ENERGY STORAGE SYSTEMS

An energy storage system is provided. The system comprises an energy storage device comprising: a pressure vessel configured to store pressurised fluid; and one or more resilient elements, wherein the resilient elements comprise a plurality of filaments of resilient material braided to form the resilient elements, wherein the resilient elements are arranged within or about the pressure vessel, and wherein the energy storage device is configured such that storing pressurised fluid within the pressure vessel acts to tension or compress the resilient elements.