Auxiliary Power Losses Research Articles

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

A Generic Model for Accurate Energy Estimation of Electric Vehicles

A systematic simulation model is proposed in this research paper to estimate the energy consumption of electric vehicles. The main advantage of this model is that it is made in a generic and simplified way in order to be adaptable to different electric vehicles. The overall electrical power corresponding to the performed maneuver is estimated considering: a tabular form of electric motor efficiency, mechanical power losses, a generalized efficiency map of the power electronics, the auxiliary power losses, and an electro-thermal Lithium-Ion battery pack model. The battery model was developed in a previous work, which simulates the open circuit voltage curves at different temperatures and the alteration in the internal resistance of the battery cells. The proposed model is validated with experimental data from the maneuver tests. The battery model proved high accuracy in estimating the voltage values relevant to the WLTP2 driving cycle on the chassis roller test bench. Furthermore, the mechanical and electrical power were estimated with excellent matching compared to actual test field driving test measurements, giving only the measured vehicle speed and auxiliary power losses. Finally, the state of charge change is predicted accurately along the performed test field dynamic maneuver.

PERFORMANCE EVALUATION OF RESIDENTIAL HEAT-PUMP WATER HEATERS (PART 2): ENERGY CONSUMPTION ESTIMATION METHOD BASED ON HEAT-PUMP COP, STORAGE HEAT LOSS AND AUXILIARY POWER LOSS

The purpose of this study was to develop a method for estimating the energy consumption of residential CO2 refrigerant heat-pump water heaters. This paper considered a calculation model involving the use of actual machine data analyzed in Part 1. It was evaluated by considering the effect of efficiency losses on the ideal system COP. The calculation model estimated "heat-pump COP", "storage heat loss" and "auxiliary power loss". The developed method was applicable to wide-ranging hot water supply conditions. The estimation and test values of the system COP agreed to within a tolerance of around ±0.2.

Simulating the effects of flow configurations on auxiliary power requirement and net power output of High-Temperature Proton Exchange Membrane Fuel Cell

High-temperature proton exchange membrane fuel cells have garnered huge attention in the recent past because of faster electrode kinetics, high CO tolerance, and possible waste heat recovery. The flow channel is a crucial component of the fuel cell, which helps to improve its performance by facilitating uniform distribution of the reactant species, current density, and temperature. Conversely, the pressure drop imposed by various flow channel configurations increases the auxiliary power requirement of the fuel cell, which is a critical issue. Here, the main objectives are to enhance the electrochemical performance and reduce the auxiliary power loss of the high-temperature proton exchange membrane fuel cell by selecting a proper flow configuration. This work compares the parallel, serpentine, and hybrid flow configurations using a physics-based fuel cell model. It involves the mass, momentum, energy, species, and current conservation equations. The simulation results show that the shape and size of the common channel width in the parallel flow configuration have a noticeable influence on the cell performance. The thermal analysis demonstrates that the temperature gradients of the serpentine and hybrid configurations are two times lower than the parallel configuration due to uniform current density distribution and heat dissipation. This study illustrates that the hybrid configuration with the net power output of 0.383 W/cm2 provides the best performance with an auxiliary power loss of 3.6% compared to the serpentine configuration with an 11% loss. The net power output of the hybrid configuration remains superior under various stoichiometric conditions, including cell starvation. The outcome of this work provides a helpful insight into the flow configuration design for maximizing the net available power from the cell.

Design and Performance of the 850-V 100-kW 16-kHz Bidirectional Isolated DC–DC Converter Using SiC-MOSFET/SBD H-Bridge Modules

This article designs, builds, and tests the 850-V 100-kW 16-kHz bidirectional isolated dc–dc converter using the latest 1.2-kV 400-A SiC- mosfet /SBD H-bridge modules, with focus on efficiency improvement. Here, SBD stands for Schottky barrier diode. It proposes intermittent operation with continuous-current mode (CCM), to reduce switching losses in partial loads. Experimental results verify that the conversion efficiency from the dc input to the dc output is as high as 99.3% at the rated power of 100 kW, and 99.2% at a partial load of 10 kW. These are measured and calculated, discarding auxiliary power losses of 82 W in total, which are produced by the digital controller, gate-drive circuits, and cooling fans. Experimental transient waveforms show that no dc magnetic flux is included in the 850-V 100-kW 16-kHz transformer at intervals of switchover between the continuous operation and the CCM intermittent operation when power reversal from $-$ 100 to 100 kW is performed at an interval of 1 ms. Finally, this article presents an experimental and theoretical discussion on the voltage ripples appearing across the dc capacitor of each bridge.

