Different Modes Of Operation Research Articles

Thermal sensitivity and adaptive comfort in mixed-mode office buildings in humid subtropical climate

ABSTRACT This study evaluates thermal sensitivity, expectations, and adaptability in mixed-mode ventilated buildings by subjective and objective assessments. A field study of simultaneous measurements of physical environmental parameters and right-here-right-now surveys was conducted in three office buildings from summer to winter in humid subtropical climates. The study confirmed previous findings that thermal adaptability and preferences changes as the ventilation system switches between natural ventilation (NV) and air-conditioning (AC). Occupants in this study showed more sensitivity to temperature changes than previously reported by ASHRAE Standards, yet thermal sensitivity was the same under different modes of operation. The neutral temperature was 0.5 oC higher than the predicted neutral temperature by ASHRAE 55 under both modes of operation. Thermal expectations were 1.5 oC warmer than the neutral temperature estimated by ASHRAE 55 when the building was operated by AC, while thermal expectations were almost the same as predicted by ASHRAE 55 under NV mode. Thermal comfort range was 0.75 oC wider than those predicted by ASHRAE 55 under NV operation, and the same as ASHRAE 55 under AC operation. The findings of this research provide a better understanding of mixed-mode building operations and perspectives from occupants, important for building designers and building operation managers.

ENHANCEMENT OF ENERGY EFFICIENCY AND BIOSPHORE COMPATIBILITY OF BUILDINGS AND STRUCTURES IN UKRAINE

The use of alternative energy sources is one of the most important areas of modern energy policy, aimed both at improving the environment and saving traditional fuel and energy resources. Adopted legislative and regulatory acts contributed to the rapid growth of "green" energy in Ukraine. The meaning of the ecological and energy optimization process is not to replace one energy source with another, but economic and industrial transformation, decarbonization and decentralization. 
 A technical solution to the problem regarding the source of alternative energy due to the use of heat in the surface layers of the earth's crust is proposed. At the depth of placement of probes-heat exchangers, which are structurally part of heat pump installations, the soil temperature is practically unchanged throughout the year and is positive. Non-freezing glycol solutions are used to increase the operational reliability of the installations. 
 To study the process of thermal interaction in the zone of placement of heat exchanger probes, mathematical modeling using the finite element method was applied. As a result, a significant array of data was obtained, which reflects the dynamics of temperature fields in different modes of operation of ground-source heat pump installations with vertical probes. 
 Of particular interest is the analysis of temperature fields along the depth of the well. After the seasonal selection of heat - the end of the heating period - the minimum temperature of the soil in the boundary zone of the geothermal probe is not lower than 0 0С. That is, freezing of soil rocks does not occur. 
 In the warm period of the year, due to, for example, the working air conditioning system of the building, the energy source of which is the heat pump installation, regeneration of the primary circuit takes place. The average temperature of the rocks between the probes at the beginning of August is, according to calculations, 6.5 0С. 
 The obtained results of analytical studies were used in the design of a ground heat pump installation for the energy supply needs of a public building with an estimated thermal capacity of 200 kW.

Analysis of the Response Signals of an Electronic Nose Sensor for Differentiation between Fusarium Species.

Fusarium is a genus of fungi found throughout the world. It includes many pathogenic species that produce toxins of agricultural importance. These fungi are also found in buildings and the toxins they spread can be harmful to humans. Distinguishing Fusarium species can be important for selecting effective preventive measures against their spread. A low-cost electronic nose applying six commercially available TGS-series gas sensors from Figaro Inc. was used in our research. Different modes of operation of the electronic nose were applied and compared, namely, gas adsorption and desorption, as well as modulation of the sensor's heating voltage. Classification models using the random forest technique were applied to differentiate between measured sample categories of four species: F. avenaceum, F. culmorum, F. greaminarum, and F. oxysporum. In our research, it was found that the mode of operation with modulation of the heating voltage had the advantage of collecting data from which features can be extracted, leading to the training of machine learning classification models with better performance compared to cases where the sensor's response to the change in composition of the measured gas was exploited. The optimization of the data collection time was investigated and led to the conclusion that the response of the sensor at the beginning of the heating voltage modulation provides the most useful information. For sensor operation in the mode of gas desorption/absorption (i.e., modulation of the gas composition), the optimal time of data collection was found to be longer.

