Ing. Jan Kasper

Lithium-ion batteries are used in a wide range of applications today. With that in mind, it is crucial to create accurate models for simulations of cell behavior under various circumstances. In this work, a 2RC electrical battery model of lithium-ion battery was developed and was enhanced by a kinetic battery model for improved accuracy in dynamic behavior. By implementing the kinetic battery model into the 2RC electrical battery model, the root-mean-square-error was reduced by 3.9 mV in average in the driving profiles and on average by 10.1 mV in the dynamic discharge performance test. The developed models are designed and validated to operate in the temperature range -5 degrees C-45 degrees C.

The degradation of the back sheet layer in photovoltaic modules has emerged as a critical issue, particularly in modules produced around 2010, drastically shortening their operational lifespan. This issue was not initially anticipated, as the materials used in back sheets, such as polyvinyl fluoride and polyethylene terephthalate, were considered durable. This degradation can lead up to the disconnection of entire photovoltaic strings due to safety concerns, causing considerable production losses. Previous studies have largely focused on accelerated laboratory testing, however, real-world conditions and short-term assessments of repair effectiveness have been insufficiently addressed. To fill this gap, our study examines the impact of field repairs using polysiloxane gel on the insulation resistance of photovoltaic modules with degraded back sheets. The experiment involved testing four photovoltaic modules, manufactured in 2010, that showed signs of back sheet degradation. Various repair methods were applied, including partial and full coating with polysiloxane gel, while one module was left unrepaired for comparison. Our findings demonstrate that fully repaired modules showed a substantial improvement in insulation resistance, maintaining values above 200 M Omega, whereas unrepaired modules exhibited significant drops below 10 M Omega during periods of high humidity. These results suggest that field repairs, particularly those using polysiloxane gel, can effectively restore insulation resistance and extend the functional lifespan of photovoltaic modules. Our results not only confirm the positive impact of these repairs on insulation resistance but also highlight the need for further long-term evaluations to fully assess the durability and reliability of these solutions over several years.

Lithium-ion batteries (LIBs) play a pivotal role in various sectors such as transportation, aerospace, and stationary systems. Accurate estimation of their state-of-charge (SOC) is crucial for efficient utilization within battery management systems. This work presents an enhanced SOC estimation method for LIBs, leveraging both open-circuit voltage (OCV) and hysteresis models. A co-estimation architecture employing two estimators is proposed, firstly focusing on battery model parameter estimation, and secondly utilizing pseudo-OCV instead of voltage measurements as output. This modification offers enhanced accuracy, reduced reliance on extensive laboratory testing, and improved robustness, especially in applications with rapid temperature fluctuations. The proposed method is evaluated through dynamic discharge profile tests across temperature levels ranging from 5 to 45 °C. Root-mean-square errors of SOC estimation for various temperatures were improved from the baseline approach (0.0185-0.0420) down to 0.0090-0.0280 in the proposed approach, showcasing the effectiveness of incorporating hysteresis models into SOC estimation.