Design, development and characterisation of a Building Integrated Concentrating Photovoltaic (BICPV) smart window system

Xiao Liu,Yupeng Wu

doi:10.1016/j.solener.2021.03.037

Abstract

Building Integrated Concentrating Photovoltaic (BICPV) window represents a promising alternative approach for improving the electricity generation of photovoltaic cells when integrated into building windows. As a new concept, BICPV smart window consisting of an optically switchable thermotropic layer with integrated PV cells offers the potential to simultaneously generate electricity and control solar heat and visible light into buildings. In this study, a BICPV smart window system with a Hydroxypropyl Cellulose (HPC) based thermotropic hydrogel membrane has been developed and characterised. The system was designed with the aid of a validated wavelength-dependent optical model based on a Monte-Carlo ray-tracing technique, where the thermal and optical properties of the thermotropic layer used for the optical model prediction were obtained from experimental measurement. Subsequently, a prototype of the BICPV smart window system has been fabricated and characterised under controlled indoor conditions. From the experiments, it was found that the maximum power output of the BICPV smart window (6 wt% HPC) increases by 17.1% with the membrane temperature increasing from 40 °C (the transition temperature) to 54 °C; meanwhile, a 70.9% reduction in the light transmittance is observed. This indicated that the BICPC smart window might potentially reduce the solar heat gain in hot periods and therefore reduce the building energy demand. In addition, the effect of different concentrations of HPC polymer (2, 4 and 6 wt%) on the electrical and optical performance of the system has been investigated.

Highlights

Global concerns over climate change and ever-increasing energy demand have led to a growing interest in developing renewable energy technologies
Semi-transparent photovoltaic cells such as amorphous silicon (a-Si) and Dye Sensitised Solar Cell (DSSC) are popular choices for window integration, as they can be manufactured in various degrees of transparency and offer more homogeneous daylighting of the indoor spaces compared to crystalline-silicon (c-Si) solar cells (Skandalos and Karamanis, 2015)
A growing number of researches have been conducted to investigate the potential use of Building Integrated Concentrating Photovoltaics (BICPVs) to improve the electricity generation, daylighting control and aesthetics of BIPV windows/facades

Summary

Introduction

Global concerns over climate change and ever-increasing energy demand have led to a growing interest in developing renewable energy technologies. Integrating photovoltaics into building trans parent façade has been increasingly seen in modern building designs (Baig et al, 2014) In such system, photovoltaic cells serve as a part of the transparent building envelope element such as window, glazed façade or skylight, offering savings in materials and generating renew able electricity on-site while reducing excess solar heat and daylight into the indoor spaces (Norton et al, 2011; Skandalos and Karamanis, 2015; Agathokleous and Kalogirou, 2016). A growing number of researches have been conducted to investigate the potential use of Building Integrated Concentrating Photovoltaics (BICPVs) to improve the electricity generation, daylighting control and aesthetics of BIPV windows/facades. The maximum power output of the BICPV façade prototype was found to be 2.27 times higher compared to its non-concentrating license (http://creativecommons.org/licenses/by/4.0/)

Methods

Results

Conclusion