High Electric Power Research Articles

High-κ La2O3 as an anode modifier to reduce leakage current for efficient perovskite solar cells

The high overall carrier recombination is widely believed to be a main hurdle towards the high electric power output for perovskite solar cells (PSCs). However, the current leakage at the interfaces of the anode and electron transport layer induced by the carrier recombination has always been overlooked. Herein, we have introduced an ultra-thin lanthanum oxide (La2O3) layer, with a high dielectric constant (κ) and a wide band gap, as an anode modifier to suppress the recombination of electrons and holes. With La2O3 locating at the ITO/SnO2 interface, the power conversion efficiency (PCE) of PSCs was enhanced to 20.23% from 18.45% of the control devices, due to the improved short-circuit current (Jsc) and fill factor (FF). Overall, this work provides a new strategy to further alleviate the hole and electron recombination for developing the high efficiency PSCs.

Increased Impedance of Wound HTS Power Cables by Quenching at a Shielding Layer for Fault Current Limiting Function

The use of high temperature superconducting (HTS) power cables is viable solution to address the growing demand for electric power, while ensuring low loss and high electric power transmission. Usually, HTS power cables and circular connection of substations reduce grid impedance, and the fault current is increased over the capacity of the circuit breaker. To protect the electric power grid, the fault current should be reduced below the allowable level. Of late, research on HTS power cables having fault current limiting (FCL) functions has increased. An inductive FCL HTS power cable uses the increased inductive impedance caused by magnetic flux leakage to a neighboring iron yoke when a quench occurs at the shielding layer of the cable core due to electromagnetic coupling with the conducting layer. Therefore, there is less heat generation, and the temperature rise is suppressed. In this study, we describe the increased inductive impedance and reduced fault current using a FCL model coil. To demonstrate the electromagnetic coupling between the conducting and shielding layers of the cable core, two concentrically wound REBCO coils were fabricated. The iron yoke inside the coil increases the inductive impedance when a fault current flows through the conducting layer, and quench occurs at the shielding layer. The results are used to develop an FCL HTS power cable with 154 kV, 600 MVA class.

Hot-spot generation model using electrical and thermal equivalent circuits for a copper indium gallium selenide photovoltaic module

Hot-spot generation is critical to the reliability and performance of copper indium gallium selenide (CIGS) solar cells; however, its occurrence mechanism has not been fully elucidated. We conducted a partial shade stress test on three large-area CIGS modules (156 cm × 62.6 cm in size, with 102 cells) connected in series. Partial shade stress can cause irreversible and unpredictable damage to the modules, and we confirmed the generation of hot spots on the shaded cells via infrared imaging. To emulate numerically the internal electrical and thermal changes in the shaded cells, we present electrical and thermal equivalent circuits based on the material properties and layered structure of the CIGS cells and modules. Furthermore, we propose a hot-spot generation model describing the irreversible damage to CIGS cells via shunt resistance degradation because the dissipated electrical power exceeds the threshold power (Pth). The current–voltage characteristics simulated by the presented method are congruent with those measured under partial shade conditions. Partial shade induces high electrical power consumption in the shaded cells, up to ~34 mW/cm2 at a 5% shade ratio, ~1,500 times higher than that in the unshaded cells. The shunt resistance is degraded to ~18.5 Ω/mm2 (only ~0.1% of the initial normal value), and the Pth-value is estimated to be ~2.4 mW/cm2 at the center of the hot-spot cells. The presented method and Pth-parameter can be used to evaluate durability with respect to the effects of partial shade stress for CIGS and various other thin-film photovoltaic cells and modules.

Power quality improvement using fuzzy logic controller based unified power flow controller

