NAC wall: An open cycle solar-DEC with naturally driven ventilation

This paper presents the general concept of the NAC (Natural Air Conditioning)-wall system and some experimental results on a first prototype. The originality of the system is to perform a solar DEC (Desiccant, Evaporative Cooling) open cycle by exploiting natural buoyancy driven ventilation, thus avoiding the use of fans. The supply air is dehumidified by a zeolite based adsorption bed and is cooled indirectly by an evaporative cooler, through a low pressure heat exchanger. Eight days measurements were performed, each including a sample with five adsorption/regeneration cycles. During the first measurements, thermal COPs were in the range 0.30 1.01, depending on duration of regeneration and absorption phases. This led to a better tuning of the system, which gave for the remaining samples an average COPth of 0.64, with an average electrical COP of 12.7, calculated considering electrical consumption of water loops pumps.