Maximum Power Reduction Research Articles

Performance and economic study of a novel high-efficiency PEMFC vehicle thermal management system applied for cold conditions

This paper proposes three different heating management systems, sysse (self priming thermal management system), syslow (low temperature thermal management system), and syssp (split flow thermal management system), which are mainly composed of PEMFC and heat pump subsystems. Simulations were conducted to compare the comprehensive performance of these systems under cold startup and cold operating conditions, and analyzed the effect of different factors on these three system. The results show that under the influence of cell stack parameters, compared to sysse and syslow, the syssp has an average power consumption reduction of 29.95 % and 20.94 %, with a maximum power reduction of 31.46 % and 27.61 %, the average range power increases by 35.09 % and 23.58 %, with a maximum range power increase of 107.53 % and 75.57 %, the average COPPEMFC (Coefficient of Performance of heating Proton Exchange Membrane Fuel Cell) increases by 0.56 and 0.37. Under the influence of heat pump parameters, the evaporating temperature has a larger impact on the performance gains of the syssp, while condensing temperature has a greater effect on power consumption, range power, and COP variations. Compared to sysse and syslow, the syssp can recover costs as quickly as 3.12 and 3.68 years.

Active vibration control using minimum actuation power: Multiple primary sources controlled by multiple secondary sources

Minimum Actuation Power (MAP) is a novel active vibration control strategy that minimizes the total input power into the structure by monitoring the input power from the secondary source. In a previous paper, we presented the theory for MAP for a single primary source controlled by a single secondary source and demonstrated the application of MAP for rotorcraft interior noise control. In this paper, we extend the theoretical framework for MAP for multiple primary sources (excitation) controlled by multiple secondary sources (control). We show that the input power from the secondary sources is zero only when the secondary sources are located such that the phase of the cross-mobility term for each primary–secondary pair is same. This condition puts a constraint on the location of the secondary sources with respect to the primary sources so that the input power from the secondary sources is zero. We present simulations for a simply supported plate excited by two primary sources and controlled by a single secondary source that validate the theoretical findings. We also study the effect of phasing between the primary sources on MAP control performance and show that the maximum power reduction is obtained when the phase difference between the primary sources is zero. Experimental results are provided that demonstrate the feasibility of the MAP theory.

Low-Voltage Distribution Network Loss-Reduction Method Based on Load-Timing Characteristics and Adjustment Capabilities

The primary contributors to elevated line losses in low-voltage distribution networks are three-phase load imbalances and variations in load peak–valley differentials. The conventional manual phase sequence adjustment fails to capitalize on the temporal characteristics of the load, and the proliferation of smart homes has opened up new scheduling possibilities for managing the load. Consequently, this paper introduces a loss-reduction method for low-voltage distribution networks that leverages load-timing characteristics and adjustment capabilities. This method combines dynamic and static methods to reduce energy consumption from different time scales. To commence, this paper introduced a hierarchical fuzzy C-means algorithm (H-FCM), taking into account the distance and similarity of load curves. Subsequently, a phase sequence adjustment method, grounded in load-timing characteristics, was developed. The typical user load curve, derived from the classification of user loads, serves as the foundation for constructing a long-term commutation model, therefore mitigating the impact of load fluctuations on artificial commutation. Following this, this paper addressed the interruptible and transferable characteristics of various smart homes. This paper proposed a multi-objective transferable load (TL) optimal timing task adjustment model and a peak-shaving control strategy specifically designed for maximum sustainable power reduction of temperature-controlled loads (TCL). These strategies aim to achieve real-time load adjustment, correct static commutation errors, and reduce peak-to-valley differences. Finally, a simulation verification model was established in MATLAB (R2022a). The results show that the proposed method mainly solves the problems of three-phase imbalance and large load peak–valley difference in low-voltage distribution networks and reduces the line loss of low-voltage distribution networks through manual commutation and load adjustment.

