Bernhard Fäßler

• Malavatu, Jayachandra & Fässler, Bernhard (2026). A multi-function shared hybrid battery energy storage system for commercial applications: Energy arbitrage, university building and electrical vehicle charging station. Results in Engineering (RINENG). 30. doi: 10.1016/j.rineng.2026.110259. Full text in Research Archive Show summary

  Battery energy storage systems play a crucial role in implementing demand-side management strategies for commercial applications. Commercial applications require batteries that meet both high energy and power demands. A single type of battery is often inefficient at satisfying both, so we propose a hybrid battery energy storage system that combines power-dense and energy-dense batteries. However, the economic feasibility of hybrid energy storage systems continues to be a major obstacle to their widespread adoption. To enhance economic viability, this paper introduces a multi-function shared hybrid energy storage system designed for various commercial applications. The system was evaluated across two Norwegian commercial sites using three different individual applications: energy arbitrage, electricity bill reduction in university buildings, and profit maximization in electric vehicle charging stations. Three years of historical data measured from smart meters were used to simulate and compare the performance of the hybrid energy storage system in both individual and shared applications. The proposed system effectively reduced overall monthly peak demand, nearly matching the performance of individual applications. Results indicate that for one site, sharing the hybrid energy storage system among three applications increased profit by 27.81 % compared to using it only for the highest profitable individual application (i.e., university buildings). For the other site, the profit increase was 21.24 %. In addition, the shared system improved grid performance, reducing the grid peak-to-average power ratio by 4.43 %, the standard deviation of grid power by 0.67 %, and the smoothness of grid power by 10.52 % compared to scenarios without any storage system.

• Malavatu, Jayachandra; Kepplinger, Peter & Fässler, Bernhard (2025). A comparative simulation study of single and hybrid battery energy storage systems for peak reduction and valley filling using norm-2 optimization. Results in Engineering (RINENG). 25. doi: 10.1016/j.rineng.2025.104389. Full text in Research Archive Show summary

  The objective of this study is to address the power imbalance between supply and demand caused by the adoption of electric vehicles and renewable energy sources. Due to power imbalance at the point of common coupling, additional peaks and valleys will be created. The novelty of this work lies in proposing a hybrid energy storage system that combines power-dense and energy-dense batteries, optimized using a Norm-2 approach, to mitigate these imbalances effectively. The methodology involves a simulation study using realistic distribution grid load curves, focusing on two case studies. The results of this study reveal that, with an optimally sized energy storage system, power-dense batteries reduce the peak power demand by 15 % and valley filling by 9.8 %, while energy-dense batteries fill the valleys by 15 % and improve the peak power demand by 9.3 %. Furthermore, a hybrid energy storage system outperforms and is useful for multiple grid applications when compared with a single type of energy storage system. The study identifies an optimal capacity share of 40 % power-dense and 60 % energy-dense batteries as providing an effective balance between power and energy requirements. The findings highlight the proposed system successfully manages not only the highest peaks and valleys, but also intermediate fluctuations caused by renewable energy and electric vehicle integration. During a one-year simulation using a hybrid energy storage system, peak power demand decreased by 11 %, peak-to-average ratio improved by 12 %, and power variance was reduced by 29 %, indicating more stable and efficient grid performance compared to without any storage system.

• Wrålsen, Benedikte & Fässler, Bernhard (2022). Multiple scenario analysis of battery energy storage system investment: measuring economic and circular viability. Batteries. 8(2). doi: 10.3390/batteries8020007. Full text in Research Archive Show summary

  Circular business models for batteries have been revealed in earlier research to achieve economic viability while reducing total resource consumption of raw materials. The objective of this study is to measure the economic performance of the preferred business model by creating different scenarios comparing second life (spent) and new battery investment for seven different European regions and four energy management strategies. Findings reveal levels of economic ability for a total of 34 scenarios simulated, including direct savings per kWh, a total change in energy costs per year, battery charge/discharge cycles, and comparative breakeven analyses. Regional effects are also measured based on day-ahead electricity prices and solar irradiation. The minimum payback time is 7 years before battery system investment costs are covered. The most viable energy management strategies also had the highest number of charge/discharge cycles, which decreases battery lifetime. Investment in a second life battery compared to a new battery reduced the payback time by 0.5 to 2 years due to lower investment costs. However, the estimated lifetime range (3 to 10 years) is lower compared to a new battery (5 to 15 years), which questions the circular business model viability for the scenarios studied. Energy management strategies should be combined and customized to increase economic benefits.

