital investment (£2.2 million) leads to an extended payback period of approximately 115 years, despite significant electricity savings and a reduction in CO 2 emissions compared to conventional systems. The findings underscore the technical feasibility and environmental merit of cascade PCM-based TES while identifying cost as the main barrier to large-scale adoption. The study contributes a general 3E framework combining thermal, economic, and environmental metrics to evaluate cascade PCM–TES integration for multi-load solar cooling. The results provide design guidance and highlight future research opportunities in cost optimisation, composite PCMs, and modular TES architectures to enhance both affordability and scalability.