<p>The Power quality of the electrical system is an important issue for industrial, commercial, and housing uses. An increasing request for high quality electrical power and an increasing number of distorting loads had led to increase the consideration of power quality by customers and utilities. The development and use of flexible alternating current transmission system (FACTs) controllers in power transmission systems had led to many applications of these controllers. A unified power flow controller (UPFC) is one of the FACTs elements which is used to control both active and reactive power flow of the transmission line. This paper tried to improve power quality using a fuzzy logic controller (FLC) based UPFC, where it used to control both active and reactive power flow, decreas the total harmonic distortion (THD), correct power factor, regulate line voltage and enhance transient stability. A comparison study of the performance between the system with a conventional PID controller and FLC has been done. The theoretical analysis has been proved by implementing the system using MATLAB/SIMULINK package.The Power quality of the electrical system is an important issue for industrial, commercial, and housing uses. An increasing request for high quality electrical power and an increasing number of distorting loads had led to increase the consideration of power quality by customers and utilities. The development and use of flexible alternating current transmission system (FACTs) controllers in power transmission systems had led to many applications of these controllers. A unified power flow controller (UPFC) is one of the FACTs elements which is used to control both active and reactive power flow of the transmission line. This paper tried to improve power quality using a fuzzy logic controller (FLC) based UPFC, where it used to control both active and reactive power flow, decreas the total harmonic distortion (THD), correct power factor, regulate line voltage and enhance transient stability. A comparison study of the performance between the system with a conventional PID controller and FLC has been done. The theoretical analysis has been proved by implementing the system using MATLAB/SIMULINK package.</p>

Giant power density produced by PIN–PMN–PT ferroelectric single crystals due to a pressure induced polar-to-nonpolar phase transformation

The search for ferroelectric materials capable of producing high electric charge and power densities is important for developing a new generation of ultrahigh-power-density ferroelectric energy storage devices and autonomous megawatt power supplies.

Coexposed TiO2’s (001) and (101) facets in TiO2/BiVO4 photoanodes for an enhanced photocatalytic fuel cell

This paper reports an investigation on the role of coexposed TiO2’s (001) and (101) facets on the performance of TiO2/BiVO4 photoanodes in the photocatalytic fuel cell. Here, the exposure of these facets was obtained by synthesizing TiO2 with different morphologies, i.e. nanospindles, nanocube, nanooctahedra and nano-truncated octahedra. Based on the result, coexposed (001) and (101) facets were found to be responsible for the enhancement of photoelectrochemical response. The highest photocurrent density was achieved when the photoanode was fabricated using TiO2 nano-truncated octahedra/BiVO4 (29.8 μA/cm2 at 0.8 V vs. NHE), which was primarily due to the improvement of charge separation as a result of the synergistic effect between the formation of type-II heterojunction of TiO2/BiVO4 and internal surface heterojunction of (001) and (101) facet. A similar trend was also observed in the PFC system when RhB was used as fuel. Under the illumination of 13 W LED light, the highest electric power (0.00232 mW/cm2) was obtained with TiO2 nano-truncated octahedra/BiVO4 photoanode. However, TiO2 nanospindles/BiVO4 was found to be more effective in removing RhB due to its high surface area. Such variation was believed due to the fact that TiO2 nanospindles had less exposure of (001) facet than TiO2 nano-truncated octahedra.

Water behavior based electric generation via charge separation

Recent studies have used water droplets to generate electricity with a substantial power output of 50.1 Wm −2 . However, the generation mechanism resulting in this high output is unclear, because only the solid–water interface is considered and water is considered to act only as a charge carrying medium. This paper reports on the generation of electricity via the charge separation of water. The charge separation owing to water movement and impact leads to an extensive accumulation of electrical charge in water. A high electric power output is generated when mobile water carrying the accumulated charge comes in contact with a metal surface. These findings serve as a basis for establishing a correlation between charge separation and electricity generation based on water. • First report of water-based electricity generation mechanism by charge separation of water. • High-output electric generation up to instantaneous power of 26.6 mW. • Electric output analysis depending on ionic and molecular solutions.

Technical feasibility evaluation of a solar PV based off-grid domestic energy system with battery and hydrogen energy storage in northern climates

Self-sustaining off-grid energy systems may require both short-term and seasonal energy storage for year-around operation, especially in northern climates where the intermittency in both solar irradiation and energy consumption throughout the year is extreme. This paper examines the technical feasibility of an off-grid energy system with short-term battery storage and seasonal hydrogen storage, comprising a water electrolyzer and a fuel cell. The study is based on data from a currently grid-connected residential single-family house in Finland with an existing 21 kWp photovoltaic (PV) installation and a ground source heat pump based heating system. Energy system performance is simulated using real PV power generation data as well as data on grid electricity import and export from the house over a three-year period to find the minimum combination of battery and hydrogen storage system capacities capable of year-round off-grid operation. It is concluded that technically feasible solutions are available for the proposed setup. The most significant factor affecting the system dimensioning is found to be high peak electric power demand during times of low PV power generation, indicating a need for smart power control. Demand for battery storage capacity is found to be significant only to about 20 kWh. Fuel cell and electrolyzer nominal powers of at least 4 kW and 5 kW to 7 kW, respectively, were found to be sufficient for off-grid operation with the studied system. The storage capacity demand for 170–190 kg of hydrogen annually is, however, impractically large for residential houses.

