Optimal solar array configuration and DC motor field parameters formaximum annual output mechanical energy

A procedure is presented for the proper design of systems comprising photovoltaic solar generators directly supplying DC motors. The method is based on maximizing the total annual gross mechanical energy delivered to a mechanical load with a given torque-speed characteristic. The seasonal variations of both the isolation level and the ambient temperature are taken into account. The proposed technique is applied to two practical case studies, and the resulting optimal design parameters are compared with those available in the literature. A comparison is also made between the optimal separately excited and series motor design alternatives regarding the annual gross mechanical output energy     

光伏阵列安装角度与安装节距的优化选择

光伏发电系统安装地点确定之后,其发电量主要受到光伏组件安装倾角和节距的影响。文章首先建立了光伏电池发电模型和斜面上的辐照度模型,以西安某公司的光伏发电系统为例,计算了不同倾角和节距下光伏阵列的年发电量。结果表明:在没有阴影遮挡的情况下,光伏组件在西安地区的最佳安装倾角为32°;在有阴影遮挡的情况下,节距越小,最佳倾角越小。光伏阵列的节距减小时,组件的发电量减少,利用效率降低。但是,由于组件安装量增多,单个组件占地面积减少,总安装容量增大,发电量增大。此计算方法可为光伏组件安装倾角和节距的选择提供参考。     

Realistic values of various parameters for PV system design

The principle of energy production evaluation of PV systems is explained and parameter definitions are given at first. Then, a new method is proposed to verify detailed system parameters from ordinary, monitored data. Data acquisition system is used for the evaluation of long-term energy performance. Monitored data are normally utilized to calculate input radiant energy, output electrical energy, system yield (equivalent operated hours), system performance ratio and so on. The author has developed sophisticated verification procedures (SV method), where system performance ratio K, power conditioner efficiency K_C, temperature factor K_PT, shading factor K_HS, load matching factor K_PM and other array parameter K_PO can be identified from only 4 monitored points with other externally available information. Especially, time series data verification process can produce more realistic results of shading and mismatch losses respectively. As a realistic example, SV method is applied to data taken from 71 systems in the Japanese Field Test Project.     

Practical values of various parameters for PV system design

In order to reasonably design a PV system, it is important to use appropriate parameter values. Few papers, however, describe design parameters that are defined systematically. The authors have been entrusted by the New Energy and Industrial Technology Development Organization (NEDO) with research and development of PV system evaluation since 1990 in order to establish optimum design and operation methods of various kinds of PV systems which are expected to be put into commercial use in the future.In this research, which is based on the data obtained from test facilities which were constructed at Hamamatsu site, various design parameters were calculated and reported as primary values provisionally estimated. This paper presents practical values of various parameters for PV system design as a table, revised with design parameter values studied later on. In particular, cell temperature factor was studied in view of regional differences and module mounting.The authors will confirm reasonable design of PV system by using such various design parameter values.     

Characterization of PV array output using a small number of measured parameters

The purpose of the present study was to develop a sufficiently good fit for the measured I–V curve of a PV module and array using only three easily measurable parameters: —the open-circuit voltage (V_oc); —the short-circuit current (I_sc); —the maximum power (P_m). With an additional three parameters ( ; ; ) it is possible to describe any I–V curve, taking into account cell temperature T and solar radiation Q. This method has been tested on various solar array panels as well as on a single 10 cm dia. solar cell. The difference between the real curve and the proposed fit was found to be less than 3 percent for a fixed temperature and radiation and about 6 percent for various combinations of temperature and radiation.     

Performance analysis of a PV powered DC motor driving a 3-phaseself-excited induction generator

Photovoltaic (PV) powered DC motors driving dedicated loads (e.g. water pumps) are increasingly used in the remote rural areas of many developing countries. The key to their success is simplicity (direct coupling, no DC-AC inversion, no storage batteries, etc.). In this paper, a PV powered DC motor is used to drive an isolated three-phase self-excited induction generator (SEIG). It is found that due to the unique torque-speed characteristics of the SEIG, utilization efficiency is close to maximum at all insolation levels with no peak-power tracking. The proposed arrangement is useful as part of an integrated renewable energy system (IRES), which takes advantage of the inherent diversity of wind and insolation in most developing countries to improve power quality. The SEIG is driven by wind turbine, DC motor, or both. Performance of the system under different insolation conditions is analyzed     

Novel heat dissipation design incorporating heat pipes for DC combiner boxes of a PV system

In a Photovoltaic (PV) system, heat is generated by an operating diode. Because DC combiner boxes are waterproof, dustproof, air tight and made of heat-insulating material, thermal energy is easily accumulated, affecting the performance and safety of power cables and other electronic components near the diodes in the DC combiner box. This study utilizes a heat pipe as a channel for heat dissipation to conduct the heat out of a DC combiner box without destroying the air-tightness of the box. An existing DC combiner box was improved upon using this method of heat dissipation. The measured heat flow and temperature demonstrate that the proposed method is feasible. The influence of the condensation section temperature on the maximum heat transfer of the heat pipe was also investigated by experiment. The maximum heat transfer rate of the heat pipe was found to increase with the condensation section temperature of the heat pipe. When the condensation temperature was 20 °C, 30 °C and 40 °C, the maximum heat transfer rate of the heat pipe was 21.6 W, 29.6 W and 39.7 W, respectively.     

