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

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 degrees 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 degrees C and 16 degrees 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 degrees 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.