Deep Water Subsea Energy Storage, Lessons Learned from the Offshore Oil and Gas Industry

In a future where a large portion of power will be supplied by highly intermittent sources such as solar- and wind-power, energy storage will form a crucial part of the power mix ensuring that there is enough flexibility in the system to cope with the intermittency. With further development of pumped storage hydro constrained by the lack of remaining suitable topography, a novel Subsea Pumped Hydro Storage concept has emerged as a promising solution to utilize the ocean space for large-scale energy storage. While previous publications address thermodynamic efficiency limits, there is a notable lack of research on turbine selection, design, and cost estimation based on best practices. This paper presents a comprehensive overview of current state-of-the-art subsea engineering and its significant achievements pioneered by the oil and gas industry. This paper introduces a robust methodological framework for calculating the costs of concrete SPHS tanks, factoring in longevity and best installation practices for structures designed to endure for half a century. The results indicate that with an optimized design, the cost of an SPSH concrete storage tank is approximately $0.15/Wh. This work lays the groundwork for future advancements in SPHS, building on the substantial progress within subsea engineering over recent decades, and marks a significant step towards realizing the potential of this concept in the renewable energy landscape.