A captive power plant is a power generation facility used and managed by an industrial or commercial energy user for their own energy consumption. Captive power plants can operate off-grid or they can be connected to the electric grid to exchange excess generation.
Captive power plants are generally used by power-intensive industries where continuity and quality of energy supply are crucial, such as aluminum smelters, steel plants, chemical industries etc.
References
Captive power plant Wikipedia(Text) CC BY-SA