Optimization of hybrid sensible-latent seasonal heat storage systems

Abstract

This study presents a coupled techno-economic and environmental model of hybrid sensible-latent thermal energy storage (TES) systems, integrating phase change material (PCM) macro-capsules to enhance storage capacity and performance. The multi-scale model accounts for stratification in the sensible storage and phase change dynamics in the PCM capsules. This framework is used to perform multi-objective optimization across the full range of thermal self-sufficiency (${\text{SS}}_{\text{th}}$) levels for a multi-family building. The results show that a 70 % ${\text{SS}}_{\text{th}}$ offers the optimal balance between economic feasibility and environmental impact, with a Levelized Cost of Heat (LCOH) of 0.27 CHF/kWh and a Global Warming Potential (GWP) reduction of 76 % compared to fossil fuel alternatives. Systems targeting up to 85 % ${\text{SS}}_{\text{th}}$ are technically feasible but come with increased costs (up to 0.33 CHF/kWh), while exceeding 85 % ${\text{SS}}_{\text{th}}$ results in exponential increases in both cost and storage volume. Maximizing photovoltaic (PV) and heat pump (HP) power is critical for optimizing system performance. Future advancements in PCM technology and decreasing PV costs could lower the LCOH to 0.23 CHF/kWh and the GWP to 21 % of fossil fuel systems, demonstrating significant potential for long-term cost reductions and sustainability.