Energy storage is the key to make renewable energy consumption independent from energy production, allowing for flexibility and reducing curtailment. The FLASC hydro-pneumatic energy storage solution specifically targets offshore applications, a crucial energy sector, where existing solutions for onshore applications are not able to feasibly address this problem due to safety and reliability issues. The solution uses compressed air and pressurised seawater in a patented, pre-charged accumulator concept, resulting in an energy storage device that is inherently safe, reliable and also cost-effective thanks to a +20 year lifetime that is independent of charging-discharging cycles.