Numerical analysis of a Small Scale Polygeneration Plant with a Desiccant-Based Air Handling Unit

Domestic and light commercial sectors, especially in the Mediterranean area, are involvedin an increasing space cooling demand, generally satisfied by electrically-driven units; this hasdetermined summer electric peak loads and black-outs. Thus, an increasing interest occurs in systems,fuelled by natural gas, able to satisfy space cooling requirements, such as polygeneration one. Theseare based on a prime mover that drives in different ways (mechanically, electrically, thermally) electricgenerators and/or electric heat pumps, absorption heat pumps, desiccant wheels, … in order to satisfythermal (heating and cooling) and electric energy requirements. In this paper, attention is paid to asmall scale polygeneration system based on a natural gas-fired Micro-CHP and a desiccant-basedhybrid HVAC system. The MCHP provides thermal power to regenerate the desiccant wheel, domestichot water and space heating purposes. It also supplies electric power for air handling unit, chiller andexternal appliances. A numerical analysis, based on design operating conditions and nominalcharacteristics of the devices, is carried out in order to compare primary energy consumptions, annualoperating costs and greenhouse gas emissions of the system with respect to a conventional coolingdehumidification HVAC system powered by separate electric and thermal “production”.