Underwater propeller turbine blade redesign based on developed inverse design method for energy performance improvement and cavitation suppression

This paper conducts a systematic study to optimize the high-speed propeller turbine blade with high energy losses and severe cavitation. The trubine blade takes the role to provide the sustainable power for the underwater vehicle, whose structure is complex and crucial. To redesign the blade effectively, a developed inverse design method to generate various design schemes has been adopted with the union of the derived constrained zone and the one-dimensional theory. Established on the design method, a design procedure comprised of the CFD simulation, the LHS sampling, the multi-source constrained screening, the Kriging model, and the MOPSO algorithm was proposed. By setting energy performances (thrust, consuming power) and the cavity size as the objectives, the adaptive optimization of the runner blade installed on the underwater vehicle has been implemented, and two optimized models were finally designed out. Via further comparative analysis of the original and the redesigned blades, the maximum thrust increasement is 6.6%, the maximum power reduction is 3.1%, while the maximum cavity size reduction can be as much as 2.67%. Moreover, there exists a large structural difference for the runner blade before and after optimization, which could provide multiple options for further application. Finally, the specific inner flow analysis consisted of the performance calculation at different cruising speeds, and 3D analysis of key flows fields has been applied to reveal the reason to improve the performance and suppress the cavitation. Further, the energy balance theory was adopted to extract the specific losses at different hydraulic components, which demonstrates that the optimized propeller turbine blades can improve the energy performance. The study is expected to provide a technical reference for the energy performance improvement and cavitation suppression of the high-speed turbine machinery.

Comparative study of elliptical fin microchannel over oblique micro‐fin heat sinks

AbstractIn the present paper, the effect of elliptical fin and its orientation were computationally examined by considering equivalent fin cross‐sectional area and height of oblique fin to enhance thermal performance. A total of seven distinctly oriented elliptical fin microchannel models were developed and analyzed using finite volume method for velocity range of 0.2 to 0.9 m/s at constant heat flux of 65 W/cm2. The results showed that the elliptical fin microchannel model reduced pressure drop significantly and consumed less pumping power than the oblique fin microchannel model. It was also found that the average Nusselt number initially increases with decreasing elliptical fin orientation angle and then it rapidly decreases on further reduction of orientation angle beyond 4°. The optimal performance factor for a 4° elliptical fin was 1.21, with only a 6.5% penalty in wall temperature at Re 436. Furthermore, the maximum pumping power reduction of 41.4% was found for the 4° elliptical fin microchannel model with a 2.3% increase in Nusselt number. Hence, for the same pumping power, the 4° elliptical fin microchannel model performs better than oblique fin microchannel.

Performance Analysis of Ship Exhaust Gas Temperature Differential Power Generation

In addition to the use of waste heat from the vessel’s exhaust gas to save energy onboard, reduce the carbon emissions of the ship, and combine the characteristics of ship waste heat, mathematical modeling and testing of ship waste heat temperature difference power generation were carried out in this study. Finally, an experimental platform for temperature differential power generation was established to assess the impact of influencing agents on the efficiency of temperature differential power generation. The results show that the effect of different thermally conductive greases on the efficiency of temperature differential power generation tablets is basically the same. In addition, the rate of flow of cooling water, the cooling plate area, and the heat source temperature have more significant effects on the open-circuit voltage and maximum output power. The results show that the maximum power output growth rate increases with increasing cooling water flow, reaching 8.26% at 4 L/min. Likewise, increasing the heat source temperature enhances the maximum output power growth rate by 15.25% at 220 °C. Conversely, the maximum output power of the temperature difference power generation device decreases as the cooling plate area increases, and the maximum output power reduction rate is 15.25% when the cooling plate area is 80 × 200 mm2 compared to the case of using a cooling plate area of 80 × 80 mm2. Moreover, the maximum output power of the temperature differential power generation device reaches 13.6 W under optimal conditions. Assuming that the temperature difference power generation plate is evenly distributed on the tailpipe of the 6260ZCD marine booster diesel engine, it could save approximately 5.44 kW·h electric power per hour and achieve a reduction in CO2 emissions of 0.3435 kg per hour.

