Papers by Keyword: Humidity

Abstract: In standard environmental reliability tests, Silicon Carbide (SiC) MOSFETs show a superior performance compared to their Silicon counterparts. This raises the question if the SiC modules are robust and reliable under all circumstances in the field and against all failure mechanisms or only in the standard laboratory tests. The HV-H³TRB (High Voltage – High Humidity High Temperature Reverse Bias) test is the standard test for humidity reliability and SiC modules survive this test for several thousand hours, easily surpassing the 1,000 h qualification requirement. However, in field service the devices are exposed to steep voltage slopes (high dv/dt) instead of the DC voltage stress applied in a standard HV-H³TRB. In this work, a dynamic HV-H³TRB test was performed on 3.3 kV SiC MOSFET modules for more than 4,000 h with switched high voltages of 80% V_nom, only observing minor degradations and reversible blocking capabilities.

Abstract: The need for efficient energy storage systems has led to intensive research on battery technology, particularly in tropical regions where environmental conditions impose unique challenges. In this review article, we examine the impact of tropical climates on the condition and storage of batteries in depth. Focus is given to all climatic aspects, including weather-ecological conditions (temperature, humidity, etc.) that affect the battery's performance, safety, and lifetime. This research compiled findings from several studies to help understand best practices in battery management in tropical environments. In tropical regions, high temperatures cause batteries to undergo a high rate of chemical reactions, reducing their lifespan and increasing the risk of damage or explosion. Additionally, high humidity levels can corrode battery components, compromise efficiency, and increase the risk of battery leaks or failure. This article examines various approaches to addressing these challenges, including designing batteries that are resilient to high temperatures, utilizing more corrosion-resistant materials, and implementing effective cooling systems. This review also highlights the optimization of battery monitoring and management technologies for tropical environments, including the use of real-time temperature and humidity sensors for monitoring. This article further examines the benefits of operating door batteries in a controlled environment and performing regular maintenance to extend door battery life and performance. The review is expected to serve as comprehensive guidance for developing battery technology that is more durable and robust than current versions in the climate extremes common to tropical regions.

Abstract: Lithium-ion (Li-ion) battery technology improvements have enabled their widespread use in various applications, ranging from portable electronics to electric vehicles. One major challenge is ensuring the safety and reliability of batteries, especially regarding the thermal runaway risks that can happen due to internal damage or degradation. The current article discusses the feasibility and potential applications of incorporating gas sensors within battery packs as a preliminary detection mechanism for monitoring and identifying potential failures before they escalate into catastrophic events. Gas sensors allow for the detection of certain volatile gases released from battery constituent materials upon degradation, such as carbon dioxide (CO₂), carbon monoxide (CO), hydrogen (H₂), and volatile organic compounds (VOCs). Gas sensors can help detect such abnormal conditions by continuously monitoring these gases and providing an early warning, thus preventing more significant damage. Gas Sensors Operating Principle: This review article provides an overview of the operating principles of gas sensors, focusing on the selective detection of target gases based on chemical reactions and electrochemical, pelletized, or semiconductor-based sensing technologies. The paper further details the value of using gas sensors in battery management systems (BMS), offering the potential for improved battery safety, validated operational lifetime, and a more proactive approach to battery health monitoring. The difficulties in making it available for real-world applications, such as the durability of the sensor, the accuracy under conditions used in practice, and its inclusion in existing BMS frameworks, are also highlighted. From gas sensors that help monitor the chemical composition of the battery to the modification of standard Li-ion cells for practical usage, the integration of complementary and interdependent technologies could enhance the safety and reliability of batteries, ultimately increasing their practical cycle life while reducing downtime and the risk of safety hazards. Gas sensors used for real-time monitoring and early recognition of danger zones represent a promising development in better battery technology with increased practical applicability of Li-ion batteries in vessels and a wide range of industrial sectors.

Abstract: Recently, silicon carbide (SiC) power modules of the 3.3 kV voltage class became available and are a promising candidate to replace silicon power modules in traction applications. However, the more than three times higher Young’s Modulus compared to silicon leads to a reduced lifetime under thermo-mechanical stress. This could pose a significant obstacle in their implementation, since traction applications are particularly demanding in their mission profiles with respect to load cycling, but also to environmental conditions. Thus, the thermo-mechanical stress is not just limiting the lifetime itself, but might also promote the humidity induced degradation due to delamination or micro-cracks. In this work, multiple power cycling tests at different temperature swings on 3.3 kV SiC MOSFET chips in a power module were performed, to assess their ruggedness under thermo-mechanical stress. Before or afterwards, these modules were tested under standard HV-H3TRB conditions to verify the interaction between thermo-mechanical and humidity stress on the robustness of the modules.

