Low cost dispatchable solar power

A method of operating a solar energy plant and a solar plant are disclosed. Thermal energy produced in the plant is used to heat a 1st volume of water and 'charge' a hot store (15) in the plant. Electricity produced in the plant operates a heat engine (13) or other device, such as a refrigeration unit, to extract heat and consequently cool a 2nd volume of water and 'charge' a cold store (17). As desired, energy is transferred from the hot store to a heat engine and energy is transferred from the heat engine to the cold store to operate the heat engine to produce power in the plant.