Performance Characteristics Of System Research Articles

System Performance Characteristics of Darrieus Turbine with Tilted Blades in Current and Wave Conditions

Indonesia has abundant sources of renewable energy from ocean currents and waves, or a mixture of currents and waves at certain times to be used as an energy source for power plants. So at the Indonesian Hydrodynamics Laboratory, a study has been carried out to determine the performance of the Darrieus-type vertical axis turbine model to utilize the energy of ocean currents and waves. But the Darrieus Turbine with the turbine blades positioned perpendicular to the turbine axis cannot rotate if there is only wave force. Then several turbine models were made with the placement of the blades in an inclined position, to produce optimal rotor rotation in current conditions or a mixture of currents and waves. This paper describes the testing of 3 turbine models by varying the angle of inclination of the turbine blades (45°, 60°, and 75°), but still having the same turbine rotor area and giving different input currents and wave periods to produce the best efficiency and rotation in absorb current energy or a mixture of current and wave energy. The test results show that the 3 models of slanted blade turbines can absorb both wave and current energy, but turbines with 75° blade inclination produce the best performance compared to the others when exposed to currents and waves

Numerical analysis of two-bed adsorption thermophysical battery

Air conditioning systems powered by waste energy sources, such as solar-driven adsorption air conditioning systems, hold significant importance. The present study delves into the performance assessment of a silica gel-based adsorption thermophysical battery (ATB) under varying operational conditions. Advanced cycles featuring a two-bed configuration have been devised to enable semi-continuous operation and refrigeration. This novel design presents a compact ATB that integrates the evaporator and condenser within a single heat exchanger, referred to as the Evaporator-Condenser Unit (ECU), thereby reducing the overall size and cost of the ATB system. The operating and design characteristics of the two-bed adsorption system were thoroughly explored using a theoretical model developed through MATLAB software. Evaluations were conducted on various performance metrics of the ATB, encompassing the coefficient of performance (COP), cooling capacity, specific cooling power, adsorption isotherm, and kinetics. A theoretical approach was formulated using the lumped parameter (LPM) and modified Freundlich adsorption equations. It can be deduced that the inlet temperature of the hot coolant exhibited a direct proportion with both refrigeration effect (RE) and specific cooling power (SCP) while inversely affecting the coefficient of performance (COP). A decrease in coolant temperature from 313 to 303 K resulted in a noteworthy 13.4 %. Furthermore, it was observed that COP exhibited a direct proportionality with the flow rate of chilled and cooled water while inversely relating to the flow rate of hot water.

Cross-Space Conduction Assessment Method of Network Attack Risk under the Strong Coupling Characteristics of Electric Power Cyber Physics

With the deep integration and wide application of advanced digital sensing, Internet of Things technology, and energy technology in power systems. Power information systems and physical systems are gradually being coupled and developed into power cyber–physical systems (CPS). A number of blackouts in recent years have shown that cyberspace cyber attacks on CPS can lead to the intensification and rapid spread of faults in the physical space of the power grid, and even system collapse. Aiming at the difficulty of analyzing the evolution of cyber–physical cross-space impacts of cyber-attacks, this paper proposes a cross-domain propagation impact assessment method that considers cyber–physical coupling risks caused by attacks. First, according to the multiple coupling relationship between the power system information space and physical space, the monitoring function model and the control function model are established. Second, under the effect of high-concealment attack, analyze the impact of the risk caused by its failure after it is transmitted to the physical space with different propagation probabilities. Finally, the experimental verification was carried out using the IEEE RTS79 standard test system. The simulation results show that the proposed method can comprehensively consider the cyber–physical energy supply coupling relationship, the risk propagation probability, and the operating characteristics of the information system, and effectively quantify and evaluate the impact of information space network attacks on the physical space entity power grid. It further reveals the objective law that information space risks can evolve and spread across domains under the condition of strong coupling of information physics.

