bjornbaa

• Walpita, Harsha Lakmal; Roosloot, Nathan Abel; Otnes, Gaute; Aarseth, Bjørn Lupton; Selj, Josefine Helene Krogh & Nysted, Vilde Stueland [Show all 7 contributors for this article] (2025). Operation and Maintenance of Floating PV Systems: A Review. IEEE Journal of Photovoltaics. ISSN 2156-3381. 15(3), p. 400–415. doi: 10.1109/JPHOTOV.2025.3548322. Full text in Research Archive
• Lofstad-Lie, Victoria; Aarseth, Bjørn Lupton; Roosloot, Nathan Abel; Marstein, Erik Stensrud & Skauli, Torbjørn (2024). Modeling Cost-Effectiveness of Photovoltaic Module Replacement Based on Quantitative Assessment of Defect Power Loss. Solar. 4(4), p. 728–743. doi: 10.3390/solar4040034. Full text in Research Archive Show summary

  The degradation of solar photovoltaic (PV) modules over time, which are aggravated by defects, significantly affects the performance of utility-scale PV parks. This study presents a quantitative assessment of the power loss from module defects and evaluates the cost-effectiveness of replacing defective modules at various stages of degradation. A module test site was established in Norway with six different defects, and continuous thermographic monitoring, combined with light IV measurements and electroluminescence (EL) imaging, provides partial support for further calculations on the long-term effects of the defects. The cumulative module energy loss is calculated over a 25-year park lifespan under both Norwegian and Chilean environmental conditions, with the latter representing higher solar irradiation levels. The energy gain from replacing the defective modules at various stages of degradation is compared to the costs of replacement, both for infant-life failures and mid-life failures. It is likely not beneficial to replace minor infant-life defects of 1% power loss in low-irradiation regions like Norway. For Chilean conditions, it can be cost-effective, but primarily if the module is replaced around mid park life, which gives a larger yield when replaced with a new module. For more severe defects of 10% loss, the replacement gain is above the replacement cost for high-irradiation locations, and replacing the 33% power loss defect is cost-effective for both locations, even when discovered late in the park lifetime. It is primarily beneficial to replace mid-life defects in high-irradiation locations.

• Riise, Heine Nygard; Nygård, Magnus Moe; Aarseth, Bjørn Lupton; Dobler, Andreas & Berge, Erik (2024). Benchmark of estimated solar irradiance data at high latitude locations. Solar Energy. ISSN 0038-092X. 282. doi: 10.1016/j.solener.2024.112975. Full text in Research Archive
• Aarseth, Bjørn Lupton; Nygård, Magnus Moe; Otnes, Gaute & Marstein, Erik Stensrud (2024). Combining Production Data Timeseries and Infrared Thermography to Assess the Impact of Thermal Signatures on Photovoltaic Yield Over Time. IEEE Journal of Photovoltaics. ISSN 2156-3381. 15(1). doi: 10.1109/JPHOTOV.2024.3483248. Full text in Research Archive
• Aarseth, Bjørn Lupton; Skomedal, Åsmund; Øgaard, Mari & Marstein, Erik Stensrud (2022). Detecting Permanently Activated Bypass Diodes in Utility-Scale PV Plant Monitoring Data. IEEE Journal of Photovoltaics. ISSN 2156-3381. 12(5), p. 1230–1236. doi: 10.1109/JPHOTOV.2022.3187381. Full text in Research Archive
• Øgaard, Mari Benedikte; Aarseth, Bjørn Lupton; Skomedal, Åsmund; Riise, Heine Nygard; Sartori, Sabrina & Selj, Josefine Helene Krogh (2021). Identifying snow in photovoltaic monitoring data for improved snow loss modeling and snow detection. Solar Energy. ISSN 0038-092X. 223, p. 238–247. doi: 10.1016/j.solener.2021.05.023. Full text in Research Archive Show summary

  As cost reductions have made photovoltaics (PV) a favorable choice also in colder climates, the number of PV plants in regions with snowfalls is increasing rapidly. Snow coverage on the PV modules will lead to significant power losses, which must be estimated and accounted for in order to achieve accurate energy yield assessment and production forecasts. Additionally, detection and separation of snow loss from other system losses is necessary to establish robust operation and maintenance (O&M) routines and performance evaluations. Snow loss models have been suggested in the literature, but developing general models is challenging, and validation of the models are lacking. Characterization and detection of snow events in PV data has not been widely discussed. In this paper, we identify the signatures in PV data caused by different types of snow cover, evaluate and improve snow loss modeling, and develop snow detection. The analysis is based on five years of data from a commercial PV system in Norway. In an evaluation of four snow loss models, the Marion model yields the best results. We find that system design and snow depth influence the natural snow clearing, and by expanding the Marion model to take this into account, the error in the modeled absolute loss for the tested system is reduced from 23% to 3%. Based on the improved modeling and the identified data signatures we detect 97% of the snow losses in the dataset. Endogenous snow detection constitutes a cost-effective improvement to current monitoring systems.

