Statistical data on potential-induced degradation (PID) testing at the panel level are discussed in terms of their field relevance and the actual occurrence of PID in the field, since the latter is strongly dependent on both the specific climate and the weather conditions at a certain location as well as on the system configuration realized in a specific power plant. The correlation of outdoor conditions and leakage current is also considered with regard to a suitable standard test for solar panels. Real outdoor data are shown for PID-affected power plants. Indoor and outdoor recovery is demonstrated for PID in real solar plants as well as in lab and outdoor set-ups. Apart from ‘measuring’ PID in suitable tests and in the field, approaches are also presented for the mitigation of PID at the panel and system level.
This paper presents recent developments of ECN’s n-Pasha (passivated on all sides H-pattern) solar cell technology. The n-Pasha cell, currently being produced on an industrial scale by Yingli Solar, is a solar cell fabricated on n-type Cz material with homogeneous diffusions, dielectric passivation and printed metallization on both sides. The metallization is applied in an open H-pattern to both sides, which makes it suitable for bifacial applications. In order to improve both cell performance and the cost of ownership of n-Pasha solar cells, the ECN R&D team has focused on several aspects of the device design and processing. By reducing metal coverage and improving the quality of the front-side metallization, tuning the back-surface field (BSF) doping and improving the front- and rear-surface passivation, it has been possible to obtain an average efficiency of 20%, with top efficiencies of 20.2%. At the same time, the amount of silver used for metallization
has been decreased by over 50% and is now similar to that used for p-type solar cells. Furthermore, it is shown that with the ECN n-Pasha cell concept, wafers from the full resistivity range of n-Cz ingots can be used to make cells without losses in efficiency. Combining the improved efficiency and the reduction in cost makes the n-Pasha cell concept a very cost effective solution for manufacturing highly efficient solar cells and modules.
Has the latest round of consolidation in the supply chain enabled a more sustainable growth curve for the solar industry or is this a blip fuelled by subsidies? In this context Photovoltaics International has never been more relevant for your business. Whether you are a glass half empty or full person, the fact remains that orders are up across the board, new markets are coming on stream and analysts’ predictions are increasing again. Optimism is starting to creep into even the most conservative of organisations.
R&D expenditure by major PV module manufacturers has not been immune to the PV industry’s period of profitless prosperity. However, spending in 2012 was not affected to the extent that many would have expected, with a number of companies increasing their R&D activities and boosting staffing levels to meet R&D roadmap requirements. This paper discusses the current trends in R&D spending and staffing levels, highlighting both leaders and laggards.
In principle solar cells are very simple: they convert sunlight to electricity and can be characterized by a single number – the solar cell efficiency. Manufacturers obviously want to achieve this efficiency at the lowest possible cost, so it is critical that the efficiency/cost ratio be optimized. To this end, knowledge of where the biggest gains can be achieved is key. This paper presents an in-depth loss analysis method developed at the Solar Energy Research Institute of Singapore (SERIS) and details how various losses in a silicon wafer solar cell can be quantified, which is not done in the case of a conventional solar cell measurement. Through a combination of high-precision measurements, it is shown that it is possible to fully quantify the various loss mechanisms which reduce short-circuit current, open-circuit voltage and fill factor. This extensive quantitative analysis, which is not limited to silicon wafer solar cells, provides solar cell researchers and production line engineers with a ‘health check’ for their solar cells–something that can be used to further improve the efficiency of their devices.
The potential for PV modules to fail before the end of their intended service life increases the perceived risk, and therefore the cost, of funding PV installations. While current IEC and UL certification testing standards for PV modules have helped to reduce the risk of early field (infant mortality) failures, they are a necessary, but not sufficient, part of determining PV module service life. The goal of the PV Durability Initiative is to establish a baseline PV durability assessment programme. PV modules are rated according to their likelihood of performing reliably over their expected service life. Modules are subjected to accelerated stress testing intended to reach the wear-out regime for a given set of environmental conditions. In parallel with the accelerated tests, modules are subjected to long-term outdoor exposure; the correlation between the accelerated tests and actual operation in the field is an ultimate goal of the programme. As understanding of PV module durability grows, the test protocols will be revised as necessary. The regular publication of durability ratings for leading PV modules will enable PV system developers and financiers to make informed deployment decisions.
Module assembly drives as much as a third of the total module cost and can have a significant impact on overall module performance in terms of efficiency and module lifetime. This paper reviews some of the newest moduling material trends, and the outlook for the module market.
Over the past two years the PV industry has been in disarray as massive global overcapacity has sent prices tumbling. In this context, technological innovation to reduce the costs of base materials and products has become increasingly important. The latest edition of the International Technology Roadmap for PV published in March offers insights into the latest developments as manufacturers continue to seek ways of cutting costs. This paper explains some of the key dynamics identified in the roadmap.
To achieve project cash flow expectations, it is necessary to operate, maintain and optimize the performance of a PV power asset to meet or exceed the pro forma operating assumptions. To assume as given the achievement of these model assumptions is both naive and risky. Experience in operating the largest fleet of solar PV power plants in the world has demonstrated that project financial hurdle rates can be missed by as much as 25% if the plant is not well maintained and its performance is not optimized. Conversely, an optimized PV asset can generate cash flows 2–10% higher than expected if the optimization approach described in this paper is implemented.
The rapid growth of the PV market during the last five to seven years entailed a considerable expansion of the encapsulation material market, which temporarily led to shortages in the supply chain. Simultaneously, module prices decreased significantly, which resulted in intense pressure on production costs and the cost of PV module components, inducing changes in the encapsulation material market towards new materials and suppliers. This pressure – together with the huge impact of the encapsulation material on module efficiency, stability and reliability – makes the selection of encapsulation technologies and materials a very important and critical decision in the module design process. This paper presents an overview of the different materials currently on the market, the general requirements of PV module encapsulation materials, and the interactions of these materials with other module components.