Performance assessment and resilience of solar mini-grids for sustainable energy access in Ghana

Mini-grids are increasingly adopted as a solution to extending electricity to remote communities in Africa. However, the system's resilience to meet increasing demand amidst degrading performance over time continues to be challenging. This study assessed mini-grid performance and explored factors that should be considered in scaling up mini-grids for sustainability in five island communities in Ghana's Volta Lake. Power generation and load data, visual inspection and thermal imaging data, and electrical systems performance characteristics data were collected and analysed using data loggers installed on site, the IEA PVPS Task 13 guidelines, and the IEC-TS 61724-3: 2016 guidelines, respectively. The study's findings indicate that the solar power conversion efficiency of the mini-grids was generally low and had a 25% - 45% performance ratio. This low efficiency was due to inefficiencies in the battery bank, distribution losses, and unused losses. The overall system efficiency of the mini-grids ranged from 4% to 7%. This is consistent with the literature, which reports that PV power systems in tropical climates have an efficiency of 5% – 15%. The research emphasises the importance of system maintenance, load management, and considering climate change's impact on mini-grid reliability and sustainability.

Characterization of a novel two-stage high ash coal gasifier for low tar and high calorific value gas

The high ash content of coal poses two critical challenges in conventional gasifiers: (a) ash agglomeration and (b) low-quality syngas. The ash agglomerations are caused by the interaction of alkali and alkaline earth metals with other inorganic compounds, localized temperature generation, and unoptimized process parameters. Whereas low-quality gas is due to moderate temperature operations and the mixing of syngas with pyrolysis products. Recognizing these challenges, the current work discusses the design, development, and performance characterization of a novel two-stage gasification system that strategically segregates oxidative pyrolysis in a cyclone reactor and oxy-steam char gasification in a packed bed reactor. Such segregation provides explicit control over parameters like local temperatures, particle and gas residence time, enabling the configuration to handle coal with a wide range of ash content. Thermodynamic analysis and performance characterization experiments have been carried out with varied temperatures, oxygen, and steam flow rates. While operating the system up to 950˚C, there was no indication of clinker formation. The gravimetric tar content was found 52 ± 3 mg/Nm3. The concentration of CO, CO2, CH4, and H2 in the product gas during experiments was 40 ± 5, 20 ± 5, 2 ± 1, and 45 ± 5%, respectively. The carbon conversion was greater than 77%, with further scope for improvement.

Mobile Proton-Exchange Membrane Fuel Cell Powered by Diesel Fuel: System Simulation and Life Cycle Analysis

Diesel engine generators used at construction sites generate noise, vibration, and large amounts of pollutant emissions. With the strengthening of emission standards for construction equipment, technologies must be developed to meet new requirements. We proposed and analyzed a mobile proton-exchange membrane fuel cell diesel-powered system to address these issues. The proposed system consisted of an autothermal reformer, a proton-exchange membrane fuel cell, and a balance of plant components. Previous studies on the system have not explored the optimal design and operating condition of the system and have not shown whether the proposed system is superior to the system using the hydrogen-fueled proton-exchange membrane fuel cell system in the life-cycle greenhouse gas emissions point of view. In this study, we clarified system operation characteristics, determined the operational design point, and evaluated system performance and life-cycle greenhouse gas emissions. The system was analyzed by constructing a zero-dimensional simulation model. Several control parameters were varied in parametric studies to determine the operational design point (steam-to-carbon ratio of 2, oxygen-to-carbon ratio of 0.5, fuel utilization factor of 0.85, and heat exchanger effectiveness of 0.85). Considering system performance, the determined design point achieved a 32.3% efficiency. Additionally, we assessed the life-cycle greenhouse gas emissions of the system and compared them with those of an alternative system, which is a hydrogen-fueled proton exchange membrane fuel cell system. It was confirmed that in the United States of America, the proposed system emits 1010.2 g-CO2-eq/kWh of greenhouse gas at a 300 km fuel transportation distance, which is similar to a hydrogen-fueled proton-exchange membrane fuel cell system (1001.1 g-CO2-eq/kWh). The proposed system emits less greenhouse gas emissions than the hydrogen-fueled proton-exchange membrane fuel cell system if the distance from the hydrogen production site to the construction site is more than 318 km. Therefore, for a construction site far from a hydrogen production plant, the proposed diesel-fueled proton-exchange membrane fuel cell system is preferable from both the greenhouse gas emissions and convenience perspectives.

