Seasonal thermal energy storage in smart energy systems: District-level applications and modelling approaches

TLDR

Seasonal thermal energy storage offers low‑cost, flexible capacity for smart energy systems, with applicability varying by geography and geology. This paper aims to identify applications and review modelling approaches for seasonal thermal energy storage within smart energy systems. The authors present a district‑scale smart energy system example and review modelling methods for borehole and aquifer thermal energy storage, including co‑simulation with energy system tools for planning and detailed design. The study identifies gaps in planning tools, control strategies, and open code, notes TRNSYS as the dominant detailed design tool, and highlights a lack of co‑simulation models that integrate both electricity and heat, concluding that STES can enhance flexibility across smart applications and scales, with co‑simulation offering a promising approach.

Abstract

Seasonal thermal energy storage can provide flexibility to smart energy systems and are characterised by low cost per unit energy capacity and varying applicability to different geographical and geological locations. This paper identifies applications and reviews modelling approaches for seasonal thermal energy storage technologies in the context of their integration in smart energy systems. An example district-scale smart energy system is outlined to analyse three potential smart applications for seasonal thermal energy storage: (i) utilisation of multiple renewable energy sources, (ii) integrating waste heat and cool, and (iii) electrical network balancing. The rest of the paper focuses on modelling methods for borehole thermal energy storage and aquifer thermal energy storage in energy system analysis. Energy system tools for planning and detailed design stages are reviewed. Gaps are identified for planning tools in control strategies and open code. TRNSYS is found to be the dominant detailed design tool used to model large-scale borehole thermal energy storage. Co-simulation methods involving detailed physics and power system tools are also reviewed, including studies using co-simulation of a detailed physics tool to represent borehole or aquifer thermal energy storage alongside an energy system tool. A gap exists in co-simulation of borehole or aquifer thermal energy storage models with energy system tools capable of simulating both electricity and heat. In conclusion, seasonal thermal energy storage can provide flexibility through different smart applications at different scales, and modelling approaches using co-simulation methods offer a promising avenue for capturing potential benefits of these smart applications.