Transient Power Research Articles

A one-dimensional modelling methodology of printed circuit heat exchangers for steady, off-design and transient feasibility in a supercritical CO[formula omitted] power block

As the most widely-used heaters and recuperators in supercritical CO2 (sCO2) power cycles, the Printed Circuit Heat Exchangers (PCHEs) have received considerable interest to investigate their steady, off-design and transient behaviour mainly by simulations, which remains a challenging task accounting for various application scenarios. After an introduction and comparison about the state-of-art PCHEs numerical approaches, this paper presents a generic one-dimensional (1D) numerical PCHE modelling methodology featured by (1) ability fulfilling the steady, off-design and transient simulation; (2) precise capture of the non-linear local variations in the thermo-physical properties of sCO2; (3) feasibility for a wide range of flow patterns, working fluids, and operation conditions. The off-design prediction via the proposed 1D PCHE modelling methodology is justified by validating its Modelica implementation against previous literature. Later, one optimal Nusselt correlation out of five candidates is identified to reproduce two typical transient power cycle operations, i.e., ‘shutdown and startup’ and ‘ramp-up’ scenario. These scenarios are validated by experiments at the Pinjarra Hills High Pressure Loop (PHPL) of the University of Queensland. The proposed 1D PCHE model successfully follows the changing rules of the time-varying temperature of both hot- and cold-side working fluids, though a slight time lag is observed between the simulation and experiment, which is caused by the modelling assumptions. In general, the presented 1D PCHE modelling methodology is credited for the steady, part-load and transient performance evaluation of sCO2 power blocks and the corresponding control strategy development. Several crucial future work is summarized for guidance.

COMPREHENSIVE STUDY OF SUPER CAPACITOR

super capacitor or ultra-super capacitor are electrostatic double layer capacitor (ELDC) are the most promising energy device they offer greater transient response power density, low weight, low volume and low internal resistance which make them suitable for several application. This paper gives brief insight into the design characteristic and application of supercapicator. Keywords: - Electrolyte, activated carbon, super capacitor.

Denoising Transient Power Quality Disturbances Using an Improved Adaptive Wavelet Threshold Method Based on Energy Optimization

Noise significantly reduces the detection accuracy of transient power quality disturbances. It is critical to denoise the disturbance. The purpose of this research is to present an improved wavelet threshold denoising method and an adaptive parameter selection strategy based on energy optimization to address the issue of unclear parameter values in existing improved wavelet threshold methods. To begin, we introduce the peak-to-sum ratio and combine it with an adaptive correction factor to modify the general threshold. After calculating the energy of each layer of wavelet coefficient, the scale with the lowest energy is chosen as the optimal critical scale, and the correction factor is adaptively adjusted according to the critical scale. Following that, an improved threshold function with a variable factor is proposed, with the variable factor being controlled by the critical scale in order to adapt to different disturbance types’ denoising. The simulation results show that the proposed method outperforms existing methods for denoising various types of power quality disturbance signals, significantly improving SNR and minimizing MSE, while retaining critical information during disturbance mutation. Meanwhile, the effective location of the denoised signal based on the proposed method is realized by singular value decomposition. The minimum location error is 0%, and the maximum is three disturbance points.

Generation of localized reactor point kinetics parameters using coupled neutronic and thermal fluid models for pebble-bed reactor transient analysis

The systems analysis of anticipated operating occurrences and design basis accidents for pebble-bed reactor systems requires knowledge of neutron point kinetics equations (PKE) parameters. Typically, the generation of PKE parameters is performed in a global manner using standalone neutronics calculations, without the inclusion of thermal fluid distributions. We utilize Griffin and Pronghorn for generating global and local PKE parameters which includes the use of thermal fluid distributions to account for localized effects. This work establishes a methodology for calculating PKE parameters for a pebble bed reactor with a coupled neutronics/thermal fluids analysis. PKE parameters generated on a global and local basis are compared against a diffusion solve for a typical load-following transient. Locally-generated neutron kinetic parameters are able to reduce the maximum error in the transient power level from 5% to below 1.5%; along with this, bulk temperature errors were reduced from 12 K to 4 K.