Performance amelioration of simultaneous up- and down-mixing contingent on a parallel SOA-MZIs design

The primary focus of this research is the creation of a first-ever experimental investigation for simultaneous up-down mixing based on three parallel semiconductor optical amplifier Mach-Zehnder interferometers (SOA-MZIs). The three mixed signals from the SOA-MZI terminals are coupled together to create a simultaneous up or down-mixed signal using an optical coupler (OC). The identified mixing function makes use of the consequences of cross-gain modulation (XGM) as well as cross-phase modulation (XPM) that have been shown at the SOA-MZI outlets. Furthermore, the performance characterization of the photonic parallel system is examined and assessed in the optical and electrical sectors. The outcomes of our experiment closely resemble those of the simulation. Several measurable factors, including power scaling measurements, optical conversion gain (OCG), power stability, beam quality factor, electrical conversion gain (ECG), and error vector magnitude (EVM), are employed to evaluate the photonic up and down-mixed signals. This three-parallel SOA-MZIs architecture has a wide range of applications involving radio over fiber and optical telecommunications. A 256-QAM (Quadrature Amplitude Modulation) up- and down-mixed signals can have a top bit rate of 64 Gbit/s with excellent EVM values. Additionally, the maximal frequency range of the concurrent up and down-mixed signal is 80 GHz. The ECG also displays significant values for up and down conversion. In the optical domain, the OCG has the highest values of 15 dB for the up-mixed signal and 12 dB for the down-mixed one, with a data input power of −10 dBm. Finally, the simultaneous mixing system tackles an outstanding beam quality factor with M2 measurement of less than 1.3 (M2<1.3).

Performance characteristics of the fork-join queuing system

Objectives. The problem of investigating a fork-join queuing system is considered. It is required to build the process of the system functioning, to find the condition for the existence of a stationary distribution, and propose algorithms for calculating the stationary distribution and the main stationary performance characteristics. The special interest of the study is to obtain the lower and upper bounds of the mean sojourn time of a customer in the system.Methods. Methods of probability theory, queuing theory and matrix theory are used.Results. The functioning of the system is described in terms of a multidimensional Markov chain. A constructive condition for the existence of a stationary distribution is found, and algorithms for calculating the stationary distribution and stationary performance characteristics of the system are proposed. Analytical expressions are obtained for the lower and upper bounds of the mean sojourn time of customers in the system.Conclusion. The functioning of the fork-join queuing system with a stationary Poisson flow has been studied. Each of the arriving customers forks into two tasks that go to two subsystems, each of which consists of a server and a buffer. We assume that the buffer to one of the servers is unlimited, and to the second server has a finite volume. Service times have, generally speaking, different phase distributions (PH-Phase type distributions). For this system, a condition for the existence of a stationary distribution is obtained, algorithms for calculating the stationary distribution and a number of stationary performance measures of the system are proposed. Analytical expressions for the lower and upper bounds of the mean sojourn time of a customer in the system from the moment it enters the system to the moment of synchronization, which is a critical performance indicator of the fork-join queues, are obtained. The results of the study can be used for modeling various computer and communication systems, in particular, systems that perform parallel computing, customer processing in distributed databases, and parallel disk access.

Assessment of the integration of a switched nuclear isomer material with a kinematic Stirling engine

