Data acquisition system for photovoltaic water pumps

In Algeria, there are several photovoltaic water pumping system (PVWPS) which are situated in remote areas. Typical problems are detected as sizing of photovoltaic (PV) generator (over-sizing) and maintenance (underestimate) by many operators. Due to the high cost of setting up and maintaining a large number of data acquisition systems for the PVWPS, we have developed a real time expert system based on central microcomputer used as a micro-server, with a low cost. This paper presents a design of a universal data acquisition system for Algeria with available components and easily accessible with a central server. This data acquisition system analyses the performance of PVWPS. The systems hardware and software architectures and an application to test its performance are described.     

Optimum load matching in direct-coupled photovoltaic powersystems-application to resistive loads

The load matching factor is used as a measure for the quality of load matching to a photovoltaic (PV) array. An optimization approach is used to solve the load matching problem with the objective of maximizing the load matching factor, and consequently the PV output energy. This approach is then applied to resistive loads (with and without an internal EMF) connected to the array. Results show that optimum matching can be achieved by carefully selecting the array parameters with respect to the load parameters. The temperature of the array has little effect on the optimum matching factor. However, the optimum matching parameters are greatly affected by the array temperature. A maximum power tracker may not be achieved     

Cooling load density characteristics of an endoreversible variable‐temperature heat reservoir air refrigerator

The performance optimization of an endoreversible air refrigerator with variable‐temperature heat reservoirs is carried out by taking the cooling load density, i.e. the ratio of cooling load density to the maximum specific volume in the cycle, as the optimization objective in this paper. The analytical relations of cooling load, cooling load density and coefficient of performance are derived with the heat resistance losses in the hot‐ and cold‐side heat exchangers. The maximum cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot‐ and cold‐side heat exchangers for the fixed total heat exchanger inventory, and the heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the heat capacitance rate of the working fluid, the inlet temperature ratio of heat reservoirs and the total heat exchanger inventory on the maximum cooling load density, the optimum heat conductance distribution, the optimum pressure ratio and the heat capacity rate matching between the working fluid and the heat reservoirs are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander and the hot‐ and cold‐side heat exchangers. Copyright © 2002 John Wiley & Sons, Ltd.     

Optimum matching of ohmic loads to the photovoltaic array

Optimum matching of loads to the photovoltaic (PV) generator is most desirable for more accurate sizing, higher system performance and maximum utilization of the costly solar array generator. The quality of load matching depends on the PV array characteristics, the load characteristics, and the insolation profile. A matching factor is defined as the ratio of the load energy to the array maximum energy over a one day period. Optimum matching is achieved by determining the optimal array parameters with respect to the load parameters. Optimization is done using direct-search techniques. Results show that the theoretical optimum matching factor for an ohmic load is 94.34%. For an electrolytic load the matching factor could reach 99.83%. A maximum power tracker can be eliminated if optimum matching is achieved.     

Optimum matching of direct-coupled electromechanical loads to aphotovoltaic generator

The objective of the paper is to present a general mathematical formulation for matching electromechanical loads connected to a photovoltaic array. An optimization method is then used to solve the matching problem with the objective of maximizing the gross mechanical energy. The analysis is extended to obtain the sizing of the array and the battery in the direct-coupled system. Results show that optimum matching can be achieved by carefully selecting the PV array rated parameters with respect to the load parameters. The rated power of the array is twice that of the load. The field constant that maximizes the gross mechanical energy can be obtained given the parameters of the load and the array temperature. The separately excited motor offers higher matching performance compared to the series motor. The rotodynamic load offers better matching compared to the viscous friction load     

蓄电池和太阳电池方阵直接耦合的小型光伏系统中电压最佳匹配的仿真研究

利用匹配因子概念,以全晴天为例,对蓄电池和太阳电池方阵直接耦合的小型光伏系统二者之间电压的最佳匹配进行仿真计算,给出了获得电压匹配的实现方法。所得结果对确定太阳电池组件生产规格具有一定意义,精心处理会带来明显的经济效益。     

