Experimental and Theoretical Performance Analysis of a Building-Integrated Photovoltaic and Thermal (BIPVT) System

Building integrated photovoltaic thermal (BIPVT) systems can generate electricity and heat from building envelope areas where deploying a photovoltaic thermal (PVT) system is challenging, as this study's experimental approach investigates and validates prediction models for a frameless curtain wall liquid BIPVT system. Eight 1 m2 modules were operated from September 1st to November 8th, 2025, and a set of operational data were recorded. This dataset encompasses parameters like vertical-plane irradiance, ambient air temperature, inlet/outlet fluid temperatures, volumetric flow rate, and inverter-based electrical power. The model calculates electrical power using a conventional power equation. It estimates cell temperatures with a NOCT-based linear temperature model and a physics-based cell temperature model. Thermal performance is predicted using a Hottel-Whillier model based on lossless efficiency and a first-order heat-loss coefficient, and a physics-based outlet temperature model that predicts outlet temperature from heat-transfer mechanisms. The model's validation is achieved through a comparative analysis of predicted and measured monthly power generation and heat collection. Daily root mean square error is recorded as 0.24, 1.68, and 1.37 kWh/day for electricity and 0.29, 1.28, and 1.50 kWh/day for heat in September, October, and November, respectively. Total power generation was 87.98 kWh. The closest prediction was 87.14 kWh from the physics-based cell temperature model with an error rate of -0.5%. The total heat collection was 113.08 kWh, and the closest prediction was 116.97 kWh from the physics-based outlet temperature model, with an error rate of +3.4%. The outlet temperature correlation for the physics-based model yielded an R2 value of 0.9612. The findings suggest that the physics-based cell/outlet temperature models exhibit the lowest prediction error for the target liquid-type BIPVT system by directly reflecting the multilayer conductive structure and tube-fluid heat transfer. The validated models can support performance prediction, system capacity sizing, and energy self-sufficiency analysis for future building applications of BIPVT systems.