Air handling unit condensate in tropical and subtropical climates - Why waste down the drain?

Abstract

In tropical and subtropical regions, air-conditioning is employed throughout the year, which poses a significant challenge to the designer in reducing its energy consumption. Buildings in these regions would have latent load that is large enough throughout the whole year to produce a substantial amount of low enthalpy condensate. This free natural by-product is typically drained away from all the air handling units (AHUs) and routed to the nearest sanitary drain. In the context of an exergy analysis, it is not difficult to see the potential to recover energy from the condensate. In this study, the condensate is collected from several AHUs and directed through another coil that pre-cools the warm and humid outdoor air which is supplying another AHU, called the Condensate Assisted Pre-cooling (CAP) AHU. The analysis shows that condensate production is large enough to make pre-cooling cost-beneficial with energy savings of approximately 10%.