# Assessment of the RACPC Performance under Diffuse Radiation for Use in BIPV System
## 1 Introduction
The CPV module achieved an electrical conversion efficiency of 10.2% when tested indoor and could achieve a potential cost reduction of 40% per m\({}^{2}\) under mass production when compared with a standard PV panel. [PERSON] et al. [26] evaluated the performance on the absorptive/reflective CCPC (AR-CCPC) module mounted on the roof top of the Heriot-Watt University building in Dubai, and found that such system is capable of achieving an overall electrical conversion efficiency of 15%. [PERSON] et al. [27] developed a CPV window incorporating rotationally asymmetrical dielectric totally internally reflecting concentrators. The CPV window was tested indoor and generated a maximum power of 0.749 W at normal incidence, 4.8 \(\times\) higher than the non- concentrating PV window. [PERSON] et al. [28] simulated the energy generated from a holographic concentrating PV-thermal (PVT) system integrated in a building in Avignon, France. The simulations indicated that such system is capable of achieving an optical efficiency of 43% and can provide 9.1% of the electricity demand of the building. [PERSON] et al. [29] studied the performance of the smart window created from the LSC using two types of dye tested at different temperatures. At 25 \({}^{\circ}\)C, the LSC obtained a maximum electrical efficiency of 3%. [PERSON] et al. [30] on the other hand, simulated the performance of an LSC coupled with bifacial PV solar cells made of mono-crystalline silicon. Their simulation achieved an electrical conversion efficiency of 16.9% under standard test conditions (STC). Table 1 summarises all the CPV work discussed previously. However, in order to maximise the electricity generation, a single or double-axis sun-tracking system is normally required on a CPV module; in addition, depending on the design, a cooling system might be required. This increases the prices when compared with a conventional PV system; although the higher efficiency and the savings on PV material may eventually compensate the costs [31]. Due to the fact that the majority of the optical concentrators are designed to work under direct solar irradiation, it has been believed that the CPV systems need to be used in locations with high direct solar irradiation for a good performance [31]. However, diffuse solar irradiation also has an impact on the performance of the concentrator; and this needs to be evaluated. \begin{table}
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The main objective of this paper is to analyse and determine the concentrator's behavior under overcast daytime conditions, which has never been explored before. An optical analysis software is used to determine the output of the system under diffuse light radiation and the results are compared to the output obtained from the fabricated sample tested through an outdoor experiment. This paper is structured as follows: Section 1 is the introduction, Section 2 defines the concentrator used in this work--the rotationally asymmetrical compound parabolic concentrator, Section 3 describes the simulation work while Section 4 explains the fabrication, the experimental setup and the results, and finally Section 5 concludes the paper.