Erik Stensrud Marstein

• Nygård, Magnus Moe; Riise, Heine Nygard; Eriksen, Erling Ween & Martsein, Erik Stensrud (2026). Nowcasting based on spatio-temporal string-level power measurements in utility-scale photovoltaic power plants. Solar Energy. ISSN 0038-092X. 310. doi: 10.1016/j.solener.2026.114480. Full text in Research Archive Show summary

  A novel method is proposed to estimate cloud motion vectors (CMVs) from endogenous photovoltaic (PV) power plant energy yield time-series data. The method is tested using three months of 1-min mean aggregated power output data collected from 8000+ string-sets in a 150+ MW PV power plant. The CMVs are used as input to a cloud speed persistence PV power forecast which is benchmarked against a smart persistence PV power forecast. Forecasts issued for the entire power plant achieve an overall forecast skill of 0.16 at a forecast horizon of 1-min. If the forecast is issued for smaller sections of the power plant with foresight provided by the remaining sections, an increase in forecast skill up to 0.47 is demonstrated. The results emphasize the potential that can be unlocked if highly resolved spatio-temporal energy-yield time-series data are coupled with exogenous data, for instance, captured through satellite imagery and all-sky imagers.

• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Lindholm, Dag; Bonesmo, Helge & Riise, Heine Nygard (2025). Wind sheltering in vertical agrivoltaics can increase crop yields: A modeling study for Northern Europe. Energy Nexus. 19. doi: 10.1016/j.nexus.2025.100516. Full text in Research Archive Show summary

  Vertical agrivoltaics can help reduce land use competition by integrating food crop cultivation between rows of vertical solar panels. However, its agricultural viability is often questioned due to panel shading. This study demonstrates that wind sheltering from vertical solar panels not only can compensate for the shading losses but lead to net-positive yield changes in Northern Europe. Crops benefit from wind shelter through improved soil moisture retention, higher ambient temperatures, and protection from wind erosion and damage. This study quantified the combined shading and wind sheltering effects on timothy grass (Phleum pratense L.) yields within large-scale vertical agrivoltaics across Norway, Sweden, and Finland. Our modeling framework integrated ERA5 weather data (2010–2023), Computational Fluid Dynamics for wind simulation (OpenFOAM), ray tracing for shading analysis (Honeybee Radiance), and a crop growth simulation model (CATIMO). Additionally, ERA5 temperature data was adjusted to explore shelter-induced warming effects. In the simulation, vertical agrivoltaics decreased ground irradiation by 15–16 % and reduced seasonal mean crop zone wind speeds by up to 40 % (up to 88 % for perpendicular winds), lowering evapotranspiration. When combining shading, wind reduction, and a conservative +0.5 ◦C shelter-induced temperature increase, the model predicted an average regional yield increase of +2.4 % compared to traditional agriculture. Yield improvements were highest in drought-prone soils (+3.7 %) and dry, sunny years (e.g., +9.2 % in 2018). This suggests that vertical agrivoltaics improves agricultural resilience under challenging conditions. These findings demonstrate that agrivoltaic modeling, particularly for vertical systems, should incorporate wind shelter effects to avoid fundamentally underestimating crop yield potential.

• Lofstad-Lie, Victoria; Simonsen, Aleksander; Nygaard, Tønnes & Marstein, Erik Stensrud (2025). Data Quality Analyses for Automatic Aerial Thermography Inspection of PV Power Plants. IEEE Journal of Photovoltaics. ISSN 2156-3381. 15(5), p. 722–731. doi: 10.1109/JPHOTOV.2025.3587297. Full text in Research Archive
• Nygård, Magnus Moe; Wiig, Marie Syre; Roosloot, Nathan Abel; Otnes, Gaute; Øgaard, Mari & Riise, Heine Nygard [Show all 7 contributors for this article] (2025). Elucidating uncertainty in bifacial photovoltaic gain estimation. Solar Energy. ISSN 0038-092X. 292, p. 1–12. doi: 10.1016/j.solener.2025.113469. Full text in Research Archive Show summary

  The bifacial gain of fielded bifacial photovoltaic (PV) systems is commonly estimated by comparing the energy yield of the system with that of a monofacial reference. However, this approach is dependent on the selected reference, and can thus be associated with significant uncertainty, since the two technologies might have very different properties. This study investigates the significance of such differences when the bifacial gain is estimated from energy yield time series data. A series of corrections are applied to account for differences in installed capacity and responses with respect to temperature and irradiance. The analysis is carried out using data collected over two years from a 22.6 kWp ground-mounted fixed-tilt PV system in Norway using four different monofacial technologies as reference systems that all rely on Si as the active material but have different cell architectures. With no corrections applied, the estimated bifacial gain with the monofacial technology that most closely resembles the bifacial is determined to 12.6 % for the two-year period considered. The estimate increases to 13.1 % when correcting for irradiance and 14.4 % when also correcting for temperature. The results demonstrate that the applied corrections reduces the range between the smallest and largest estimate of the bifacial gain from 6.3 to 3.5 percentage points. Although it is possible that the range can be reduced further if differences in spectral response and degradation are accounted for, it should also be expected that some of the remaining variation reflects the measurement uncertainty inherent to this method of estimating the bifacial gain.

• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Nygård, Magnus Moe; Wiig, Marie Syre & Riise, Heine Nygard (2025). Benchmarking irradiation models for photovoltaic applications: A comparative analysis of radiance-based tools. Solar Energy. ISSN 0038-092X. 296. doi: 10.1016/j.solener.2025.113566. Full text in Research Archive Show summary

  This study compared the accuracy, efficiency, and capabilities of three ray tracing tools—bifacial_radiance, ClimateStudio, and Honeybee Radiance—in modeling irradiance for photovoltaic (PV) systems. Despite similar performance in modeling hourly irradiance and monthly and annual cumulative irradiation levels, the tools exhibited differences in functionalities and computational efficiency. All models estimated cumulative annual front irradiation within 1.3% of measured values, with bifacial_radiance showing the largest error. For rear side irradiance, bifacial_radiance, ClimateStudio, and Honeybee Radiance underestimated irradiance by 2.82%, 5.40% and 8.74%, respectively. bifacial_radiance showed the highest model stochasticity in cumulative simulations due to its reliance on a single cumulative sky model. In contrast, ClimateStudio and Honeybee Radiance employ matrix-based approaches with hourly resolution within the period, averaging out stochasticity and making them more dependable for precise cumulative irradiation values. These matrix-based methods also significantly enhanced time-series analysis efficiency by modeling yearly irradiance with hourly resolution faster than bifacial_radiance analyzes a single point-in-time, while maintaining similar hourly error and bias levels. However, bifacial_radiance exhibited lower model stochasticity in hourly simulations. Enabled by the efficient simulation capabilities of ClimateStudio and Honeybee Radiance, a method for improving rear side irradiance modeling was tested. By combining simulations with different ground albedo values, this approach significantly reduced error and bias in rear side irradiance modeling. Ultimately, the choice of tool depends on study requirements, with bifacial_radiance being advantageous for hourly and sub-hourly resolution in short-term analyzes, while ClimateStudio and Honeybee Radiance are better suited for cumulative and extended time-series analyzes.

• 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.

• 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
• Klyve, Øyvind Sommer; Grab, Robin; Olkkonen, Ville & Marstein, Erik Stensrud (2024). Influence of high-resolution data on accurate curtailment loss estimation and optimal design of hybrid PV–wind power plants. Applied Energy. ISSN 0306-2619. 372, p. 1–13. doi: 10.1016/j.apenergy.2024.123784. Full text in Research Archive Show summary

  Hybrid photovoltaic (PV) - wind power plants (HyPPs), i.e., where the PV and wind systems are co-located and share the Point of Interconnection (POI) with the grid, have recently attracted more attention. This trend is driven by the expected reduced capital and operational expenditures achieved through, e.g., shared land and POI infrastructure for HyPPs compared to two individual PV and wind installations. However, if the POI is underdimensioned relative to the PV and wind capacities, the generation from either or both of the assets must at times be curtailed, unless mitigated by solutions like energy storage. This curtailment might lead to income losses. Moreover, as HyPPs typically are designed using wind and PV generation data on hourly resolution, the actual curtailment losses can be underestimated. This might in turn lead to HyPP designs which are techno-economically sub-optimal. In this study, a comparative analysis is conducted to analyze how the curtailment and income loss estimations for HyPPs, as well as the techno-economic optimal HyPP topologies, are impacted by varying the input data time resolution. One year of site measured PV and wind power generation data on 5 s resolution from an existing HyPP located in Eastern Germany are used as basis for the study. For a HyPP topology with an undersized POI, where the installed capacities of the POI, PV, and wind systems are all equal, the curtailment losses are estimated to be 1.45%, 1.43% and 1.09% using the 5 s, 1 min and 1 h resolution datasets, respectively. Moreover, using the 1 h instead of the 1 min dataset leads to a 1.86% overestimation of the total Net Present Value (NPV) for this HyPP topology. As the shares of the PV and wind systems increase relative to the POI capacity, the differences in the estimation of the curtailment losses and NPVs between the high- and low-resolution datasets become more significant.

• Klyve, Øyvind Sommer; Olkkonen, Ville; Nygård, Magnus Moe; Lingfors, David; Marstein, Erik Stensrud & Lindberg, Oskar (2024). Retrofitting wind power plants into hybrid PV–wind power plants: Impact of resource related characteristics on techno-economic feasibility. Applied Energy. ISSN 0306-2619. 379. doi: 10.1016/j.apenergy.2024.124895. Full text in Research Archive Show summary

  The concept of hybrid power plants (HPPs), wherein co-located solar photovoltaic (PV) and wind assets share a common point of interconnection (POI) with the grid, is gaining traction. The wind and solar resources can be anti-correlated, and this opens for oversizing the capacity of these HPPs relative to their nominal POI capacity while ensuring low curtailment losses. Thus, retrofitting existing wind power plants into PV-wind HPPs can be a promising strategy in regions where access to the grid is a barrier to capacity expansion. However, it is not clear how the resource availability and anti-correlation of the solar and wind resources at a given location impact the techno-economic feasibility for retrofitting an existing wind power plant with PV capacity. In this study, 128 existing wind power plants in Norway and Sweden were assessed for retrofitting with PV using a techno-economic model, measured wind power and modeled PV power generation data. Multiple linear regression (MLR) analysis was applied to the resulting cost-optimal HPPs in order to determine which of a site’s resource characteristics that are influencing the feasibility of such retrofitting, and to what extent. The results suggests that the top three key characteristics sorted in order of decreasing importance are: (i) high mean PV capacity factors, (ii) low mean wind capacity factors and (iii) strong anti-correlation between the hourly PV and wind power generation. The results thus demonstrate that developers aiming to retrofit wind power plants with PV capacity should target those located in areas with high solar irradiance and performing badly, i.e., with low wind capacity factors, rather than prioritizing wind power plants at sites with strong anti-correlation between the PV and wind generation. Finally, it is demonstrated how the analysis framework can be used as a screening tool, i.e., as a means of predicting the techno-economic potential for PV retrofitting, also for wind power plants where power generation time series are unavailable.