Low-Cost MnO2 Nanoflowers and La2O3 Nanospheres as Efficient Electrodes for Asymmetric Supercapacitors

While supercapacitors can deliver high electrical power, their low energy density limits their application. Here, we designed and fabricated a facile asymmetric supercapacitor (ASC) with excellent ...

Design, Modeling, and Experiments of Electromagnetic Energy Harvester Embedded in Smart Watch and Wristband as Power Source

In this article, we investigated an embedded energy harvester to translate the kinetic energy of arm swing into electricity for powering smart watch and wristband. The embedded energy harvester integrates coaxially arranged motion capture unit, magnetic frequency-up converter, and electromagnetic transducer-based power generation unit to achieve high electricity production and power density. System model is built based on analytical and finite element method to estimate the performances and optimize the coils' parameters. To experimentally validate the performance of the embedded energy harvester, a highly compact prototype is fabricated and tested under pseudowalking excitation. The results show that the maximum power of 1.74 mW and power density of 346.61 μW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at an excitation frequency of 0.65 Hz can be achieved by this device, which demonstrates great potential in realizing self-powered purpose for smart watch and wristband. Compared with the previous works, the proposed energy harvester accomplishes tremendous improvement both in power output and power density. To provide design guideline for various wearable devices, the constructed model is used to investigate the effects of inertial weight and speed transmission ratio on the power output and power density.

Bioelectricity Generation From Single-Chamber Microbial Fuel Cells With Various Local Soil Media and Green Bean Sprouts as Nutrient

In this experiment, seven single-chamber microbial fuel cells (MFCs) were made and filled with various types of local agricultural soil and sediments found in irrigation channels, which were mixed with glucose and green bean sprouts mashed as nutrients for microbial survival. MFC electric power was measured every day for 35 days. Every time low electric power indicated weak microbial activity, green bean sprouts were added. The highest electric power of 118 µW (23.4 mW/m2) was observed in fuel cells filled with agricultural land planted with rice. Power density reached the range of 120–140 mW/m2, whereas the incubation time showed a maximum of 35 days. This study found that adding green bean sprouts can increase the length of the MFC cycle and strengthen the generated power up to 122 mW. ©2020. CBIORE-IJRED. All rights reserved

Design and Implementation of High Reliability Electrical Power System for 2U NutSat

This article proposes the design and implementation of an electrical power system (EPS) for 2U CubeSat using a single-ended primary-inductor converter (SEPIC) along with the perturbed and observe method for the maximum power point tracking (MPPT). SEPIC converters have the advantages of input current continuity, voltage boosting and bucking, short-circuit protection, low-side driver, and noninverted input and output voltages. When the battery voltage is too low, by adding a low power consumption latching relay to develop a novel topology, the battery can be directly charged with solar panels without the MPPT algorithm and to improve the system reliability. In addition to the on-board computer subsystem, we can independently control whether to turn on the power according to the battery capacity and importance priority for each subsystem of CubeSat. The satellite is operated in outer space that the environment is wide temperature variation, vacuum, and high electromagnetic radiation. Therefore, the satellite was subjected to various types of tests, such as vacuum, thermal cycling, and radiation tests, to verify the system's capacity for enduring the aforementioned environmental changes. Finally, implementations and various tests were carried out to verify the viability and the accuracy, and reliability of the EPS of the satellite.

Thermal Loads and Cost Reduction for a Residential House by Change Its Orientation and Add Roof Shading

