The combination of metal-wrap-through technology with a unit cell design, referred to as AP-MWT architecture, is proposed for the purpose of operating under low and concentrated irradiance. On the illuminated side, the negative polarity is electrically separated by using an emitter window surrounding the perimeter of each unit cell. The final functioning silicon-based device consists of an arbitrary amount of unit cells with perimeter dimensions ranging from 1cm x 2.25cm to 14cm x 13.5cm. The Czochralski-based bulk material, as well as the assembly approach, conforms with state-of-the-art industrially feasible technologies. For irradiances corresponding to 1 and 10 suns, median efficiencies of 19.8% and 20.9% and top efficiencies of 20.2% and 21.0% have been achieved. Thanks to the flexibility in size, interconnection and irradiance, awide range of current-voltage ratios are covered, providing customized solutions beyond the conventional flat-panel market.
As PV systems proliferate and become an important part of the global energy mix, it is increasingly important to forecast their energy output in order to ensure a safe and reliable integration of their variable output into electric power grids. One of the main prerequisites for that is the detailed recording and interpolation of the actual irradiance in a spatially resolved way. Such 2D irradiance maps would also allow the assessment of the performance of the many PV systems that do not have irradiance sensors installed at the site. The maps are
ideally based on a dense network of irradiance sensors; however, in many cases the costs of high-precision pyranometers, real-time monitoring and frequent maintenance are prohibitive for such operational forecasting systems. On the other hand, many PV installations are in fact equipped with reference cells in the plane of array (POA) for evaluating and monitoring the performance of the systems. Adding this network of reference cells to existing pyranometer networks (from meteorological services or research institutes) would substantially help
in improving the accuracy of the irradiance maps. This paper introduces an irradiance conversion technique that allows POA irradiance measurements from an on-site reference cell to be converted to global horizontal irradiance data, which can then collectively be used to generate large-area irradiance maps.
Two years of overcapacity in the global PV supply chain have led to investment in new manufacturing capacity grinding to a halt. However, booming global end-market demand has brought the supply–demand imbalance under control and as a result the world’s leading equipment suppliers have begun looking at serious capacity expenditure. On the basis of recent announcements and annual report publications by some of the leading manufacturers, this article examines where, when and by whom capacity expansions are now planned.
This issue of Photovoltaics International, our 23rd, offers key insights into some of the technologies that are ready to move from lab to fab in support of these goals. ISC Konstanz offer a glimpse of what the low-cost, high-efficiency solar cells of the future might look like. On page 35 the institute’s authors give an overview of what they call Konstanz’ “technology zooâ€, encompassing their so-called BiSoN, PELICAN and ZEBRA cell concepts, all of which are aimed at increasing energy yield at the lowest possible cost.
The n-Pasha n-type silicon solar cell currently achieves an average conversion efficiency of 20.2% using a relatively simple process flow. This bifacial cell concept developed by ECN is based on homogeneously doped p+ front and n+ back surfaces. To enhance the cell efficiency, it is important to reduce the carrier recombination within the boron-diffused p+ region and at its surface. This paper addresses a novel way to tune the boron-doping profile and presents advanced surface passivation schemes. In particular, it is demonstrated that a very thin (2nm) Al2O3 interlayer improves the passivation of the boron-doped surface; the Al2O3 films were deposited in industrial atomic layer deposition (ALD) reactors (batch or spatial). Moreover, it is shown that the boron-doping profile can be improved by etching back the boron diffusion. On the basis of the results presented, it is expect that n-Pasha solar cells with 21% efficiency will soon be within reach.
This paper presents the minimum aspects to consider for the commissioning of large-scale PV plants. This methodology has been successfully implemented in the commissioning of more than 40 PV facilities worldwide and it represents a very useful tool to assure the good performance of the PV project.
The crystalline silicon (c-Si) module price has been fluctuating slightly around the US$0.72/Wp level for the last 18 months. This pricing, at an estimated cumulative PV module shipment volume of 149GWp, indicates a trend change for the PV industry. C-Si module pricing appears to be currently above the production cost and should therefore yield a profit margin. However, there is still a mismatch between manufacturing capacity and future market demand. A closer look at the pricing figures reveals that there is no indication to give the allclear during the ongoing consolidation process in the PV industry. C-Si module pricing is not reflecting the
increase in polysilicon and wafer prices, and therefore the pressure to reduce the cell and module conversion costs remains a looming fact. This paper describes state-of-the-art c-Si cell manufacturing solutions that are in line with identified trends in materials, processes and products recently published in the 5th edition of the International Technology Roadmap for Photovoltaic (ITRPV). Currently available c-Si cell technologies offering higher efficiencies as well as materials savings will be discussed. The need for implementing these technologies in mass production without significantly increasing the cost per piece and in the face of more complex manufacturing processes will be established. The findings of the ITRPV regarding the reduction in levelized cost of electricity (LCOE) will be discussed, leading to the conclusion that contemporary cell technology supports the long-term competitiveness of PV-based power generation.
Recent advances at the cell level and in tabber-stringer equipment have led to the development of the next generation of cell interconnection architecture, resulting in an increase in cell and module performance. The multi-busbar (MBB) concept discussed in this paper delivers the benefits of a saving in material costs, a reduction in total series resistance and an improved light utilization for higher performance at lower cost. The combination of the cell and module concept and the stringer equipment works for a wide variety of cell types and enables an appreciable decrease in cost per watt and module size per watt.
The pioneers of utility-scale PV construction have drawn on methods used in other industries to make power plants more efficient and more competitive. This paper investigates how cutting-edge techniques in modularndesign are being used to drive down plant costs. The evolution of modular design and its attractiveness to theinvestor community are discussed.
Metal wrap-through (MWT) module technology is an attractive approach for increasing module efficiency. This paper shares the results of MWT module fabrication using a silicone electrically conductive adhesive (ECA), a conductive backsheet (CBS) with a thin organic layer surface finish, and an automated module assembly line. Very low cell-to-module (CTM) power losses are observed, leading to a multicrystalline Si module power of 266W and a full-area efficiency of 16.8%. The modules are very stable in damp-heat conditions and thermal cycling, demonstrating minimal degradation after 1.5 x IEC requirements in terms of damp heat and thermal cycling, and well below 2% degradation after 2 x IEC requirements. These MWT modules have received IEC 61215 and IEC 61730 certification.
