Discharge Operation Research Articles

Operating regimes of a constricted arc discharge in a forevacuum-pressure, plasma-cathode electron source of pulsed large-radius electron beams

We have investigated the operating regimes of a pulsed constricted arc discharge in a forevacuum plasma-cathode electron source of large-radius electron beams. The configuration of the intermediate electrode (IE) with a constricting channel (CC) determines the maximum parameters (current and pulse duration) and operating regimes of the constricted arc. An IE with ceramic (aluminum nitride) CC and an IE with sectional tantalum CC, formed by several electrically insulated tantalum disks with co-axial holes, lead to an increase in the maximum parameters compared to an IE with metal CC. In particular, an IE with sectional tantalum CC provides the highest maximum parameters. The ceramic and sectional tantalum constricting channels also provide lower minimum pressure for which the constricted arc operates stably. When the pressure reaches a certain threshold value, which depends on arc current, a discharge system with IE with sectional tantalum CC provides stable operation for pulse duration up to 10 ms. An increase in pressure provides higher discharge current in the millisecond regime of the discharge operation. When the arc current reaches threshold values from 84 to 92 A (depending on gas pressure), a self-compressed (pinched) mode of operation of the constricted arc occurs. The pinched arc regime is characterized by the highest current and the longest pulse duration. The forevacuum electron source based on the constricted arc discharge with IE with sectional tantalum CC offers generation of low-energy (up to 8 keV) electron beam with current up to tens of amperes and pulse duration up to 10 ms.

Multidimensional ecosystem assessment of Poyang Lake under anthropogenic influences

Watershed anthropogenic activities, including pollutant discharge, sand mining, and upstream reservoir operation, have increased nutrient loads and decreased water levels and sediment concentrations in Poyang Lake, and thus affected the aqueous ecosystem. In this study, we developed an ecological model from the framework of AQUATOX to simulate the physical, chemical, and biological evolution of Poyang Lake under watershed anthropogenic influences, and used model output for a multidimensional ecosystem assessment of ecosystem structure, function, service, material flow, temporal dynamics, and collapse probability. The potential impacts of a proposed Poyang Lake water conservancy project (PYWCP) to build a sluice near the outlet of Poyang Lake to regulate lake level were explored. Results show that the watershed anthropogenic activities have worsened the Poyang Lake ecosystem. Specifically, the phytoplankton biomass increased, while benthos and fish decreased; the exergy, capacity of nutrient change, and the total biomass-gross primary production ratio decreased; as the lake's volume decreased, fishes’ trophic levels and food web robustness decreased, the food web shrank, single species dependence increased, and ecosystem stability decreased. The PYWCP could mitigate most of these effects, however, it would not recover Poyang Lake to historical conditions, and close monitoring with attention to sluice operational scheduling are required.

Comparing Study on Formation of Large Discharge Currents in Atmospheric Pulse-Modulated Radio Frequency Discharges

In recent years, pulse-modulation is introduced in atmospheric radio frequency (RF) discharges to further control the discharge operation. In this article, a comparing study is performed by a 1-D fluid model to investigate the formation of large discharge currents (LDCs) in the first RF cycle during the power-on phase in an atmospheric pulse-modulated RF discharge controlled by dielectric barriers. The current–voltage characteristics and helium metastable (He*) distributions show the enhancement of a pulsed voltage on the ignition of RF discharge, which agrees well with the experimental observation. On the other hand, in a dielectric barrier discharge driven by a sinusoidal voltage of 500 MHz, double LDCs are observed in the positive and negative half-cycles, respectively, and the large pulse rise rate of applied voltage essentially influences the distribution of charged particles in the first cycle during the power-on phase. In this study, according to computational data the reverse electric field near the anode contributes greatly to the generation of LDCs in both types of discharge, and the appropriate discharge conditions are suggested to optimize the pulse-modulated RF discharges in applications.

