Evaluation of multi-generation alternatives: an approach based on load transformations

Multi-generation (MG) solutions to produce for instance electricity, heat and cooling power, are increasing their diffusion, above all on a small-scale basis (below 1 MWe), owing to their enhanced energy, environmental and economic performance with respect to conventional solutions for the separate production of the same energy vectors. Planning of MG systems, including proper equipment selection and operation strategy, represents a challenging issue. This paper presents an approach to MG planning based on evaluating how the different energy vectors demanded by the user can be transformed into equivalent electricity and heat loads seen from the cogeneration side and, in turn, into electricity and fuel demands seen from the energy network side. The proposed approach is discussed and illustrated through numerical examples referred to different types of trigeneration systems for electricity, heat and cooling production, considering specific evaluation criteria used for carrying out energy saving and economic analyses. The results of these analyses highlight the main differences emerging from the adoption of various MG alternatives.