Experimental investigation to optimise a desiccant HVAC system coupled to a small size cogenerator

In the Mediterranean area, the increasing demand of summer cooling in domestic and small commercial sectors is usually satisfied by electrically-driven units; this involves electric load peaks and black-outs. Thus, an increasing interest occurs in small scale polygeneration systems fuelled by natural gas: a prime mover drives (mechanically, electrically, thermally) electric generators and/or heat pumps, desiccant wheels, etc., matching thermal (heating and cooling) and electric end-user requirements. In this paper, a test facility, located in Southern Italy, has been used to experimentally evaluate a small scale polygeneration system based on a natural gas-fired Micro-CHP and a desiccant-based hybrid HVAC system. The MCHP provides thermal power for the desiccant wheel regeneration and electric power for air handling unit auxiliaries, chiller and external units (computers, lights, etc.). The HVAC system can also operate in traditional way, interacting with the electric grid and a gas-fired boiler. An overview of the main results is shown, identifying the operating conditions (outdoor and supply air thermal-hygrometric conditions, electric grid efficiency, partial load operation of the MCHP) which guarantee significant primary energy savings (up to around 30 %) and greenhouse-gas emission reductions (up to around 40 %) of the polygeneration system compared to the conventional one