Jan Ove Odden

Initial light-induced degradation study of multicrystalline modules made from silicon material processed through different manufacturing routes

The paper presents results of initial light-induced degradation (LID) of multicrystalline silicon photovoltaic (PV) modules made of crystalline silicon from different manufacturing processes. The modules were installed within the Sunbelt, in Hyderabad, India. Current-voltage (I-V) characteristics are measured and infra-red (IR) images of the modules are taken at regular intervals. A relationship of the IV degradation with the IR images is discussed. Results from laboratory LID tests at room temperature are performed parallel to the outdoor degradation of PV modules. It was found that the total LID, measured on the module level, after the initial 40 hours is similar for both materials resulting in approximately 1.0% degradation of the maximum module power output. This is slightly higher than what was found in laboratory accelerated light induced degradation (ALID) tests at 120°C on the cell level [1].

Two years performance comparison of Elkem Solar multicrystalline silicon with polysilicon in a PV grid-connected system

Summarizes two years performance of an Elkem Solar and polysilicon photovoltaic (PV) system installed in the Sunbelt Region, which has been fully operational since 2011. The PV system consists of 28 multicrystalline silicon PV modules made from the standard Siemens process and from material produced by a metallurgical route - the Elkem Solar Silicon (ESS®) process. The present study suggests that after two years of field operation, both types of modules show similar degradation of power at STC. The ESS® PV modules have better performance than standard polysilicon modules as a function of solar irradiation, and thereby the total kWh generated has been slightly higher for the ESS® modules.

Performance assessment of a grid-connected mc-Si PV system made up of silicon material from different manufacturing routes

Summarises the performance of an Elkem Solar photovoltaic (PV) system installed in the Sunbelt Region (between 35 North and 35 South) in Hyderabad, India, which has been fully operational since August 2012. The PV system consists of 28 multicrystalline silicon PV modules made from the standard Siemens process and from material produced by a metallurgical route - the Elkem Solar Silicon (ESS™) process. A comparative performance study of the ESS™ modules with respect to standard polysilicon has been carried out under the various climatic and solar radiation conditions at the location. The present study suggests that the ESS™ PV modules have a slightly better performance than standard polysilicon modules as a function of solar irradiation, and thereby the total kWh generated has also been higher for the ESS™ modules.

Performance of grid-connected PV system in Southern Norway

This paper presents performance results from one of the first grid-connected photovoltaic (PV) systems in Norway. The 45 kWp system is mounted on top of a flat roof at the headquarters of a local utility company, Agder Energi, in the coastal town of Kristiansand. The system consists mainly of multi-crystalline silicon modules, with one thin film array. The system has been in operation since May 2011 and is instrumented for research and monitoring purposes. Data recorded include global and diffuse horizontal irradiation, tilted irradiation and other weather parameters, PV module temperatures, DC and AC current and voltage for three arrays, in addition to inverter power data and voltage quality measurements. Similar performance data has not yet been published for Norway. The results so far indicate good conditions for solar utilization at this location with global horizontal irradiation around 1065 W/(m2yr) and around 50 % diffuse fraction. The system produces as expected from a design perspective, with specific yield reaching 950 kWh/kWp and PR approaching 0.8 in 2014. Improvement in PR is seen as operational experience increases and system downtime is reduced. PR loss can be attributed to part-shading of PV arrays from the surrounding building structures, snow coverage in winter and inverter outages.

Influence of spectral composition on the temperature coefficients of solar cells from Elkem Solar

The temperature coefficients of solar cells from two different feedstocks - a compensated silicon, the Elkem Solar Silicon (ESS®), and polysilicon - under full and selective parts of the light spectrum are presented based on results obtained using a AAA sun simulator. These results are of particular interest in understanding the possible causes behind the better temperature coefficients usually observed for ESS® compared to polysilicon solar cells when measured with a full AM1.5 spectrum. The optical filtered lights from four different regions of the spectrum have been used to examine the influence of temperature coefficients on the spectral composition. ESS® solar cells showed considerable advantage over polysilicon solar cells in all spectral regions.

Impurity analyses of silicon wafers from different manufacturing routes and their impact on LID of finished solar cells

Summarizes the measurements of impurity concentrations in directionally solidified silicon ingots from different feedstocks. The substitutional Carbon and interstitial Oxygen are measured on as-sawn wafers using FTIR. Active iron concentration is mapped on a-Si:H passivated wafers. It is observed that these impurities present in Elkem Solar Grade Silicon (ESS™) concentrations are comparable to the standard polysilicon which are in the acceptable ranges for silicon for solar industry. The measured LID of the finished solar cells is also comparable.

Resistivity profiles in multicrystalline silicon ingots featuring gallium co-doping

Three ingots with different doping concentrations have been produced using Elkem Solar Silicon feedstock. Gallium dopants are added to the compensated Elkem Solar Silicon ingots in order to obtain ...

Reduced temperature sensitivity of multicrystalline silicon solar cells with low ingot resistivity

This study presents experimental data on the reduction of temperature sensitivity of multicrystalline silicon solar cells made from low resistivity ingot. The temperature coefficients of solar cells produced from different ingot resistivities are compared, and the advantages of increasing the net doping are explained.

Reduction of temperature coefficients in multicrystalline silicon solar cells after light-induced degradation

This study focuses on the variations of the temperature coefficients after light-induced degradation (LID) of compensated multicrystalline silicon solar cells from three different ingots. The ingots have been chosen to see the effect of the compensation level, the resistivity and the impact of adding gallium to keep the resistivity as constant as possible along the ingot. The temperature coefficients of the efficiency experience a major decrease after LID on all ingots. We found that this decrease varies along the ingot height and does not correspond to the VOC drop. Moreover, no direct correlation with the interstitial oxygen concentration profiles could be seen.

Scanning electron microscopy analysis of defect clusters in multicrystalline solar grade silicon solar cells

Solar cells from an identical commercial manufacturing unit have been investigated by electroluminescence to first detect the defect clusters. A further analysis has been done by scanning electron microscopy in secondary electron imaging mode to understand the propagation mechanism of defects. It appears that defect cluster boundaries can be very sharp or spread in the bulk with little apparent effect on the overall cell efficiency. And it is shown that grain boundaries act clearly as arrests to further propagation of these defects.