基于数据手册的光伏电池特性及参数实用估算方法

利用光伏电池数据手册提供的标准测试条件下的开路电压、短路电流、最大功率点电压和最大功率点电流,得到光伏电池的详细模型参数;提出一种光伏电池模型的等效并联电阻和串联电阻的估算新方法。利用数据手册中的光伏电池短路电流和开路电压温度系数,得到了任意光强和任意温度下的光伏电池模型。为降低求解隐函数模型方程的复杂性,采用近似方法求解隐函数超越方程,得到了光伏电池模型显函数表达式。通过与两种光伏电池在不同光强和温度下的测试数据及同类模型的比较,验证了所提出的模型及参数估算方法的正确性、有效性,具有较高的精度。     

Comparison of two PV array models for the simulation of PV systems using five different algorithms for the parameters identification

Simulation is of primal importance in the prediction of the produced power and automatic fault detection in PV grid-connected systems (PVGCS). The accuracy of simulation results depends on the models used for main components of the PV system, especially for the PV module. The present paper compares two PV array models, the five-parameter model (5PM) and the Sandia Array Performance Model (SAPM). Five different algorithms are used for estimating the unknown parameters of both PV models in order to see how they affect the accuracy of simulations in reproducing the outdoor behavior of three PVGCS. The arrays of the PVGCS are of three different PV module technologies: Crystalline silicon (c-Si), amorphous silicon (a-Si:H) and micromorph silicon (a-Si:H/μc-Si:H).The accuracy of PV module models based on the five algorithms is evaluated by means of the Route Mean Square Error (RMSE) and the Normalized Mean Absolute Error (NMAE), calculated for different weather conditions (clear sky, semi-cloudy and cloudy days). For both models considered in this study, the best accuracy is obtained from simulations using the estimated values of unknown parameters delivered by the ABC algorithm. Where, the maximum error values of RMSE and NMAE stay below 6.61% and 2.66% respectively.     

Performance and costs of a roof-sized PV/thermal array combined with a ground coupled heat pump

A photovoltaic/thermal (PVT) panel is a combination of photovoltaic cells with a solar thermal collector, generating solar electricity and solar heat simultaneously. Hence, PVT panels are an alternative for a combination of separate PV panels and solar thermal collectors. A promising system concept, consisting of 25 m² of PVT panels and a ground coupled heat pump, has been simulated in TRNSYS. It has been found that this system is able to cover 100% of the total heat demand for a typical newly-built Dutch one-family dwelling, while covering nearly all of its own electricity use and keeping the long-term average ground temperature constant.The cost of such a system has been compared to the cost of a reference system, where the PVT panels have been replaced with separate PV panels (26 m²) and solar thermal collectors (7 m²), but which is otherwise identical. The electrical and thermal yield of this reference system is equal to that of the PVT system. It has been found that both systems require a nearly identical initial investment.Finally, a view on future PVT markets is given. In general, the residential market is by far the most promising market. The system discussed in this paper is expected to be most successful in newly-built low-energy housing concepts.     

Speed control of a PV powered DC motor driving a self-excited3-phase induction generator for maximum utilization efficiency

Photovoltaic (PV) powered DC motors driving dedicated loads (e.g. water pumps) are increasingly used in the remote rural areas of many developing countries. The key to their success is simplicity (direct coupling, no DC-AC conversion, no storage batteries, etc.). Because of the relatively high cost of the PV array, the system designer is interested in maximizing its utilization efficiency. A PV powered DC motor can also be used to drive a three-phase self-excited induction generator (SEIG). This arrangement is useful as part of an integrated renewable energy system (IRES), which takes advantage of the inherent diversity of wind and solar energy in most developing countries to improve power quality. The SEIG is driven by a wind-turbine, DC motor, or both. Another advantage of this arrangement is its versatile control characteristics through the DC motor control. This paper describes a technique to maximize the utilization efficiency of the PV array by controlling the field current of the DC motor through a DC chopper     

Optimal design of a storage system coupled with intermittent renewables

In this paper, two ways of increasing the integration of wind and solar energy into the electricity grid through energy storage are analyzed. The first service (S1) to the electricity grid is related to a smoothed and hourly scheduled daily production while the second one (S2) concerns a constant and guaranteed minimal production. A power bid, based on meteorological forecasts, is transmitted a day ahead by the producer to the utility grid operator. This leads to a yearly default time rate for which the actual power supplied does not meet the announcement within a given tolerance. The modelling approach developed in this study enables to infer the optimal operation of the system and more specifically the optimal size of the energy storage, aiming at reducing the default time rate (DTR) under 5%. The simulations consider PV or wind with storage systems having discharge time in the range of minutes. Two real test cases are examined: Guadeloupe Island for wind and Reunion Island for PV. The results show that both of the two services can be achieved under specific conditions and that an optimal day-ahead power bid with a 2% DTR is possible with a storage capacity of 1 MWh per installed MWp. In addition, a linear strategy of forecasting this optimal power is highly correlated to the precision of upstream meteorological forecast.     