Presently, power systems are limited by the source and energy density of the chemical fuels that are currently in use. In response to this challenge, nuclear energy sources are being developed. Metastable nuclear states, or isomers, have an intrinsic energy density that is many orders of magnitude larger than chemical fuels. Through isomer depletion (or switching), these materials can be transformed from a long-lived half-life energy-storage state to a shorter-lived half-life energy-releasing state. The abundance of energy released by switched nuclear isomer (SNI) materials introduces unique engineering challenges for the power conversion system. Once an SNI material has been switched, its heat output decays with time. In contrast to hydrocarbon-based fuels, which can be throttled, generating constant power from an SNI system requires sufficient material based on duration of use and system efficiency. Despite these challenges, SNI materials could be used to replace chemical fuels for relatively high-power applications providing months of power from a compact energy source.The purpose of this work is to explore the coupling of an SNI heat source to a kinematic Stirling engine in order to assess the potential of such a system. First, the characteristics of a reference SNI material are discussed in the context of the conversion efficiency and power density of the power conversion system that it is coupled to. Second, the integration of an SNI with a kinematic Stirling engine is explored at two power levels, 6 kWe and 60 kWe, in order to explore the feasibility and efficiency of such a power system. In order to carry out this study, a second-order Stirling engine model (the Stirling Engine Trade-space Tool, or SETT) has been developed. The potential of the SETT tool to predict performance trends has been shown through comparison of the predicted to the measured performance for two baseline, well-documented Stirling engines: the GPU-3 (nominally 6 kW) and Mod II (nominally 60 kW) engines. The SETT model is then used to optimize the design of the integration heat exchanger that is used to thermally couple a Stirling engine to the SNI and evaluate the performance characteristics of this energy conversion system. The resulting model is also used to show that the kinematic Stirling engine has advantages related to its inherent ability to modulate its output through speed or inventory control, allowing it to effectively deal with the time varying rate of heat transfer that is inevitably provided by the SNI. This work shows that the kinematic Stirling engine is an attractive power conversion system to use with SNI material as it can achieve high conversion efficiency, high power density, and provides inherent modulation capability.

A thermally-coupled cascade free-piston Stirling engine-based cogeneration system

Resonant Stirling/thermoacoustic cycle engines show great potential in efficiently recovering waste heat in small- or micro-scale applications. However, there is a significant research gap regarding the development of resonant Stirling/thermoacoustic cycle engines capable of effectively harnessing variable-temperature heat sources through cascade utilization. In this paper, a cogeneration system was proposed based on a thermally-coupled cascade dual-opposed free-piston Stirling engine. Through a multi-stage arrangement, the prototype enhances overall exergy efficiency by scavenging different grade heat. According to test results, with an input heating power of 20 kW for each stage, the corresponding heating temperatures for the three stages were 418.7 °C, 348.2 °C, and 302.8 °C, respectively. The demonstration setup provided simultaneous thermal power of 44.72 kW and electric power of 10.18 kW, resulting in an overall thermal-to-electric efficiency of 16.48% and an overall combined heat and power efficiency of 88.87%. Theoretically, compared with a single-stage system, the exergy efficiency improved from 36.3% to 43.9%, representing a relative improvement of more than 20%. This study provides valuable insights into the operating characteristics of multi-stage free-piston Stirling engine-based cogeneration systems and contributes to the development of waste heat recovery systems.

Performance characteristics of a compact self-circulating liquid desiccant air dehumidification system coupled with a heat pump: A comprehensive parametric study

Integration of a heat pump with a liquid desiccant system for air dehumidification has received growing attention in recent years in view of its more compact size and lower electricity consumption. This paper presents a compact combined heat pump and self-circulating liquid desiccant air dehumidification system targeted at small cooling load applications. The compactness lies in the integration of the dehumidifier and evaporator as well as the integration of the regenerator and condenser. Besides, the design of solution self-circulation (SSC) is intended for energy savings and the auxiliaries are employed to help achieve energy matching between the heat pump and the air dehumidification system. First, a comparative study is performed to identify the more energy efficient one of the two strategies for energy matching. Based on this, a thermodynamic model-based parametric study is conducted to investigate the effects of various influencing factors on the energy matching relationship and performance of the proposed system, as well as the energy-saving potential relative to the basic system without SSC. The results show that there exists an optimum solution self-circulation ratio (SCR) to achieve the maximum COP under a given condition. Basically, the proposed system with a proper SCR could yield a significant energy-saving effect regardless of the performance variations under studied operation conditions. It is found that a reduction of 29.68 % in energy consumption and an improvement of 42.20 % in COP are achieved under the ambient condition of 30 ℃ temperature and 20 g/kg humidity ratio. Furthermore, a correlation analysis is used to reveal the association strength and direction between any two main operation and performance parameters. Finally, the heat recovery is proved to effectively reduce the cooling coils load. This paper provides an in-depth understanding of the energy matching relationship and demonstrates the energy-saving performance benefiting from SSC for future practical applications of the proposed system.

