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Present address: Arizona State University, School of Electrical, Computer and Energy Engineering, 551 E. Tyler Mall, Tempe, AZ 85287, USA.Reducing wafer thickness while increasing power conversion efficiency is the most effective way to reduce cost per Watt of a silicon photovoltaic module. Within the European project 20 percent efficiency on less than 100-mm-thick, industrially feasible crystalline silicon solar cells ("20plms"), we study the whole process chain for thin wafers, from wafering to module integration and life-cycle analysis. We investigate three different solar cell fabrication routes, categorized according to the temperature of the junction formation process and the wafer doping type: p-type silicon high temperature, n-type silicon high temperature and n-type silicon low temperature. For each route, an efficiency of 19.5% or greater is achieved on wafers less than 100 mm thick, with a maximum efficiency of 21.1% on an 80-mm-thick wafer. The n-type high temperature route is then transferred to a pilot production line, and a median solar cell efficiency of 20.0% is demonstrated on 100-mm-thick wafers.

The deposition of dust on photovoltaic modules is of importance as parameter for economic analysis and life cycle assessments to evaluate this kind of technology for generation of electricity. Even though during the last two decades several photovoltaic plants were implemented, only a few studies about this issue were performed. This work tries to estimate the annual loss of generated energy caused by dust deposition on PV modules based on an experimental setup of a grid connected PV plant, monitoring of solar irradiation, onsite determination of dust deposition rate, and processing climatic data to obtain information about the frequency of rainfall occurrence. In Mexico City, air pollution with suspended particulate matter with diameter below 10 μm (PM 10) is almost permanently over 50 μg m -3 . This contamination contributed to an average dust deposition rate of 65 g m -2 d -1 on horizontal surfaces. Dust accumulation during rainless periods of more than 60 days can reduce production of PV systems up to 15%. With the capacity of natural cleaning by rainfalls, annual loss of production is estimated to be 3.6%.

Recycling of P is a common strategy in efficient use of P. The aims of our investigation were to study the P extractability of biochars produced by low temperature conversion and to determine the effect of soda application on low‐temperature conversion of organic compounds and the bioavailability of P to rye grass (Lolium perenne L., cv. Grazer). In this study canola cake, dried distillers grains with solubles, and meat‐and‐bone meal were converted to biochars with thermo‐chemical conversion at 400°C. The P availability was measured in terms of solubility in water, 2% citric, and 2% formic acid, and in a pot experiment with rye grass (Lolium perenne L.) which was cut three times. Application of 8% (w/w) soda to the process of thermo‐chemical conversion of canola cake, dried distillers grains with soluble and meat‐and‐bone meal resulted in an increase of water‐, 2% citric‐, and 2% formic‐acid‐extractable P in the biochars. In contrast to the application of soda, addition of 12% wood ash (w/w) to the conversion of dried distillers grains with solubles resulted in a lower increase of water‐soluble P in the corresponding biochar compared to processing biochar without additives. Addition of biochar P (100 mg P [kg soil]–1) to a Luvisol resulted in an increase of CAL‐extractable soil P. The P uptake of rye grass from biochars produced with the addition of soda was as effective as basic slag and MgNH4 phosphate fertilizers and even better than rock phosphate.

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