## 1 Introduction  
According to DNV's Energy Transition Outlook [1], offshore wind alone is expected to make up approximately 11.4% of the world's electricity generation if net zero greenhouse gas emissions are to be achieved by 2050. This value implies an average annual growth in offshore wind of approximately 13% up to the mid-21 st century, without considering other renewable energy sources (RES), such as offshore solar photovoltaics (PVs) [1]. An increase in RES installations directly implies increases in energy curtailment, given that the supply of intermittent wind and solar power often does not match the actual demand by energy consumers. Energy storage is a primary solution for reducing intermittency issues associated with renewables and, thus, avoiding curtailment. The European Commission stated that the only way that renewable energy (RE) generation can reach full capacity is if energy storage systems (ESSs) are applied in tandem with renewable energy sources (RESs), with an increasing relevance set on long-duration energy storage (LDES) requirements due to the potential for avoiding up to 88% of generation curtailment [2, 3]. [PERSON] et al. [4] provided a comprehensive literature review of different marine renewable energy storage technologies, stating that no individual technology has emerged as a solution to all storage requirements. [PERSON] et al. [5] provided a review of a variety of software tools used for ESS valuation, emphasising that research gaps exist in simulation models accounting for non-linear operating characteristics and in the provision of better capability to the tool users. [PERSON] et al. [6] carried out a cost and performance assessment on coupling an offshore compressed air energy storage (CAES) system with an offshore wind farm, with findings suggesting that viability is highly dependent on system conditions. [PERSON] et al. [7] created and implemented a cost model to test a CAES system with a hydraulic power transmission, concluding that such a concept may reduce project costs for up and coming wind turbine technology during the 2020-2030 decade, yet expressing that further software and hardware technology research is heavily required. [PERSON] et al. [8] simulated the performance of a battery energy storage system (BESS) co-located with a wind farm with the aim of providing enhanced frequency response service and storing the otherwise-curtailed energy generated. Their results indicated that cost saving due to avoiding an independent connection for the BESS was significant compared to obtaining approximately 1% less in revenue from the system's enhanced frequency response service. [PERSON] et al. [9] developed an electrical power conversion system for an isothermal CAES system which operated via kilowatt-scale centrifugal pumps. [PERSON] et al. [10] created a digital twin of a combustion engine-based power plant combined with a battery energy storage system in Simulink(r) with the aim of providing a computationally time-efficient numerical model, while also considering the system's governing physics. [PERSON] et al. [11] modelled a hybrid energy storage system made up of a combination of BESS and hydrogen with solar PVs as the primary RES. [PERSON] et al. [12] numerically modelled a BESS for verification of results with experimental testing, highlighting that numerical models can provide quick and realistic projections of how the same system would perform in real life. [PERSON] et al. [13] simulated RES energy production combined with three ESSs, where one of the findings was that an undersized battery system can lead to curtailment due to batteries not being able to store all RES energy produced when the generation is high for long periods of time. [PERSON] et al. [14] experimentally tested a combined pumped-hydro CAES system made up of two storage tanks, one with compressed air and the other with water in order to generate electricity via a Pelton turbine.