• Nøvik, Hanne; Krogh, Espen; Stokke, Maria Kristina; Marstein, Erik Stensrud; Kong, Jiehong & Ramos, Daryl Homer (2023). The challenge of a real, complex hybrid project, 22nd Wind and Solar Integration Workshop - WIW 2023. IET Digital Library. ISSN 9781839539664. p. 308–315. doi: 10.1049/icp.2023.2753. Full text in Research Archive Show summary

  This paper explores the implementation process of a hybrid power plant project (HyPP) in the Philippines' deregulated and complex energy market. SN Aboitiz Power (SNAP) owns and operates the Magat HyPP which involves integrating a 388 MW hydropower plant with a 24 MW/32 MWh battery system and a 280 kW pilot floating solar (FPV), planned for expansion. Scatec ASA, OceanSun and Prediktor, with support from the research partners IFE and SINTEF Energy Research, are contributing to the development of Magat HyPP under the HydroSun innovation program with financial support from Innovation Norway and the Research Council of Norway. No regulatory framework exists in the Philippines for implementing FPV or HyPPs. During the development of Magat HyPP, it was uncovered that 50 permits and agreements were required to implement the project. Ocean Sun, the FPV system supplier used methodologies for design and verification from offshore aquaculture and has thus ensured insurable guaranties for the installations. Prediktor has developed an Energy Management System for real-time hybrid optimization. The value creation potential from Magat HyPP is assessed with the Short-term Hydro Optimization Program (SHOP) developed by SINTEF. The results indicate that the annual revenue can increase by 4 % under a hybrid power purchase agreement compared to standalone production.

• Vázquez-López, Antonio; García-Carrión, Marina; Maestre, David; Karazhanov, Smagul; Marstein, Erik Stensrud & Mendez, Bianchi [Show all 7 contributors for this article] (2023). UV and aging effect on the degradation of PEDOT:PSS/nSi films for Hybrid Silicon solar cells. Polymer degradation and stability. ISSN 0141-3910. 209. doi: 10.1016/j.polymdegradstab.2023.110272. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Bonesmo, Helge; Marstein, Erik Stensrud; Völler, Steve & Riise, Heine Nygard (2023). Autonomous Optimization of Agrivoltaic Systems With Vertical Bifacial PV Panels and the Grass Crop Timothy. EU PVSEC 2023. doi: 10.4229/EUPVSEC2023/4BV.3.13. Full text in Research Archive
• Nygård, Magnus Moe; Skomedal, Åsmund; Wiig, Marie Syre & Marstein, Erik Stensrud (2023). Combined Degradation and Soiling With Validation Against Independent Soiling Station Measurements. IEEE Journal of Photovoltaics. ISSN 2156-3381. 13(2), p. 296–304. doi: 10.1109/JPHOTOV.2023.3239752. Full text in Research Archive
• Fagerström, Jonathan; Das, Soumya; Klyve, Øyvind Sommer; Olkkonen, Ville & Marstein, Erik Stensrud (2023). Profitability of battery storage in hybrid hydropower–solar photovoltaic plants. Journal of Energy Storage. ISSN 2352-152X. 77. doi: 10.1016/j.est.2023.109827. Full text in Research Archive Show summary

  Increased energy demand and rapid environmental changes triggered by global greenhouse gas emissions have forced numerous countries to consider renewable energy sources (RES) as possible alternatives to conventional fossil-fuel energy sources. Due to the inherent uncertainty, intermittency, and generally uncontrollable power generation by single-source renewable power plants, hybrid power plants (HPPs) incorporating several mutually complementary RES have lately gained much interest. Integrating battery storage systems with such HPPs has the potential to run them more similarly to conventional fossil-fueled power plants, providing controllable power generation, and reducing its variability. Given such a future scenario and the lack of existing detailed studies, this paper investigates the profitability potential for a viable business case for battery storage integration with utility-scale hybrid hydropower–solar photovoltaic (PV) plants. The study presented here is based on a hypothetical, two-reservoir cascaded hydropower plant in Sub-Saharan Africa. The role of the battery is assessed by considering the overall profitability of the HPP when participating in capacity markets, ancillary services, and energy arbitrage. The relationship between the value stacking of battery services and its impact on battery life has been critically examined. This study provides estimates on increased profitability, cost-optimal battery capacities, battery degradation estimates, and the HPP-battery interoperability aspects under various hydropower and electricity market operating scenarios. Batteries will likely increase cost-effectiveness by co-optimization with PV-system as well as power market contracts. In this case, adding a battery increased the profitability by about 2% when combining revenues from capacity markets and ancillary services.

• Klyve, Øyvind Sommer; Klæboe, Gro; Nygård, Magnus Moe & Marstein, Erik Stensrud (2023). Limiting imbalance settlement costs from variable renewable energy sources in the Nordics: Internal balancing vs. balancing market participation. Applied Energy. ISSN 0306-2619. 350, p. 1–12. doi: 10.1016/j.apenergy.2023.121696. Full text in Research Archive Show summary

  Due to the market gate closures in the Nordic energy markets, producers with variable renewable energy (VRE) assets, e.g., PV and wind power plants, must forecast their production prior to delivery, leaving room for significant forecast errors. These forecast errors can lead to imbalances between the contractual market agreements and physical delivery, which have to be financially accounted for through the imbalance settlement. The increasing shares of VREs in the Nordic energy mix and the increasing variability in the price of regulating the imbalances, can lead to potential large revenue losses for the producers. This study investigates how different producer balancing strategies can limit the uncertainty and potential revenue losses in the imbalance settlement. The study focuses on available balancing measures the producers are able to use in the period starting from the last energy market gate closure, i.e., the manual Frequency Restoration Reserve (mFRR, tertiary reserves) balancing market, and throughout the subsequent settlement period. During this settlement period, producers have the option within the Nordic imbalance settlement framework to prevent VRE imbalances by performing internal balancing, i.e., ramping up or down their dispatchable assets which are located in the same bidding area as the VRE assets. However, this study shows both theoretically and quantitatively that such internal balancing is not economically beneficial compared to offering this regulating energy to the mFRR market.

