An Assessment Framework for PV Parallel MPPT Configuration with a New Utilization for UIPS Loads

The prevalence rate of photovoltaics (PV)-based generation systems has increased by more than 15 folds in the last decade, putting it on the top compared to any other power generation system from the expandability point of view. A portion of this huge expansion serves to energize standalone remote areas. Seeking improvements from different aspects of PV systems has been the focus of many studies. In the track of these improvements, parallel MPPT configuration for PV standalone systems have been introduced in the literature as an alternative to a series configuration to improve the overall efficiency of standalone PV systems. However, this efficiency improvement of the parallel MPPT configuration over the series one is not valid for any standalone application, therefore an assessment procedure is required to determine the most efficient MPPT configuration for different standalone applications. Therefore, in this study, an assessment procedure of parallel MPPT is conducted to demonstrate the suitability of utilizing such a configuration compared to series one, based on load daytime energy contributions. This assessment will help PV system designers to determine which MPPT configuration should be selected for applications under study. Furthermore, a new utilization of parallel MPPT configuration is introduced for operating universal input power supply (UIPS) loads to eliminate the inverter stage, thereby increasing the overall system efficiency and reliability. Finally, a systematic procedure to size the complete system is introduced and reinforced by a sizing example.

Probabilistic assessment of complex system consisting three subsystems, multi-failure threats and copula repair approach

PurposeThe purpose of this paper is to deliberate the system reliability of a system in combination of three subsystems in a series configuration in which all three subsystems function under a k-out-of-n: G operational scheme. Based on computed results, it has been demonstrated that copula repair is better than general repair for system better performance. The supplementary variable approach with implications of copula distribution has been employed for assessing the system performance.Design/methodology/approachProbabilistic assessment of complex system consisting three subsystems, multi-failure threats and copula repair approach is used in this study. Abbas Jubrin Bin, V.V. Singh, D.K. Rawal, in this research paper, have analyzed a system consisting of three subsystems in a series configuration in which all three subsystems function under a k-out-of-n: G operational scheme. The supplementary variable approach with implications of copula distribution has been employed for assessing the system performance. Based on computed results, it has been demonstrated that copula repair is better than general repair for system better performance.FindingsIn this analysis, four different cases of availability are analysed for Gumbel–Hougaard family copula and also four cases for general repair with similar failure rates are studied. The authors found that when failure rates increase, the system availability decreases, and when the system follows copula repair distribution, the system availability is better than general repair.Research limitations/implicationsThis research may be implemented in various industrial systems where the subsystems are configured under k-out-of-n: G working policy. It is also advisable that copula repair is highly recommended for best performances from the system. On the basis of mean time to system failure (MTSF) computations, the failure rate which affects system failure more needs to be controlled by monitoring, servicing and replacing stratagem.Practical implicationsThis research work has great implications in various industrial systems like power plant systems, nuclear power plant, electricity distributions system, etc. where the k-out-of-n-type of system operation scheme is validated for system operations with the multi-repair.Originality/valueThis work is a new work by authors. In the previously available technical analysis of the system, the researchers have analyzed the repairable system either supplementary variable approach, supplementary variable and system which have two subsystems in a series configuration. This research work analyzed a system with three subsystems with a multi-repair approach and supplementary variables.

Performance assessment of stacked air-cathode microbial fuel cells under series and parallel electrical connections

Microbial fuel cells (MFCs) are playing an important role in the context of sustainable energy development. They represent a sustainable approach to harvest electricity from biodegradable materials. However, harvesting energy from MFCs represents a critical issue because of the low output voltage and power produced. Realizing stacked configurations may involve an increase in MFCs performances in terms of output voltage, current and electric power. In this paper, two stacked configurations under different electrical connection modes have been designed, developed, modeled and tested. The stacked MFCs consist of 4 reactors (28 mL x4) that are connected in series, and parallel-series modes. Three different tests have been carried out, which involves: 1) performing the polarization and power curves by applying decreasing resistances; 2) assessment of the electric behavior of each reactor over time at a fixed resistance, 3) performing the polarization and power curves by applying increasing resistances. Moreover, a numerical model for predicting the transient behavior of the electrical quantities for one reactor, has been developed and validated by using the experimental data. As expected, the results highlighted that the parallel-series configuration assures the highest volumetric power density compared to the series configuration, reaching the maximum value of 1248.5 mW/m3 (139.8 µW) at 0.291 mA. Eventually, by comparing the numerical and the experimental data, it has been demonstrated that the developed model is able to predict the reactor’s electrical trend with a good accuracy.

