This paper focuses on the latest developments from research on MWT (metal wrap-through) solar cells at Fraunhofer ISE. An overview of the current cell results for mc-Si and Cz-Si material with both Al-BSF and passivated rear side is presented. Recent progress in cell technology and challenges to reaching efficiencies of 20% for industrially processed large-area MWT solar cells are also discussed. Up to recently, MWT cell efficiencies of up to 19% for Cz-Si and up to 17.5% for mc-Si have been reached with industrially feasible processing. Improvements to the design of the MWT cell to increase cell efficiency and to allow an easy module assembly are also presented in this paper, as are first calibrated IV measurements of MWT solar cells.
Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust these stock levels at short notice, thus creating a spot market. Spot markets serve the short-term trade of different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.
As PV power generation adoption becomes more widely adopted globally, the grid-connected inverter market looks set to take its rightful role as a critically important element of solar installations. The grid-connected inverter market will deliver power quality and the stability of the electricity networks in order to ensure a stable and reliable grid operation. In order to keep up with these developments, network operators will release new grid codes to monitor the increased uptake, to which manufacturers must adhere. An additional obstacle for the inverter manufacturers is the wide range of requirements and norms that vary from country to country and, in many cases, even from utility to utility. This article presents a review of the new challenges facing grid-connected PV inverters in the light of these new developments.
One of the most important ways in which inorganic thin-film photovoltaics (TFPV) and organic photovoltaics (OPV) can distinguish themselves from more conventional crystalline silicon photovoltaics (c-Si PV) in the marketplace is through the commercialization of flexible photovoltaic products using those technologies. But flexible photovoltaics brings with it some challenges of its own in terms of excluding air and moisture from the cells; challenges that translate into opportunities for suppliers of advanced encapsulation materials and systems as well as for TFPV and OPV firms.
As yet, procedures for long-term tests of photovoltaic modules in outdoor conditions have not been considered by international standardization committees. Although many laboratories perform long-term PV outdoor tests, a commonly agreed and standardized procedure has so far not been adopted. The European Distributed Energy Resources Laboratories’ (DERlab) approach to filling the gap of international standardization has led to the development of a basic protocol that complies with European and international standards, while providing specific common guidelines and procedures for measuring the energy yield of PV modules for at least one year in outdoor conditions. The DERlab procedures for long-term PV module testing are described in this paper, and the range of analyses that can be derived from the data, such as module degradation, are discussed. The paper also presents the DERlab approach to measuring module performance in outdoor conditions, which can be used to complement energy-rating methods suggested in international standards. DERlab has created consistent measuring procedures that allow the direct comparison of the energy yield of solar modules taking into account the site-specific factors of different locations and varying climatic conditions, as well as a maintenance guideline.
This article provides an overview of the typical waste water treatment methods for crystalline silicon solar cell production. Firstly, a short description is provided of the main process steps of photovoltaic production and the types of waste water generated during these steps. Secondly, the typical waste water treatment methods of hydrogen fluoride (HF) precipitation and neutralization are presented. Furthermore, some options for the reuse of rinse water are discussed and several guidelines for the design of waste water treatment systems are given. Finally, the relative environmental impact of the waste water treatment compared to the emissions of the whole fab is presented using the life-cycle assessment (LCA) methodology.
This paper discusses the wire sawing process and its impact on the wafer surface and subsurface. Surface damage is found to be the main determinant in wafer stability, while an outline of the sawing parameters that have a strong influence on the surface and subsurface damage is presented. The results indicate how it is possible to decrease the breakage rate of wafers and improve the homogeneity (e.g. TTV) of wafer surfaces. A further goal in the development of the wire sawing process is to successfully reduce material consumption. This can be achieved by sawing thinner wafers with thinner wires, which leads to a reduction of the kerf loss per produced silicon surface. The second option is to increase the material yield by decreasing the wafer breakage. It will be shown that silicon wafers with less and shorter cracks and smoother surfaces will give a higher yield, while proceeding to discuss some of the important factors that affect the microcrack formation.
Recent industry analysis from NanoMarkets has suggested that although current business cases for PV are running out of steam, the building-integrated PV (BIPV) sector may be able to revive PV’s fortunes. The arrival of ‘true’ BIPV – not just flush-mounted BIPV panels, but PV-enabled glass, tiles, siding, etc. – renders possible new business cases that would otherwise simply not be an option with conventional PV. This paper puts forth a business analysis of the BIPV industry, providing case studies and data on the burgeoning sector.
One of the busiest of the couple-dozen solar manufacturing factory floors I’ve seen this year belonged to ECD Uni-Solar, at its Auburn Hills 2 (AH2) facility just up the road from the Palace where the NBA’s Detroit Pistons play hoops. When I toured the plant in late July, the three production areas – cell
deposition, cell finishing, and module stringing/lamination/final assembly – were humming, as the 1.5-milelong rolls of flexible stainless-steel starting material were transformed into triplejunction amorphous-silicon thin-film PV laminates. The company’s latest quarterly results confirm those observations at the factory, as production output grew some 58% over the previous period – from 21.2MW to 33.6MW – pushing capacity utilization to about 90%.
A selective emitter is a doping layer that is heavily doped beneath the electrode and lightly doped in between the electrode grids. One of the disadvantages of conventional selective-emitter techniques is the need for a high phosphorus surface concentration to obtain low contact resistance and limit the shunts in the emitter. Effective emitter passivation below the contact is difficult because of the use of emitters with low sheet resistances and high doping concentrations. In this study, the selective emitter in the optimized light/light sheet-resistance combination was formed to reduce recombination under the metal contact. The fabrication of optimized light/light doped emitters was performed using a single-step diffusion process. Besides the benefit of low surface recombination for light/light combination, this approach also removes the need for a very precise alignment between the opened emitter pattern and the front screen-printed silver fingers. This work illustrates the achievement of an efficiency improvement of more than 0.4% absolute in large-scale production for selective emitter solar cells.