Multi-operational solar photovoltaic microgrid with synchronization, backup and power quality enhancement ability

The proposed three phase solar photovoltaic microgrid (SPV-MG) works as a multi-mode operational system. It operates under different modes of operations: 1) Daytime, in presence of sunlight, it transfers real power to three-phase loads and grid, also mitigates power quality issues and provides power balance, 2) During grid absence, it operates in standalone mode, gives power backup to local demand and stores excess solar generation into the battery storage (BS). 3) At night, in the absence of sunlight, the SPV-MG has zero power generation so the VSI (Voltage Source Inverter) acts as a Distribution Static Compensator (DSTATCOM). It is capable of providing reactive power compensation, power factor correction (PFC), harmonics elimination, voltage regulation etc. which in turn improves the utilization factor of devices by nearly double-fold. 4) It has re-synchronization and isolation capability with respect to grid availability. A battery storage (BS) is attached at the DC bus of VSI to support the SPV-MG during peak demands and during grid and solar uncertainties. A laboratory prototype is developed to validate the performance with the experimental results.

Two Stroke Dual Fuel Engine Performance Analysis on Liquid and Gas Fuel Mode Related to the New Training Demands for Marine Engineers

The present publication shows the results of the planned experiment with a two-stroke dual fuel engine with low pressure of the fuel gas supply in simulated environment on the Wartsila Voyage technological simulator available in Nikola Vaptsarov Naval Academy. The aim of the publication is to facilitate the training process for the specific features in the two different modes of operation of the dual fuel engines on liquid and gas fuel in the context of the turbocharging system condition. The outcomes of the training need to cover the minimum knowledge for safe operation of the ship power plant by the trainees. The subject of the research is a low-speed two-stroke dual fuel engine WIN GD 6X72 DF. The plan of the experiment includes variation in the degree of fouling of the turbine and compressor side of the engine turbocharger ABB A180L and the associated deviations in the engine performance parameters. The variety of performance parameters selected for examination allows the conclusion of several outcomes with technical and educational benefits for the training process. They could be used in the lectures and exercises carried out with the under- and post-graduates in the marine engineering specialty.

Evaluation of the energy efficiency of electric vehicle drivetrains under urban operating conditions

In electric vehicles, as in hybrids vehicles, a very important factor affecting the energy efficiency of the powertrain is the ability to use the regenerative braking energy. Depending on the settings available in electric vehicles, the driver can choose different modes of operation: switch off the regenerative braking mode altogether, select the intensity of regenerative braking, or leave the control system in automatic mode. The last mode is often the only one available on eclectic vehicles, so the driver cannot decide whether to switch off or increase intensity of the regenerative braking. This paper presents a new method for evaluating the energy efficiency of electric vehicle powertrains under urban operating conditions. The presented method uses a procedure for mapping the operating conditions allowing to determine the reference level of energy consumption in relation to those recorded during the identifica-tion tests. Identification tests were carried out in the Tri-City area using electric vehicles of different purposes and operating parameters. Performed tests allowed to evaluate the regenerative braking efficiency of tested vehicle, which varies over a relatively wide range, for vehicle A from 33% to 77%, for vehicle B from 27% to 55% and for vehicle C from 36% to 58%. It can be concluded that one of the main factors determining the regenerative braking efficiency is the level of state of charge of the accumu-lator and the management algorithm used by the vehicle for controlling this parameter.

The impact of non-ideal phase change properties on phase change thermal energy storage device performance

Phase change materials have been known to improve the performance of energy storage devices by shifting or reducing thermal/electrical loads. While an ideal phase change material is one that undergoes a sharp, reversible phase transition, real phase change materials do not exhibit this behavior and often have one or more non-idealities – glide, hysteresis, supercooling – associated with them. Experimental and modeling techniques to characterize these non-ideal properties are reasonably well understood, however, their impact on the performance of a thermal energy storage system is not fully understood. Here, we analyze the performance of a heat exchanger with a phase change material as a function of the different non-idealities, for a heating and a cooling application. We focus on the impact of these non-ideal behaviors on different modes of operation of the thermal energy storage device, which will serve as a useful guide to researchers on the relative importance of the non-ideal properties, along with the necessary accuracy required during an experimental characterization.

Intelligent Energy Management for Distributed Power Plants and Battery Storage

A smart energy management controller is required for effective source coordination and load demand management. This work proposes a novel instantaneous current reference technique for use in power management of hybrid power systems (HPS), both autonomous and interconnected with the grid. A grid integrated hybrid power system (GI-HPS) includes both the AC grid and additional sources used in industrial and commercial environments. Solar photovoltaic (SPV) panels, wind turbine generators, proton exchange membrane fuel cells, and batteries are all part of the test system. The suggested energy management system (SEMS) manages power from the hybrid power source and the energy storage components to meet the load needs. The recommended SEMS can transit between 12 different modes of operation to fulfil the load demand requirements. The SEMS employs a scaling factor N to accelerate the rate at which the measured current approaches the reference current. The proposed scaling factor significantly improves the SEMS’s dynamic performance since it can quickly respond to the changes in the source and load characteristics. The dependability of an HPS powered by a variety of renewable energy sources can also be improved.