Experimental study of gas flow rate influence on a dielectric barrier discharge in helium

A systematic study was performed to investigate the influence of gas flow rate on a helium dielectric barrier discharge. A closed-chamber barrier discharge with plane electrodes was examined through electrical and spectroscopic measurements for a set of gas flow rates varying from 0.05 l min−1 to 5 l min−1. The work was concentrated on the presumed connection between the gas flow rate and the impurity level, and consequential change of the discharge operation. A method was developed for estimation of impurities from the emission spectrum and applied in our discharge. The obtained results showed a strongly non-linear decrease of impurities concentration with increasing flow rate of the working gas. Experimental results showed a significant change of electrical properties, like breakdown voltage and current density with the gas flow. The measured electric field distribution did not show important change. The increase of the gas electrical capacitance with gas flow rate was detected, due to the rise of the transferred charge. The intensity of atomic and molecular emissions, along with space time development of certain emissions indicated the change in excitation mechanism with the variation of the gas flow. Analysis shows that the main mechanism of the changes in the discharge is the decrease of impurities, which leads to reduction of helium metastable quenching which, in turn, increases the density of helium metastables important for ionization and excitation processes. The obtained results mostly agree with the models of the discharge behavior with change of impurity level.

Bromine Crossover in Operando Analysis of Proton Exchange Membranes in Hydrogen-Bromate Flow Batteries.

The manuscript deals with the fundamental problem of platinum hydrogen oxidation catalyst poisoning of the hybrid chemical power source based on bromate electroreduction and hydrogen electro-oxidation reactions. The poisoning is caused by the crossover of bromine-containing species through the proton exchange membrane separating compartments of the flow cell. Poisoning results in a drastic decrease in the flow cell performance. This paper describes the results of the direct measurement of bromine-containing species’ crossover through perfluorosulfonic acid membranes of popular vendors in a hydrogen−bromate flow cell and proposes corresponding scenarios for the flow battery charge−discharge operation based on the electrolyte’s control of the pH value. The rate of the crossover of the bromine-containing species through the membrane is found to be inversely proportional to the membrane thickness.

An optimization approach to increasing sustainability and enhancing resilience against environmental constraints in LNG supply chains: A Qatar case study

Natural gas is an essential fuel in the transition towards a sustainable energy future as it is a cleaner source of fuel compared to other hydrocarbon sources. To enable natural gas delivery from the producer to consumers, natural gas is liquified to enhance transportation efficiency and reliability. This study contributes towards advancing decision support systems within the LNG supply chain to enhance sustainability and resilience. Five scenarios are investigated in terms of vessel types (Conventional, Q-Flex, Q-Max, and mixed fleet), delivery operation modes (single discharge and multi-discharge), and different bunker fuels (HFO, LNG, and dual-fuel). The Mixed Integer Programming model is used to schedule, assign and deliver a fixed number of LNG cargoes within one month considering total transportation costs and emissions. The developed model, which is implemented using the Binary Particle Swarm Optimization algorithm subjected to economic and environmental objectives within an overarching strategic aim for sustainability and resilience. The results demonstrate that using LNG as a bunker fuel supports the reduction in the total emissions within LNG transportation leading to enhancing the resilience of LNG delivery operations against growing environmental constraints. Outputs of the study indicate that the multi-discharge LNG-fuelled operation mode can achieve a cost reduction of 23.4% and a total emission reduction of 19.7% relative to a single discharge operation mode, where boil-off gas has a minor impact compared to the emissions released from fuel consumption.

Performance study of large capacity industrial lead‑carbon battery for energy storage

Electrochemical energy storage is a vital component of the renewable energy power generating system, and it helps to build a low-carbon society. The lead-carbon battery is an improved lead-acid battery that incorporates carbon into the negative plate. It compensates for the drawback of lead-acid batteries' inability to handle instantaneous high current charging, and it has the benefits of high safety, high-cost performance, and sustainable development. The recycling efficiency of lead-carbon batteries is 98 %, and the recycling process complies with all environmental and other standards. Deep discharge capability is also required for the lead-carbon battery for energy storage, although the depth of discharge has a significant impact on the lead-carbon battery's positive plate failure. This study optimizes and enhances the lead-carbon battery's positive plate, allowing it to perform both high-current charging (340.255 A) and deep discharge (70 % DOD) operations. Selecting acceptable lead alloys, improving the structure of the positive grid, and regulating the grid's curing and drying processes are all part of the optimization and improvement process. The upgraded lead-carbon battery has a cycle life of 7680 times, which is 93.5 % longer than the unimproved lead-carbon battery under the same conditions. The large-capacity (200 Ah) industrial lead-carbon batteries manufactured in this paper is a dependable and cost-effective energy storage option.