• Klyve, Øyvind Sommer; Nygård, Magnus Moe; Riise, Heine Nygard; Fagerström, Jonathan & Marstein, Erik Stensrud (2023). The value of forecasts for PV power plants operating in the past, present and future Scandinavian energy markets. Solar Energy. ISSN 0038-092X. 255, p. 208–221. doi: 10.1016/j.solener.2023.03.044. Full text in Research Archive Show summary

  When participating in the Scandinavian wholesale energy markets with intermittent PV power, imbalances between market-committed and actual energy generation need to be economically accounted for in the imbalance settlement. The market-committed energy is based on forecasts issued at specific timestamps defined by the market. The economic value of such forecasts can be quantified for the past, present and future energy market regulations by comparing the achieved income using perfect forecasts to the income with imperfect forecasts. Differences between these regulations include changing from 60 min to 15 min market intervals, and from a dual-price to a single-price imbalance settlement structure. PV power production data were modelled from meteorological measurements carried out at 11 locations in each of the Nord Pool bidding areas. Forecasts generated from a smart persistence model and a more sophisticated numerical weather prediction (NWP) model were compared for these locations, and the value of these forecasts was estimated from historical market data for each of the 11 bidding areas. The results show that the estimated income, and income losses, are dependent on the electricity mix of the bidding areas. In addition, the transition from the dual-price to the single-price imbalance settlement structure reduces the value of providing accurate forecasts. Moreover, the added incentive to provide accurate forecasts when settling the markets and imbalances on 15 min instead of 60 min intervals is negligible with the single-price imbalance settlement. Finally, the results show that intraday trading is generally beneficial for PV power plants in Scandinavia.

• Wiig, Marie Syre; Søndenå, Rune; Marstein, Erik Stensrud & Haug, Halvard (2022). Identifying defect parameters for common recombination centers in multicrystalline silicon by temperature and injection dependent lifetime spectroscopy. In Brendel, Rolf; Ballif, Christophe; Dubois, Sebastien; Glunz, Stefan; Hahn, Giso; Poortmans, Jeff; Verlinden, Pierre & Weeber, Arthur (Ed.), SiliconPV 2021, The 11th International Conference on Crystalline Silicon Photovoltaics. AIP Publishing (American Institute of Physics). ISSN 9780735443624. doi: 10.1063/5.0090236. 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
• Sørby, Magnus Helgerud; Martinsen, Fredrik Aleksander; Karazhanov, Smagul; Hauback, Bjørn Christian & Marstein, Erik Stensrud (2022). On the Crystal Chemistry of Photochromic Yttrium Oxyhydride. Energies. 15(5). doi: 10.3390/en15051903. Full text in Research Archive
• Martinsen, Dina C.; Øgaard, Mari; Nygård, Magnus Moe; Wiig, Marie Syre; Sabatino, Marisa Di & Marstein, Erik Stensrud [Show all 7 contributors for this article] (2022). Evaluation of Irradiance Decomposition and Transposition Models for a Nordic Climate. Proceedings of the European Photovoltaic Solar Energy Conference. ISSN 2196-100X. doi: 10.4229/WCPEC-82022-4BV.4.22. Full text in Research Archive
• Lofstad-Lie, Victoria; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2022). Cost-Effective Flight Strategy for Aerial Thermography Inspection of Photovoltaic Power Plants. IEEE Journal of Photovoltaics. ISSN 2156-3381. 12(6). doi: 10.1109/JPHOTOV.2022.3202072. Full text in Research Archive Show summary

  Thermography from unmanned aerial vehicles (UAV) is widely used for module condition surveys and defect detection in solar (photovoltaic) power plants. This article presents an optimized defect inspection procedure in which a two-stage autonomous flight strategy is adopted to reduce the operation time, and thereby the cost. The first stage is a fast high-altitude flight for rapid coverage of the entire plant. The resolution on the modules is then somewhat degraded, but adequate for detection of possible defect locations. In the second stage, an optimized flight path is calculated to revisit and image only the detected locations from a lower altitude, where the resolution is sufficient for the classification of defects. This concept is studied through simulations of different plant geometries and defect densities. The simulations are supported by actual data, including a plant-scale survey. The proposed strategy is shown to have the potential for significant savings in operation time, on the order of 60% in the experimental case with 2% module defects. Commonly reported defect densities of 0.5% to 1% will give even larger savings. The inspection strategy is shown to be especially beneficial for plant geometries representative of high latitudes.

• Brandsrud, Maren Anna; Blümel, Reinhold; Lukacs, Rozalia; Seim, Eivind; Marstein, Erik Stensrud & Olsen, Espen [Show all 7 contributors for this article] (2021). Investigation of resonance structures in optically thin solar cells. Journal of Photonics for Energy. 11(2). doi: 10.1117/1.JPE.11.024501. Full text in Research Archive Show summary

  To reduce costs, the solar cell industry aims at producing thinner solar cells. Structuring the surfaces of optically thin devices is important for avoiding transmission-related losses and, hence, increasing their efficiency. Light trapping leads to longer optical pathlengths and increased absorption of energy. In addition, resonances in the nanostructures enhance the absorption in the energy-converting material. Further, resonances in periodic structures may couple with each other and thereby increase the absorption. Here, we establish a model system consisting of a multilayered solar cell to study resonances and coupling of resonances in a one-dimensional system. We show that resonances in energy-converting and nonenergy converting layers exist, evaluate the resonances and the coupling of resonances in different thin-film systems, and show how they affect the total absorption of energy in the energy-converting layer. We optimize the parameters of the multilayered thin-film systems to achieve an increase in the amount of the absorbed energy. We find that resonances in nonabsorbing material at the top may lead to absorption enhancement, while we cannot find any enhancement effect due to the coupling of resonances.

