Photovoltaics International Papers

It is essential to understand the investment and operating costs of photovoltaic power plants in terms of economic parameter calculations such as levelized cost of electricity (LCoE). The dynamic behaviour of national and international markets requires a precise and detailed estimation of costs, and this knowledge is especially important to investors and policymakers. Only if the investment and operating costs of PV power plants are known can the price of electricity and the more detailed levelized cost of electricity be precisely calculated. High investment costs also require reliable investment policies and close cooperation between financial institutions (such as banks and investment funds) and power plant owners. Investment in large-scale PV power plants requires a detailed evaluation of solar radiation potential and grid availability, as well as a load analysis and a precise economic evaluation. When the investment cost based on the above-mentioned parameters is known, an estimation of the operating costs should be the next step. When all the costs of a PV power plant have been estimated, the price of electricity, or even a more detailed LCoE, can be calculated. This paper presents the trend of investment costs and some typical maintenance costs, and calculations of electricity price based on recent real data for large-scale PV power plants.

The benefits of solar photovoltaic (PV) power are well known, and, as this awareness rises and the cost of generating PV electricity declines, the technology is becoming more competitive with conventional electricity sources in market segments all across Europe. But bureaucratic hurdles remain a persistent threat to the widespread installation and integration of PV, often making it difficult to take advantage of the technology. In many countries, administrative processes and permitting procedures still require significant improvement. As a result, planning and connecting a solar photovoltaic system to the grid can still take several years in Europe.

The PV industry stands on the verge of an enormous achievement – an installed base of PV plants with 100GW of energy generation capability. This milestone has come about because of the contributions of a fully global industry that has blossomed in the past decade. Yet even though the PV industry traces its heritage to before the space programme, as with any dynamically growing industry most industry members have joined in the past five years. And each generation often makes the same mistakes that a previous generation made. Sometimes the same people move from one industry to another and repeat the same mistakes there. The PV industry is rediscovering ultra-competitive market dynamics that have previously been seen in other high-technology commodity markets. This paper begins with a discussion of one such market – the dynamic random access memory (DRAM) industry – and then looks at the current PV market and the industry outlook.

Approximately 80% of today’s silicon solar cells industrially manufactured worldwide apply screen printing for the metallization of the silver front and aluminium rear contacts. In production, conversion efficiencies of ~18–18.5% are achieved using monocrystalline silicon wafers. A baseline process has been implemented at ISFH that is very similar to the industry-standard process, displaying conversion efficiencies of up to 18.5%. An analysis of the solar cells reveals that the conversion efficiency is limited in particular by the shadowing loss due to the silver front-side metallization, as well as infrared light being absorbed in the aluminium rear-side metallization. This paper summarizes recent developments at ISFH that resulted in a 19.4% efficient large-area screen-printed solar cell, when applying a print-on-print silver front-side metallization and an SiO2/SiNx rear-surface passivation.

Competition in the premium sector is becoming more and more fierce. This is forcing PV module manufacturers to differentiate themselves through product benefits and better performance in terms of efficiency. While attention has previously been focused on cell technology, it is likely that, in the future, all module components will become part of this competition – a competition in which premium front glasses present an especially promising element. Antireflective coating (ARC) is only the beginning of this evolution. Not only do deeply textured front glasses promise significant increases in output – up to 7% – but their specific product characteristics also make them suitable for niche applications, such as airplane entry lanes and airport buildings. EuPD Research has issued a white paper devoted to solar glass, of which a synopsis is presented here.

Transparent conductive oxides (TCOs), such as aluminium-doped zinc oxide (ZnO:Al), play an important role in thin-film photovoltaics. As a material for front contacts, ZnO:Al is standard in industrial-scale production, especially in the field of Cu(In,Ga)Se2 solar cells. Over the last few years, there has been a strong push to use ZnO:Al films on glass as substrates for amorphous or amorphous/microcrystalline silicon solar cells, and these films have now been introduced as an alternative to the typically used fluorine-doped tin oxide (SnO2:F) films in production. Sputtering coaters for large area deposition of ZnO:Al are widely available, and ZnO:Al films are produced in these coaters by sputtering of ceramic targets. This technology offers high process stability and is therefore favoured over reactive sputtering of metallic targets. With respect to cost and quality, however, the reactive process is an interesting alternative. In this paper we will give an overview of the process of reactive sputtering of ZnO:Al and discuss the most important insights.

In a multicrystalline silicon (mc-Si) cell production process, acid texturing is the most popular way of carrying out surface texturing. In general, the surface reflectivity and etch depth are the criteria used for quantifying the texture quality. In this study, four groups of cells were created with different etch depths of 2.82μm, 3.83μm, 4.41μm and 5.92μm. It was found that the etch depth had a notable effect on the efficiency of a cell. Also, the best texture was obtained with an etch depth of 4.41μm, at which there was a balance between a low reflectance and the removal of the saw-damage layer. As the etch depth increased, the film deposition thickness and the front bus-bar tensile strength were seen to increase. However, no linear relationship was found to exist between the diffusion sheet resistance and the etch depth.

The last several years have seen a significant number of publications on wire saw data in regard to process optimization theory applied to solar wafering. The methods vary, but fundamentals concern the mechanical dynamics of the wire sawing process, where measurements of the wire forces in the silicon slot using free abrasive are studied; however, these data are not yet fully correlated to a complete thermodynamic analysis of the problem. The objectives of the empirical development of the process theory are also widely varied, but there is industry agreement that it is being faced with the fundamental limits of cutting rates in processes that use free abrasive slurries and a single wire. The limit arises from intrinsic thermodynamic limits of the delivery of work energy to the silicon slot. Similarly, these same principles prevent us from increasing the wafer load to overcome the limitation as work energy transfer rates are countered by higher entropic losses that occur as power and wafer load are increased. The effect results in the problem that the wafer load may not be increased without proportionately reducing table speed. The fundamental nature of these limits suggests that they involve theoretically calculable energy quantities of thermodynamic limiting functions, which restrict the ‘useful’ work that we can extract from the system, where the work energy of interest is the abrasion of the silicon in forming the wafers. The present work reviews the theoretical issues of determining process efficiency optimums that could be used to achieve throughput gains.

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 stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in 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.

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.