Patterns of internal nitrogen and phosphorus loadings in a cascade reservoir with a large water level gradient: Effects of reservoir operation and water depth

Internal nutrient loadings pose a high risk of being an additional N and P source, exacerbating eutrophication and deteriorating water quality. In this study, we selected the Daheiting Reservoir (DHTR) in North China, with a pronounced water level gradient, to investigate internal N and P loadings, estimate N and P fluxes across the sediment‒water interface based on the pore water profiles, and reveal the potential effects of water discharge from an upstream reservoir and high-intensity cage aquaculture on the risks of internal N and P release. The results indicated that DHTR presented with severe internal nutrient loadings, and the N and P fluxes showed significant spatiotemporal variations. NH4+−N and soluble reactive phosphorus (SRP) fluxes were higher in deep areas (averages of 26.14 and 9.9 mgm−2d−1, respectively) than in shallow areas near inflows (averages of 5.0 and 1.24 mgm−2d−1, respectively). Unexpectedly, the estimated NH4+−N and SRP fluxes were the lowest in summer (averages of 3.94 and 0.33 mgm−2d−1, respectively), which may have been influenced by seasonal thermal stratification and copious discharge from the hypolimnion of the upstream reservoir (Panjiakou Reservoir). Comparison of annual internal and external N and P loadings revealed that water discharge from the upstream Panjiakou Reservoir was the dominant source of N and P to the reservoir, contributing up to 83.6% of N input and 55.4% of P input. The internal P loading also contributed to water eutrophication to a great extent, accounting for 34.7% of the total P input. Our results highlight the impact of upstream reservoir discharge operation on downstream reservoir water quality and the importance of controlling the internal nutrient loading in cascade reservoirs, and further provide theoretical and practical foundations for the development of policies and strategies to conserve reservoir ecosystems.

Operational intra-cycle temporal and current mode effects on battery capacity loss

As part of an on-going research effort towards developing a comprehensive overview of contributing operational factors to lithium ion battery degradation, new analysis and results are presented here which demonstrate the durational effects of battery charge and discharge operations on cell capacity loss. A set of cell cycling tests with a range of different discharge amplitudes provided data for this analysis which led to an advance on how to quantitatively account for the degradation effects in terms of their temporal duration. A factor accounting for operational duration effects usable as a parameter in battery life models was a key result of this project. An additional set of cell cycling experiments was conducted with the aim of decoupling degradation rates attributable to either the discharge or recharge portion of the complete cycle, and some differences were observed and quantified. • Uniquely patterned battery cycling experiments isolated cell degradation factors. • In particular, variable amplitudes and asymmetric cycle forms were tested. • Functionality obtained for a degradation driver based in operational duration. • Decoupling of discharge and recharge effects on degradation; recharge is costlier. • These cycle patterns relate to duty cycles found in the transportation sector.

Analytical Model and Experimental Study of a Cylindrical DBD Discharge Operating in the Filamentary Mode

In this work, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz.

Demand response approach in the presence of plug-in hybrid electric vehicle for profit maximization of utility

• Scheduling of battery ESS and EV in the presence of multiple DG resources. • Analysing the impact of the proposed DR during the different operating nature of battery ESS and EV as uniform and converse operation respectively. • Evaluating the proposed DR program at its full potential for profit maximization. The efficient operation of available resources and the penetration of renewable resources into the existing power network require prior and proper scheduling. The potency of Demand Response (DR) relies on its capability to revise the load demand in accordance with the conditions of the grid. The proper implementation of a DR program can reduce the import cost of the consumer and reduces the peak load of the utility which will assist in the smooth operation. The appropriate Battery Energy Storage System (BESS) and a suitable DR program aid in managing the loads to maintain a balance in the demand–supply chain. The influence of extensive integration of Electric Vehicles (EV) into the system is inevitable which also demands a suitable scheduling scheme along with all the available resources. Renewable energy generation, energy storage systems with the inclusion of EVs, and the utilization of grid power are all planned using the real-time electricity tariff profile. The profit of the system is analyzed in the presence of multiple DG resources incorporating plug-in hybrid EV and ESS along with Demand Response (DR) under the converse (any one is charging while other is discharging) and uniform (either one is charging and the other is discharging) operation. The proposed DR approach is scalable and generalized, claiming to be suitable for huge-scale renewable energy integrated power systems as well. The proposed method is tested on IEEE 33 and 69 bus systems and the accomplished results are promising.