• Malavatu, Jayachandra; O'Born, Reyn Joseph; Peter, Kepplinger & Fässler, Bernhard (2022). Hybrid energy storage systems of energy- and power-dense batteries: a survey on modelling techniques and control methods. Procedia CIRP. 105, p. 794–798. doi: 10.1016/j.procir.2022.02.193. Full text in Research Archive
• Wrålsen, Benedikte; Prieto-Sandoval, Vanessa; Mejia-Villa, Andres; O'Born, Reyn Joseph; Hellström, Magnus Mikael & Fässler, Bernhard (2021). Circular business models for lithium-ion batteries - Stakeholders, barriers, and drivers. Journal of Cleaner Production. ISSN 0959-6526. 317. doi: 10.1016/j.jclepro.2021.128393. Full text in Research Archive
• Fässler, Bernhard & Jakobsen, Aleksander Bogunovic (2021). Autonomous Operation of Stationary Battery Energy Storage Systems—Optimal Storage Design and Economic Potential. Energies. 14(5). doi: 10.3390/en14051333. Full text in Research Archive Show summary

  Global warming requires a changeover from fossil fuel based to renewable energy sources on the electrical supply side and electrification of the demand side. Due to the transient nature of renewables and fluctuating demand, buffer capacities are necessary to compensate for supply/demand imbalances. Battery energy storage systems are promising. However, the initial costs are high. Repurposing electric vehicle batteries can reduce initial costs. Further, storage design optimization could significantly improve costs. Therefore, a battery control algorithm was developed, and a simulation study was performed to identify the optimal storage design and its economic potential. The algorithm used is based on autonomous (on-site) optimization, which relies on an incentive determining the operation mode (charge, discharge, or idle). The incentive used was the historic day-ahead stock market price for electricity, and the resulting potential economic gains for different European countries were compared for the years 2015–2019. This showed that there is a correlation between economic gain, optimal storage design (capacity-to-power ratio), and the mean standard deviation, as well as the mean relative change of the different day-ahead prices. Low yearly mean standard deviations of about 0.5 Euro Cents per kWh battery capacity lead to yearly earnings of about 1 €/kWh, deviations of 1 Euro Cent to 10 €/kWh, and deviations of 2 Euro Cents to 20 €/kWh. Small yearly mean relative changes, lower than 5%, lead to capacity-to-power ratios greater than 3, relative changes around 10% to an optimal capacity-to-power between 1.5 and 3, and for relative changes greater than 10% to an optimal capacity-to-power ratios of 1. While in countries like the United Kingdom, high potential earnings are expected, the economic prospective in countries like Norway is low due to limited day-ahead price performance.

• Fässler, Bernhard (2021). Stationary, Second Use Battery Energy Storage Systems and Their Applications: A Research Review. Energies. 14(8). doi: 10.3390/en14082335. Full text in Research Archive
• Kepplinger, Peter; Fässler, Bernhard; Huber, Gerhard; Arachchige, Subodha Tharangi Muhandiram; Rheinberger, Klaus & Preißinger, Markus (2019). Autonomes Demand Side Management verteilter Energiespeicher Ein Überblick über die Forschungsarbeiten der Forschungsgruppe ,,Energiesysteme und -komponenten“ an der Fachhochschule Vorarlberg. E & I. Elektrotechnik und Informationstechnik. ISSN 0932-383X. 137. doi: 10.1007/s00502-019-00782-9. Full text in Research Archive
• Fässler, Bernhard; Kepplinger, Peter & Petrasch, Jörg (2019). Field testing of repurposed electric vehicle batteries for price-driven grid balancing. Journal of Energy Storage. ISSN 2352-152X. 21, p. 40–47. doi: 10.1016/j.est.2018.10.010. Full text in Research Archive
• Fässler, Bernhard; Schuler, Michael; Preißinger, Markus & Kepplinger, Peter (2017). Battery Storage Systems as Grid-Balancing Measure in Low-Voltage Distribution Grids with Distributed Generation. Energies. 10(12), p. 1–14. doi: 10.3390/en10122161. Full text in Research Archive
• Fässler, Bernhard; Kepplinger, Peter & Petrasch, Jörg (2017). Decentralized price-driven grid balancing via repurposed electric vehicle batteries. Energy. ISSN 0360-5442. 118, p. 446–455. doi: 10.1016/j.energy.2016.12.013. Full text in Research Archive
• Fässler, Bernhard; Kepplinger, P; Kolhe, Mohan Lal & Petrasch, J (2015). Decentralized on-site optimization of a battery storage system using one-way communication. In NN, NN (Eds.), The 4th IET Renewable Power Generation Conference, IET RPG 2015. IET Digital Library. ISSN 9781785610400. doi: 10.1049/cp.2015.0304. Full text in Research Archive