Inherently boosted switched inductor hybrid converter with AC and DC outputs for DC nanogrid applications

This paper presents a novel hybrid converter which is capable of carrying AC and DC loads simultaneously at different ports. The converter is designed by using a full bridge inverter at the nodes between the active switched inductor based high gain DC-DC converter. After inserting impedance into the current path, the inherent protection against the shoot through that often happens with a voltage source converter (VSI) is established. In addition, the modulation is such that the converter does not have to rely on shoot through to work, like most hybrid converters do. Instead, an extra charging mode has been added. This not only increases the voltage gain but also provides a flexible control with two duty ratios. The steady state operation of the converter is analyzed in five modes and their voltage relations are found out. A suitable pulse width modulation is realized to generate the different modes of operations. A prototype of the proposed converter is developed in the laboratory which is tested for suitable duty ratios operating for a maximum power of 600 W when the input voltage is maintained at 32 V. The converter finds its suitability in the nanogrid/microgrid where different loads are to be supplied from a single source.

Newly designed single‐stage dual leg DC‐DC/AC buck‐boost converter for grid connected solar system

SummaryThis paper proposes a novel single‐stage buck‐boost inverter based on dual leg. Modulation techniques, working principle, guidelines for components design, and guidelines are discussed and presented. A theoretical concept is initially tested in Simulink platform and practically verified with a test bench model. A practical model is developed to verify the simulation model and tested different modes of operation are analyzed. The main advantages of the proposed work are as follows: The number of passive components is less, switching frequency components are not high so leakage current is very less, and voltage control in a wide range is achieved without using a DC link capacitor. High efficiency can be achieved due to multi‐stage operation. This proposed work is suitable for high/low voltage PV‐based energy conversion. Electromagnetic interference is also reduced due to continuous input current.

Miniaturized Dual-Wideband Millimeter-Wave Filtenna in Package for 5G Applications

This letter presents a miniaturized dual-wideband millimeter-wave (mm-wave) antenna in package with filtering function. The proposed antenna mainly consists of four radiation patches and metallized vias. By introducing a pair of shorting pins underneath each radiation patch, the proposed antenna realizes dual-band operation in different modes. The upper band operates in the magnetoelectric dipole mode, while the lower band radiates through a new magnetic dipole. Besides, a radiation null is generated in-between the two operating bands to suppress signals. Furthermore, another pair of shorting pins is loaded on both sides of the probe, which generates two radiation nulls in the upper stopband. The dimensions of antenna are only 0.28 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_l</i> × 0.28 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_l</i> × 0.075 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_l</i> at 24 GHz. To verify the proposed approach, a prototype of 1×4 array is fabricated using a high density interconnection (HDI) process. The measured −10 dB bandwidth of the array covers 24−30 GHz and 37−43.5 GHz with an average gain of 8 dBi and 9.1 dBi, respectively. Besides, three radiation nulls are formed, suppressing the out-of-band gain by more than 13dB. The proposed antenna with such superior performance demonstrates great potential for millimeter-wave applications.

Establishment of Parameters of Electric Pulse Equipment Storage Device for Exhaust Gas Purification

. The physics of the process of electric pulse purification of exhaust gas is outlined. The article analyzes the mode of operation of the electropulse equipment of the storage device, designed to clean the exhaust gases of the car. The scheme and a description of the laboratory bench operation are given. On the basis of the analysis of the experimental results the conditions of corona discharge occurrence at the experimental stand are established. The data confirming the best cleaning efficiency when corona discharge occurs in comparison with pulse and arc discharges are given. The dependences of the luminosity of the cleaned gas, on the pulse exposure time, pulse frequency and the distance between the electrodes are obtained. The results of calculating the cleaning efficiency for 1 minute of ionization exposure at different modes of operation of the equipment are given

Determining the quality of photosupercapacitors and photobatteries in different modes of operation — A new approach

