Emergy evaluation of polygeneration systems

To expand the application range of the emergy evaluation method, an emergy evaluation index, which can reflect the particular feature of polygeneration systems, has been elaborated on the basis of energy and emergy conservation, guided by the fundamental principle of emergy analysis. With this index, the cost structure, emission effect and energy saved were all considered on the same level of importance. To exemplify, some power polygeneration systems (methanol-power generation, hydrogen-power generation) are considered using coal as the basic fuel. The results showed that emergy evaluation indices are practical for comprehensively evaluating polygeneration systems and their sustainability, which is influenced by such factors as the joining mode of polygeneration and the technologies used. The sustainability of polygeneration systems, which work on an appropriate ratio of fuel-to-electric power basis, is higher than that of singular production systems. © Higher Education Press 2007.