A Comprehensive Review on Bypass Diode Application on Photovoltaic Modules

Abstract

Solar photovoltaic (PV) energy has shown significant expansion on the installed capacity over the last years. Most of its power systems are installed on rooftops, integrated into buildings. Considering the fast development of PV plants, it has becoming even more critical to understand the performance and reliability of such systems. One of the most common problems faced in PV plants occurs when solar cells receive non-uniform irradiance or partially shaded. The consequences of shading generally are prevented by bypass diodes. A significant number of studies and technical reports have been published as of today, based on extensive experience from research and field feedbacks. However, such material has not been cataloged or analyzed from a perspective of the technological evolution of bypass diodes devices. This paper presents a comprehensive review and highlights recent advances, ongoing research, and prospects, as reported in the literature, on bypass diode application on photovoltaic modules. First, it outlines the shading effect and hotspot problem on PV modules. Following, it explains bypass diodes’ working principle, as well as discusses how such devices can impact power output and PV modules’ reliability. Then, it gives a thorough review of recently published research, as well as the state of the art in the field. In conclusion, it makes a discussion on the overview and challenges to bypass diode as a mitigation technique.

Low-Temperature Graphene-Based Paste for Large-Area Carbon Perovskite Solar Cells

“… 7 In principle, bypass diodes (BPDs) may be used to bypass the irradiated solar cells. 111 , 112 This approach is commonly used in commercial Si solar modules, in which a BPD is connected in parallel to strings of 15–24 cells connected in series to prevent shaded cells from reaching the junction breakdown. 112 However, we expect two crucial complications on the use of BPDs for the case of perovskite solar minimodules.…”

“… 111 , 112 This approach is commonly used in commercial Si solar modules, in which a BPD is connected in parallel to strings of 15–24 cells connected in series to prevent shaded cells from reaching the junction breakdown. 112 However, we expect two crucial complications on the use of BPDs for the case of perovskite solar minimodules. (1) The current generated in the unshaded subcells must be transported toward the PBDs parallel to the shaded cells through the current collectors (e.g., in an n–i–p configuration, TCO from the front side, and Au or C-CE from the back side), which must therefore display low electrical resistance values.…”

“… 61 Based on these considerations, the low V BD of the PSCs would require a large amount of BPDs to prevent damages and such an amount of BPDs would inevitably increase the system costs of perovskite PVs to an uncompetitive value. 112 In this context, wafer-like area C-PSCs could intrinsically overcome the above limits of perovskite minimodule serial configurations while providing a solution-processed cell fabrication (except for the starting TCO substrate) without recurring to expensive high-resolution film patterning processes (e.g., laser scribing), 114 whose implementation is still unreported on tens of micrometers thick C-CEs. To the best of our knowledge, just screen printing and one example of mechanical scribing 44 are reported for C-CEs, resulting in FF geom lower than 80% (more commonly ≤70%).…”

A Modification of the Perturb and Observe Method to Improve the Energy Harvesting of PV Systems under Partial Shading Conditions

“…These diodes are connected in parallel to the cells to limit the reverse voltage and power losses in the shaded cells [4]. This diode provides an alternative path for the current circulating through the panels which suffer PSC [21]; however, the diode may or may not trigger, depending on the operating point. The bypass diode could protect the panel; however, it reduces the available energy from the system.…”

Mitigating Potential-Induced Degradation (PID) Using SiO2 ARC Layer

“…Secondly, every solar cell affected by PID reduces the total string voltage [7]. Thirdly, it is difficult to detect this problem quickly when overall PV installations are up and running [8] because degradation of PV output power is not only due to the impact of PID but also the existence of faulty bypass diodes [9], faulty PV modules [10][11][12] and hotspots [13].…”