Experimental investigation on thermal characteristics and novel thermal estimation method of BIPV façade air channel under actual operation

Air channel heat of BIPV façade system provides significant useful thermal energy for building utilization. However, accurate thermal estimation under actual operation conditions remains a challenge due to unprecise air channel heat transfer models. This research proposes a novel method for highly accurate thermal estimation of air channel heat transfer under actual operating conditions. Based on long-term outdoor experimental test on actual BIPV façade system, important heat transfer parameters were measured with heat transfer mechanism analyzed. Results revealed temperature gradient on component surfaces and inside air channel along the height direction, as well as the chimney effect inside air channel when solar radiation exceeded 100 W/m2. Novel air channel heat transfer model was established and verified with percentage relative error of less than 7.49% for thermal estimation of BIPV façade system under actual operation conditions. Additionally, dual functionalities of air channel ventilation were analyzed including low-grade thermal energy supply and shield effect, realizing small temperature fluctuations and heat transfer intensity at building insulation surface. Research provides reliable approach for designing BIPV façade systems with high accuracy of thermal estimation for building energy-saving potential.