Effect of crucible rotation on the temperature and oxygen distributions in Czochralski grown silicon for photovoltaic applications

Temperature and oxygen distributions were numerically studied for the Czochralski (Cz) growth of 8′′ diameter silicon single crystals for photovoltaic applications. Fluctuations in the dopant concentration (striation pattern) in the grown crystal obtained by lateral photovoltage scanning (LPS) technique seems to be better correlated with simulated temperature fluctuations near the solid–liquid interface than with oxygen concentration oscillations. From the transient simulations of different crucible rotation rates, 2, 4, 6 and 8 rpm, it is indicated that the average oxygen melt concentration first decreases with increasing rotation rate and later increases. This suggests that a critical rotation rate exists where the oxygen concentration below the solid–liquid interface increases with increasing rotation rate. When comparing the temperature and oxygen distributions in the melt it was found that oxygen is more sensitive to changes in the rotation rate than the temperature.acceptedVersio

Multi‐Stage Validation of a Solar Irradiance Model Chain: An Application at High Latitudes

Evaluating how the sources of uncertainty in solar modelling (e.g., input parameters, developed model chain) can influence the results’ accuracy is one of the main challenges when applied at high latitudes. In this study, a multi-stage validation workflow is implemented around five main stages: data acquisition, data quality check, solar radiation modelling, photovoltaic energy modelling, and experimental validation. Different data sources such as satellite observations, numerical reanalysis, and on-site ground measurements are considered as inputs, while the outcomes from each step of the model chain (e.g., decomposition modelling, transposition modelling, photovoltaic energy modelling) are compared against observations recorded from the solar radiation network at the Norwegian University of Science and Technology (NTNU-Solarnet) in Trondheim (Norway). In the first and second validation stages, the decomposition and transposition models with measured input parameters show the best accuracy indicators, but they do not fulfill the validation criteria. Conversely, in the third validation stage, the photovoltaic energy models with on-site ground measurements as inputs are experimentally validated. In conclusion, at high latitudes, the most accurate results are obtained when monitored solar irradiation data are used instead of satellite observations and numerical reanalysis. Furthermore, the shortest model chain is preferred, with equal data sources.publishedVersio

NTNU-SINTEF SolarNet: A solar irradiation monitoring network at high latitudes

This study presents a monitoring network for solar irradiation at high latitudes, called NTNU-SINTEF SolarNet. The network collects, with a time resolution ranging from seconds to hours, solar irradiance data, e.g. global horizontal irradiation, diffuse horizontal irradiation, direct normal irradiation, global tilted irradiation, solar energy generation, which are required in solar irradiation modelling in built environments. The network will be used for specific applications, such as (i) anomalies detection, (ii) influences of ground albedo, and (iii) ageing/degradation of solar modules, that are described in this paper. Some characteristics that make the NTNU-SINTEF SolarNet relevant for solar energy research at high latitudes are identified: short distances among the sensors, the ease of data accessibility, the use of the same sensor typologies, and different solar module technologies. The research holds the potential to boost the solar energy digitalization, impacting on several aspects such as predictive and adaptive control strategies for energy management, design of renewable energy system, multi-scale optimization and efficient exploitation of solar energy.publishedVersio

Effect of crucible rotation on the temperature and oxygen distributions in Czochralski grown silicon for photovoltaic applications

Temperature and oxygen distributions were numerically studied for the Czochralski (Cz) growth of 8′′ diameter silicon single crystals for photovoltaic applications. Fluctuations in the dopant concentration (striation pattern) in the grown crystal obtained by lateral photovoltage scanning (LPS) technique seems to be better correlated with simulated temperature fluctuations near the solid–liquid interface than with oxygen concentration oscillations. From the transient simulations of different crucible rotation rates, 2, 4, 6 and 8 rpm, it is indicated that the average oxygen melt concentration first decreases with increasing rotation rate and later increases. This suggests that a critical rotation rate exists where the oxygen concentration below the solid–liquid interface increases with increasing rotation rate. When comparing the temperature and oxygen distributions in the melt it was found that oxygen is more sensitive to changes in the rotation rate than the temperature

Automatic solar cell diagnosis and treatment

Solar cells represent one of the most important sources of clean energy in modern societies. Solar cell manufacturing is a delicate process that often introduces defects that reduce cell efficiency or compromise durability. Current inspection systems detect and discard faulty cells, wasting a significant percentage of resources. We introduce Cell Doctor, a new inspection system that uses state of the art techniques to locate and classify defects in solar cells and performs a diagnostic and treatment process to isolate or eliminate the defects. Cell Doctor uses a fully automatic process that can be included in a manufacturing line. Incoming solar cells are first moved with a robotic arm to an Electroluminescence diagnostic station, where they are imaged and analysed with a set of Gabor filters, a Principal Component Analysis technique, a Random Forest classifier and different image processing techniques to detect possible defects in the surface of the cell. After the diagnosis, a laser station performs an isolation or cutting process depending on the detected defects. In a final stage, the solar cells are characterised in terms of their I–V Curve and I–V Parameters, in a Solar Simulator station. We validated and tested Cell Doctor with a labelled dataset of images of monocrystalline silicon cells, obtaining an accuracy and recall above 90% for Cracks, Area Defects and Finger interruptions; and precision values of 77% for Finger Interruptions and above 90% for Cracks and Area Defects. Which allows Cell Doctor to diagnose and repair solar cells in an industrial environment in a fully automatic way

Silicon anodes for lithium-ion batteries produced from recovered kerf powders

Silicon kerf waste from a photovoltaic silicon production process is assessed as an anode material for application as a lithium ion battery anode. In contrast to previous studies, the Si-kerf is used as-produced, with no chemical treatment or physical processing beyond solvent PEG removal. The as-produced Si-kerf performed as well as, or better than, previously reported Si-kerf anodes and is found to outperform a cleaned Si-kerf sample from blade sawing with a larger particle size. This highlights the advantage of the diamond wire cutting process, which yields relatively small particles. In half-cell testing, a cycle life >300 cycles at a capacity of 1000 mAh g−1 is achieved with high levels of FEC addition. Full-cell testing against an NMC 442 cathode resulted in specific capacities up to 150 mAh g−1 (NMC). A relatively high degree of lithium consumption arising from repeated SEI formation is present. It is concluded that pure Si-kerf is unsuitable for commercial application in Li-ion cells