• Lindholm, Dag; Kjeldstad, Torunn; Selj, Josefine; Marstein, Erik Stensrud & Fjær, Hallvard Gustav (2021). Heat loss coefficients computed for floating PV modules. Progress in Photovoltaics. ISSN 1062-7995. 29(12), p. 1262–1273. doi: 10.1002/pip.3451. Full text in Research Archive
• Seim, Eivind; Kohler, Achim; Lukacs, Rozalia; Brandsrud, Maren Anna; Marstein, E.S. & Olsen, Espen [Show all 7 contributors for this article] (2021). Wave chaos enhanced light trapping in optically thin solar cells. Chaos. ISSN 1054-1500. 31(6), p. 1–17. doi: 10.1063/5.0049330. Full text in Research Archive Show summary

  Enhancing the energy output of solar cells increases their competitiveness as a source of energy. Producing thinner solar cells is attractive, but a thin absorbing layer demands excellent light management in order to keep transmission- and reflection-related losses of incident photons at a minimum. We maximize absorption by trapping light rays to make the mean average path length in the absorber as long as possible. In chaotic scattering systems, there are ray trajectories with very long lifetimes. In this paper, we investigate the scattering dynamics of waves in a model system using principles from the field of quantum chaotic scattering. We quantitatively find that the transition from regular to chaotic scattering dynamics correlates with the enhancement of the absorption cross section and propose the use of an autocorrelation function to assess the average path length of rays as a possible way to verify the light-trapping efficiency experimentally. Classical chaotic scattering leads to trapped rays with long lifetimes, which are of importance in improving light management for more efficient solar cells. In this paper, we study the wave dynamics in solar-cell models with proven chaotic dynamics on the classical level. We show a connection between the emergence of wave chaos and the enhancement of absorption efficiency due to light trapping.

• Skomedal, Åsmund; Øgaard, Mari Benedikte; Haug, Halvard & Marstein, Erik Stensrud (2021). Robust and Fast Detection of Small Power Losses in Large-Scale PV Systems. IEEE Journal of Photovoltaics. ISSN 2156-3381. 11(3), p. 819–826. doi: 10.1109/JPHOTOV.2021.3060732. Full text in Research Archive Show summary

  Due to the fast growth in global installed photovoltaic (PV) capacity, performance monitoring for large-scale PV systems is an increasingly relevant and important topic. A large volume of research exists in this field, but there is a need for comparison of different methods and their performance toward relevant metrics, a broad discussion of the different choices involved, and subsequent consolidation. In this article, we focus on the detection of small power losses on string-level. We discuss the different choices involved in building a robust string performance monitoring scheme. We suggest the following approach: 1) identify bad data quality and do data-filtering; 2) calculate the daily specific yield on string level; 3) calculate the relative difference in specific yield between the strings (relative yield); 4) identify historical faults; 5) correct for seasonal variations; and 6) apply control charts to detect performance losses in new data and issue alarms/report to the system operators. Based on data from a utility scale PV power plant we compare different control charts in terms of detection time and sensitivity. We show that the cumulative sum (CUSUM) median and the Tukey-CUSUM charts are the most promising fault detection methods of the ones we have tested. We can robustly detect faults causing a performance loss of about 1% within 35 days of the drop in performance.

• Lofstad-Lie, Victoria; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2021). Cost-effective flight strategy for aerial thermography inspection of photovoltaic power plants. In Angus, Rockett (Eds.), 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781665419222. p. 0023–0025. doi: 10.1109/PVSC43889.2021.9518710. Full text in Research Archive Show summary

  Thermography from an unmanned aerial vehicle (UAV) offers efficient fault inspection in solar parks. This paper presents an optimized fault detection procedure, including a two-stage autonomous flight strategy. The first stage images the entire park quickly at low resolution, flying fast at high altitude to detect possible faults. In the second stage, the detections are imaged at higher resolution, by flying an optimized path at lower altitude, for fault classification. Based on actual data, including a park-scale survey, this strategy is shown to have potential for significant savings in operation time, on the order of 70% or more, at realistic fault densities.

• Roosloot, Nathan; Neder, Verena; Haug, Halvard; You, Chang Chuan; Polman, A. & Marstein, Erik Stensrud (2021). Broadband angular color stability of dielectric thin film-coated pyramidal textured Si for photovoltaics. Journal of Applied Physics. ISSN 0021-8979. 129. doi: 10.1063/5.0048102. Full text in Research Archive
• Brandsrud, Maren Anna; Blümel, Reinhold; You, Chang Chuan; Marstein, Erik Stensrud; Seim, Eivind & Lukacs, Rozalia [Show all 8 contributors for this article] (2021). An exact ray model for oblique incident light on planar films. Physica. E, Low-Dimensional systems and nanostructures. ISSN 1386-9477. 126. doi: 10.1016/j.physe.2020.114374. Full text in Research Archive Show summary

  During recent years, ray tracing has frequently been used to study the absorption characteristics of structured solar cells. However, wave properties such as absorption enhancement due to resonances in optically thin solar films, cannot be explained by pure classical ray models. Here we present an exact three-dimensional ray model for oblique incidence of a plane electromagnetic wave on a thin film and show that the resonant structure of the absorption cross section calculated from our ray model is identical to exact calculations by electromagnetic wave theory. Both parallel and perpendicular polarized light are described exactly by the ray model presented. We validate the resonant structure of the absorption cross section of our ray model by an experimentally realized layered film, where we obtain perfect agreement between experiment and theory. We demonstrate further that for a beam with a finite beam waist, in accordance with Beer-Lambert's law, absorption occurs along the path of the beam, while, in the case of a plane wave incident on an optically thin film, and contrary to Beer-Lambert's law, absorption occurs along the axis perpendicular to the surface of the film.