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• Fässler, Bernhard & Birkeland, Terese (2021). Research and regulatory obstacles for stationary second use battery energy storage systems. Full text in Research Archive Show summary

  The global demand for electricity is rising due to the increased electrification of multiple sectors of economic activity and an increased focus on sustainable consumption. Simultaneously, the share of cleaner electricity generated by transient, renewable sources such as wind and solar energy is increasing. This has made additional buffer capacities for electrical grids necessary. Battery energy storage systems have been investigated as storage solutions due to their responsiveness, efficiency, and scalability. Storage systems based on the second use of discarded electric vehicle batteries have been identified as cost-efficient and sustainable alternatives to first use battery storage systems. Large quantities of such batteries with a variety of capacities and chemistries are expected to be available in the future, as electric vehicles are more widely adopted. These batteries usually still possess about 80% of their initial capacity and can be used in storage solutions for high-energy as well as high-power applications, and even hybrid solutions encompassing both. The presentation will highlight potential applications for second use battery energy storage systems making use of decommissioned electric vehicle batteries. It shows ongoing research on second use battery energy storage systems within Europe and compares it to activities outside of Europe. The presentation will also identify economic, environmental, technological, and regulatory obstacles to the incorporation of repurposed batteries in second use battery energy storage systems and lists the developments needed to allow their future uptake. Especially regulatory obstacles need to be overcome. This will be addressed through assessing implications of EU battery legislation. In December 2020, the European Commission put forth their proposal for a battery regulation. The regulation proposal both updates the targets from the battery directive from 2006 in addition to regulating the upstream part of the battery value chain. In other words, the Commission seeks to regulate the entire battery value chain with this being proposed as the first product-specific regulation under the European Green Deal and Circular Economy Action Plan. Potential impacts this regulation proposal will have on the market for reuse, second life and recycling of batteries in Europe will be discussed.

• Fässler, Bernhard (2020). Battery Seminar. Full text in Research Archive
• Fässler, Bernhard (2019). Battery Activities at the University of Agder. Full text in Research Archive
• Fässler, Bernhard; Choux, Martin Marie Hubert & Wrålsen, Benedikte (2019). Trailblazing Resource Management Through the Upcoming Battery Wave. Full text in Research Archive
• Wrålsen, Benedikte; Fässler, Bernhard; Choux, Martin Marie Hubert & Wrålsen, Benedikte (2019). Batterier og sirkulær økonomi - forskning ved UiA. Full text in Research Archive
• Fässler, Bernhard (2019). Characterization, reassembly, and battery control of second use battery storage systems. Full text in Research Archive
• Fässler, Bernhard (2018). Reuse of Lithium-Ion Electric Vehicle Batteries for Stationary Applications (ReLIEVe). Full text in Research Archive
• Fässler, Bernhard (2018). Defense Presentation: Autonomous Optimization of Repurposed Electric Vehicle Batteries for Grid Balancing. Full text in Research Archive
• Fässler, Bernhard (2018). Trial Lecture: Scaling up a storage system with autonomous optimization of repurposed electric vehicle batteries for grid balancing: methods and techno-economic challenges. Full text in Research Archive
• Fässler, Bernhard (2018). A Method for Grid Simulation Assessing Demand Side Management Strategies. Full text in Research Archive
• Fässler, Bernhard (2018). Wasserkraft und Energiespeicher Batteriespeicher-Szenarios. Full text in Research Archive
• Fässler, Bernhard (2017). Autonomous, decentralized battery storage systems for load balancing in low voltage distribution grids. Full text in Research Archive
• Fässler, Bernhard (2015). Decentralized on-site optimization of a battery storage system using one-way communication. Full text in Research Archive
• Fässler, Bernhard; Kolhe, Mohan Lal & Petrasch, Jörg (2018). Autonomous Optimization of Repurposed Electric Vehicle Batteries for Grid Balancing: Doctoral Dissertation for the Degree of Doctor of Philosophy (PhD) at the Faculty of Engineering and Science, Specialization in Renewable Energy. Universitetet i Agder. ISSN 9788271178925. Full text in Research Archive

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