This paper presents a summary of the status of bifacial PV in respect of the technology in mass production, the installed PV systems, and the costs relating both to module production (cost of ownership – COO) and to electricity (levelized cost of energy – LCOE). Since the first bifacial workshop, organized by ISC Konstanz and the University of Konstanz, in 2012, many things have changed. Bifacial cells and modules have become cost effective, with installed systems now adding up to more than 120MWp and the technology becoming bankable. Large electricity providers have recognized the beauty of bifacial installations, as the lowest costs per kWh are attainable with these systems. The authors are sure that by the end of 2017, bifacial PV systems amounting to around 500MWp will have been installed, and that by 2025 this type of system will become the major technology in large ground-mounted installations.
For many applications, bifacial modules offer a cost-effective way of increasing energy yields, which explains why the interest in bifacial cells in the PV industry is steadily growing and is expected to continue. However, the metallization of bifacial cells creates new challenges, as the same materials and techniques developed for n surfaces are generally not directly, or simultaneously, applicable to p surfaces; this necessitates sequential metallization of each side, resulting in added cost and/or complexity. This paper introduces a simple co-plating approach with the objective of simplifying the metallization of bifacial cells in a cost-effective way, and which is designed for multi-wire module integration. The metallization route is described, and high cell efficiencies of up to 22.4% are demonstrated using this co-plating approach with bifacial nPERT+ cells (where ‘+’ signifies the bifacial nature of these cells). Initial thermal-cycling reliability data of test structures and 1-cell laminates is presented. Finally, cost-of-ownership (COO) estimates are given, which predict the co-plating approach to be ~40% cheaper than bifacial screen-printed metallization. It is shown that the combination of the high efficiency potential of nPERT+ cells and the reduced costs of co-plating has the potential to deliver module-level costs of ~$0.25/Wpe (glass–glass configuration).
There are numerous tools and methods available on the market for the optical and electrical quality control of high-efficiency silicon solar cells during their industrial production, and even more are discussed in the literature. This paper presents a critical review of the possibilities and limitations of these tools along the value chain, from wafer to cell, in the case of passivated emitter and rear cells, as well as a discussion of some showcases. Economic and technological challenges and future trends are addressed.
High-performance multicrystalline (HPM) silicon, achieved by nucleation on special seed layers at the crucible bottom, is now increasingly replacing conventional multicrystalline (mc) silicon, which is solidified on the standard silicon nitride coating. The HPM material is characterized by a very fine initial grain structure consisting of small, regularly shaped grains surrounded by a large number of random-angle grain boundaries. These grain structure properties, which differ significantly from those of conventional multicrystalline silicon, lead to a much lower dislocation content in the material, and therefore result in higher efficiencies of the silicon solar cells produced. This paper gives a rough overview of the worldwide R&D activities on HPM silicon in recent years, supplemented by several research results obtained at Fraunhofer IISB/THM. The focus is on the different seeding methods, the grain structure properties and the development of the grain and defect structure over the ingot height, as well as on the main challenges for further improvements in material quality and production costs.
Having installed more than 75 gigawatts in 2016, the solar industry continues to create opportunities for cell and module manufacturers to expand capacities, while upgrading technologies and improving process flows. Supply remains dominated by p-type crystalline silicon modules, despite ongoing research into n-type variants and the addition of PERC on p-type mono cells. The efficiency increases from p-type mono are now driving p-type multi cell producers to accelerate changes to production lines from both black silicon and PERC. This is now setting new benchmarks for the supply of solar modules in 2017 to utility-scale solar installations.
A novel nanoscale pseudo-pit texture has been formed on the surface of a multicrystalline silicon (mc-Si) wafer by using a metal-catalysed chemical etching (MCCE) technique and an additional chemical treatment.
A desirable nanoscale inverted-pyramid texture was created by optimizing the recipe of the MCCE solution and using a proprietary in-house chemical post-treatment; the depth and width of the inverted pyramid was adjustable within a 100–900nm range. MCCE black mc-Si solar cells with an average efficiency of 18.90% have been fabricated on CSI’s industrial production line, equating to an efficiency gain of ~0.4%abs. at the cell level. A maximum cell efficiency of 19.31% was achieved.
The thirty-fifth issue of Photovoltaics International brings you insights into how investment in high-efficiency cell technology production appears to be showing no signs of slowing down and more about scientists from the R&D team at Canadian Solar look at so-called ‘black’ silicon, one of the new cell technology concepts beginning to gain currency. Additionally, how researchers from Germany’s Fraunhofer ISE take up the theme with a paper exploring the question of quality control in the production of high-efficiency silicon solar cells and not forgetting the growing importance of thin-film technologies in the overall PV mix.
Asset management | As one of the biggest utility PV owners in the UK, Foresight has extensive experience of getting the most out of operational solar plants. Its technical director Arnoud Klaren draws on some of the lessons the company has learned from minimising the risks that affect solar projects over their lifetime.
Business models | Solar is forecast to have another strong year of growth, but in spite rather than because of political support in many parts of the world. Simon Currie and Rob Marsh assess some of the commercial drivers for solar in 2017 and beyond as it finds itself increasingly at the mercy of market forces but arguably better placed to become a true global competitor.
