In the last decade, a higher level of reliability has become a compulsory demand when it comes to modern DC-DC converters. This work addresses the main reliability metrics: in many studies, the failure rate λ and MTBF of an output capacitor bank used within a high-current low-voltage buck converter have shown that the output capacitor bank is the most critical component within the converter. Many authors dealt with this issue by performing reliability predictions. The majority of studies use only one specific standard prediction to solve the problem. Herein, the calculation was performed using both the older standard, MIL-HDBK-217, and the latest one, Telcordia SR-332, providing a benchmark comparison between the two, which is a helpful tool for output capacitor selection in early-stage design. The military standard was well accepted for decades in reliability prediction, even in industrial electronics, and is still used today in a critical manner because there have been no more updates after the latest version, MIL-HDBK-217F—Notice 2, was released in 1995. Since then, newer prediction standards have appeared in the electronics reliability market. Over time, this standard was mostly used, but it does not accurately model the reliability because of a lack of taking account of the mission profile. The above-mentioned newer standard—i.e., Telcordia SR-332—also tries to compensate for the lack of the newest component technology in the older standard (which is the first standard released on the market), supplying useful design data for design engineers who use the so-called “design with reliability in mind” concept. This provides the designer of DC-DC converters with a comparison between the reliability values when the two mentioned standards are used. This paper establishes the environmental condition for the passive components by means of a point of load (PoL) buck converter that is used for both calculation methods. The influence of temperature and several specific concepts, like reference conditions, operating conditions, ripple, and internal self-heating, were taken into account in order to display the results. The temperature for the capacitor’s capsule needed in πT stress factor calculation was derived using PSPICE simulation. High-fidelity and dedicated SPICE models provided by the manufacturer were used for MOSFETs, polymer electrolytic, and MLCC capacitors that comprise the converter.
Solar Chimney Power Plants (SCPP) consist of three main components: solar collector, chimney and turbine. Air under the collector is heated by the greenhouse effect, the air density is reduced and the air flows toward the chimney located at the center of the collector. Thus, electricity is produced at the turbine mounted at the entrance of the chimney. In this study, measurements have been carried out on the Solar Chimney Power Plant (SCPP) system built at Ad & imath;yaman University Campus area, with specifications 15 m in height, 0.8 m in diameter of chimney, 0.004 m thick transparent glass floor and a collector having maximum of 27 m in diameter. For this purpose, air flow rate and temperature in the chimney at certain times of the day, ambient temperature, ambient wind speed, ground temperature heated by the greenhouse effect of the collector, temperature and air velocity under the collector, the number of revolutions of turbines of different diameters and Ad & imath;yaman solar radiation values were evaluated. In this study, it has been determined that solar radiation, ambient temperature, chimney height and diameter, solar radiation absorption rate of the ground under the collector are the parameters that affect the efficiency performance of the system. It is also observed that temperature and air velocity at the point where the turbine assembly is located are maximum. In addition, it was determined that the turbine model with a diameter of 0.8 m was the most efficient model for the system. It is concluded that Solar Chimney Power Plant (SCPP) can be considered as alternative energy sources for Ad & imath;yaman.
The usage of clean energy sources, like solar energy, has been becoming more and more important because of the scarcity of fuel reserves and the need to reduce emissions of carbon to prevent global warming. In this context, a nanofluid-based PV/T (photovoltaic thermal) system has been developed to boost solar energy utilization for a variety of residential and industrial applications. The PV/T system pumps the SiO2 -nanofluid through the lowest part of the panel, decreasing the temperature of solar panel and increasing the overall amount of electricity produced. Furthermore, the heat generated through the panel can be used to raise the SiO2 nanofluid's temperature. This temperature may be utilized later to heat the building's interior or provide hot water. To evaluate the performance of the PV/T system and the existing PV system under identical weather conditions, comparative measurements were made. The results showed that the PV/T system improves the PV system in terms of power generation efficiency because it utilizes the nanofluid (SiO2) as the working fluid. Additionally, the working (SiO2) nanofluid can be utilized for heating and supply of hot water because the PV/T system raised its temperature at the outlet to about 2-2.5%. SiO2 nanofluid-based PV/T systems may, on average, significantly increase solar power utilization, more than two times that of traditional PV systems. The PV/T system is simple to install in buildings and needs minimal maintenance or repair. As a result, this technology may help to lower carbon emissions and encourage the use of renewable energy in various applications.
This paper presents an experimental study of the effect of the mass of dust retained on a fibrous filter bed operating singly and in a “cyclone-filter-bed” system on changes in filtration efficiency and accuracy, as well as the increase in flow resistance. The research was carried out using a novel and unprecedented method, determining the dust absorption coefficient km of the filter baffle under laboratory conditions. A filtration system built of a single cyclone and a cylindrical filter cartridge with an appropriately sized surface set behind it was studied. Conditions corresponding to the actual operating conditions of the air filter were maintained: dust concentration, filtration speed and dust extraction from the cyclone settling tank. The purpose of the research was to evaluate filter materials with different structures in terms of filtration efficiency and accuracy, as well as flow resistance. The study showed that the parameters of the structure of filter materials—permeability, grammage and thickness—affect the process of retaining dust particles. It was shown that the increase in the flow resistance of the filter bed has a higher intensity when dust grains of small sizes are directed at it, which is the case when the bed is operated behind a cyclone, which separates larger dust grains from the air. There is a reduction in the operating time of the filtration system due to the limitation of the permissible resistance ∆pfdop, and the corresponding dust absorption km has a lower value. For a fixed value of the flow resistance, the dust absorption coefficient km2 of three different filtration baffles AC, B2, and B, working with a cyclone, take values 50–100% smaller than when working in a single-stage system. It has been shown that the “cyclone-filter baffle” unit, due to its greater dust separation capability, allows the filter cartridge to operate for a longer time until a certain flow resistance is reached. This allows the unit to operate longer at lower flow resistance without changing the filter cartridge, thus saving energy. The km values obtained during the tests, using the proposed original method, allow the selection of the filter bed for specific vehicle operating conditions by modelling its course.
The rise of an integrated energy system requires the integration of multiple sources of energy to be embraced and transited over the power grid; that means the information and communication systems of traditional power systems will be extended, and their complexity will be increased. As the information and communication systems play a more important role in the infrastructure of the power system, a cyber-attack on them may have an impact on the power system and cause a serious threat to the integrated energy system. To analyze the threat to the complex and integrated system, some researchers provide some modeling methods to study the impact of cyber-attacks on the information and communication systems, such as the Attack Tree Model, Attack Graph Model, Petri Net Model for cyber-attack, Attack Description Language Model, State Transition Graph Model, etc. However, these modeling methods have some shortcomings. For example, they cannot describe the systematical cyber-attack and show the secure status during the cyber-attack; it is hard for them to analyze the larger and more complicated information and communication systems. To overcome the shortages, in this paper, a correlated matrix-based object-oriented model is proposed for cyber-attack modeling. With this model, the relationship between the attacker and victim can be directly built; the cyber-attack path and packets from the attacker can be tracked; and the status of the nodes and links can be shown during a cyber-attack. There are two steps to build the cyber-attack model. Firstly, the procedure and approach of the cyber-attack will be modeled by an object-oriented method; then, a correlated matrix model will be built for network topology, attack path, and attack procedure. By combining these two models, the whole cyber-attack model is created. Finally, to demonstrate the modeling method and its benefits, we use the MITM (Man-in-the-middle Attack) attack on measurement data of an AVC (Automation Voltage Control) system as examples, and build a hardware-in-the-loop (HIL) co-simulation platform to verify the model.