Electron power absorption in capacitively coupled neon–oxygen plasmas: a comparison of experimental and computational results

Phase resolved optical emission spectroscopy (PROES) measurements combined with 1d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations are used to study the electron power absorption and excitation/ionization dynamics in capacitively coupled plasmas (CCPs) in mixtures of neon and oxygen gases. The study is performed for a geometrically symmetric CCP reactor with a gap length of 2.5 cm at a driving frequency of 10 MHz and a peak-to-peak voltage of 350 V. The pressure of the gas mixture is varied between 15 Pa and 500 Pa, while the neon/oxygen concentration is tuned between 10% and 90%. For all discharge conditions, the spatio-temporal distributions of the electron-impact excitation rate from the Ne ground state into the Ne 2p53p0 state measured by PROES and obtained from PIC/MCC simulations show good qualitative agreement. Based on the emission/excitation patterns, multiple operation regimes are identified. Localized bright emission features at the bulk boundaries, caused by local maxima in the electronegativity are found at high pressures and high O2 concentrations. The relative contributions of the ambipolar and the Ohmic electron power absorption are found to vary strongly with the discharge parameters: the Ohmic power absorption is enhanced by both the high collisionality at high pressures and the high electronegativity at low pressures. In the wide parameter regime covered in this study, the PROES measurements are found to accurately represent the ionization dynamics, i.e. the discharge operation mode. This work represents also a successful experimental validation of the discharge model developed for neon–oxygen CCPs.

Thermal design and analysis of an organic rankine cycle system utilizing the main engine and cargo oil pump turbine based waste heats in a large tanker ship

The utilization of main engine-based waste heat sources using organic Rankine cycle (ORC) systems is only available during the navigation phases of marine vessels, which leads to reductions in the system uptake time and economic viability of the investment during cargo loading/discharging operations and waiting periods in ports. The novel perspective of this study is to propose the cargo oil pump turbine (COPT) based waste heat as a utilizable source, which has not been introduced in the literature yet, and show the economic viability of ORC systems for tanker ships. In this regard, a new waste heat recovery system specifically designed for a reference crude oil tanker ship was introduced that can utilize both main engine-based waste heat during navigation and COPT-based waste heat during cargo discharge operations. The optimal heat exchanger network of the main engine and COPT-based waste heats was designed using pinch point analysis method for achieving optimum waste heat recovery. Energy and exergy analyses were conducted for the proposed ORC integrated waste heat recovery system for both navigation and discharge operation modes of the ship. The economic performance of the ORC system was further assessed by calculating payback periods and levelized energy costs for eleven design points. The highest energy conversion efficiency (16.2%) was achieved when the ORC condenser outlet temperature was taken as 15 °C for R1233zd(E). COPT based waste heat reduced the levelized energy cost of the system by at least 8.9% and the minimum levelized energy cost value was obtained as 0.1307. The best economic performance was yielded with COPT utilization at design point 9 with a payback period of 6.2 years, which was reduced by at least 0.7 years with the utilization of COPT based waste heat.

Analysis of a direct vapor generation system using cascade steam-organic Rankine cycle and two-tank oil storage

A direct vapor generation solar power system using cascade steam-organic Rankine cycle and two-stage oil tanks is proposed. It offers a significantly enlarged storage capacity due to the unique discharge operation mode. Synthetic oil Therminol® VP-1 is used as the heat carrier and storage medium. Compared with the direct steam generation system, the steam turbine inlet temperature is elevated from 270 °C to 311 °C. Thermodynamic analysis indicates that the optimal equivalent heat-to-power conversion efficiency (ηeq,opt) is 27.91% when benzene is used as the bottom fluid and the mass of oil is 1000 tonnes. ηeq,opt is raised by 7.72–11.60% for the selected four organic fluids as compared with the direct steam generation type. The temperature drop of oil during discharge can reach about 280 °C. Economic studies demonstrate that the proposed system is more cost-effective. Its equivalent payback period is less than 5 years for a 10 MW system with 2000 tonnes of oil. Further investigation shows that it is also more advantageous than a conventional thermal oil-based indirect solar power system due to the cost reduction in heat storage.

