Energy storage system

An energy storage system for regulating power output of a power generation plant that has a heat exchanger, a primary circuit and a secondary circuit, the primary circuit directs a primary fluid flow to components of a primary region and the secondary circuit directs a secondary fluid flow to components of a secondary region, and the heat exchanger is arranged so that the secondary fluid flow is heated from the primary fluid flow, the energy storage arrangement comprising:

• a vessel;
• a fluid transfer arrangement connected to the vessel and connectable to the heat exchanger of the power generation system so as to arrange the fluid transfer arrangement in fluid communication with the heat exchanger and the vessel;
• and
• a bidirectional flow arrangement configured to control a flow direction of fluid between the vessel and the fluid transfer arrangement so as to selectively store heat energy from secondary fluid exiting the heat exchanger in the vessel, and to selectively transfer heat energy stored in the vessel to the heat exchanger.