Performance characteristics of a prototype dialysate turbidity monitoring system to detect peritonitis in patients receiving peritoneal dialysis.

The risk of peritonitis has limited wider adoption of peritoneal dialysis (PD) in the United States. We developed a prototype bedside dialysate turbidity monitoring system, aiming to improve diagnostic accuracy relative to conventional approaches which depend on visual inspection and reporting of insensitive and non-specific symptoms. The prototype system was tested in a single-centre, proof-of-principle clinical study in patients receiving intermittent PD. We obtained multiple effluent dialysate samples from each consenting participant. We compared turbidity measurements with diagnostic criteria endorsed by the International Society of Peritoneal Dialysis (ISPD). Overall, we analysed 983 specimens from 65 patients, including 105 samples from patients with peritonitis and 878 samples from patients without peritonitis. An operating point derived from a previous in vitro study yielded an unadjusted sensitivity and specificity of 95.2% and 91.5%, respectively. The majority of samples that did not meet ISPD diagnostic criteria were either cases detected before criteria were met or were related to active peritonitis treatment and resolution. This proof-of-principle study demonstrates the feasibility and diagnostic accuracy of a prototype dialysate turbidity monitoring system for peritonitis surveillance.

Nonlinear response of laterally cyclic loaded pile in cohesionless soil based on conical strain wedge model

The response to environmental lateral cyclic loads is an important design consideration for offshore piles installed in sand. This paper proposes a novel conical strain wedge (CSW) model to simulate the pile-cohesionless soil interaction under lateral cyclic loads. The CSW model enhances the depiction of passive compression soil zone resistance and failure pattern compared to the conventional strain wedge (SW). The developed model is incorporated in a simplified and efficient method to calculate the nonlinear pile response to lateral cyclic loads. The performance of the developed theoretical model is validated by comparing its predictions with observations from several experimental studies reported in the literature. The validated CSW model and its solutions are then employed to elucidate the performance characteristics of the pile-soil system under cyclic loading. The results revealed that: (1) the degradation of soil stiffness is more pronounced at the onset of cyclic loading and the rate of increase in pile response due to degradation diminishes with the increase in the number of loading cycles; (2) as the cyclic load amplitude increases, the increase in pile displacement becomes increasingly severe; (3) the number of loading cycles has greater influence on the response of piles with lower flexural stiffness; and (4) the effect of soil shear strength on the pile displacement becomes significant as the number of loading cycles increases, whereas its effect on the pile maximum bending moment diminishes gradually.

Effect of Recirculation Ratio on the Combustion Characteristics of an Asymmetric Swirling Flameless Combustor using Biogas

This study investigates the influence of recirculation ratio on the combustion characteristics of an asymmetric swirling flameless combustor. The recirculation ratio, defined as the ratio of the total recirculation mass flow rate to the primary air mass flow rate, plays a crucial role in determining the performance and emission characteristics of combustion systems. The asymmetric swirling flameless combustor offers potential advantages in terms of enhanced fuel flexibility, reduced pollutant emissions, and improved combustion stability. Through varying the recirculation ratio, the combustion performance and emission characteristics can be optimized to meet specific requirements. In this research, experimental investigations were conducted to analyse the effect of recirculation ratio on the combustion stability, temperature field and emission of the asymmetric swirling flameless combustion. From the results obtained, it was observed that recirculation ratio has significant effect on the performance of the combustor i.e., as the recirculation ratio increases due to decrease in the exhaust area, more uniform temperature and less emission was observed. At 30mm exhaust diameter and lean condition, average recirculation of 7.21 was obtained with 2ppm NOx emission and 118ppm CO emission along with uniform temperature in the combustion zone.

