Abstract: A method and to an apparatus for providing additional control power of a power plant process. The power plant process includes a steam turbine connected into a water vapor circuit, having at least one high-pressure part and a medium-pressure and/or no-pressure part, which are connected to one another via a cold intermediate superheating line, a steam generator and a condenser. A steam reservoir is provided, which is formed as a Ruths reservoir and in which an encapsulated PCM reservoir is integrated. To charge the steam reservoir, hot steam is taken from the cold intermediate superheating line, between the high-pressure and the medium-pressure and/or low-pressure part of the steam turbine, and for charging, and thus for providing additional control power, steam is taken from the steam reservoir and fed back into the water vapor circuit between the steam generator and the condenser.