Near Neutral Aqueous Fe-Cr Complex Flow Battery

A redox-flow battery (RFB), as schematically shown is a unique type of rechargeable battery in which the electrochemical energy is stored in soluble redox couples contained in electrolyte tanks, and the electrical energy and the chemical energy are converted back and forth inside a device called “stack”. This unique structure successfully separates the power (stack) and the energy (electrolyte) of the battery system and can be economically designed for long-duration energy storage applications. While vanadium flow batteries have achieved initial commercial deployments, the cost of a four-hour system at deployment-scale is still more than $300/kWh, more than 50% of which comes from the cost of the energy storage media – Vanadium element. DOE’s multiple programs clearly indicates that future capital cost reductions will require replacing vanadium with lower cost raw materials to approach the $100/kWh targets required for wider-scale deployment of energy storage systems. Since 2018, attracted by its low electrolyte cost, our team have been working on the legendary Fe-Cr redox flow battery system, which was first invented by Dr. Lawrence Thaller of US NASA in 1975, to develop a low[1]cost flow battery product. The energy storage capacity decay caused by H2 generation, which comes from the negative electrode due to the low standard potential of Cr 2+ /Cr 3+ , makes it not practical for long-term energy[1]storage operations. After two years’ research, we have successfully developed an advanced Fe-Cr redox flow battery system. In this system, no capacity decay over continuous charge and discharge operation has been successfully achieved by an extremely low H2 generation design and a unique capacity recovery technology using a reductant and a homogeneous catalyst. Continuous operation of a test stand using a kW-scale stack and 100L electrolyte for a total 1000 cycles has been successfully achieved. Related information and results were published in the granted US patents US 10,826,102 and US 10,777,836, and the US patent applications 20200373594, 20200373595, 20200373600, 20200373601. During our previous development of the advance Fe-Cr redox flow battery, we discovered that the stability and electrochemical activity of Fe- and Cr-containing species in the aqueous solution can be remarkably improved by complexing them with some ligands. The acidity of this novel electrolyte solution is much weaker than that of the traditional Fe-Cr flow battery system, i.e., ~0.1M vs. >2M, which largely reduces the corrosivity of the electrolyte and allows for wider applications of this system with minimal environmental impact, especially for residential users and small-scale commercial and industrial users. Several different complexing ligands were identified. All showed very stable performance and low side reactions. Up to now, the test has been continuously carried out for more than three months and more than 500 cycles, using a kW-scale stack and 100 L electrolyte solution. Much-improved electrochemical reactivity of the Fe- and Cr-complex also eliminates the need for metal catalysts for the Cr 2+ +e ↔ Cr 3+ reaction, significantly improved the stability of the system for long-term operation.

Modeling Study of Commercial NCA Cylindrical Battery Cells’ Impedance Behavior Under Different Operation Conditions

The classic 18650 and 21700 format cylindrical Li-ion batteries have been widely used today to power electric vehicles (EVs). Their wound jelly-roll structure (in a form of an Archimedean spiral) can provide a relatively higher energy density in the limited EV given space comparing with the battery cells using stacked electrodes. As the rapid development and deployment of EV technology require high performance and reliable Li-ion batteries, it is critical to understand the mechanism and process behind battery cell behaviors under various driving conditions. In this study, a series of impedance experiments is designed to explore the impact of battery state of charge (SOC), temperature, C-rates and other operating conditions. Then, an impedance mathematical model is developed to explore the potential mechanisms behind experimental observations. Our obtained results show that the impedance response of cylindrical NCA battery cells varies with the state of charge in both charge and discharge operation, and the SOC dependent impedance existed in different operating temperatures and C-rates. Through modeling analysis, results indicate the operating temperature and charge-discharge rate could significantly influence the impedance response of the battery cell but could not directly cause the variation of the impedance response at different SOC conditions. Besides, modeling results also show that the contact resistance variation, resulted from the expansion and contraction of cell electrodes during charge and discharge, could lead to a SOC dependent impedance behavior of the commercial cell and influence battery output performance.