Transient, Implantable, Ultrathin Biofuel Cells Enabled by Laser-Induced Graphene and Gold Nanoparticles Composite.

Transient power sources with excellent biocompatibility and bioresorablility have attracted significant attention. Here, we report high-performance, transient glucose enzymatic biofuel cells (TEBFCs) based on the laser-induced graphene (LIG)/gold nanoparticles (Au NPs) composite electrodes. Such LIG electrodes can be easily fabricated from polyimide (PI) with an infrared CO2 laser and exhibit a low impedance (16 Ω). The resulted TEBFC yields a high open circuit potential (OCP) of 0.77 V and a maximum power density of 483.1 μW/cm2. The TEBFC not only exhibits a quick response time that enables reaching the maximum OCP within 1 min but also owns a long lifetime over 28 days in vitro. The excellent biocompatibility and transient performance from in vitro and in vivo tests allow long-term implantation of TEBFCs in rats for energy harvesting. The TEBFCs with advanced processing methods provide a promising power solution for transient electronics.

Supporting Design Analysis of the VTR Using MCNP and TRACE

The Versatile Test Reactor (VTR) is a sodium-cooled fast reactor designed to accelerate the design and approval of new nuclear material and reactor concepts by providing a high neutron fast flux environment on U.S. soil. To ensure that the reactor simultaneously achieves the target irradiation environment while maintaining sufficient margin to safety limits, supporting design analysis of the VTR has been performed using MCNP and TRACE. High-fidelity MCNP calculations have been performed that confirm design parameters, such as control rod worth and neutron and photon flux distributions, and provide needed reactivity coefficients for TRACE analyses. The MCNP simulations additionally provide fuel rod power profiles of interest to fuel performance designers and provide an excellent model for experimental cartridge design within the VTR core. TRACE simulations of several postulated transients, such as station blackout, loss of heat sink, and transient overpower, have been performed (results included here are limited to the transient overpower), and the obtained results confirm the robust safety behavior of the VTR. The TRACE simulations provide a valuable confirmatory transient analysis capability using a U.S. Nuclear Regulatory Commission–developed safety analysis tool incorporating inputs from the high-fidelity neutronic simulations performed with MCNP. Taken together, the confirmatory analysis capability provided by MCNP and TRACE serves to further strengthen the understanding of and confidence in the VTR’s performance.

A new correlation for post-dryout heat transfer in upward vertical flow

The present study established a new experimental databank of stable post-dryout (PDO) heat transfer which contains 31,603 data points in total. It is demonstrated by the assessment work with the new databank that previous PDO heat transfer prediction methods could not provide high prediction accuracy to various working conditions. Therefore, this study aims to develop a universal correlation for stable PDO heat transfer. With effect of convective and radiation heat transfer considered, a new prediction model for stable PDO heat transfer is developed, which is a dimensionless one and independent to upstream information. By identifying significant dimensionless parameters with Spearman’s rank correlation coefficient method and the group-wise statistic method, three dimensionless parameters (ReTP, PrW, and xe) are selected to establish the new PDO correlation. Though developed from water experiments for vertical flow in uniformly heated round tubes, the new correlation shows good predictive capability when validated against water experiments with non-uniform heating and R134a experiments with uniform heating, which means the new correlation can be applied to various working conditions. However, if applied to cryogenic pipeline chill-down transient or nuclear power plant accident scenarios, validation with transient experiments needs to be completed in the future.

