Experimental and exergy analysis of air-conditioning condensate energy recovery in HVAC and cold storage units

Air-conditioning (AC) condensate, a valuable source of chilled energy, holds significant potential for energy recovery. Preliminary assessments showed daily condensate collection rates of 0.8-1.1 L/h for split AC (1.5 TR), 34 L/h for packaged AC (88 TR), and 180-195 L for cold storage plants (5000 TR). This study investigates the use of an Air-Water Heat Exchanger (AWHX) and Thermal Energy Storage (TES) system for condensate energy recovery across different air-conditioning capacities. Theoretical analysis (energy and exergy) and pilot experiments were conducted to design an effective condensate energy recovery system. Exergy analysis performed in the AWHX system, reveals the efficiency was improved with increase in temperature from 15 to 20 degrees C. Likewise, TES-assisted recovery exhibited a decrease in exergy efficiency at high ambient temperatures. Experiments were carried out in packaged AC and cold storage units integrated with a condensate energy recovery system. Additionally, the usefulness of the packaged AC with AWHX and TES was assessed by measuring indoor air quality (IAQ). Condensate with 17 degrees C and 7.5 L/h effectively pre-cooled the air by 3-3.2 degrees C which significantly improved the IAQ. Similarly, experiments conducted in cold storage units with a TES-based condensate recovery system resulted in 3-4 degrees C reduction in product temperature. Economic analysis indicated annual energy cost savings of $40, $99, and $32 for systems of split AC, packaged AC, and cold storage, respectively. The packaged AC system exhibited a 57 % greater reduction in environmental impact compared to the cold storage plant, highlighting its environmental sustainability benefits.