The Iraqi climate is characterized by high temperatures in summer that require a&#x0D; large capacity of air conditioning systems to meet the suitable climate conditions&#x0D; which they are appropriate for the comfortable conditions for human especially&#x0D; housing units. The demerits of these systems are the high-maintenance-cost as well&#x0D; as high electrical power consumption, whereas the last considers currently one of&#x0D; the major obstacles in Iraq. This research studies the influence of two significant&#x0D; factors to reduce the thermal loads of the building which leads to decrease the&#x0D; consumption of the energy. The Study of the effect for the building's direction to&#x0D; the falling angle of the sunlight during the daylight in addition to the probability of&#x0D; reducing the thermal load of the building, and studying the effect of shading the&#x0D; buildings' roofs with red tile to prevent the falling sunlight on the roofs using the&#x0D; design method cooling load temperature difference (Cooling Load Temperature&#x0D; Difference –CLTD-) to calculate the thermal loads of a building designed&#x0D; according to the modern Iraqi design Located in Baghdad. The results explained a&#x0D; decrease in the thermal load through external walls by (12.32%) when directing the&#x0D; building to the direction West (W) compared to the South-West (SW) trend, while&#x0D; the thermal load through the glass decreased by 24.9% when directing the building&#x0D; to the North (N )direction with a trend of South-West (SW) as well as a decrease&#x0D; of 8.5% for the total thermal load of the building when directing the building to the&#x0D; direction North (N) compared to other trends and when shading the roof with a&#x0D; material preventing the sun reduces the rate of thermal load of the roof by 55%&#x0D; compared to the exposed roof. The study also shows in terms of the costs per&#x0D; building provides about (108787 ID / Day) of the supported governmental costs&#x0D; whereas the non-governmental cost is about (55987 ID / Day).

Experimental comparison of the performance of basic and regenerative organic Rankine cycles

Adding the regenerator to recover extra heat from the exhaust can improve the system overall performance. Based on a 10 kW organic Rankine cycle (ORC) experimental prototype, a comparison between the basic and regenerative organic Rankine cycle is investigated. The heat input is in range of 30–90 kW and R245fa is used as working fluid. The heat source temperature utilization rate is defined to appraise the heat source utilization. The detailed behaviors for heat source loop, ORC loop and cooling water loop are examined. Research demonstrates that the BORC has a better heat source temperature utilization than the RORC. RORC has a maximum thermal efficiency of 5.5%, which is 25.5% higher than BORC of 4.1%. The maximum condenser heat transfer coefficients for BORC and RORC are 501.4 W/m2 K and 1701.4 W/m2 K, respectively. The BORC has higher electrical power and generating efficiency than the RORC. The maximum generating efficiency for BORC is 3.4%, while that for RORC is 2.5%. Besides, the exergy destructions of the main components are addressed, and the evaporator has a very large percentage of exergy destruction for BORC and RORC. Therefore, system performance can be heightened by improving the temperature difference matching of the heat sources.

High voltage electric power supply system with contactless power take-off

Autonomous power supplies of light marking, monitoring, relay protection and emergency control systems of digital high voltage networks are considered, in particular, capacitive power take-offs from high-voltage three-phase power lines with voltage of 110 and 220 kV. Energy is collected in the immediate vicinity of the equipment, ensuring its operation without laying a separate power supply network and with minimal human involvement. The results of the analysis show a rather high technical and economic efficiency of the considered power supply system.

Development of a compact simple unpressurized Watt‐level low‐temperature‐differential Stirling engine

Despite the fast advance of modern technology, poverty is still a serious problem in many developing countries; and more than 1 billion people are having no access to electricity. For these people, even a few Watts of electricity supply for lighting can make a big difference. In this study, a simple, compact, unpressurized, Watt-level low-temperature-differential Stirling engine has been developed aiming to solve the lighting problem in developing countries. The engine in this study is compact. Yet, it is capable of delivering useful electrical power. It is a γ-type Stirling engine with twin power pistons. The diameter of the displacer cylinder is 220 mm, comparable to the size of a cooking pot, and the weight of the engine is under 5 kg. Two energy-conservation/heat-transfer enhancement measures have been incorporated into the engine's design: one is adopting a displacer/regenerator unit, and the other is machining engine-turn slotted grooves on its hot- and cold-end plates. CFD analysis showed that the combination of both measures could effectively improve the performance of the engine. Experiments were conducted to examine the engine's performance. In one experiment, the engine produced 3.7 W of electric power as temperature difference was 100°C, and its power was found to be almost linearly proportional to temperature difference. With a higher temperature difference of 140°C, the electric power reached 5.3 W. Another experiment that operated the engine for a prolonged period has proven the reliability of the engine's performance for long-time use. In practice, the engine can be operated by putting it on a stove table, and the residual heat from cooking is good enough to power the engine to produce usable electricity. Or it can be directly put on a wood fire to generate even higher electrical power.