Multiterminal Hybrid DC Line Protection Based on Intrinsic Mode Energy Entropy

In view of the UHV multiterminal hybrid DC transmission system, the DC line protection with universal applicability, fast response speed, stability, and reliability is particularly important for its safe and economic operation. In this article, the boundary frequency characteristics of the UHV multiterminal hybrid DC transmission system are analyzed by considering the DC boundary of the rectifier side and inverter side, line frequency variation, and other factors. According to the fact that the boundary of the fault line has a strong attenuation effect on the high-frequency component of the transient current, a protection method based on the intrinsic mode energy entropy is proposed to distinguish the faults inside and outside. The criterion to initiate the protection is constructed by using the amplitude of the transient power; the fault direction criterion is constructed by using the positive and negative characteristics of the transient energy of the fault power detected by power direction elements on both sides of the T-zone; the fault pole selection criterion is constructed by using the ratio of low-frequency transient power changes of positive and negative poles. Finally, the Kun–Liu–Long line UHV three-terminal hybrid DC transmission system model is built on the PSCAD/EMTDC simulation platform, and a large number of simulation examples verify that the protection can operate reliably under different fault poles, fault positions, and transition resistances.

Hybrid Fuzzy-PI and ANFIS Controller Design for Rotor Current Control of DFIG Based Wind Turbine

Wind energy generation provides one of the best and economical solution to the growing power demand. Doubly Fed induction generator is one of the most important variable speed wind generators. Integrating advanced controllers improves its performance and efficiency. The purpose of this research work is to optimize the wind energy conversion and efficient wind power extraction by controlling rotor current. Four controllers that are PI, Fuzzy, Hybrid Fuzzy-PI and Neural network based Adaptive Neuro Fuzzy controller are designed and implemented on DFIG. Controllers’ performance is assessed in terms of transients in rotor current i.e., percentage overshoot, settling time and steady state error under varying wind speed operation. Comparison of the results demonstrates that Adaptive Neuro Fuzzy controller outperforms as compared to that of Hybrid Fuzzy-PI, Fuzzy and conventional PI regarding transient response and maximum power extraction efficiency.

Inherent Safety Characteristics of Lead Bismuth Eutectic-Cooled Accelerator Driven Subcritical Systems

An accelerator driven subcritical system (ADS) is a new nuclear energy system which could not only produce clean energy but also incinerate nuclear waste. In this paper, inherent safety analysis of an ADS is performed with neutronics and thermal-hydraulics coupled code named ARTAP. Five typical accidents are carried out, including the cases of proton beam interruption, transient overpower, reactivity insertion, loss of flow, and loss of heat sink. The transient simulations are performed in the average channel and the hottest channel of the fuel pin in the ADS core. The simulation results for beam interruption show that the highest temperature of the pellet is in the middle of the fuel element in the average channel, while the peak temperature of the cladding is in the top of the fuel element. After the beam is interrupted for 20s, the maximum temperature drops at the fuel center, the cladding inner surface, and the outlet coolant in the hottest channel are 644.46K, 162.27K, and 136.42K respectively. For transient overpower accidents with the increase of beam intensity, the maximum temperature of the fuel and the cladding are below the safety limit. Concerning the reactivity insertion accident, it is found that the ADS has good inherent safety and its margin of criticality safety is large. The calculation results for loss of flow show that the power drop is small due to low sensitivity of the subcritical core to negative reactivity feedback, and the maximum temperature of the cladding reaches 1726K, which means the fuel element would rupture. However, the power and the temperatures of fuel, cladding, and coolant could decrease quickly to the safety level after the proton accelerator is cut off under a loss of flow accident. The results also show that the peak temperature of the cladding is lower than the safety limit under a loss of heat sink accident. The present simulation results reveal that the ADS has a remarkable advantage against severe accidents. It also implies that its inherent safety characteristics could ensure reactor shutdown by cutting off the proton beam after accidents occur.