Multi-objective maintenance planning under preventive maintenance

PurposeThis research developed and examined a mathematical model for concurrent corrective and preventive maintenance policy of a system of series configuration.Design/methodology/approachA mathematical model was developed to maximize availability, and maximal net revenues, and minimal cost. Different probability distributions for time to failure and time to repair were considered. The model was then implemented on a real case study, which was studied under corrective maintenance policy and concurrent corrective and preventive policy.FindingsA comparison between results at current policy (90 days) and optimal period of corrective and preventive policy was conducted. It was found that availability, profit was increased from 94.4% and $20.091 – 96.5% and $24.803, respectively. Further, the cost was reduced from $1104.8 to $797.22.Research limitations/implicationsThe proposed optimization model can be adopted in planning maintenance activities for a single machine as well as for a system of series configuration machines under various probability distributions.Practical implicationsThe proposed model can significantly enhance performance of the production as well as maintenance systems. In addition, the developed model may support maintenance engineering in effective management of maintenance resources and the performance of its activities.Originality/valueThis research considers a mathematical model with multi-objective functions and distinct probability distributions for time-to-failure for a system of series machines. Moreover, appropriate approximation solution was deployed to find integral of some functions. Finally, it provides maintenance planning for a single machine or a series of machines.

Experimental design and numerical validation of a low-cost water heater by electromagnetic induction

This study shows a new approach to heat water in a residential environment. An electromagnetic heating method is proposed. A steel bar inside a pipeline filled with water is heated by five arrangements of a copper coil which incites the steel bar by electromagnetic induction. Consequently, numerical simulation and experimental evaluation are compared. The outcomes evaluated two different scenarios: steady water and a water flow of 0.16 kg/s. Three rods demonstrated that current induction of 20 A at the surface of the steel bar heats at 157°C. Also, the maximum value reached is 58°C. Heating the water upon for those conditions, the proposed tankless instantaneous water heater (TIWH) reaches a temperature of 41.01°C with one rod but only reaches 37.92°C with three rods in a series configuration, in a parallel configuration, the maximum temperature reached was 28.73°C.

Optimal Control of Dengue Transmission with Vaccination

Dengue disease is caused by four serotypes of the dengue virus: DEN-1, DEN-2, DEN-3, and DEN-4. The chimeric yellow fever dengue tetravalent dengue vaccine (CYD-TDV) is a vaccine currently used in Thailand. This research investigates what the optimal control is when only individuals having documented past dengue infection history are vaccinated. This is the present practice in Thailand and is the latest recommendation of the WHO. The model used is the Susceptible-Infected-Recovered (SIR) model in series configuration for the human population and the Susceptible-Infected (SI) model for the vector population. Both dynamical models for the two populations were recast as optimal control problems with two optimal control parameters. The analysis showed that the equilibrium states were locally asymptotically stable. The numerical solution of the control systems and conclusions are presented.

Application of Numerical Methods for the Analysis of Damped Parallel RLC Circuit

A sudden application of sources results in time-varying currents and voltages in the circuit known as transients. This phenomenon occurs frequently during switching. A simple circuit constituting a resistor, an inductor, and a capacitor is termed an RLC circuit. It may be in parallel or series configuration or both. Different values of damping factors determine the different nature of the transient response. We applied different numerical solution methods such as explicit (forward) Euler method, third-order Runge-Kutta (RK3) method, and Butcher's fifth-order Runge-Kutta (BRK5) method to approximate the solution of second-order differential equation with initial value problem (IVP). We thoroughly compared the numerical solutions obtained by these methods with the necessary visualization and analysis of error. We also examined the superiority of these methods over one another and the appropriateness of numerical methods for different damping conditions is explored. With high accuracy of the approximation and thorough analysis of the observation, we found Butcher's fifth-order Runge-Kutta (BRK5) method to be the best numerical technique. Regarding the different values of damping factors, we considered the further possibility of discussion and analysis of this iterative method.