Abstract: The crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.

Abstract: In recent years, great attention has been paid to the development of porous materials with excellent reactivity and absorbency. The poly(lactic acid) (PLA) microfibers with uniform nanopores were successfully prepared by rotary centrifugal spinning using PLA/chloroform solution. Previous research showed that PLA microfibers have extremely high oil absorbing capacity. In this study, the changes in fiber diameter and nanopore diameter of nanoporous PLA microfibers under different fabrication conditions and the adsorption capacity of Prussian blue nanoparticles were systematically evaluated. The results showed that the fiber diameter increased with increasing PLA/chloroform solution concentration. Furthermore, it was found that the amount of adsorbed Prussian blue nanoparticles increased with the increase in fiber diameter. Prussian blue nanoparticles are known to adsorb radioactive materials such as cesium, and are expected to be applied to the recovery of cesium diffused in the atmosphere and ocean.

Abstract: The objective of this study was to evaluate the effect of three types of surface protectors: Protector with and without ultraviolet pigment and hydrophobic protector, on cracking and discoloration of Pinus radiata wood, after accelerated aging caused by temperature variation, UV-A radiation and humidity. For the tests, a QUV/Spray model accelerated aging chamber was used, which simulates the spectrum of radiation emitted by the sun under controlled climatic conditions in accordance with the EN 927-6 standard. The main results show that after 11 cycles (1848 hours) of testing, the color change decreased and the presence of the number and size of cracks occurred in the order of samples with Hydrophobic protection, followed by samples with UV pigment protector. and finally, in sample with protector without UV pigment. When wood is exposed to UV radiation, it undergoes photo-oxidation, causing an alteration of the properties and the original colour. This radiation burns the surface cells (lignin) of the wood, this effect produces cracking and flaking of the wood.

Abstract: The building envelope is considered the boundary in which a building interacts with the surrounding environment. This paper aims to enhance building envelope design by biomimicry of the termite mound shape for reducing the energy demand as well as maintaining comfortable indoor temperatures. In this paper, two models with the same internal dimensions, cross-sectional area, and block material were constructed. The first model is a regular block model (RB) that represents a typical house construction. The second model (TM) development including the form and the envelope design is inspired by the termite mounds. The building model used the same principles of ventilation and thermoregulation in the same way as termite responds to extremely hot and humid conditions. Infrared thermography (IR) was carried out to measure the thermal performance of building envelopes throughout a full year. The influence of the termite model on the thermal properties such as the Decrement Factor (DF), Temperature Difference Ratio (TDR), and Time lag (Tlg) was investigated. The results suggest that the termite model (TM) can accumulate time lag for up to three hours on average. Investigation results indicated that the termite model improved for thermal repletion, unlike the regular model. The termite model absorbed more heat while the regular block model (RB) was thermally reflective.

Abstract: Silicon carbide (SiC) MOSFETs are gaining more and more market share in typical silicon (Si) IGBT applications such as traction or renewable energies. Especially in reliability sensitive traction applications, medium voltage IGBT-modules (3.3 kV-6.5 kV) are widely used and introducing SiC-MOSFETs to such industries is the next self-evident step already on the way. While their superior electrical performance has been generally accepted already (e.g. [1]), SiC-modules have not yet established a track record of high reliability in this voltage class. For this study, 3.3kV SiC-MOSFET-switches were compared to standard Si-IGBTs regarding their humidity robustness under high voltage bias. Both chip types had been assembled in the same traction rated packages to exclude this influence. The Si-IGBTs resembled the well-known industry standard performance, while the SiC-MOSFETs show no degradation within the reported test time of 2000 h. Given the fact [2], that the latest Si-IGBT generation offers a much better humidity performance as well, the standardised HV-H³TRB is no longer sufficient to provoke failures within a reasonable testing time. On the one hand, this suggests that humidity driven failures will not be an issue under field conditions anymore. On the other hand, even harsher tests are required to investigate differences in humidity performance.

Abstract: Studies have shown the effect of ultra-low doses of surfactants on the compressive strength of cement stone and fine-grained concrete, which harden under conditions of heat-wet treatment, due to lack of research and widespread use of such treatment in concrete technology. It is proved that in this case the effect of ultra-low doses of surfactants is to reduce the number of open pores in cement stone and concrete. Experimental studies have confirmed that the molecules of surfactants, such as sodium oleate, polyhydric alcohol or others, significantly changes the hydrogen content of water used for the manufacture of concrete. This increases the mechanical strength of cement stone and concrete. It is determined that the increase in temperature and humidity of the medium in which the concrete hardens leads to an increase in the effectiveness of ultra-low doses of surfactants on the formation of compressive strength