Transient Differentiation Maximum Power Point Tracker (Td-MPPT) for Optimized Tracking under Very Fast-Changing Irradiance: A Theoretical Approach for Mobile PV Applications

This work presents an algorithm for Maximum Power Point Tracking (MPPT) that measures transitory states to prevent drift issues and that can reduce steady-state oscillations. The traditional MPPT algorithms can become confused under very fast-changing irradiance and perform tracking in the wrong direction. Errors occur because these algorithms operate under the assumption that power changes in the system are triggered exclusively due to perturbations introduced by them. However, the power increase triggered by irradiance changes could be more significant than those caused by the perturbation effect. The proposed method modifies the Perturb and Observe algorithm (P&O) with an additional measurement stage performed close to the maximum overshoot peak after the perturbation stage. By comparing power changes between three measurement points, the algorithm can accurately identify whether the perturbation was made in the correct direction or not. Furthermore, the algorithm can use additional information to determine if the operating point after the perturbation stage is beyond the maximum power point (MPP) and perturb in the opposite direction for the next iteration. Thus, the proposed algorithm shows reduced steady-state oscillations and improved tracking under fast irradiance changes compared to conventional P&O and P&O with power differences (dP-P&O). The design is validated via simulations using fast-changing irradiance tests based on the standard EN 50530 accelerated by a factor of 100×. The proposed algorithm achieved 99.74% of global efficiency versus 97.4% of the classical P&O and 99.54% of the dP-P&O under the tested conditions.

Detailed transient assessment of a small-scale concentrated solar power plant based on the organic Rankine cycle

• New procedures for modeling the components of solar-ORC power plant are proposed. • A routine for optimizing the turbine geometry and evaluating its performance is used. • The power plant results are obtained by coupling the accurate components models. • A power plant continuously supplying electricity to remote communities is designed. • The low ODP and GWP refrigerant R1233zd(E) provided the best performance. Motivated by environmental issues and the needs of communities that live far from the electricity grid, this work presents an innovative methodology for modeling a small-scale concentrated solar power plant based on the organic Rankine cycle. An integrated simulation tool, which consists of accurate computational routines of the energy storage tank, parabolic trough collector, plate heat exchanger, finned air-cooled condenser, and inward-flow radial turbine, is developed. The components are modeled according to distributed models and the mean line method for the turbine in homemade codes to account for local property changes. The transient power plant performance is assessed by employing solar irradiation data of three locations that present mean direct normal irradiation rates of 6306, 4712, and 3220 Wh/m 2 .day. The following working fluids were considered: a low GWP and ODP refrigerant (R1233zd(E)), a natural one (R600a), and a high GWP fluid that is currently employed for such applications (R245fa). The smallest configuration that led to annual uninterrupted power production is a 565-m 2 collector and a 90-m 3 storage tank. The R1233zd(E) refrigerant presented the best overall performance by providing about 2% and 30% higher turbine power output, 3% and 29% higher turbine efficiency, and 4% and 36% higher ORC first-law efficiency than R245fa and R600a, respectively. The designed solar power plant generated 48.396 MWh/year of electricity and 80.621 MWh/year of cogeneration energy with R1233zd(E), which is enough to provide electricity and sanitary hot water to about 33 and 64 houses, respectively.

A Composite Porous Membrane Based on Derived Cellulose for Transient Gel Electrolyte in Transient Lithium-Ion Batteries.

The transient lithium-ion battery is a potential candidate as an integrated energy storage unit in transient electronics. In this study, a mechanically robust, transient, and high-performance composite porous membrane for a transient gel electrolyte in transient lithium-ion batteries is studied and reported. By introducing a unique and controllable circular skeleton of methylcellulose to the carboxymethyl cellulose-based membrane, the elastic modulus and tensile strength of the composite porous membrane (CPM) are greatly improved, while maintaining its micropores structure and fast transiency. Results show that CPM with 5% methylcellulose has the best overall performance. The elastic modulus, tensile strength, porosity, and contact angle of the optimized CPM are 335.18 MPa, 9.73 MPa, 62.26%, and 21.22°, respectively. The water-triggered transient time for CPM is less than 20 min. The ionic conductivity and bulk resistance of the CPM gel electrolyte are 0.54 mS cm−1 and 4.45 Ω, respectively. The obtained results suggest that this transient high-performance CPM has great potential applications as a transient power source in transient electronics.

