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 residential and tertiary sectors is usually satisfied by electrically-driven units; this often determines electric load peaks and black-outs. Thus, a wide interest is spreading in small scale natural gas-fired polygeneration systems: 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, laboratory tests have been considered to experimentally evaluate a small scale polygeneration system based on a natural gas-fired Micro-CHP and a desiccant-based HVAC system. Cogenerated thermal power is used for the desiccant wheel regeneration, while electric power for auxiliaries, chiller and external units. The HVAC system can also interact with electric and thermal separate “production” systems. The main results of the experimental tests are shown, stating the increase of the COP of the chiller in desiccant-based HVAC systems. Then the paper identifies the operating conditions (outdoor and supply air thermal-hygrometric conditions, electric grid efficiency and partial load operation of the MCHP) which guarantee significant primary energy savings (up to around 30%) and CO2 equivalent emission reductions (up to around 40%) of the polygeneration system compared to the conventional HVAC system