Load shifting and operational cost optimization in cold-climate ground source heat pumps using phase change material (PCM) -based thermal energy storage

Abstract

This study investigates the integration of a phase change material (PCM) thermal storage tank with a ground-source heat pump (GSHP) system for residential heating in a cold-climate region (Erzurum, Türkiye) under a time-of-use (TOU) electricity pricing scheme. The configuration incorporating a PCM tank (ATP52) and a buffer tank was modeled using TRNSYS software to enhance energy storage during off-peak periods and reduce reliance on the grid during high-tariff hours. Nine different configurations were analyzed by varying the PCM mass fraction (75%, 100%, and 125%) and the charging set-point temperature, which was defined with respect to the PCM melting temperature. (Tmelting, Tmelting +2 °C, and Tmelting +5 °C). Simulation results show that PCM integration enables significant load shifting, reducing peak-period heat pump electricity use by up to 95% and lowering annual operating costs by 9% (from 163,848 TRY to 149.002 TRY), despite a 10% increase in total energy consumption. Consequently, annual electricity costs are reduced, with the highest savings observed in the PCM High–2 scenario. In addition, compared to a conventional water-based system, similar or greater economic benefits were achieved with a PCM tank volume of only 15 m3, versus the 50 m3 required for water storage. These results highlight the efficiency and economic advantages of PCM-based storage for optimizing building heating systems in cold climates under dynamic tariff structures.