Air Pre-Cooling Through Phase Change Material to Reduce Peak Air-Conditioning Demand
Buildings are responsible for 45% of the total world annual energy consumption. A significant amount of this
energy, nearly 30%, is used for heating, cooling, and ventilation purposes in buildings. Air conditioning is the major energy
consumer in buildings that poses serious challenges to achieve building greening targets. The peak time air conditioning
demand drives the rise in energy consumption, cooling system capacity and nominal power supply from power plants and
transmission/distribution networks. Air Pre-Cooling through Phase Change Materials (PCM) comprising of paraffin waxes,
salt hydrates and fatty acids may be used to reduce air conditioning capacity for buildings by reducing peak load. This study
investigates PCM based air pre-cooling concept that retains night time ambient cooling and releases the same to fresh air
supply stream during daytime to reduce peak cooling demand. A detailed review of previous work conducted by different
researchers on PCM based free cooling is presented. The system is employed in extremely hot conditions of Al Ain, United
Arab Emirates (UAE) in summer season in July. A paraffin based PCM with melting range of 30–33°C is integrated at the
containers placed in the test chamber mimic the air conditioning duct system, and its cooling effect is monitored. The precooling
of the outlet air produced by PCM system is compared to non-cooled system. A Conjugate heat transfer model
employing enthalpy based formulation is developed to predict the optimized PCM container size and optimum air flow rate.
A reduction of 4oC and 5.5oC in the outlet air temperature is achieved applying a velocity of 4m/s and 1 m/s, respectively in
case of employing single column of PCM containers. Inclusion of series PCM containers yield double the reduction in air
temperature as compared with the single column of PCMs. The proposed full size test chamber is under investigation to
provide air pre-cooling in summer. The thermal model will be validated by experimental results to optimize the system.
Keywords- Air pre-cooling, Energy efficiency, Phase Change Materials, UAE.