Energy consumption model for milling processes considering auxiliary load loss and its applications

With the modern manufacturing industry evolving and advancing and amid a more energy conscious society, high energy demand in manufacturing—particularly in machining—has drawn more and more attention. Accurate energy consumption modelling is critical to the improvement of energy efficiency in machining. In the existing energy models of machining processes, typically the so-called auxiliary load loss (which is whatever the difference between the total energy consumption and the amount of energy consumed due to the physical cutting of material and the idle running of the machine tool) is not considered. However, the auxiliary load loss could account for as much as 15–20% of the total energy consumption; simply ignoring it or making crude assumption on it would obviously lead to a less accurate energy consumption model. In this paper, a new energy consumption model for milling that takes full account of the auxiliary load loss is proposed. The proposed energy consumption model is crucially based on an empirical validation work that correctly characterizes the auxiliary power loss as a quadratic function of the cutting power. Cutting experiments are then carried out that convincingly confirm the correctness of the proposed energy consumption model. Moreover, as an application of the proposed energy consumption model, we perform two deep slot cutting experiments and show how our new energy model can help find the best process parameter—the number of intermediate layers to cut—that will consume the minimum amount of energy, which is as much as more than 52% less than that without considering the auxiliary load loss. It is expected that the proposed energy consumption model will have its application in minimization of energy consumption to a wider range of machining tasks, not limited to only the simplest deep slot cutting operation.

Experimental Characterization of a T100 Micro Gas Turbine Converted to Full Humid Air Operation

Micro Gas Turbines (mGTs) were considered very promising for small-scale Combined Heat and Power (CHP) production. They however never fully penetrated the CHP market, resulting in a limited market share. Due to their low electric efficiency (30% versus 80% CHP efficiency), the operation of the mGT is strongly heat-driven. In applications with a non-continuous yearly heat demand, like domestic heating systems, the mGT would be shut down for long periods, resulting in a reduced amount of yearly running hours. These limited running hours make the mGT as small-scale CHP less profitable compared to other technologies, like reciprocating engines. Converting the mGT into a micro Humid Air Turbine (mHAT) offers a solution. The waste heat in the exhausted gases is recovered in the mHAT by evaporating auto-raised hot water behind the mGT compressor, resulting in a higher electric efficiency and a more flexible mGT operation. In this paper, we present the results of experiments on a modified Turbec T100 mGT. As a proof of concept, the mGT has been equipped with a spray saturation tower to humidify the compressed air. The goal of these experiments was to evaluate the beneficial effect of compressed air humidification on the mGT performance. Two stable runs at constant pressure ratio and rotation speed were recorded during water injection. Final electric efficiency results show a relative electric efficiency increase of 1.2% and 2.4%. These changes are however in the range of the accuracy of the measurements. Further experiments are therefore necessary to fully characterise the behaviour of the mHAT at part and nominal load. Fine-tuning of the water injection control strategy is also identified as a key parameter to reduce the auxiliary power losses.

Predictable Auxiliary Switching Strategy to Improve Unloading Transient Response Performance for DC–DC Buck Converter

In this paper, a novel control strategy is presented, which is capable of controlling a 12-V-1.5-V main buck converter and an auxiliary circuit to achieve significantly improved unloading response performance. While the charge balance controller minimizes the settling time of the main buck converter, the auxiliary circuit is controlled in boundary conduction mode (BCM) for a predictable pattern of auxiliary switching to reduce the output overshoot. Therefore, the reliability and dynamic performance of the entire system is significantly enhanced. Compared with existing technologies, the proposed BCM auxiliary switching strategy achieves improved output voltage overshoot and reduced auxiliary power losses at the same time. Furthermore, numerical analysis of the improved output voltage overshoot and reduced auxiliary power losses has been conducted for a design guideline. Finally, simulation and experimental results are provided to verify the proposed scheme on a 12-V-1.5-V 10-A buck converter prototype.