Flight performance of helicopter tail rotors with extendable chord

To investigate the potential of Statically and Dynamically Extendable Chord (SEC/DEC) in performance improvement of helicopter tail rotors, a prediction model of helicopter flight performance is developed and validated. It is suitable to deploy the SEC and DEC close to the blade tip for power reduction of tail rotor in hover and high-speed flight. The deployment locations of SEC and DEC for tail rotors are similar to that of main rotors. In hover, the deployment of the SEC and DEC results in little power reduction. From low to medium speed flight, the deployment of the DEC and SEC increases the power. In high-speed flight, the SEC and DEC can significantly decrease the power, especially at a large take-off weight. At 300 km/h, when the chord extension is 20% of blade chord, the SEC and DEC with 1/rev input decrease the power by 14.44% and 20.47% at a take-off weight coefficient of 0.0091. The DEC shows greater potential in power reduction than the SEC. There is an optimal phase input for the maximum power reduction, which does not vary with forward speed. For the DEC with 1/rev input, the optimal phase is [Formula: see text]. The optimal phase input for the maximum power reduction of tail rotors is different from that of main rotors.

A Demand Response Implementation with Building Energy Management System

The demand response (DR) program is one of the most promising components in the development of the Smart Grid. However, there are many challenges in practical operation to improve the existing and outdated system to comply with the DR programs. In Thailand, the major pain point of the office building owner in the DR program is the additional equipment, modification and operation cost of the existing equipment. Moreover, the sophisticated solution and control are other obstacles that need more measurements and data, and they make the operation difficult to work with. In this paper, we implemented a simple yet cost-effective hardware and software solution targeting an outdated air-conditioning system without voiding the warranty of the outdated equipment and without installing any additional measurements. In addition, the proposed operation is designed to be easy to operate under the equipment limitation and unskilled labor. More importantly, indoor temperature setpoint schedules during the DR event are forecasted with some public datasets to determine the capacity of the energy management system that can reduce the power consumption in the office building without an effect on the occupants’ comfort. To confirm the practicality of the proposed solution, the actual operation of the proposed solution can achieve the maximum power reduction at 19.80 kW (43.79% of the maximum power consumption) while keeping only 1 °C of difference from the typical room temperature (26–28 °C).

Aerodynamic study of a Hyperloop pod equipped with compressor to overcome the Kantrowitz limit

This paper describes an investigation of the aerodynamic performance of a Hyperloop pod equipped with an axial compressor using CFD simulation. The compressor is expected to reduce the drag if the operational speed of the pod exceeds the Kantrowitz Limit (KL). To evaluate the effectiveness of the compressor, two types of pod have been designed: those with and those without a compressor. A validation study was undertaken for supersonic flow around a cylindrical body in a wind tunnel. Several combinations of pod Mach number and blockage ratios were examined. The axial compressor was modeled with the fan interface model and our original method, which we call the source terms model. Results are similar, but our model has the advantage that it can be applied to higher pressure ratios without inducing numerical instabilities. The power consumption was reduced owing to the compressor by decreasing the pressure accumulated in front of the pod. The effectiveness of the compressor was shown to be greater for conditions well above the KL, with a maximum power reduction of 47.5%. Simulations performed half-scale, and at a different system pressure, showed that the effectiveness of the compressor was not greatly influenced by these parameters.

Effects of marine environment on electrical output characteristics of PV module

In the context of green ships, solar photovoltaic (PV) as an important clean energy technology has attracted the attention of many scholars in the shipping industry. To ensure the stable electrical output of PV modules is the premise for the effective use of solar photovoltaic technology on ships. Different from the terrestrial environment, the disturbance of marine environmental factors to the electrical output characteristics of PV modules should be considered. It is clear that salt spray and seawater are the most important marine environmental factors that affect the electrical output characteristics of PV modules, and the corresponding mechanism is analyzed. A marine environment simulation experimental platform for PV modules is built, and experiment verification is carried out. The results show that salt spray and seawater have different perturbations on the electrical output characteristics of PV modules, and the effects will change with the change of salt spray and seawater. The combined influence of salt spray on the electrical output of the PV module is a maximum power reduction of about 6%, and the combined influence of seawater on the electrical output of the PV module is a maximum power increase of about 20%. The experiment results can provide the research basis for further research on environmental disturbance suppression methods for PV modules.