Evaluation of Multi-Modal Learning for Predicting Coolant Pump Failures in Heavy Duty Vehicles

Coolant Pump failures in heavy-duty vehicles can cause severe collateral damage if they are not detected and resolved in time; the engine will overheat quickly, rendering the vehicle inoperable. Nowadays, a vast amount of heterogeneous sensor data from different sources is being collected in the automotive industry. Such multi-modal data include onboard signals reflecting the overall usage of the vehicle, multi-dimensional histograms that capture the relation between physical quantities, and categorical variables that encode the physical configuration of the vehicle. This work evaluates several multi-modal learning approaches leveraging this diverse data to build a prognosis and health management system for coolant pumps in commercial heavy-duty vehicles. Four auto-encoder architectures are examined to extract features from 2D histograms. These trained models are anticipated to capture key characteristics of the healthy system operation and yield large reconstruction errors when applied on faulty, or near end-of-life samples. Such learned representations are then combined with expert-engineered features. Both early and intermediate fusion are evaluated on a real-world coolant pump replacement dataset. Results indicate that the combination of diverse features was the most effective approach, thereby motivating further research on multimodal methods.

Comparative Study of Thermodynamic Performance and System Characteristics of Solid Oxide Fuel Cell System with Three Different Fuels

The global demand for hydrogen is increasing as the global warming problem emerges. Hydrogen, which does not produce air pollutants, is attracting attention in various fields such as transportation and power generation. However, there are drawbacks in storing and transporting hydrogen in its own form. Hydrogen must be stored in the form of low-temperature and high-pressure liquefied hydrogen, which requires a lot of energy, and transportation costs are also high due to the low mass energy density of hydrogen. Therefore, there is a need to store and transport hydrogen in different forms, and a means to convert and use these different forms of hydrogen is needed.Solid oxide fuel cell (SOFC) is one of the energy conversion devices capable of using various types of hydrogen with high efficiency. Due to the high operating temperature of SOFC, fuel can receive adequate heat for reforming process from high temperature SOFC exhaust gas. Therefore, SOFC can use various types of fuels, such as methane and ammonia.Due to the fuel flexibility of SOFC, many SOFC system study using various fuels have been conducted. However, the SOFC operating conditions and system layout used in each study are all different. Also, most of studies lacked parasitic power consideration due to the pressure drop in system components. These limitations make it difficult to compare each SOFC system and find out effect of fuel on SOFC system.In this study, a quantitative comparison of SOFC using three different fuels, methane, ammonia, and hydrogen, was conducted. Thermodynamic models of a SOFC stack and balance of plant components developed from the previous study are used for the system simulations. Two system layouts, non-recirculation, and anode recirculation were chosen, and thermodynamic feasibility test was conducted based on T-Q diagram analysis at heat exchanger and reformer. With these system layouts, thermodynamic performance of the system and the design characteristics of the system components were compared. Boundary conditions, such as SOFC operating temperature, air and fuel utilization remains the same to compare each system result quantitatively. Also, most of design variables of system components are fixed to find out the effect of fuel on system components.Among three non-recirculation systems, ammonia fed non-recirculation system showed the highest electrical efficiency, while methane fed anode recirculation system showed the highest electrical efficiency among the anode recirculation systems. With the anode recirculation, SOFC power drop occurs due to the lower hydrogen concentration in the SOFC. However, fuel input drop due to anode recirculation is greater than the SOFC power drop, which positively affects system performance. But parasitic power is also increased due to recycle blower and higher mass flow rate of anode recirculation flow. In the case of ammonia fueled system, this increase in parasitic power leads to decrease in electrical efficiency.In this study, there are many constraints in operating conditions and BoPs designs to compare each system with different fuel. Therefore, operating conditions and BoPs designs are not optimized, so each system performance for each fuel may increase with appropriate system design. This optimization will be done in further study. Figure 1

An experimental study on the performance of fire extinguishing system according to the agent charging condition and nozzle type

In confined environments such as aircraft, an increase in mass impacts the overall system’s performance, thus requiring sophisticated management. To verify whether the performance characteristics of fire extinguishing systems used in aircraft are satisfied, in this study was built a 1:1 scale test model. We examined the influence of the initial charge state and nozzles. Further, it measured the pressure inside the pipelines and vessels where multiple nozzles are installed to identify the flow and diffusivity characteristics of HFC-125 inside the pipelines and vessels. At a charging ratio of 54%, the initial pressure drop was smaller, and the lowest pressure before the bubble release point appeared 0.26 s later than when the charging ratio was 76%. The average pressure of each nozzle was 275.8 kPa higher under a charging ratio of 54% than 76% and increased further when the average concentration change was 54%, indicating that diffusivity increased. Although improvements occurred according to the charging ratio, the improvements according to the HFC-125 charging mass were more significant.

