Are the optimum angles of photovoltaic systems so important?. (May 2020)

• Record Type: Journal Article
• Authors: Chen, X.M.; Li, Y.; Zhao, B.Y.; Wang, R.Z.
• Is Part Of: Renewable & sustainable energy reviews. Volume 124(2020)
• Publication Date: 2020-05
• Subjects: Solar energy -- Photovoltaic -- Installation -- Loss bound -- Tilt angle -- Azimuth angle -- Building-integrated photovoltaics (BIPV); Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.rser.2020.109791
• Languages: English
• ISSNs: 1364-0321

Abstract

Abstract: The traditional point of view suggests photovoltaic systems to be installed at the optimum angles. However, various reasons require more flexible photovoltaic installations, especially for building-integrated photovoltaics. Some site-specific cases based on local irradiance data show that small deviations from the optimum will not cause big energy losses, while more theoretical insights on the flexible installation problem are required to achieve higher photovoltaic penetration. This paper tries to demonstrate that quite a large range of photovoltaic installation angles causes ignorable energy losses annually. Furthermore, this paper developed and validated a universal and convenient Loss Bound Equation to determine the 5% Loss Bound worldwide with high accuracy. The 5% Loss Bound is defined as a group of tilt and azimuth angle combinations where the plane-of-array energy losses are limited within 5% of the annual maximum plane-of-array irradiation. The universal Loss Bound Equation is independent of local irradiance data, which is totally different from conventional irradiance-based approaches and it is significantly faster and more convenient to use. The 5% Loss Bound will provide great flexibility for planning array spacing, decreasing dust deposition, sustainable retrofits to existing buildings, design for building-integrated photovoltaics, and so on. Graphical abstract: A universal and convenient Loss Bound Equation is derived to determine the 5% Loss Bound worldwide, which is independent of local irradiance data. The 5% Loss Bound is theoretically analyzed to cover quite a large range of tilt and azimuth angles, and the angle range length is at least larger than 36.38° at any site worldwide. Image 1 Highlights: A Loss Bound Equation is derived for the 5% Loss Bound. The equation is independent of local irradiance data. The 5% Loss Bound covers quite a large range of angles. The angle range length is at least larger than 36.38° at any site worldwide. This study provides theoretical supports for flexible PV installations worldwide.