An optimal thrust allocation algorithm with bivariate thrust efficiency function considering hydrodynamic interactions

Thrust allocation is of great importance for the application of Dynamic Positioning System (DPS). For dynamically positioned vessels, the thrust allocation is formulated as a nonlinear optimization problem, where the demanded forces and moments are distributed among the available thrusters. Both hydrodynamic interaction effects and physical limitations of thrusters affect the thrust generation. Therefore, the thrust allocation algorithm can be improved if these effects are considered. We propose a bivariate thrust efficiency function, dealing with both the forward thruster angle and the rear thruster angle, to describe the thrust loss. The thrust efficiency function is obtained from the model tests and approximated by the Radial Basis Function (RBF) neural network. The consequent thrust allocation problem is solved by the Sequential Quadratic Programming (SQP) algorithm with slack variables. The numerical simulations demonstrate a maximum power reduction of 16.03% compared with the forbidden zone algorithm. The proposed algorithm can also enhance system stability, highlighting the advantages of taking bivariate thrust efficiency function into account.

Investigation of fly ash soiling effects on solar modules performances

The increase of solar modules installation worldwide has led to an increase in the investigation of the phenomena that may cause adverse effects on the performance of solar modules, such as soiling. Soiling of solar modules surface leads to a reduction in their performance due to reduced quantity of solar radiation reaching solar cells. Having in mind that (in Serbia) solar modules on the roofs are often located near chimneys, and that for heating fossil fuels are mostly used, during the heating season fly ash is accumulated on solar modules reducing their performances. This paper presents results of the outdoor experimental investigation of the impact of accumulated fly ash during the heating season on solar modules surface set at an angle of 0° (horizontal), and at an optimal angle of 32° for the area of ​​Niš on their power. The experiment was carried out for a period of 168 days. The maximum power reduction (greatest reduction of solar modules power due to fly ash soiling) both for the horizontal and optimally installed module due to the fly ash accumulation was measured on the 45th day of the measurement. The maximum power reduction of the horizontal module was 87.2%, and of the optimally set module 30.6%. The morphology of the fuel oil fly ash was analyzed using scanning electron microscopy (SEM). The fly ash particles were generally spherical in shape, of a porous structure and the largest number of particles had diameters of 20 μm to 50 μm.

Evaluating the impact of thermostat control strategies on the energy flexibility of residential buildings for space heating

Buildings can be operated in an energy-flexible manner while respecting occupant thermal comfort. This energy flexibility of building operations, both in time and quantity, can be harnessed by the electrical grid for load balancing. In the context of smart grid and intelligent buildings, the concept of energy flexibility in buildings broadens the existing demand management thinking from the top-down one-way control to two-way communications. This paper, extending studies on thermostat controls of heating and air conditioning systems for demand response, evaluates the impact of different control schemes on the energy flexibility of residential buildings. Two control strategies, Model Predictive Control (MPC) and Rule-Based Control (RBC), are investigated for a space heating system using co-simulation studies. Four indicators are introduced and adapted from the literature to assess the control performances of the strategies. Simulation results show that different flexibility indicators favour different control strategies in this case study. For demand response events of four hours, the MPC strategy presents two to three times of flexible energy than that of RBC. MPC also delivers 20% more of maximum power reduction during the events against RBC. The RBC strategy, on the other hand, is twice of MPC for flexible energy efficiency. This evaluation work can be beneficial to guide the control system design of new buildings or control retrofits of existing buildings that consider better grid-building interactions for the future.

A Layer Jamming Soft Glove for Hand Tremor Suppression

Tremors are a common movement disorder that affects a person's life adversely. With various drawbacks of current treatment methods, there is a need for a mechanical solution. The authors present a soft orthosis based on layer jamming for the suppression of hand tremors. A vacuum supplied to the layer jamming elements which contain a stack of layers attached to the glove leads to increased stiffness in the glove, suppressing the tremor. The behavior of the tremor in a cohort of patients in Sri Lanka was studied and showed that the tremor's mean frequency was 5.05 ± 2.03 Hz. An existing analytical model was modified and verified experimentally to select the layer jamming element. An element with sandpaper (320 grade) and tracing paper was chosen based on the high stiffness provided at a lower weight (total weight of the glove = 30g). Experimental results show minimal variation in stiffness for vacuum pressures between 10-50 kPa (abs.). The performance evaluation on a test rig was used to verify the efficacy of the glove and showed optimal placement on the palmar side with a mean tremor amplitude reduction of 78.32%. Clinical trials conducted on 11 recruited tremor patients showed a mean frequency power reduction of 41.74 ± 12.11%, 41.99 ± 14.82%, and 24.71 ± 12.18% in the index and middle fingers and in grasping, respectively with a maximum power reduction of 59.15%. The soft, low weight orthosis shows a high tremor suppression in both the test rig and clinical experiments.