• Kjeldstad, Torunn; Lindholm, Dag; Marstein, Erik & Selj, Josefine (2021). Cooling of floating photovoltaics and the importance of water temperature. Solar Energy. ISSN 0038-092X. 218, p. 544–551. doi: 10.1016/j.solener.2021.03.022. Full text in Research Archive
• Adler, Scott W.; Wiig, Marie Syre; Skomedal, Åsmund; Haug, Halvard & Marstein, Erik Stensrud (2020). Degradation analysis of utility-scale PV plants in different climate zones. IEEE Journal of Photovoltaics. ISSN 2156-3381. 11(2), p. 513–518. doi: 10.1109/JPHOTOV.2020.3043120. Full text in Research Archive
• Vázquez-López, Antonio; Yaseen, Anisa; Maestre, David; Ramírez-Castellanos, Julio; Marstein, Erik Stensrud & Karazhanov, Smagul [Show all 7 contributors for this article] (2020). Synergetic Improvement of Stability and Conductivity of Hybrid Composites formed by PEDOT:PSS and SnO Nanoparticles. Molecules. ISSN 1431-5157. 25(3). doi: 10.3390/molecules25030695. Full text in Research Archive
• Moldarev, Dimitrii; Taeno, M.; Maestre, David; Cremades, A.; Karazhanov, Smagul & Marstein, Erik Stensrud (2020). Electrical and optical properties of composite PEDOT:PSS-based thin films with NiO nanoparticles. Materials Today: Proceedings. 33, p. 2499–2502. doi: 10.1016/j.matpr.2020.04.549. Full text in Research Archive

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• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Bonesmo, Helge; Lindholm, Dag; Rizzi, Jonathan & Riise, Heine Nygard (2026). Vertical Agrivoltaic Systems Support Crop Growth. Full text in Research Archive
• 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.

