Energy saving potential in radiant cooling system by utilizing air-conditioning condensate: A strategy for green building rating

Abstract

The applicability of recovered air-conditioning condensate in Ceiling Mounted Radiant Cooling Unit (CMRCU) for achieving thermal comfort in a cabin is studied through field assessment, exergy analysis, simulation, and experiments. The field assessment study in a 35 kW cooling capacity air-conditioned building reveals the condensate generation of 8.2 L/h at 15 ± 1 °C which can be effectively utilized as a cooling source in CMRCU. In addition, an exergy analysis is carried out to understand the effect of cooling by CMRCU using recovered condensate. Condensate-assisted CMRCU was shown to be beneficial in enhancing the system performance, as evidenced by a 31 % reduction in exergy consumption which contributed to a 5 % increase in exergy efficiency. Further, the cabin thermal comfort was examined using TRNSYS simulation at supply water temperatures of 14 °C and 16 °C and the results are compared with standards of EN ISO 7730:2005. Simulation studies confirmed the performance of CMRCU to attain thermal comfort with minimized ceiling condensation is at 16 °C, and the same is considered for the experiment. The experiment and predicted cabin temperature are in good agreement with a maximum variation of 5 %. Moreover, the study was extended with a thermal energy storage system utilizing polyethylene glycol 600 as the energy storage material, resulting in a 20-minute prolongation of thermal comfort through stored latent heat. Energy and economic analysis reveal the effective use of condensate resulting in 35 % of energy savings with a payback period of 6.2 years, fulfilling GRIHA Criterion-14, with offers to earn a maximum of 8 credits for green building certification.