Dynamic performance assessment of a micro-trigeneration system with a desiccant-based air handling unit in Southern Italy climatic conditions

In this work, a system consisting of a small scale trigeneration system, in which a heat-led microcogenerator interacts with a desiccant-based cooling system, equipped with a silica-gel desiccant wheel, is analyzed. The system provides the air-conditioning service to a lecture room during summer and winter periods and, over the whole year, thermal energy for domestic hot water production to a nearby multifamily house. Electricity from the cogenerator is used to drive the electric chiller, the auxiliaries as well as further electric appliances of the lecture room. This trigeneration system is compared with a reference system, equipped with a conventional air handling unit, based on cooling dehumidification for summer air conditioning. Electricity to power the electric chiller, the auxiliaries, as well as electric appliances is drawn from the grid. Thermal energy for winter space heating, air post-heating during summer and domestic hot water purposes is provided by a natural gas boiler. Experimental tests, as well as data derived from manufacturers, are used to implement a model of both systems. Simulations were then performed by means of TRNSYS software to compare their thermo-economic performance. A sensitivity analysis has been performed, to analyse the effect of the share of cogenerated electricity consumed on-site. The analysis shows encouraging results, given the Italian energy context for the small scale trigeneration system, in terms of primary energy consumption and equivalent carbon dioxide emissions reductions, with maximum values of 7.70% and 15.3%, respectively; on the other hand, it is difficult to achieve a reasonably short pay-back period for the system, even if it accesses all the support mechanisms introduced by Italian legislation for small scale gas fuelled trigeneration systems and a very high amount of cogenerated electricity is used on-site.