In the conceptual design of trigeneration systems, which combine the production of chemicals, power, and heat, an energy conversion device is considered a chemical plant＇s unit operation. A method is presented whereby options can be identified for the integration of such devices in chemical plants. Firstly, all functions of the energy conversion device must be described. Secondly, the functions of the auxiliary equipment present in a stand-alone power system must be summarised. Third, a chemical process has to be selected which can perform some of the functions of the power system＇s auxiliary equipment. The integration of a fuel cell in a methanol plant illustrates the application of the method.