Optimal charging scheduling and management for a fast-charging battery electric bus system

Battery electric buses (BEBs) are rapidly being embraced by public transit agencies because of their environmental and economic benefits. To address the problems of limited driving range and time-consuming charging for BEBs, manufacturers have developed rapid on-route charging technology that utilizes typical layovers at terminals to charge buses in operation using high power. With on-route fast-charging, BEBs are as capable as their diesel counterparts in terms of range and operating time. However, on-route fast-charging makes it more challenging to schedule and manage charging events for a BEB system. First, on-route fast-charging may lead to high electricity power demand charges. Second, it may increase electricity energy charges because of charging that occurs during on-peak hours. Without careful charging scheduling and management, on-route fast-charging may significantly increase fuel costs and reduce the economic attractiveness of BEBs. The present study proposes a network modeling framework to optimize the charging scheduling and management for a fast-charging BEB system, effectively minimizing total charging costs. The charging schedule determines when to charge a BEB, while the charging management strategically controls the actual charging power. Charging costs include both electricity demand charges and energy charges. The charging scheduling and management problem is first formulated as a nonlinear nonconvex program with time-continuous variables. A discretizing method and a linear reformulation technique are then adopted to reformulate the model as a linear program, which can be easily solved using off-the-shelf solvers, even for large-scale problems. Finally, the model is demonstrated with extensive numerical studies based on two real-world bus networks. The results demonstrate that the proposed model can effectively determine the optimal charging scheduling and management for a fast-charging BEB system, which carries the potential for use in large-scale real-world bus networks.

Temperature characteristics of a copper/zinc thermally-regenerative ammonia battery

Bimetallic thermally-regenerative ammonia battery (B-TRAB) is a new way to harvest low-grade waste heat as high-power electricity. Among B-TRABs, copper/zinc thermally-regenerative ammonia battery (Cu/Zn-TRAB) shows the most cost-effective and a relatively high discharge voltage. Within a temperature range of 10–40 °C, the maximum power density of Cu/Zn-TRAB is promoted from 389 W m−2 to 723 ± 45 W m−2 with a linear slope of 12.25 W m−2 °C−1. There is an intense drop in power generation as the operating temperature reaches 45 °C, while ion diffusion and reaction kinetics are not negatively affected by high temperature, indicating that self-discharge caused by ion cross-contamination is the main reason. The cyclic voltammetry tests show that the cathode reaction during discharging is more susceptible to ion cross-contamination at high temperatures. The net energy density first increases and then decreases with the increase of temperature and varies with discharge current, and a maximum of 635 W h m−3 is achieved at 35 °C and a current density of 100 A m−2, with a thermoelectric conversion efficiency ηt of 0.37% (the Carnot-relative efficiency ηt/C is 3.52%). From the simulation results, the condenser temperature has a crucial influence on the energy conversion efficiency, and the ηt can be improved from 0.37% to 1.28% (ηt/C = 12.3%) by reducing the condenser temperature from 43 °C to 21 °C. The highest ηt/C of 14.6% is received at 45 °C.

Dielectric characterization of vegetable oils during a heating cycle.

The knowledge of the dielectric properties of oils is of great importance for several industrial applications, such as microwave-assisted oil frying for foods and high voltage electric power transmission. In this paper, we present the complex permittivity of vegetable oils (canola, olive, soybean, coconut) at 2.50GHz using the cavity perturbation technique from 28 to 200°C (temperature close to the smoking point of oils). The measurements were taken with a cylindrical cavity operating at the TE111 mode with an unloaded Q of 4950. In addition, free fatty acids, peroxide index and color were measured before and after heating.

Experimental investigations on the thermal performance of an ice storage system using twin concentric helical coil

The cool thermal energy storage (CTES) offers a big advantage for peak shift of high electrical power consumed by air conditioning systems. An experimental analysis for studying the thermal performance of ice storage system with twin concentric helical coil (TCHC) is conducted in the present work. Effects of operating conditions such as the heat transfer fluid (HTF) inlet temperature and flow rate on the solidified/melted mass fraction, percentage energy stored/regained, and average charging/discharging rate during charging and discharging processes are investigated. An experimental setup composed of TCHC immersed in distilled water as a phase change material (PCM) in an insulated tank is used in the present study. Three different HTF inlet temperatures of (−8, −10, and −12 °C) and (10, 12, and 14 °C) for charging and discharging processes, respectively and HTF volume flow rates (5.0, 7.5, and 10 l/min) are investigated. The results show that, about 90% of the energy stored is achieved at 59–74% of the complete charging time according to the tested parameter range in the current study. Moreover, the HTF volume flow rates have a relatively small effect on the percentage energy stored and seems to be less effective compared to the inlet HTF temperature during charging process.