Optimum matching parameters of an MPPT unit used for a PVG‐powered water pumping system for maximum power transfer

Photovoltaic generator (PVG)‐powered water pumping has the potential to bring potable water to millions of people in developing countries. However, due to the high initial cost of PVG units, sophisticated load matching is required between the water pumping system and PVG, in order to be able to extract maximum available power from an available PVG unit at all solar radiation levels. This requires an intermediate circuitry between the PVG unit and the motor driving the water pump, which is usually termed as maximum power point trackers (MPPT). This present paper therefore investigates the optimum matching parameters of a power conditioning circuit, which is composed of a double step‐up dc–dc converter (DSUC). This MPTT circuit is used for interfacing a permanent magnet (PM) motor‐driven water pumping system to a PVG for extracting maximum available power from PVG, hence maximizing the energy utilization efficiency and price–performance ratio of the whole system. It is shown that two key parameters of the DSUC, which are the duty cycle and chopping frequency, are dominating the performance of the whole system, and they are interrelated and load dependent. Therefore, optimum values of these parameters need to be determined. An example system is provided in which a complete modelling is presented in time domain and through numerical experiments it is demonstrated how the optimum values of these two key matching parameters can be determined for a given system. The MPPT circuit used in this investigation is suitable for optimum matching of all types of loads to PVG units, provided that an optimum frequency–duty cycle pair is determined for the choppers in DSUC for every 5% bands of solar radiation between 20 and 100%. Copyright © 2005 John Wiley & Sons, Ltd.     

Matching of a DC motor to a photovoltaic generator using a step-upconverter with a current-locked loop

A photovoltaic (PV) generator is a nonlinear device having insolation-dependent volt-ampere characteristics. Because of its relatively high cost, the system designer is interested in optimum matching of the motor and its mechanical load to the PV generator so that maximum power is obtained during the entire operating period. However, since the maximum-power point varies with solar insolation, it is difficult to achieve an optimum matching that is valid for all insolation levels. In this paper it is shown that for maximum power, the generator current must be directly proportional to insolation. This remarkable property is utilized to achieve insolation-independent optimum matching. A shunt DC motor driving a centrifugal water pump is supplied from a PV generator via a step-up converter whose duty ratio is controlled using a current-locked feedback loop     

Alternative energy facilities based on site matching and generation unit sizing for remote area power supply

This paper presents the decision support technique and influencing factors in the design of an integrated solar-wind power system for stand-alone applications. Results of investigations on application of alternative energy facility like wind, photovoltaic (PV), and Integration of wind–PV power generating systems for Remote Area Power Supply have been presented. A weather model-based site matching of equipment and a simple numerical algorithm for generation unit sizing have been presented. The program has been used to determine the optimum generation capacity and storage needs for a stand-alone Wind, PV, and integrated wind–PV system for a remote site in India (Sukhalai situated near Suktawa in Hoshangabad district of Madhya Pradesh) that satisfies a typical load. Generation and storage units for each system are properly sized in order to meet the annual load demand for the above three scenarios. Annual average hourly values for load, wind speed, and insolation have been used for analysis. The results are used to justify the use of renewable energy source as a reliable option for remote areas.     

Multi-objective optimisation analysis and load matching of a phosphoric acid fuel cell system

Based on the current model of a phosphoric acid fuel cell (PAFC) system, the electrolyte concentration is optimised. New analytical expressions for the power output and efficiency of the PAFC system are derived by considering the effects of multi-irreversibilities resulting from the activation overpotential, concentration overpotential, ohmic overpotential, and leakage resistance on the performance of the PAFC system. These parameters are used to evaluate the general performance characteristics of the PAFC system. Accordingly, the upper and lower limits of the optimised values for some main parameters, such as the current density, power output, and efficiency, are determined. Moreover, a multi-objective function, including both the power output and efficiency, is introduced and used to further subdivide the parametric optimum regions according to different requirements. In addition, a general formula for the load of the system is derived. The relations between the power output and efficiency of the system and the load are discussed in detail, and the optimum matching conditions of the load are obtained.