Monolithically integrated photosupercapacitors and photobatteries (photostorage devices) are a growing field of research and development. Yet there is currently no universally agreed-upon figure of merit for these devices that is independent of arbitrary testing parameters and also applicable to all possible operating scenarios.In this work we address this issue by introducing a way of defining a set of quality functions that can be evaluated unambiguously for any given device and that provide useful metrics for all operating scenarios. This is achieved by first identifying three distinct fundamental modes of operation for a photostorage device. Secondly we demonstrate a method to calculate a quality function for each mode from the parameters of an equivalent circuit model.This strategy avoids using variable physical parameters to evaluate a real device, such as a capacitance that depends on an arbitrary charging or discharging current. Rather, the combination of the three fundamental modes of operation and the constant nature of the model parameters allows a rigid definition of the quality of a device and reliable predictions of its performance under any conditions. This could serve to better compare the performance of photostorage devices and to determine design criteria in view of specific applications.

Design and Implementation of Nonisolated High Step-Up DC-DC Converter

This article presents a novel structure for a high step-up DC-DC converter. The proposed converter offers several advantages, including a simple structure, high voltage gain, high efficiency, reduced voltage stress on the semiconductors, and fewer components. A two-winding coupled inductor has been employed to enhance the output voltage level in this topology. The suggested structure has only one power switch with low ON-state resistance (RDS-ON), reducing power losses. Moreover, the zero-voltage switching (ZVS) and zero-current switching (ZCS) features of the diodes of the proposed converter result have improved overall efficiency. To evaluate and ascertain the enhanced performance of this configuration, the study of different modes of operation, steady-state investigation, and a comparative study between the proposed and other relevant topologies are presented. A laboratory prototype is designed and implemented with an input voltage of 12 V, an output voltage of 150 V, and a 200 W rated power level under a 50 kHz switching frequency. The maximum efficiency of the recommended topology is measured at the rated output power, equal to 96.98%. Also, for an output power range from 50 W to 350 W, the efficiency is obtained higher than 95%.

ЕЛЕКТРОМАГНІТНІ ПРОЦЕСИ У ТРИФАЗНОМУ МОСТОВОМУ КОМПЕНСАЦІЙНОМУ ПЕРЕТВОРЮВАЧІ

Electromagnetic processes are investigated in two versions of a three-phase bridge converter with improved energy characteristics, one of which contains one switching link, and the other two. The commutating link consists of a three-phase capacitor battery and a three-phase group of fully controlled devices. This technical solution makes it possible to ensure the recharging of the capacitors of the commutating link and the control of the energy process of the converter. The main content of the study is the analysis of electromagnetic processes in terms of the features of commutating processes and the proof of the energy capabilities of the options for implementing the converter. The amount of scientific research required for this is divided into three options. Each takes into account the peculiarities of electromagnetic processes associated with different modes of operation of converters, at different frequencies of control pulses of transistors of a commutating link and a shift in the moment of switching on transistors relative to the interval of operation of power electric diodes. As a result, a generalized mathematical model was created. She describes a variety of electromagnetic processes in converters, allows you to calculate the commutating and adjustment angles. They are the main characteristics of the energy process and prove that the developed versions of the converter are compensation. They are able not only to compensate for their own reactive energy, but also, if necessary, to generate reactive energy to the grid. References 12, figures 2, table 1.

Active debris removal: A review and case study on LEOPARD Phase 0-A mission

The growing number of space debris is alarming as it threatens space-borne services. Hence, there is an increasing demand to remove space debris to ensure sustainability and protect valuable orbital assets. Over the past few years, the research community, agencies and industries have studied many passive and active debris removal methods. However, the current technology readiness for space debris removal is still low. This paper first presents a comparative study of various space debris removal technologies to address the knowledge gap and quantify the challenges. This paper reviews the current state-of-the-art space technologies relevant to Active Debris Removal (ADR) missions. Detailed trade-off analysis is then presented based on the Low Earth Orbit Pursuit for Active Removal of Debris (LEOPARD) Phase 0-A study; this study is part of the United Kingdom (UK) Space Agency’s Active Debris Removal programme. The ADR mission scenario considered in this paper comprises a chaser spacecraft equipped with recommended technologies to capture non-cooperative targets safely. The final capture technology for the LEOPARD mission consists of an active robotic manipulator and a passive net capture mechanism. An analysis of the coupled-body dynamics of the chaser spacecraft carrying the robot manipulator and the targeted debris is carried out in simulation using SimscapeTM. The chaser spacecraft comprises Airbus’s Versatile In-Space and Planetary Arm (VISPA) mounted on a base spacecraft from Surrey Satellite Technology Ltd. (SSTL); the targeted debris is SSTL’s Tactical Operational Satellite (TOPSAT). The simulation results show dynamic changes in the chaser robot and the target satellite while performing non-cooperative capture. The simulation study accounted for various operational scenarios where the target is stationary or in motion. Further, for different modes of operation, the worst-case end-effector capture force limits were determined using open-loop control to execute a safe capture. Overall, the results presented in the paper advance the current state-of-the-art of robotic ADR and offer a significant leap in designing close-range motion and force control for stabilising the coupled multi-body system during capture and post-capture phases. In summary, this paper pinpoints the technological gaps, identifies barriers to realising ADR missions and offers solutions to catalyse technology maturity for protecting the space ecosystem.