Investigation on a Solar Thermal Power Plant With a Packed Bed Heat Storage Unit

Abstract The objective of the present work is to research the dynamic thermal performance of the solar power plant during the phase change material (PCM) capsule heat storage tank discharging process. Therefore, a transient, one-dimensional two-phase model for a packed bed latent heat storage unit and a comprehensive concentrating solar power generation system that combines a CO2 Brayton cycle and organic Rankine cycle were integrated. The influences of the key parameters of the packed bed PCM capsule heat storage tank on the overall power output and thermal efficiency of the system during discharge have been investigated, including the heat transfer fluid (HTF) velocity, the diameter of the PCM capsule, and the height of heat storage tank. The orthogonal analysis method is selected in this article, and the results showed that the maximal transient power output and overall power output of the actual combined cycle mode are decreased about 22% and 25%, respectively, in this research, compared with the idea Carnot cycle mode. That the HTF velocity in the thermal energy storage tank can be used to control the transient power output of the solar thermal power system. Using the small-sized filler capsule is an effective method to increase the thermal performance of the concentrated solar power (CSP) combined cycle system. Moreover, the corresponding discharging time is increased obviously, and the CSP with a high packed bed height can generate a more stable power output value during thermal energy discharging.

Transient analysis of multiple straight wires in the presence of a half-space using different time-domain measures

The paper deals with a direct time-domain (TD) analysis of multiple wire configurations using various TD measures based on the energy stored in the near field. The currents along the wires are obtained solving the coupled Hallen integral equations. Once the current distribution is determined it is possible to calculate the charge via continuity equation. Knowing the distribution of current and charge along the wires, TD energy measures involving spatial integrals of squared values of transient current and charge, the energy stored in the electric and magnetic fields of wires are evaluated. Then total TD power measure defined as the time derivative of the total energy measure is computed. Finally, according to the definition stemming from the circuit theory the distribution of root-mean-square (RMS) values of transient current is calculated. Some computational examples for transient current, TD energy, and power measures, respectively, and RMS distribution along the wires are presented.

BISON automation to predict transient power history based off prescribed cladding temperature

Since the restart of the Transient Reactor Test Facility (TREAT) at Idaho National Laboratory (INL) in 2017, advanced testing using various modules within the minimal activation retrievable capsule holder system has been underway with other types being considered for future work due to customer interest. In this work, one such test module—the Temperature Heat-sink Overpower Response module (THOR)—was simulated within BISON with UO2 fuel with zircaloy cladding and U-10Zr fuel with HT9 cladding, and a steel-alloy heat sink with a desired customer prescribed maximum cladding temperature profile. The THOR module is an instrumented capsule within which fuel rods can be irradiated in a liquid–sodium-filled hole in a thick-wall metal heat sink so that, along with TREAT’s unique transient power-shaping capability, experimenters can simulate numerous transient irradiation conditions. For transient testing, specimen temperature history is a primary driver in experiment design, which is primarily driven by the balance of power input to the nuclear heated specimen and the heat-transfer boundary condition associated with a particular experiment design. A simple iterative method was implemented in Python to write a BISON linear heat generation rate (LHGR) power history to produce desired customer-prescribed cladding-temperature values. The BISON LHGR power profile will later be used to write the control rod positions within TREAT to yield the customer-prescribed temperature values. Not all customer prescribed temperature values were achieved when desired temperatures were decreasing due to system limitations of THOR. However, the iterative method shown allows for temporal power histories to be derived, such that all BISON-produced temperatures are within 5% of customer values when increasing or maintaining a constant cladding temperature. The iterative method used allows for the dimensions, materials, and material properties of the THOR module to be customer specific, as well as different customer-prescribed parameters, such as fuel temperature, to be used in place of maximum cladding temperature. This tool allows for different designs and transient scenarios to be explored without manual fitting, allowing for rapid development for customer needs.

