The feasibility study of a trigeneration plant intended to integrate the existing natural gas fired-boiler central plant serving a 714 bed hospital located in Parma, North of Italy, is presented. The electric load and the heat load for both sanitary hot water and process steam are estimated on an hourly basis from the monitored actual consumption. The space heating and the cooling loads, instead, are computed, on an hourly basis, by the building energy software tool TRNSYS, version 16, by accounting for the actual climate of the considered location. The energy analysis points out that the Primary Energy Saving (PES) index is inadequate for sizing the Combined Heat and Power generation system (CHP). The approach based on the second principle of thermodynamics, instead, allows to identify its optimal configuration and size, i.e. Combined generation of Heat, Cooling and Power (CHCP) with prime mover overall nominal capacity equal or higher than about 7 MW. The economic analysis confirms that the maximum annual money saving occurs with trigeneration at a prime mover overall nominal capacity of about 7 MW. At higher values the operating financial budget deteriorates because of a too low electricity selling price. At the optimal economic condition the CHCP system simple payback period is of about 15 months. The national policies supporting cogeneration have a great effect on the results of the economic analysis and beyond them cogeneration may loose its economic appeal.
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