A High Power Factor LED Driver with Intrinsic Current Balancing Capability

The research proposed a novel LED driver with the functions of power-factor correction (PFC) and current balancing. A flyback converter and a Class-D series resonant converter were integrated by sharing an active switch to form a single-stage circuit topology. The flyback converter played the role of a PFC circuit. The component parameters were designed to make the flyback converter to operate at discontinuous-conduction mode (DCM). In this way, the input line current can be sinusoidal, resulting in near unity power factor and low total harmonic distortion in current (THDi). The resonant converter was connected in series with a differential-mode transformer with a turns ratio of 1 to drive four LED strings. The current of the four LED strings will be automatically and evenly balanced by using the 1:1 transformer. This article analyzed the different modes of operation in detail, derived the mathematical equations and designed the parameters of the circuit components. Finally, a 72-W prototype LED driver was implemented and tested. A satisfactory performance has verified the feasibility of the proposed LED driver.

Study on Commercially Available Membranes for Alkaline Direct Ethanol Fuel Cells.

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm-2 at 80 °C.

Carbon-Energy Impact Analysis of Heavy Residue Gasification Plant Integration into Oil Refinery

A gasification plant may partially replace an industrial thermal plant and hydrogen production plant by polygenerating valuable products (hydrogen, power, steam) from low-value materials. Carbon energy analysis is one way of conceptually evaluating such processes. In this paper, the integration of a heavy residue (HR) gasification plant into a mid-size oil refinery (5 million t per year crude processing rate) is conceptually assessed via the comparison of electricity, natural gas and heavy residue consumption, and CO2 emissions. The main purpose of the integration is to reduce the consumption of natural gas currently used for hydrogen production at the expense of increased HR consumption and to achieve a reduction in CO2 emissions. Two case studies with different modes of operation were compared to base case showing that annual reduction of 2280 GWh in natural gas consumption with constant heat and hydrogen production is possible, accompanied with a slight increase in electricity purchase by 28 GWh per year. HR processing in the refinery increases by over 2800 GWh per year. The refinery’s CO2 emissions increase by more than 20% (up to 350 kt per year) as a result, while, after incorporating external emissions into the balance, a decrease of more than 460 kt CO2 per year can be achieved. This confirms that the integration of gasification plants within industrial enterprises and clusters has a positive environmental and energy impact and supports the idea of converting low-value material to more valuable products in polygeneration plants. The economics of HR gasifier integration in varying operations under real refinery conditions remain to be explored.

A fuzzy-logic-based smart power management strategy for reliability enhancement of energy storage system in a hybrid AC-DC microgrid with EV charging station

Abstract As Electric Vehicles (EVs) are considered as the future of the automobile industry, the demand for EV charging stations immensely rises. Though grid support can be expected for a microgrid (MG), it is highly advantageous to be self-reliant and be prepared for standalone operation for a long duration. This paper proposes a hybrid ac/dc microgrid (HMG) with an EV charging station in standalone mode with a smart power management strategy that increases the reliability of operation. Different modes of operation are designed according to power consumption levels and the operation of MG is switched between these modes considering the solar irradiance and battery bank state of charge. The decision-making system uses a combination of (a) fuzzy logic approach based on the state of charge of the energy storage system (ESS) and solar irradiance, adding to the intelligence of the system and providing smart reasoning capability and (b) logical decisions based on solar power and battery state of charge, considering all possible operating scenarios. With the proposed power management strategy in place, the standalone hybrid microgrid system is found to be able to prolong the discharge of the energy storage system under critical conditions of low battery state of charge and PV power availability and also under highly critical situations will be able to meet the critical load demand making use of the power available in the EV connected. Emphasis has also been given to maintaining the stability of the system while performing shifts in operating modes and during sudden changes in the scenario. Different operating conditions are recognized by the power management module in the model and an appropriate power management strategy is applied. Real-time simulation of the model was done in OPAL-RT real-time simulator using RT-LAB software and simulation results were reproduced.