Plasma-based microwave power limitation in a printed transmission line: a self-consistent model compared with experimental data

Plasma-based microwave power limitation in a suspended microstrip transmission line integrating a micro hollow cathode discharge (MHCD) in its centre is experimentally and numerically studied. Transient and steady state microwave power measurements exhibit a limitation threshold of 28 dBm and time responses of 25 microseconds. Intensified charge-coupled device imaging shows that microwave breakdown occurs at the top of the MHCD. The plasma then extends towards the microwave source within the suspended microstrip transmission line. Besides, a self-consistent model is proposed to simulate the non-linear interaction between microwave and plasma. It gives numerical results in agreement with the measurements, and show that the plasma expansion during the transient response is related to a shift between the ionization source term and the electron density maximum. The propagation speed, under the tested conditions, depends mainly on the stepwise ionization from the excited states.

Runge–Kutta type-2 method for solving reactor point kinetics equations and its validation by analysing thermal and fast reactor benchmarks

Runge – Kutta type-2 method is used for solving point kinetic equations. Time step size chosen ranging from 10−3-10−4 sec. RK-2 method is applied to estimate power transients of thermal reactor and fast breeder reactors with step, ramp and sinusoidal neutron reactivity perturbations. Results are compared with the standard problem results at different time steps with different numerical methods ie. Modified ETD and Cohen’s methods. This comparison of transient power values shows that RK-2 method is predicting accurately for fast and thermal reactors for longer duration of time.

Coupling dynamic characteristics and transient power angle instability of grid-connected hydropower station with surge tank

This paper investigates the coupling dynamic characteristics and transient power angle instability of grid-connected hydropower station (GCHS) with surge tank. Firstly, the model of GCHS with surge tank is established. Secondly, the coupling bifurcation characteristics are analyzed to illuminate the stability and dynamic response under effect of coupling relationships. Based on decoupling analysis of dynamic characteristics, the coupling mechanism and interaction among sub-systems are revealed. Then, the cause of transient power angle instability is revealed. The appearance and characteristics of power angle instability are analyzed. Finally, the coupling influence of factors on the stability of GCHS is studied. The results show that the GCHS with surge tank has twofold coupling relationships. The twofold coupling relationships generate three sub-oscillations. The stable domain of GCHS is determined by three bifurcation lines. The power angle instability is caused by the nonlinearity of power angle. The dynamic response process of power angle enters the state of instability when the dynamic saddle point appears. The state point of power angle instability locates in unstable domain and has a certain distance to bifurcation line. The factors of generator and power grid have a significant influence on the bifurcation lines and stability of GCHS.

Improved Optimal Control of Transient Power Sharing in Microgrid Using H-Infinity Controller with Artificial Bee Colony Algorithm

The microgrid has two main steady-state modes: grid-connected mode and islanded mode. The microgrid needs a high-performance controller to reduce the overshoot value that affects the efficiency of the network. However, the high voltage value causes the inverter to stop. Thus, an improved power-sharing response to the transfer between these two modes must be insured. More important points to study in a microgrid are the current sharing and power (active or reactive) sharing, besides the match percentage of power sharing among parallel inverters and the overshoot of both active and reactive power. This article aims to optimize the power response in addition to voltage and frequency stability, in order to make this network’s performance more robust against external disturbance. This can be achieved through a self-tuning control method using an optimization algorithm. Here, the optimized droop control is provided by the H-infinity (H∞) method improved with the artificial bee colony algorithm. To verify the results, it was compared with different algorithms such as conventional droop control, conventional particle swarm optimization, and artificial bee colony algorithms. The implementation of the optimization algorithm is explained using the time domain MATLAB/SIMULINK simulation model.