PID –1,500V readiness of PV modules: Some solutions and how to assess them in the lab

By Benoit Braisaz1, Benjamin Commault2,3, Nam Le Quang4, Samuel Williatte4, Marc Pirot2,3, Eric Gerritsen2,3, Maryline Joanny2,3, Didier Binesti1, Thierry Galvez4, Gilles Goaer4 & Khalid Radouane, 1EDF R&D, ENERBAT, F-77250 Moret sur Loing; 2Univ. Grenoble Alpes, INES, Le Bourget du Lac; 3CEA, LITEN, Le Bourget du Lac; 4EDF ENR PWT, Bourgoin-Jallieu; 5EDF EN, La Défense, France

Even though it is now more than five years since potential-induced degradation (PID) began to proliferate, and despite the fact that solutions are under development, it is currently still the most discussed mode of degradation associated with cracking in PV modules.

Salvador Ponce-Alcántara & Guillermo Sánchez,

By Salvador Ponce-Alcántara & Guillermo Sánchez,, Valencia Nanophotonics Technology Center – UPV, Spain

Conventional ribbons used for interconnecting solar cells in PV modules act like mirrors, causing a large proportion of incident light to be lost. Experimental results indicate that only around 5% of the perpendicular incident light on the connections can be reused; as a result, this area contributes very little, if at all, to the current generation.

Top 5 solar module manufacturers in 2016

By Mark Osborne, Senior News Editor

PV Tech can reveal the preliminary top 5 solar module manufacturers in 2016, based as usual on final shipment guidance from third quarter financial results.

Investigation of cell-to-module (CTM) ratios of PV modules by analysis of loss and gain mechanisms

By Hamed Hanifi, Charlotte Pfau, David Dassler, Sebastian Schindler, Jens Schneider, Marko Turek & Joerg Bagdahn Fraunhofer Center for Silicon Photovoltaics CSP, Halle; Anhalt University of Applied Sciences, Faculty EMW, Koethen, Germany

The output power of a solar module is the sum of the powers of all the individual cells in the module multiplied by the cell-to-module (CTM) power ratio. The CTM ratio is determined by interacting optical losses and gains as well as by electrical losses. Higher efficiency and output power at the module level can be achieved by using novel ideas in module technology. This paper reviews methods for reducing different optical and electrical loss mechanisms in PV modules and for increasing the optical gains in order to achieve higher CTM ratios. Various solutions for optimizing PV modules by means of simulations and experimental prototypes are recommended. Finally, it is shown that designing PV modules on the basis of standard test conditions (STC) alone is not adequate, and that, to achieve higher CTM ratios by improving the module designs in respect of environmental conditions, an energy yield analysis is essential.

Back-contact technology: Will we need it in the future?

By Radovan Kopecek, Joris Libal, Andreas Halm, Haifeng Chu, Giuseppe Galbiati, Valentin D. Mihailetchi, Jens Theobald & Andreas Schneider, International Solar Energy Research Center (ISC) Konstanz, Germany

The back-contact (BC) technology currently available on the market is considered to be either highly efficient but extremely expensive (interdigitated back contact – IBC – from SunPower) or, if cost-effective, not very efficient (metal wrap-through – MWT) compared with what is becoming today’s new standard: passivated emitter and rear contact (PERC) technology. Something in between, such as low-cost, high-efficiency IBC cells and modules, would therefore be desirable. This paper briefly describes the past, focuses on the present, and forecasts the possible future developments of BC technology in respect of efficiencies, costs and applications.

All about PID – testing and avoidance in the field

By Peter Hacke, Senior scientist, National Renewable energy Laboratory; Steve Johnston, National Renewable Energy Laboratory

Potential-induced degradation can cause significant power loss in modules if the appropriate precautions are not taken. In the first part of a new series in PV Tech Power on module failure, Peter Hacke and Steve Johnston assess the current state-of-the-art in detecting, avoiding and mitigating the worst effects of PID.

