Photovoltaics International Papers

How much carbon is emitted in producing a solar PV module and launching it on the market? This could be an important question which project developers, installers, investors, government agencies and end customers might ask solar PV manufacturers in the future. To answer it, producers need to know the direct emissions from the manufacturing process, as well as those generated from the activities of manufacturers in the upstream supply chain (including raw material acquisition, upstream energy use, packaging, transportation and procurement), and also those arising from module usage and eventual recycling. This paper, written in a cooperation between EuPD Research and Deutsches CleanTech Institut (DCTI), presents an overview of PV’s carbon footprint.

In the photovoltaic industry, laser edge isolation (LEI) is a well-established process at the end of the process chain. However, because the cell properties vary from one cell producer to the next, no systematic approach is defined in industry for establishing an efficient isolation groove. Nevertheless, a general approach has to be defined for analyzing the LEI process for silicon solar cells. Besides the material aspects and laser parameters, atmospheric boundary conditions must be considered. This paper presents investigations into the ablation of a specific type of mc-silicon solar cell, and the most suitable laser, as well as the ambient parameters, is determined based on the results of the experiments.

For a vertically integrated solar cell production starting with purification of silicon feedstock and ending with the production of solar cells, it is necessary to have control over all possible parameters that may affect yield, efficiency and product quality. This paper presents an approach for tracking products with minimal effort using a contactless technique. The method allows wafers to be virtually reconstructed into bricks and ingots, as well as recognizing the precursor wafer for each solar cell.

With new industrial challenges faced by the PV industry – such as the striking development of Chinese manufacturers, and ever more demanding investors and financial institutions – the quality of PV modules has never been as important as it is today. Because normative requirements are not matching the buyers’ expectations, the questions of what the real quality of a PV module is and how to assess it still remain. This paper analyzes the current situation in terms of quality and the causes of problems, and proposes some ways of addressing the issues in order for the industry to progress on the long path to excellence.

Traditional markets for PV will be scaling back on the level of demand for PV, but there are already signs that the developing countries will be stepping in to pick up the slack. This will be a combination of both standard grid-connected and micro-grid types of installation. Micro-grids present the opportunity for countries to develop a cellphone type of model for power distribution whereby regions without electrification can have a regional power source that allows for local access. This market is projected to become significant in the next several years, as the access to lower cost PV makes this option more easily implemented. This paper evaluates the market size of what has been an overlooked ‘niche’ for PV and describes the key considerations for a micro-grid installation, the developing conditions favouring installation, and some of the specifics of a micro-grid case study. The point is made that the grid-connected market will be increasingly assisted by the micro-grid segment as the latter becomes a significant source of PV demand and energy provision. Contrary to common notions, the micro-grid and hybrid off-grid segments will play an increasing role, even in areas with a grid in place.

Al2O3 deposition has received a lot of attention in the last few years for its attractive passivation properties of c-Si surfaces. Within the local Al back-surface field (BSF) cell concept, we considered several avenues of study: surface preparation, thermal stability, charge investigation and the ‘blistering’ phenomenon. The investigations converged on a passivation stack that includes a thin interfacial SiO2 like layer and a thin Al2O3 layer (~10nm), which undergoes a high-temperature anneal (> 600°C). In order for a surface passivation with Al2O3 to be a cost-effective step for the PV industry, a high Al2O3 deposition rate is required. Compared to the different high-throughput tools that have recently emerged on the PV market, such as atomic layer deposition (ALD) and plasma-enhanced chemical vapour deposition (PECVD), our tool screening revealed quite similar results. The differences therefore seem to have an origin primarily in the tool specifications rather than in the achievable Al2O3 material properties.

t is well known that the cost of silicon materials is the major cost factor in crystalline silicon PV module production. Polysilicon price accounts for about 30% of total module production costs. While the PV industry has set a polysilicon price target of US$40/kg by 2015, this goal will not be reached if demand continues to exceed supply and if new plants cannot reduce operating costs below US$25/kg. Given a continued 30% annual growth in demand for PV modules, new polysilicon plants and expansions are needed to avoid shortages of high-purity, cost-effective polysilicon. This paper discusses the major factors in polysilicon production costs, the important elements of polysilicon plant design for reducing operating costs, the key cost elements of polysilicon plant operations, and how the design of polysilicon products can reduce crystal growth costs.

In recent years, Germany has seen impressive growth in its PV market. From a virtually non-existent market based on the 1,000 roof support program at the end of the 1990s, Germany now represents the world’s biggest PV market and has created a strong PV industry base. With approximately 17GW of installed PV capacity at the end of 2010 – accounting for 2% of its electricity consumption, Germany has become a solar super power and triggered market growth and technology development worldwide. Nevertheless, the innovative scheme of feed-in tariffs (FiT), which provided incentives for solar PV installations and helped to ramp up an unknown cycle of innovation, will have to evolve towards more diversified ways of supporting system transformation of the electricity market and PV market integration until full competiveness of PV technology is reached in Germany, anticipated for 2017.

Various economic and political influences continue to push high-volume manufacturing of semiconductor and PV devices into relatively arid and water-constrained geographies. As the social, economic and political focus on water resources and sustainability increases daily, the need to address the supply, use and disposal of water at manufacturing facilities is growing increasingly more complex. Historically, PV manufacturing has not been considered a major water consumer so there has been little scrutiny of water management. As the costs of water and wastewater disposal spiral upwards, water resource management becomes a significantly more important factor in the capital and operating costs of PV manufacturing. This paper outlines the preparation of a water management diagram (WMD) with reference to the development of water systems for new PV manufacturing plants, and discusses some cautionary design considerations.

The need for higher efficiency solar cells is becoming more and more urgent nowadays in the photovoltaic industry. In this paper, a new method of increasing efficiency is described whereby SiN is coated by a special commercial chemical after the final step of manufacturing, which is screen printing. No mask is required for this method, but a drying temperature of 200–400°C is mandatory to activate the SiN layer. It is shown that the efficiency of a crystalline solar cell can be increased by at least 0.16% (absolute value) on average. At the same time, modules made from these solar cells do not degrade after sun exposure, and have the potential to pass the stringent standards of a potential-induced degradation (PID) test. The total cost for all the equipment and the chemical is around US$300,000 for retrofitting two (30MW each) production lines.