A 0.85mm2 BLE Transceiver Using an On-Chip Harmonic-Suppressed RFIO Circuitry With T/R Switch

This article presents a small-area Bluetooth Low-Energy (BLE) transceiver (TRX) for short-range Internet-of-Things (IoT) applications in 65-nm CMOS. An integrated Radio-Frequency Input-Output (RFIO) circuitry embedded with transmitter/receiver (TX/RX) switch function and on-chip impedance matching is proposed. A hybrid-loop TRX structure based on a wide-bandwidth fractional-N digital phase-locked loop (DPLL) is implemented to achieve the maximum power reduction. A -94dBm receiver sensitivity is achieved with 2.3mW receiver power consumption, while a RF receiving bypass route integration enhances the input power tolerance. The BLE transceiver delivers -6dBm output power while consuming 2.6mW and delivers 0dBm output power while achieving 18.5% maximum TX efficiency. Thanks to the RFIO with harmonic suppression, -56dBc of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> -order harmonic distortion (HD2) and -48dBc of 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -order harmonic distortion (HD3) suppression are achieved with 0.85mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on-chip area. This transceiver satisfied the BLE radio specification without the need for external filters and with low-power consumption, which enables minimum size and long life-time modules.

Approximate Multipliers Using Bio-Inspired Algorithm

As most of the real-world problems are imprecise, dedicating a lot of hardware for precise computations is futile for low-power applications and few applications where the precision is not of paramount importance. For such applications an imprecise computational block is sufficient if it has other performance benefits like low power and low area. We propose Constrained Cartesian Genetic Programming (CCGP), a variant of CGP to evolve lower order imprecise multipliers and further the higher order multipliers are constructed from them. Gate-level architectures for 2 × 2, 3 × 2, 3 × 3 and 4 × 4 imprecise multipliers are evolved. Also, we propose few partitioning methodologies for the construction of higher order multipliers using the evolved imprecise lower order multipliers. The constructed evolved-partitioned multiplier (EPM) of orders 8 × 8 and 16 × 16 has significant performance benefits over the existing multiplier architectures in terms of cell area and power. The circuits are synthesized using Cadence SoC Encounter® using TSMC® 180 nm standard cell library. The 16-bit EPMs show a maximum power reduction of 33% compared to other truncated multipliers and an area improvement of 2%.

Design of energy‐efficient ternary circuits using differential cascode voltage switch strategies in carbon nanotube field effect transistor technology

Differential cascode voltage switch (DCVS) is a static technique which offers the advantages of layout density, logic flexibility together with improved delay and power consumption. In this study, DCVS-based ternary logic gates and unary operators are reported using static diode voltage divider topology. The main focus of the proposed ternary designs using DCVS logic style is to provide minimum energy consumption with less area overhead. In the presented method, a new power efficient and compact solution is being provided to improve the driving capability of the ternary DCVS circuits. All the simulations are performed on HSPICE synopsis simulator using 32 nm technology under different operational conditions. For the inversion and logical operations, the proposed method has a maximum power reduction of 45% and an energy reduction of 30% as compared to earlier reported DCVS designs. In the case of shifting operators, the maximum power reduction of 38.93% and an energy reduction of 39% are achieved. The design performance is robust when subjected to various process variation effects and have sufficient noise margins.