• Marstein, Erik Stensrud (2025). Solkraft som eksportnæring - hvor står vi? Full text in Research Archive
• Marstein, Erik Stensrud (2025). Solenergi for fremtiden - Insentiver for høsting på næringsbygg. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Fra vekst til bråstopp - Hvor skal den norske solbransjen? Glass og fasade. ISSN 0802-295X. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Leker seg med BIPV. Glass og fasade. ISSN 0802-295X. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Mer solstøtte i Oslo. [Journal]. Elmagasinet. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Norge på jumboplass på sol globalt. [Journal]. Montel News. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Solkraft kan bli Norges neste store eksporteventyr. [Journal]. EnergiAktuelt. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Forskningssenteret FME SUSOLTECH. Glass og fasade. ISSN 0802-295X. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Mystiske funn i solkraftanlegg skaper uro. [Journal]. NrK . Full text in Research Archive
• Marstein, Erik Stensrud (2025). Slik rammer finansstormen solbransjen. [Internet]. Energi og klima. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Solkraft i Norge og FME SOLAR. Glass og fasade. ISSN 0802-295X. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Verden blir mer og mer soldrevet. [Journal]. forskning.no. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Mer areal brukes til golfbaner enn til sol- og vindkraft i flere land. [Journal]. forskning.no. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Verden blir soldrevet - himla fort. [Journal]. Titan. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Forsker advarer: Norge henger etter i den globale solkraftrevolusjonen. [Journal]. ITB Aktuelt. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Håper batteriløsninger kan redde solkraftmarkedet. [Journal]. NrK Innlandet. Full text in Research Archive
• Marstein, Erik Stensrud & Selj, Josefine Helene Krogh (2025). Roadmap for the Norwegian PV industry. Full text in Research Archive
• Marstein, Erik Stensrud (2025). The Norwegian PV industry. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Norsk forskningssenter for solkraft. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Veikart for norsk solbransje mot 2030. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Status for solkraft og BIPV. Full text in Research Archive
• Marstein, Erik Stensrud (2025). En kort oppdatering fra solindustrien. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Status og potensial for solkraft i Norge. Full text in Research Archive
• Marstein, Erik Stensrud; Klyve, Øyvind Sommer; Nygård, Magnus Moe; Olkkonen, Ville & Riise, Heine Nygard (2025). Quantifying the Benefits of Hybrid PV-wind Power Plants. Full text in Research Archive
• Marstein, Erik Stensrud; Fagerström, Jonathan; Ollas, Patrik & Archer, Dan-Eric (2025). Assessing Cold-Weather Reliability of PV + BESS. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Solbransjen som eksportindustri. Full text in Research Archive
• Marstein, Erik Stensrud (2025). FME SUSOLTECH – Hva fikk vi til? Full text in Research Archive
• Marstein, Erik Stensrud (2025). Reliability of PV + BESS. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Batterisystemenes rolle. Full text in Research Archive
• Marstein, Erik Stensrud (2025). The state of the PV industry in 2025. Full text in Research Archive
• Marstein, Erik Stensrud (2025). FME SUSOLTECH – What did we achieve? Full text in Research Archive
• Marstein, Erik Stensrud (2025). The solar (PV) industry. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Design and optimization of hybrid PV + wind power plants. Full text in Research Archive
• Marstein, Erik Stensrud (2025). FME SOLAR in a nutshell. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Reliability of PV + BESS. Full text in Research Archive
• Marstein, Erik Stensrud (2025). Reliability of PV + BESS. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Mehlhoop, Anne Catriona; Skrindo, Astrid Brekke; Solstad, Heidi & Riise, Heine Nygard (2025). Microclimate and Biodiversity Measurements in Norway’s First East-West Tilted Agrivoltaic System. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Walpita, Harsha Lakmal; Nysted, Vilde Stueland; Marstein, Erik Stensrud; Selj, Josefine Helene Krogh & Riise, Heine Nygard (2025). Satellite Analysis of Floating PV Construction and Extreme Weather Resilience. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2025). Modellering og validering av avling i vertikale solparker. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2025). Modeling and validation of crop yields in vertical solar parks. Full text in Research Archive
• Walpita, Harsha Lakmal; Marstein, Erik Stensrud & Aarseth, Bjørn Lupton (2024). Operation & Maintenance of Floating PV Systems. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Riise, Heine Nygard; Kjeldstad, Torunn; Marstein, Erik Stensrud; Stokkan, Gaute & Randle-Boggis, Richard [Show all 10 contributors for this article] (2024). Fordeler med solkraftverk på jord- og skogbruksarealer. Bondebladet. ISSN 0332-8414. Full text in Research Archive
• Klyve, Øyvind Sommer; Olkkonen, Ville; Nygård, Magnus Moe; Lingfors, David; Marstein, Erik Stensrud & Lindberg, Oskar (2024). Identifying wind power plants suitable for being retrofitted with PV capacity into PV-wind hybrids. Full text in Research Archive
• Klyve, Øyvind Sommer; Grab, Robin; Olkkonen, Ville & Marstein, Erik Stensrud (2024). Enhancing Accuracy in Curtailment Loss and Profitability Predictions for Oversized Hybrid PV-Wind Power Plants Using High, Instead of Hourly, Resolution Data. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2024). Microclimatic Changes in Norwegian Solar Power Systems. Full text in Research Archive
• Milani, Simone; Marstein, Erik Stensrud; Honningdalsnes, Erlend Hustad & Riise, Heine Nygard (2024). Water Reduction Potential for Olive Orchards within AgriPV Systems in Southern Italy. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Lindholm, Dag; Bonesmo, Helge & Riise, Heine Nygard (2024). Reducing Wind Speeds and Boosting Agricultural Productivity with Vertical Bifacial Solar Panels. Full text in Research Archive
• Klyve, Øyvind Sommer; Olkkonen, Ville; Nygård, Magnus Moe; Lingfors, David; Marstein, Erik Stensrud & Lindberg, Oskar (2024). Tilknytt solkraft til eksisterende vindkraftverk – utnytt nettilkoblingspunktene med begrensede tap. Full text in Research Archive
• Kjeldstad, Torunn; Selj, Josefine Helene Krogh; Otnes, Gaute; Roosloot, Nathan Abel; Nysted, Vilde Stueland & Marstein, Erik Stensrud [Show all 8 contributors for this article] (2023). Quantifying module level stressors in floating PV systems. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2023). The Effect of PV Panels on Microclimatic Growth Conditions and Crop Yield in Agrivoltaic Systems. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Bonesmo, Helge; Marstein, Erik Stensrud; Völler, Steve & Riise, Heine Nygard (2023). Autonomous Optimization of Agrivoltaic Systems - A Case Study on Grass and Vertical Bifacial PV. Full text in Research Archive
• Klyve, Øyvind Sommer; Klæboe, Gro; Nygård, Magnus Moe & Marstein, Erik Stensrud (2023). Limiting imbalance settlement costs from variable renewable energy sources in the Nordics - Internal balancing vs. balancing market participation. Full text in Research Archive
• Klyve, Øyvind Sommer; Nygård, Magnus Moe; Riise, Heine Nygard; Fagerström, Jonathan & Marstein, Erik Stensrud (2023). What is the economic value of solar power forecasts in energy markets? - Scandinavian case study. Full text in Research Archive
• Wiig, Marie Syre; Nygård, Magnus Moe & Marstein, Erik Stensrud (2023). Impact of albedo variations and sensor positions on rear irradiance for bifacial power plants. Full text in Research Archive
• Nygård, Magnus Moe; Skomedal, Åsmund; Wiig, Marie Syre & Marstein, Erik Stensrud (2022). Combined Degradation and Soiling (CODS) With Validation Against Independent Soiling Station Measurements. Full text in Research Archive
• Nygård, Magnus Moe; Klyve, Øyvind Sommer; Riise, Heine Nygard; Fagerström, Jonathan; Selj, Josefine Helene Krogh & Marstein, Erik Stensrud (2022). The value of PV forecasts in the current and future Scandinavian energy market. Full text in Research Archive
• Martinsen, Dina C.; Øgaard, Mari; Nygård, Magnus Moe; Wiig, Marie Syre; Sabatino, Marisa Di & Marstein, Erik Stensrud [Show all 7 contributors for this article] (2022). Evaluation of irradiance decomposition and transposition models for a Nordic climate. Full text in Research Archive
• Klyve, Øyvind Sommer; Haaskjold, Kristina; Olkkonen, Ville; Fagerström, Jonathan & Marstein, Erik Stensrud (2022). Technoeconomic optimization model for utility-scale FPV/hydro power plants. Full text in Research Archive
• Lofstad-Lie, Victoria Emilie; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2021). Cost-Effective Flight Strategy for Aerial Thermography Inspection of Photovoltaic Power Plants. Full text in Research Archive
• Nygård, Magnus Moe; Wiig, Marie Syre; Otnes, Gaute; Roosloot, Nathan Abel; Riise, Heine Nygard & Øgaard, Mari [Show all 7 contributors for this article] (2021). Bifacial Gain In Nordic Conditions. Full text in Research Archive
• Hultgreen, Liv Randi; Kallbekken, Steffen; Marstein, Erik Stensrud; Tomasgard, Asgeir & Winther, Tanja (2020). Krisepakker som forsterker krisen. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Riise, Heine Nygard & Marstein, Erik Stensrud (2026). Vertical agrivoltaic systems: Modeling, optimization, and monitoring - With special emphasis on northern climates. Universitetet i Oslo. Full text in Research Archive Show summary