Reducing the electrical and optical losses of PV modules incorporating PERC solar cells

By Henning Schulte-Huxel, Robert Witteck, Malte Ruben Vogt, Hendrik Holst, Susanne Blankemeyer, David Hinken, Till Brendemühl, Thorsten Dullweber, Karsten Bothe, Marc Köntges & Rolf Brendel, Institute for Solar Energy Research Hamelin (ISFH), Emmerthal, Germa

The continual increase in cell efficiency of passivated emitter and rear cells (PERCs), as well as the optimization of the module processes, has led to significant advances in module power and efficiency. To achieve the highest module power output, one important aspect to consider is the optimization of the solar cell front metallization and the cell interconnection.

Positive cell-to-module change: Getting more power out of back-contact modules

By Bas B. van Aken & Lenneke H. Slooff-Hoek, ECN – Solar Energy, Petten, The Netherlands

Cell-to-module (CtM) loss is the loss in power when a number of cells are interconnected and laminated in the creation of a PV module. These losses can be differentiated into optical losses, leading to a lower photogenerated current, and resistive losses, leading to a decrease in fill factor. However, since the application of anti-reflection (AR) coatings and other optical ‘tricks’ can sometimes increase the Isc of the module with respect to the average cell Isc, the CtM loss in such cases needs to be expressed as a negative value, which gives rise to confusion. It is proposed to use the CtM change, where a negative value corresponds to a loss in current or power, and a positive value to a gain. In this paper, the CtM changes for back-contact modules utilizing a conductive foil are described and compared with other mature module technologies. A detailed analysis of the CtM change for a full-size metal-wrap-through (MWT) module is presented.

Electroluminescence (EL) studies of multicrystalline PV modules

By Sreenivasa Murty Dasari, Chandra Mauli Kumar, Amresh Mahajan & Nagesh C, Tata Power Solar, Bengaluru, India

Higher power generation yield is the prime objective of any solar power plant developer. The quality and reliability of the modules used are therefore a key aspect, with customers placing stringent criteria on cell and module manufacturers with regard to product quality. Electroluminescence (EL) image monitoring, which gives a clear picture of defect distribution across a module, is an increasingly popular quality criterion.

Double-glass PV modules with silicone encapsulation

By Shencun Wang & Xiang Sun, BYD; Yujian Wu & Yanxia Huang, Dow Corning (China) Holding Co; Nick Shephard, Dow Corning Corporation; Guy Beaucarne, Dow Corning Europe

Double-glass PV modules are emerging as a technology which can deliver excellent performance and excellent durability at a competitive cost. In this paper a glass–glass module technology that uses liquid silicone encapsulation is described. The combination of the glass–glass structure and silicone is shown to lead to exceptional durability. The concept enables safe module operation at a system voltage of 1,500V, as well as innovative, low-cost module mounting through pad bonding.

Cell-to-module power loss/gain analysis of silicon wafer-based PV modules

By Jai Prakash Singh, Yong Sheng Khoo, Jing Chai, Zhe Liu & Yan Wang, Solar Energy Research Institute of Singapore, National University of Singapore

We are always hearing about champion cells demonstrating efficiencies of 24% or higher, yet only 20 or 21% can be obtained at the module level. This paper highlights the different loss mechanisms in a module, and how they can be quantified. Once it is known where photons and electrons are lost, it is possible to develop strategies to avoid this happening.

Reliability and durability comparison of PV module backsheets

By Haidan Gong & Guofeng Wang, Wuxi Suntech Power Co

The backsheet is the first barrier for ensuring the reliability and durability of PV modules for 25+ years. To reduce cost, backsheets with a variety of compositions and constructions have been developed and introduced in PV modules. For PV module manufacturers, a major challenge is choosing a low-cost backsheet that can maintain the current levels of high reliability and durability performance. In the work reported in this paper, the properties of several backsheets of various compositions and constructions were compared.

Cost/kWh thinking and bifaciality: Two allies for low-cost PV of the future

By Radovan Kopecek, Ismail Shoukry & Joris Libal, ISC Konstanz

This paper demonstrates that the future of the lowest-cost electricity generation from PV is not all about increasing cell and module efficiencies and minimizing cost/Wp, but rather squeezing the best out of a system using a few simple tricks, such as bifaciality, tracking and ground reflection improvements, to achieve the lowest cost/kWh.