The US has steadily developed what is now among the world’s leading solar markets. John Parnell explores how its conservative approach has allowed it to build a solid industry that will now prepare it for challenges that lie ahead.
Signs earlier in the year of the global industry entering a growth phase have now been confirmed beyond any doubt. Almost all the big-name suppliers have now announced some form of manufacturing capacity expansion, a trend that analysts agree will only gather pace as long as the levels of demand predicted over the next few years turn out to be correct.
For some years CIGS was seen as the great white hope of the PV industry, until c-Si revealed its true competitiveness in mass production. Most companies dedicated to the commercialization of CIGS, many of which were VC financed, did not survive this development. Nonetheless, the industry has recently seen new corporate entrants with impressive plans for the roll-out of CIGS. The motives for these strategic actions are of interest, so a cost-of-ownership calculation was performed for a state-of-the-art CIGS production: the result is that current production cost for a CIGS module is €0.44/Wp, with material and depreciation being the main cost drivers. Although significant progress has been made in the last few years, this is still higher than the production costs for standard c-Si modules. However, the costs for CIGS coating materials, which correspond to the wafer in a c-Si module, are significantly lower than those for a wafer. Could this be a motive for the actions that have been witnessed in the CIGS industry? The next task would be to evaluate the further costreduction potential of CIGS and the likelihood of its realization.
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 by themselves insufficient for determining PV module service life. The goal of the Fraunhofer 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. This paper provides summary data for eight module types from the two rounds of testing to date.
The positive expectations for the global PV market are driven by state-of-the-art PV products which have become economically attractive because of technical optimization. Nonetheless, scientists and engineers face the next generation of wafer-based PV technologies in terms of processing recipes and automation techniques. In this paper, motivations, challenges and advances relating to the handling of ultrathin PV substrates are identified for future application. A brief look out of the PV box at neighbouring disciplines in high-tech sectors will also be taken. The differences and advances in the automated handling of ultrathin substrates will be highlighted as well as the difficulties for transportation. The advanced production challenges of a gripperbased
substrate movement will be accompanied by increased cleanliness requirements, as test results from the Fraunhofer IPA automation lab show.
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.