• Aarseth, Bjørn Lupton; Granerød, Cecilie Skjold; Galeckas, Augustinas; Azarov, Alexander; Nguyen, Phuong Dan & Prytz, Øystein [Show all 7 contributors for this article] (2021). Formation and functionalization of Ge-nanoparticles in ZnO. Nanotechnology. ISSN 0957-4484. 32(50). doi: 10.1088/1361-6528/ac264a. Full text in Research Archive Show summary

  Semiconductor nanocrystals are often proposed as a viable route to improve solar energy conversion in photovoltaics and photoelectrochemical systems. Embedding the nanocrystals in, e.g. a transparent and conducting electrode of a solar cell will promote the photon absorption and subsequent transfer of the generated charge carriers from the nanocrystal, and thereby enhance the function of the electrode. This can be accomplished by embedding a semiconducting nanocrystal with a small bandgap in a transparent conducting oxide (TCO), which is commonly utilized as electrode in new generation solar cells. Here, we demonstrate the incorporation, formation, and functionalization of germanium (Ge) nanocrystals in zinc oxide utilizing ion implantation, where post implantation annealing at 800 °C results in diamond cubic Ge nanocrystals with sizes between 2 and 20 nm. Photoluminecence spectra show a distinct emission around 0.7 eV arising from the Ge nanocrystals, and with additional emission features up to 1.15 eV due to quantum confinement, demonstrating a novel functionalization and tunability of the TCO electrode.

• Aarseth, Bjørn Lupton; Skomedal, Åsmund; Øgaard, Mari Benedikte & Marstein, Erik Stensrud (2020). The Influence of Thermal Signatures Observed with Infrared Thermography on Power Production in a Utility Scale Power Plant. Proceedings of the European Photovoltaic Solar Energy Conference. ISSN 2196-100X. doi: 10.4229/EUPVSEC20202020-5DO.3.1. Full text in Research Archive
• Skomedal, Åsmund; Aarseth, Bjørn Lupton; Selj, Josefine Helene Krogh; Haug, Halvard & Marstein, Erik Stensrud (2020). How much power is lost in a hot-spot? A case study quantifying the effect of thermal anomalies in two utility scale PV power plants. Solar Energy. ISSN 0038-092X. 211, p. 1255–1262. doi: 10.1016/j.solener.2020.10.065. Full text in Research Archive Show summary

  Methods for quick and accurate detection and diagnosis of defects in PV systems are increasingly important as the global photovoltaic (PV) capacity continues to grow at a rapid pace. Two of the most used methods for defect detection involve aerial infrared thermography and data analysis of production data. In this work, we combine the two methods to analyze two utility scale PV plants, providing new understanding about the two methods. We report on the percentage and distribution of thermal anomalies of different categories and quantify their relationship with performance on string level. We find that the most important parameter for determining production losses on string level is the number of module substrings containing thermal anomalies. Due to the large variability of the effect of different thermal signatures, as well as uncertainties in the estimate of the string performance, we find no clear correlation between performance and thermal signature category or temperature. However, a whole hot cell is the thermal signature that on average has the smallest impact on the power output on string level. Finally, in our data, the performance of a string of 20 modules with 3 bypass diodes is on average reduced by 1.16 ± 0.12% per module substring containing thermal anomalies.

• Azarov, Alexander; Aarseth, Bjørn Lupton; Vines, Lasse; Hallen, Anders; Monakhov, Eduard & Kuznetsov, Andrej (2019). Defect annealing kinetics in ZnO implanted with Zn substituting elements: Zn interstitials and Li redistribution. Journal of Applied Physics. ISSN 0021-8979. 125(7). doi: 10.1063/1.5083226. Full text in Research Archive Show summary

  It is known that the behavior of residual Li in ion implanted ZnO depends on the preferential localization of the implants, in particular, forming characteristic Li depleted or Li pile-up regions for Zn or O sublattice occupation of the implants due to the corresponding excess generation of Zn and O interstitials in accordance with the so-called “+1 model.” However, the present study reveals that conditions for the radiation damage annealing introduce additional complexity into the interpretation of the Li redistribution trends. Specifically, four implants residing predominantly in the Zn-sublattice, but exhibiting different lattice recovery routes, were considered. Analyzing Li redistribution trends in these samples, it is clearly shown that Li behavior depends on the defect annealing kinetics which is a strong function of the implanted fluence and ion species. Thus, Li depleted and Li pile-up regions (or even combinations of the two) were observed and correlated with the defect evolution in the samples. It is discussed how the observed Li redistribution trends can be used for better understanding a thermal evolution of point defects in ZnO and, in particular, energetics and migration properties of Zn interstitials.

