Comprehensive investigation of a building integrated crossed compound parabolic concentrator photovoltaic window system: Thermal, optical and electrical performance

Li, Xue; Li, Kexin; Sun, Yanyi; Wilson, Robin; Peng, Jinqing; Shanks, Katie; Mallick, Tapas; Wu, Yupeng

Abstract

Integrating PV solar cells with concentrators into window systems can not only generate electricity for a building, but also has the potential to enhance the thermal resistance of the building's windows without a significant sacrifice of light transmittance for passive daylight. A novel system, known as the crossed compound parabolic concentrator photovoltaic window, has been recently studied for its electrical properties. However, its thermal and optical performance, particularly in terms of the overall heat transfer coefficient (U-value) and total optical transmittance when integrated into a building, remains unexamined. These factors are crucial for predicting the system's impact on a building's energy efficiency and indoor comfort. Therefore, this paper aims to investigate the U-value of this window system under various temperature scenarios and the optical transmittance of the window at different incident angles. The thermal conductance was assessed through numerical simulations using a computational fluid dynamics model, which was validated by experimental measurements conducted in a large climate chamber. The optical transmittance was investigated using a validated 3D ray-tracing model. The total optical transmittance and electricity generation were calculated for typical sunny days in winter and summer under London's climate conditions. Additionally, alternative designs were developed to explore the impact of pitch between adjacent optics on the thermal conductance and optical transmittance of the window. The results showed that the window with a configuration of Dx=Dy=5mm (where Dx and Dy represent the horizontal and vertical pitches, respectively, between two adjacent solar optics) achieved the lowest U-value (2.566W/m2·K). This U-value is slightly lower than that of the original window design, which has a U-value of 2.575W/m2·K. The original window configuration with Dx=Dy=1.77mm produces the highest power output. Specifically, it generates 499.25Wh/m2 on a typical sunny day in winter and 162.73Wh/m2 on a typical sunny day in summer. However, it exhibits the lowest transmittance (14.6% on a typical sunny day in winter and 25.2% on a typical sunny day in summer, respectively), indicating that it is more suitable for buildings with a higher window-to-wall ratio to ensure an adequate amount of natural light. For buildings with a lower window-to-wall ratio, the CCPC-PV window should be designed with a larger horizontal pitch, such as 15mm and 30mm, to meet indoor illuminance requirements while also providing enhanced thermal performance and additional power output.

Citation

Li, X., Li, K., Sun, Y., Wilson, R., Peng, J., Shanks, K., Mallick, T., & Wu, Y. (2024). Comprehensive investigation of a building integrated crossed compound parabolic concentrator photovoltaic window system: Thermal, optical and electrical performance. Renewable Energy, 223, Article 119791. https://doi.org/10.1016/j.renene.2023.119791

• Journal Article Type: Article
• Acceptance Date: Dec 6, 2023
• Online Publication Date: Feb 2, 2024
• Publication Date: 2024-03
• Deposit Date: Jan 5, 2024
• Publicly Available Date: Feb 3, 2026
• Journal: Renewable Energy
• Print ISSN: 0960-1481
• Electronic ISSN: 1879-0682
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 223
• Article Number: 119791
• DOI: https://doi.org/10.1016/j.renene.2023.119791
• Keywords: Photovoltaic window, Crossed compound parabolic concentrator, U-value, Optical transmittance, Electricity generation
• Public URL: https://nottingham-repository.worktribe.com/output/28434279
• Additional Information: This article is maintained by: Elsevier; Article Title: Comprehensive investigation of a building integrated crossed compound parabolic concentrator photovoltaic window system: Thermal, optical and electrical performance; Journal Title: Renewable Energy; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.renene.2023.119791; Content Type: article; Copyright: © 2023 The Authors. Published by Elsevier Ltd.