  Agricultural activities occupy nearly half of the world’s habitable land, an area larger than the Americas and the European Union combined. This has largely come at the expense of natural habitats, and today, new land uses such as utility-scale photovoltaic (PV) electricity production add further pressure. Agrivoltaic systems, in which PV modules and agricultural crops coexist on the same land, offer a pathway to greater land-use efficiency without claiming additional territory from nature. Although both PV modules and food crops rely on sunlight as their primary energy source, synergistic effects between the two have been demonstrated worldwide. PV modules can, for instance, harvest irradiance that exceeds a crop’s biological saturation point, or provide shade and shelter under harsh environmental conditions. The efficacy of these synergies, however, depends strongly on the specific crops and climates involved. In Northern Europe, short growing seasons and, in some places, strong regulatory protection of scarce agricultural land may require that crop yields are maintained or improved. In this context, vertical bifacial agrivoltaic systems have attracted particular interest due to their low physical footprint and limited crop shading. In these systems, vertically mounted PV modules arranged in rows leave the inter-row space accessible for agricultural machinery while simultaneously functioning as windbreaks that improve the local microclimate in ways that most other agrivoltaic designs do not. This thesis develops computational frameworks for the design and evaluation of agrivoltaic systems, with particular emphasis on vertical bifacial systems in northern climates. The research is structured around methodological gaps identified in the literature. Paper I reviews the state of the art of agrivoltaic modeling, identifying weaknesses that several subsequent papers help address. Among these is the need for accurate optical modeling without the high computational cost of ray tracing tools commonly used for PV production modeling. Paper II addresses this bottleneck by identifying and benchmarking efficient matrix-based ray-tracing tools against industry-standard approaches, demonstrating that they deliver both the accuracy and speed required for autonomous optimization of agrivoltaic system design. Paper III then utilizes one of the identified ray-tracing tools within an autonomous optimization framework. The framework identifies system designs that maximize the Land Equivalent Ratio through optimal light sharing between food crops and PV modules. Optical modeling alone, however, neglects thermodynamic and aerodynamic changes that are especially relevant where vertical systems act as windbreaks. Paper IV therefore integrates computational fluid dynamics to analyze this windbreak effect. The results demonstrate how vertical photovoltaic rows create sheltered zones with significantly reduced wind speeds, which leads to reduced evapotranspiration and increased temperatures. The subsequent crop yield analysis shows that these beneficial mechanisms can compensate for shading, resulting in net-positive crop yields in high-latitude climates, particularly during years of drought. Finally, Paper V uses satellite remote sensing to monitor operating vertical systems across the world, offering a scalable way to independently verify agricultural productivity in commercial systems. The analysis finds no reduction in vegetation indices after installation, indicating that commercial systems maintain agricultural performance.

• 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.

• Marstein, Erik Stensrud; Fagerström, Jonathan; Zeyringer, Marianne & Klyve, Øyvind Sommer (2024). Value of Hybrid Solar-Wind Power Plants in Deregulated Markets. Universitetet i Oslo. Full text in Research Archive Show summary

  Co-locating and co-operating solar and wind power assets in hybrid power plants (HyPPs) presents a promising solution for increasing the share of renewable energy and reducing global carbon emissions. This research investigates how HyPPs can economically outperform stand-alone solar or wind plants in deregulated electricity markets, focusing on the Nordic region. The primary advantages of HyPPs lie in their ability to share the infrastructure that connects them to the grid with minimal energy curtailment losses. This thesis demonstrates how this can lead to lower investment, operational, and development costs. Moreover, HyPPs can bypass some of the delays associated with concessions for grid connection and land access, thereby accelerating the deployment of renewable energy. However, in terms of market dynamics, the thesis shows that HyPPs offer limited improvements in forecasting accuracy or market price capture compared to stand-alone wind and solar plants with equivalent capacities under Nordic market conditions. The main financial benefits of HyPPs are thus primarily related to infrastructure cost savings rather than improved market performance. Overall, the findings suggest that developing HyPPs is a cost-effective strategy for scaling up renewable energy, supporting climate goals while addressing practical barriers that currently hinder the growth of solar and wind power.

• Belsnes, Michael Martin; Bjørndal, Mette; Elverhøi, Anders; Espegren, Kari Aamodt; Fæhn, Taran & Jaehnert, Stefan [Show all 16 contributors for this article] (2023). Energikrisen i Europa og det norske kraftmarkedet. Norges teknisk-naturvitenskapelige universitet. Full text in Research Archive Show summary

  Dette notatet oppsummerer en serie workshoper som ble organisert våren 2022 av FME-sentrene NTRANS, CINELDI, ZEN, HighEFF, Include, NorthWind og HydroCEN, sammen med NTVA og DNVA. Ved noen workshoper ble flere partnere invitert inn på arrangørsiden. Bakgrunnen for workshopene var en lengre periode med svært høye energipriser i Europa, som forplantet seg til høye strømpriser i Norge og store prisforskjeller mellom regioner. Målet med seminarserien var å diskutere og systematisere det tverrfaglige faktaunderlaget som forskningsmiljøene har utviklet innenfor tematikken. Med tanke på tidsperspektivet så vi at dette kunne gjøres som en serie seminarer/workshops med avgrenset tematikk. Konklusjonene oppsummeres i denne rapporten, som trekker sammen læring og syntese på tvers av workshopene

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