Optimal design and off-design performance improvement for power-to-methane system integrating solid oxide electrolysis cell with methanation reactor

Power-to-methane (PtM) is a prospective solution to the mismatching between the supply and consumption of renewable energy resources (RES) by converting renewable power into methane. However, the continuous fluctuation of RES causes the PtM system to deviate from the design condition in the vast majority of cases, and thus it is significantly vital to study the operating characteristics of the PtM system under off-design conditions. This paper proposes a comprehensive investigation framework from design to off-design steps for the performance improvement of a PtM system combining solid oxide electrolysis cell with methanation reactor, and solar energy is selected as renewable energy input. Firstly, the system with the total exergy efficiency (ηEX,tot) of 11.83% and levelized cost of exergy (LCOE) of 150.76 $/MWh is selected as the optimal design condition based on the homogeneous assessment from both thermodynamic and economic aspects, by means of Non-dominated sorting genetic algorithm-II. Then, based on the optimal design point, the off-design performances are quantitatively investigated under varying solar radiation and key operating parameters, in terms of synthetic natural gas (SNG) yield and ηEX,tot. The results indicate that with the increment in solar radiation, the SNG yield rises, while the ηEX,tot increases first and then decreases. Finally, the multi-objective optimization based on the Artificial Neural Network models is implemented for the system under off-design conditions to acquire the best trade-off between hourly SNG yield and ηEX,tot. The off-design optimization solutions reveal that the hourly optimal SNG yield is located in the range of 275.06–946.53 kW, achieving a total annual SNG yield of 1697 MWh/y, and the hourly optimal ηEX,tot mainly varies in the range of 10.40–11.40%.

Investigation on the performance coupling characteristics between a compound anti-frosting method and air source heat pump system

Air source heat pump systems are prone to frosting when operating under low temperature and high humidity working conditions, leading to reduced operational stability and performance. The traditional defrosting methods suffer from defects including high energy consumption, heating interruption, and system pressure surges. To address these issues, a novel active–passive compound anti-frosting method for air source heat pump systems is introduced in this work, which involves utilizing the synergistic effect of high-speed airflow and superhydrophobic modification. To reveal the coupling characteristics between the energy consumption of the anti-frosting method and the system performance, the airflow parameter model based on droplet growth and force taken is established, the simulation algorithm for system frosting and defrosting is developed, and the system's operating characteristics and performance under different operation modes are compared within typical frosting condition. The results indicate that the active–passive compound method can realize frost-free operation and reduce the ant-frosting and defrosting energy consumption by more than 90%. Consequently, it improves the system's comprehensive performance coefficient in a single frosting-defrosting period by 9.7%∼14.3%, compared to the control group without any anti-frosting measures. The introduction of the active method further enhances the frost suppression effect of the superhydrophobic modification.

An optimal load curtailment method for operational risk assessment of integrated electricity, natural gas and heating systems

The rapid development of gas-fired generators and combined heat and power (CHP) units promotes the wide application of integrated electricity, natural gas and heating systems (IEGHSs). IEGHSs bring many opportunities to energy supply systems, but also produce huge challenges for ensuring secure and reliable energy supply. Therefore, it is indispensable to investigate the risk assessment for IEGHS operations, especially considering the complexity of system operations. First, a steady-state system model of IEGHSs is developed and linearized taking into account system operation characteristics, including generator operation constraints and the flexibility of CHP units. To reduce computation complexity, an optimal load curtailment method using a mixed integer linear programming algorithm is proposed, which considers both energy types and consumer importance of IEGHSs. Moreover, a contingency set based on the N-1 guideline is constructed taking into account the failures of IEGHSs with high probability. Additionally, the risk indices of IEGHSs are developed in two hierarchies: contingency level and system level. Furthermore, the operational risk of IEGHSs under the constructed contingency set is quantitatively evaluated using the proposed load curtailment method and the developed risk indices. Finally, case studies demonstrate the necessity of operational risk assessment and the effectiveness of the proposed method.