A multifunctional energy system (MES) capable of consuming coke oven gas (COG) and coal, and simultaneously producing coking heat, methanol and electricity, was subject to an exergy analyses based on Energy Utilization Diagrams (EUDs). In this system a coal-fired coke oven is adopted to produce coke and COG, where non-coking coal is burned to supply thermal energy to the coking process. The COG and coal gas gasified from coal in a gasifier, were mixed to produce syngas for methanol synthesis. Since COG rich in hydrogen and coal gas rich in CO, the mixture of COG and coal gas can easily adjust the mole ratio of CO to H(2) of syngas instead of the conversional reforming and shift processes. The active component of syngas is firstly converted into methanol and then the rest is introduced to a gas turbine for power generation. As a result, the overall efficiency of the MES system is about 62.3%, and its energy savings ratio is about 15% comparing with individual systems. The paper provides a new approach to use coal more efficiently and cleanly. (C) 2009 Elsevier Ltd. All rights reserved.