A Fluid Dynamic Analysis of Mixing Phenomena inside Electrolyte Tanks to Enhance Performance of Industrial-Scale Vanadium Redox Flow Batteries

The control of electrolyte concentration supplied to the stack of a redox flow battery is crucial to determine voltage output and so power performance of Redox Flow Batteries (RFBs). In common lab-scale RFBs systems, in particular vanadium ones, perfect mixing hypothesis is usually assumed regarding mixing in tanks, due to small volumes involved. The State of Charge (SOC) of large-scale vanadium redox flow batteries is usually measured by means of Open Circuit Voltage (OCV) cell. The Industrial Scale Vanadium Redox Flow Battery (IS-VRFB) which is currently in operation at the Electrochemical Energy Storage and Conversion Laboratory (EESCoLab) of the University of Padua (Padova, Italy) with a rated power/energy of 9 kW/27 kWh is equipped with two 550 L electrolyte tanks. This experimental facility is suitable for the evaluation of differences between the measured SOC and the real one in the tanks. In fact, galvanostatic constant flow factor charge and discharge operations show unpredicted behaviour in the SOC curves measured through the OCV cell upstream the stack. In particular, a step size variation results from low current charge operations after a long quasi-flat plateau whose duration is correlated to current and flow rate values considered. Due to the lack of similar studies in scientific literature, a computational fluid dynamic analysis has been performed by using commercial software. Common adopted transient models where flow-field is considered time-independent resulted in numerical plateau which is orders of magnitude smaller than the experimentally measured. Therefore, it is reasonable to hypothesize that other time-dependant physical phenomena are involved in mixing and should be taken into account. Thermal effects due to electrochemical reactions were considered negligeable with respect to buoyancy phenomenon that is triggered from electrolyte density variation in charging-discharging operations. Considering high estimated Richardson number for tank, natural convection inside stored electrolyte volume is modelled through Boussinesq hypothesis, identifying a fictitious temperature gradient between bulk and inflow electrolyte. Taking advantage from buoyancy driven segregation phenomena can lead to control concentration distributions in the electrolyte volume and therefore manage power performance of the tank in charge and discharge. This study intends to provide skills for the RFB designer in order to proper size tanks according to their needs.

Comparative study of two cold plasma technologies on apple juice antioxidant capacity, phenolic contents, and enzymatic activity

Cold plasma technologies are being developed as an alternative to thermal processes aiming toward preservation while retaining or improving several quality parameters. This research evaluates the use of dielectric barrier discharge (DBD) plasma and glow discharge plasma on browning enzyme activity, antioxidant capacity, and total phenolic content of apple juice. This work evaluated the effects of the main DBD plasma operating conditions, such as excitation frequencies (50–900 Hz), and glow plasma discharge operating conditions, such as air plasma flow rates (10–30 ml/min) and processing time (10–30 min). Both plasma systems partially inactivated the enzymes polyphenol oxidase and peroxidase and consequently increased apple juice's total phenolic content and antioxidant activity. DBD plasma technology presented better efficacy in increasing apple juice's total phenolic content and antioxidant capacity. DBD plasma and glow discharge plasma have the same effectiveness in inactivating browning enzymes in apple juice. Novelty impact statement This work compares two cold plasma technologies for apple juice processing. The results showed that different plasma technologies lead to different outcomes and that the right choice of technology should be made for a given goal.

Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects

In recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO3−), nitrite (NO2−) and hydrogen peroxide (H2O2), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O3) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.

CFD simulation of an integrated PCM-based thermal energy storage within a nuclear power plant connected to a grid with constant or variable power demand

The current numerical study investigates the integration of a phase change material (PCM)-based thermal energy storage (TES) system within a nuclear power plant (NPP) to enhance the capability of such proposed plant to better follow the variations of power grid demand especially in countries with a high share of nuclear in their energy mix. This study focuses on the transient behavior of the PCM during the simultaneous charging and discharging (SCD) operation mode during one day. For this, an enthalpy-porosity method is used to simulate the SCD operation mode of PCM within an axisymmetric vertical triplex tube. Hot and cold heat transfer fluids (HTFs) are simultaneously co-circulating within the TES for downward-inner heating and upward-outer cooling. Constant and variable loads are considered to study the load-following ability of the coupled system. During the SCD mode with a constant load, results show that an equilibrium between melting and solidification (charging and discharging) is established and the liquid fraction (20%) is not changing with time. Under the variable load, the suggested TES system is able to follow the daily variation of the grid demand and, hence, fill the gap between reactor supplied energy and grid power demand with the reactor constantly operated at full rated capacity. During the variable load, the liquid fraction within PCM is altering from solid to liquid phases and vice versa depending on the deviations of the grid as expected.