Polypyrrole/sewage sludge carbon as low-cost and high-effective catalyst for enhancing hexavalent chromium reduction and bio-power generation in dual chamber microbial fuel cells

Microbial fuel cell, a potential bio-electrochemical energy transducer can extract the bio-energy from wastewater by the consumption of the electro-active microorganism adhered the surface of anode, and the MFC performance is greatly inhibited by the cathode catalysts. Herein, polypyrrole/sewage sludge carbon electrode is fabricated by an electro-polymerization loading method and the electrode is employed as the cathode electrode in MFC for the removal of Cr(VI) and bio-energy release at the same time. The electrochemical analysis finds the polypyrrole/sewage sludge carbon electrode exhibits the low charge transfer resistance and Tafel slope, which can demonstrate that the polypyrrole/sewage sludge carbon electrode possesses strong conductivity and excellent electrochemical activity. In addition, Cr(VI) in the cathode chamber of MFC with the polypyrrole/sewage sludge carbon electrode can be totally removed at 30 h. And the maximum output power and Cr(VI) reduction rate of MFCs are 760.7 mW m−2 and 2.16 g·m−3·h−3, which are 2.79 and 1.51 times higher than those of carbon cloth electrode (272.5 mW·m−2 and 1.43 g·m−3·h−3). Moreover, Cr(VI) can be removed and deposited on the electrode in the form of Cr(OH)3. And polypyrrole plays an electron shuttling role in reducing the internal resistance of MFC and enhancing electrochemical activity of the electrode for Cr(VI) reduction. Consequently, the polypyrrole/sewage sludge composite can achieve more stable Cr(VI) removal and power than those of sewage sludge carbon, polypyrrole, and carbon cloth electrodes, demonstrating an effective and low-cost catalyst for accelerating Cr(VI) reduction and strengthening bio-power production.

A 4:1 multiplexer using low-power high-speed domino technique for large fan-in gates using FinFET

PurposeThis paper aims to propose a new fin field-effect transistor (FinFET)-based domino technique low-power series connected foot-driven transistors logic in 32 nm technology and examine its performance parameters by performing transient analysis.Design/methodology/approachIn the proposed technique, the leakage current is reduced at footer node by a division of current to improve the performance of the circuit in terms of average power consumption, propagation delay and noise margin. Simulation of existing and proposed techniques are carried out in FinFET and complementary metal-oxide semiconductor technology at FinFET 32 nm technology for 2-, 4-, 8- and 16-input domino OR gates on a supply voltage of 0.9 V using HSPICE.FindingsThe proposed technique shows maximum power reduction of 77.74% in FinFET short gate (SG) mode in comparison with current-mirror-based process variation tolerant (CPVT) technique and maximum delay reduction of 51.34% in low power (LP) mode in comparison with CPVT technique at a frequency of 100 MHz. The unity noise gain of the proposed circuit is 1.10× to 1.54× higher in comparison with different existing techniques in FinFET SG mode and 1.11× to 1.71× higher in FinFET LP mode. The figure of merit of the proposed circuit is up to 15.77× higher in comparison with existing domino techniques.Originality/valueThe research proposes a new FinFET-based domino technique and shows improvement in power, delay, area and noise performance. The proposed design can be used for implementing high-speed digital circuits such as microprocessors and memories.

SCDNDTDL: a technique for designing low-power domino circuits in FinFET technology

A new technique called series-connected dynamic node-driven transistor domino logic (SCDNDTDL) is proposed for the design of circuits with high speed and low power consumption in fin-shaped field-effect transistor (FinFET) technology. HSPICE is used to simulate 2-, 4-, 8-, and 16-input domino OR gates in complementary metal–oxide–semiconductor (CMOS) and FinFET technology using the 32-nm Predictive Technology Model (PTM) library with a supply voltage of 0.9 V. The proposed technique shows a maximum power reduction of 73.16% in the FinFET short gate (SG) mode as compared with the conditional stacked keeper domino logic (CSK-DL) technique and a maximum delay reduction of 36.36% in the FinFET SG mode as compared with the voltage comparison-based domino (VCD) technique at a frequency of 50 MHz. The unity noise gain of the proposed circuit is 1.64 to 3.77 times higher in the FinFET SG mode and 1.39 to 3.77 times higher in the FinFET low-power (LP) mode compared with different existing techniques. The proposed circuit has up to 18.94 times higher figure of merit (FOM) in the SG mode and up to 7.14 times higher FOM in the LP mode compared with existing techniques. The proposed circuit in FinFET technology shows a maximum power reduction of 68.47% as compared with its counterpart in CMOS technology for a 16-input OR gate. The proposed circuit has 6.06 times lower energy–delay product and 4.53 times lower power–delay product compared with its counterpart in CMOS technology for a 16-input OR gate.