Energy and water conservation from air handling unit condensate in hot and humid climates

This study investigates the potential for energy and water sustainability in hot and humid climates by utilizing the condensate captured from large dedicated air handling units (AHUs) for pre-cooling outdoor air in another AHU and subsequently offsetting cooling tower water needs. In such climates, latent load is large enough throughout the year to produce a substantial amount of condensate, which is typically drained away from all the AHUs. In this study, 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. During the same time, the cooling towers require considerable amounts of make-up water to replace water losses occurring on a regular basis. The condensate, including that from the main cooling coil of the CAP AHU, is first supplied to the pre-cooling coil of the CAP AHU and is then routed through the cooling tower, which significantly reduces potable water usage and improves cooling tower water chemistry. It is found that condensate production is large enough to make pre-cooling cost-beneficial with energy savings of approximately 10% and the ability to offset cooling tower water demand in excess of 50%.

► We study energy and water conservation potential from AHU condensate in hot and humid climate.
► Study (with and without heat pipes) is based on dedicated outdoor air handling units (DOAHUs).
► 6 DOAHUs studied – energy savings for 6th unit is 9.3% (without heat pipe) and 10.9% (with heat pipe).
► After recovering energy from condensate, it can be used for cooling tower “make up” water (up to 50%).