• Energy Research

The development of a Mach–Zehnder interferometer based on tapered optical fiber for temperature sensing applications is presented. Two tapers, 24 mm apart, were fabricated on SMF-28e+ using the fusion splicer. The optical structures were coated with a 100 nm layer of gold. The influence of the gold deposition on the temperature sensitivity of the fabricated sensors is presented. The sensor was characterized in O-, S-, C-, and L-bands in a temperature range of 0–70 °C. The highest temperature sensitivity of 72 pm/°C with R2 = 0.9974 was obtained for the gold-coated sensor. During the investigation, the average transmission loss was low and did not exceed 7 dB.

Abstract Lithium-ion battery systems are becoming a major component in numerous applications. The thermal behaviour of cells should be monitored for many reasons. In this paper, the investigation of the energy balance for lithium-ion battery system is described. The electrothermal model allows to describe heat generation and heat dissipation processes in all components of a battery pack (BP). Moreover, this model can be easily adapted for bigger, modular battery systems, since the primitive in the proposed model is a single cell. A method to determine the energy balance through experimental investigations and to validate the model is also proposed. Four types of BPs with sixteen cylindrical 18650 lithium-ion cells were tested. The influence of both busbar material and the presence of heatsinks on the BP thermal conditions was investigated. The results show that the heat accumulated in cells can be decreased by 20% and the cell temperature lowered by 8 °C if additional elements are used in a BP.

In contemporary vehicle applications, lithium-ion batteries have become a leading option among the diverse array of battery technologies available. This preference is attributed to their advantageous properties, which include low self-discharge rates and no memory effect. Despite these benefits, lithium-ion batteries are not without their challenges. The key issues include a restricted driving range, concerns regarding longevity, safety risks, and prolonged charging durations. Efforts aimed at minimizing the charging duration frequently entail the introduction of elevated currents into the battery, a practice that can significantly elevate its temperature and, in turn, diminish its operational lifespan. Generally, battery packs in electric vehicles are equipped with flat cooling plates located on their side or bottom surfaces, which also serve the dual purpose of providing heating in colder conditions. Nevertheless, this cooling configuration faces difficulties during fast charging and may not efficiently heat or cool the batteries. In this work, a novel thermal management approach is proposed, in which a battery module is cooled not only with a bottom cooling plate but also using another cooling plate in contact with the busbars, located on the top of the battery module. The simulations and experimental tests show that this new configuration demonstrates significant improvements. The thermal time constant is reduced by 47%, enabling faster cooling of the module. Additionally, the maximum temperature reached by the battery during charging with dual cooling is lowered by 6 °C compared to the conventional approach. In this configuration, the top cooling plate acts as a thermal bridge. This is a key advantage that promotes temperature homogenization within the battery module. As a result, it supports an even aging process of batteries, ensuring their longevity and optimal performance.