• Aarseth, Bjørn Lupton & Marstein, Erik Stensrud (2019). Defect Recognition and Power Loss Estimation Using Infrared Thermography. Proceedings of the European Photovoltaic Solar Energy Conference. ISSN 2196-100X. p. 1563–1568. doi: 10.4229/EUPVSEC20192019-5CV.4.5. Full text in Research Archive Show summary

  This study investigates how thermal signatures observed in PV systems using infrared thermography (IRT) affect the performance of PV modules and strings. To assess this, we use IRT images as a basis for circuit modeling of modules with defected solar cells. This allows us to calculate the performance of the individual modules with thermal signatures and the module string. We model the IV characteristics of defective modules based on IRT images and fit the results to field IV traces of the imaged modules. By IRT imaging, several thermal signatures have been identified, and by using a portable IV tracer, the power loss related to each defect under the given conditions has been found. Information from the IRT images are used as input to a model we have developed for defect evaluation, and a comparison of model and IV tracer data for a range of defective solar modules is presented. The string modeling shows that the power loss from a given thermal signature is highly dependent on string length and circuit design. For string sizes larger than 20 modules, only defects that affect two or more module substrings are expected to give a power loss higher than 3%.

• Granerød, Cecilie Skjold; Aarseth, Bjørn Lupton; Nguyen, Phuong Dan; Bazioti, Kalliopi; Azarov, Alexander & Svensson, Bengt Gunnar [Show all 8 contributors for this article] (2019). Structural and optical properties of individual Zn2GeO4 particles embedded in ZnO. Nanotechnology. ISSN 0957-4484. 30(22), p. 1–6. doi: 10.1088/1361-6528/ab061c. Full text in Research Archive
• Aarseth, Bjørn Lupton; Øgaard, Mari Benedikte; Zhu, Junjie; Strömberg, Tommy; Tsanakas, John A. & Selj, Josefine Helene Krogh [Show all 7 contributors for this article] (2018). Mitigating Snow on Rooftop PV Systems for Higher Energy Yield and Safer Roofs. Proceedings of the European Photovoltaic Solar Energy Conference. ISSN 2196-100X. p. 1630–1635. doi: 10.4229/35thEUPVSEC20182018-6CO.3.5. Full text in Research Archive

View all works in NVA

• Nygård, Magnus Moe; Aarseth, Bjørn Lupton; Otnes, Gaute; Wiig, Marie Syre & Marstein, Erik Stensrud (2025). Towards a cost-priority number for module replacements informed by energy yield time series and infrared thermography data. Full text in Research Archive Show summary

  In this presentation, we combine infrared thermography (IRT) and energy yield time series data to detect thermal signatures in photovoltaic (PV) modules in a 75 MWp PV power plant and assess the associated power loss over nearly a decade of operation in the field. An IRT scan carried out after 5 years of operation reveals that 0.2% of the PV modules in the power plant are affected by thermal signatures which corresponds to a 0.06% reduction in yield from the power plant. Moreover, the power loss associated with thermal signatures seems to develop nonlinearly over time which underlines the importance of continuous monitoring and informed operations and maintenance (O&M) of the power plant. Thus, the results presented is an important contribution to the available literature on degradation mode statistics and the temporal development of their associated power loss. This information is essential to determine a cost-priority number (CPN) and enable a cost-based approach to prioritization of replacements of PV modules suffering from such issues over other O&M tasks.

