Energy and environmental analysis of a condensate recovery thermal energy storage for the building cooling system.

In the pursuit of sustainability and reduced environmental impact, waste-to-energy conversion methods are gaining importance. This study investigates the untapped potential of air-conditioning (AC) condensate as a source of chilled energy in AC systems of varying cooling capacities expressed in tons of refrigeration (TR) including 10 TR, 25 TR, and 50 TR. Field assessments revealed daily condensate generation of 37-148 L at 15 ± 1 °C, indicating significant cooling potential for energy recovery. Waste coconut oil (WCO) is proposed as a phase change material (PCM) for this purpose, aiming to examine its thermal characteristics and effectiveness for energy storage. Characterization of WCO reveals a latent heat of 101 J/g and a phase transition temperature of 22.1 °C. Thermal degradation occurs between 346 and 462 °C, while stability is maintained below 60 °C. WCO exhibits solid thermal conductivity of 0.181 W/mK at 10 °C and liquid conductivity of 0.175 W/mK at 30 °C, with specific heat capacities of 1.19 J/g K (solid) and 2.43 J/g K (liquid), ensuring efficient heat transfer during phase change. A pilot experiment examines the charging and discharging dynamics of WCO. It achieves complete solidification in 160 min at a freezing temperature of 21.3 °C, with 1.1 °C supercooling. During melting at ambient conditions (32 ± 1 °C), it takes 92 min, with a melting temperature of 21.9 °C. The study extends to evaluate the reduction in environmental impact through life cycle assessment (LCA). The significant impact values such as acidification, eutrophication, ozone depletion, fossil depletion, climate change, and metal depletion are calculated using the ecoinvent database. Overall, our study underscores the promise of WCO-based energy recovery systems in advancing sustainability efforts within the realm of air conditioning.