• Walpita, Harsha Lakmal; Marstein, Erik Stensrud & Aarseth, Bjørn Lupton (2024). Operation & Maintenance of Floating PV Systems. Full text in Research Archive
• Øgaard, Mari Benedikte; Aarseth, Bjørn Lupton; Skomedal, Åsmund; Riise, Heine Nygard; Sartori, Sabrina & Selj, Josefine Helene Krogh (2020). Identifying snow events in PV system data. Full text in Research Archive
• Aarseth, Bjørn Lupton; Øgaard, Mari Benedikte & Marstein, Erik Stensrud (2019). The influence of Nordic conditions on defect formation in photovoltaic systems. Full text in Research Archive
• Øgaard, Mari Benedikte; Aarseth, Bjørn Lupton & Selj, Josefine Helene Krogh (2019). Kan bruke strøm til å smelte snøen på solcellene. Dagens næringsliv. ISSN 0803-9372. Full text in Research Archive
• Nguyen, Phuong Dan; Granerød, Cecilie Skjold; Aarseth, Bjørn Lupton; Bazioti, Kalliopi; Azarov, Alexander & Svensson, Bengt Gunnar [Show all 8 contributors for this article] (2019). Structural and optical properties of individual Zn2GeO4 particles embedded in ZnO. Full text in Research Archive
• Aarseth, Bjørn Lupton & Marstein, Erik Stensrud (2019). Defect Recognition and Power Loss Estimation Using Infrared Thermography. Full text in Research Archive
• Lofstad, Victoria Emilie; Solend, Tor Atle; Øgaard, Mari Benedikte & Aarseth, Bjørn Lupton (2019). Thermal imaging from drones for automatic fault detection in photovoltaic systems. Full text in Research Archive
• Aarseth, Bjørn Brevig; Øgaard, Mari Benedikte; Zhu, Junjie; Strömberg, Tommy; Tsanakas, John A. & Selj, Josefine Helene Krogh [Show all 7 contributors for this article] (2018). Technical assessment of a snow mitigation solution for rooftop PV systems. Full text in Research Archive
• Aarseth, Bjørn Brevig; Øgaard, Mari Benedikte; Zhu, Junjie; Strömberg, Tommy; Tsanakas, John A. & Selj, Josefine Helene Krogh [Show all 7 contributors for this article] (2018). Mitigating Snow on Rooftop PV systems for Higher Energy Yield and Safer Roofs. Full text in Research Archive
• Riise, Heine Nygard; Aarseth, Bjørn Brevig; Kjeldstad, Torunn; Borgersen, Jon Arthur & Olsen, Vegard Skiftestad (2017). Besøk frå deltakarar i Fysikk-OL. Full text in Research Archive
• Bathen, Marianne Etzelmüller; Bergum, Kristin; Ellingsen, Josef Gert Åsheim; Grini, Sigbjørn; Sky, Thomas Neset & Aarseth, Bjørn Brevig (2017). Omvisning for Arendal VGS. Full text in Research Archive
• Granerød, Cecilie Skjold; Zhan, Wei; Aarseth, Bjørn Brevig; Nguyen, Phuong Dan; Johansen, Klaus Magnus H & Vines, Lasse [Show all 7 contributors for this article] (2016). Bandgap measurements by STEM-EELS. Full text in Research Archive
• Granerød, Cecilie Skjold; Zhan, Wei; Aarseth, Bjørn Brevig; Vines, Lasse & Prytz, Øystein (2015). Band gap measurements by STEM EELS. Full text in Research Archive
• Tran, Gia Bao Nguyen; Frausig, Jesper; Ullah, Habib; Marstein, Erik Stensrud & Aarseth, Bjørn Lupton (2024). A comparison of the performance ratio and degradation rate for two industrial scale PV systems in Nordic conditions. Norges miljø- og biovitenskapelige universitet (NMBU). Full text in Research Archive Show summary

  The performance and degradation of photovoltaics is important. To receive investments, the solar bankability of the system must be assessed. A high degradation rate causes the risk to be high, which increases the interest rate, and lowers the chance for adaptation. The methods for the calculation of the performance and degradation are not always compatible however, due to differences in the climate and the weather conditions. In this thesis the performance ratio (PR), corrected performance ratio (CPR) and year on year (YoY) degradation was calculated for two locations in Norway, at ASKO Vestby and ASKO Hedmark. The PR and CPR were calculated using python, and the degradation rate was calculated using a python library called RdTools. To perform the analysis, the data was preprocessed using filters and removing outliers. Most of the time was used to tweak the filters then checking the changes before the data could then be used to calculate the metrics for the analysis. The results show that ASKO Vestby has had a very consistent performance where the yearly Corrected Performance Ratio (CPR) was hovering around 90% for most of the period, with a maximum of 92.5% and minimum of 89.2% for a period of 8 years. The stability of the performance caused the yearly degradation rate overall to be 0.37%. ASKO Hedmarks performance has had higher variance, where the CPR was at around 99% 2018 to 2020 and lowering down to 90% at 2023 with a maximum of 99.3% and minimum of 90% for a period of 6 years. This higher variance, combined with the fact that the performance was surprisingly high for the first years caused the yearly degradation overall to be 1.56%. A quick analysis of the potential effects of the high degradation was also done. The conclusion for this study is that ASKO Vestby is performing well, and slightly better than expectation, and that ASKO Hedmark is still performing decent, even though the degradation seems very high. This is most likely due to the high performance during the early years before it fell to more expected levels. More data is required to see if ASKO Hedmarks performance will stabilize, or if the high rate of degradation continues.

View all works in NVA