A technique for mismatched PV array simulation

In this paper a computationally efficient approach to the modeling of a photovoltaic array is presented. It is especially suited for simulating mismatched operating conditions, in which the different modules of the array work at different irradiation levels and temperatures. The model used allows to keep into account parametric tolerances and drifts among the modules. The proposed technique is based on the use of the Lambert W-function, which allows to obtain an explicit relationship between the voltage and the current of any photovoltaic module. The non linear system of equations describing the photovoltaic array is easily solved thanks to the explicit symbolic calculation of the inverse of the Jacobian matrix. The performances of the proposed numerical approach are discussed especially in cases where a deep mismatch affects the photovoltaic array.     

Optimal Su-Do-Ku based interconnection scheme for increased power output from PV array under partial shading conditions

Partial shading is a common phenomenon in PV arrays. They drastically reduce the power output because of mismatch losses, which are reliant on the shape of the shade as well as the locations of shaded panels in the array. The power output can be improved by distributing the shade over various rows to maximize the current entering the node. A Su-Do-Ku configuration can be used to rearrange the physical locations of the PV modules in a total cross tied PV array with the electrical connections left unchanged. However, this arrangement increases the length of the wire required to interconnect the panels thus increasing the line losses. In this paper, an improved Su-Do-Ku arrangement that reduces the length of the wire required for the connection is proposed. The system is designed and simulated in a Matlab/Simulink environment for various shading patterns and the efficacies of various arrangements are compared. The results prove that the power output is higher in the proposed improved Su-Do-Ku reconfiguration technique compared to the earlier proposed Su-Do-Ku technique.     

Integrated solar pump design incorporating a brushless DC motor for use in a solar heating system

Most solar thermal hot water heating systems utilize a pump for circulation of the working fluid. An elegant approach to powering the pump is via solar energy. A “solar pump” employs a photovoltaic module, electric motor, and pump to collect and convert solar energy to circulate the working fluid. This article presents an experimental investigation of a new integrated solar pump design that employs the stator of a brushless DC motor and a magnetically coupled pump that has no dynamic seal. This design significantly reduces total volume and mass, and eliminates redundant components.The integrated design meets a hydraulic load of 1.7 bar and 1.4 litres per minute, equal to 4.0 watts, at a rotational speed of 500 revolutions per minute. The brushless DC motor and positive displacement pump achieve efficiencies of 62% and 52%, respectively, resulting in an electric to hydraulic efficiency of 32%. Thus, a readily available photovoltaic module rated 15 watts output is suitable to power the system.A variety of design variations were tested to determine the impact of the armature winding, pump size, pulse width modulation frequency, seal can material, etcetera. The physical and magnetic design was found to dominate efficiency. The efficiency characteristics of a photovoltaic module are such that over-sizing is wasteful.The integrated design presents a robust, efficient package for use as a solar pump. Although focus has been placed on application to a solar thermal collector system, variations of the design are suitable for a wide variety of applications such as remote location water pumping.     

Optimum photovoltaic array size for a hybrid wind/PV system

A methodology for calculation of the optimum size of a PV array for a stand-alone hybrid wind/PV power system is developed. Long term data of wind speed and irradiance recorded for every hour of the day for 30 years were used. These data were used to calculate the probability density functions of the wind speed and the irradiance for each hour of a typical day in a month. The wind speed and irradiance probability density functions and manufacturer's specification on a wind turbine and a PV module were used to calculate the average power generated by the wind turbine and the PV module for each hour of a typical day in a month. The least square method is used to determine the best fit of the PV array and wind turbine to a given load. On the basis of the energy concept an algorithm was developed to find the optimum size of the PV array in the system     

适用于大规模光伏阵列的无水清扫机器人

基于目前国内光伏电站光伏电池板的主流安装模式,设计了光伏阵列无水清扫机器人。根据机器人所要具有的自动实现上下行走足错位调节功能、停靠位置躲避遮挡功能和无死角全面清扫功能,确定其整体运行控制策略。利用模糊控制方法重点研究了机器人行走过程中上下行走足的错位调节。通过在Matlab/Simulink下的仿真及现场实验表明,所设计的模糊控制器合理、实用,能够实现预期的目标。     

Methodology for optimally sizing the combination of a battery bankand PV array in a wind/PV hybrid system

In this paper, a methodology for calculation of the optimum size of a battery bank and the PV array for a standalone hybrid wind/PV power system is developed. Long term data of wind speed and irradiance recorded for every hour of the day for 30 years were used. These data were used to calculate the average power generated by a wind turbine and a PV module for every hour of a typical day in a month. A load of a typical house in Massachusetts, USA, was used as a load demand of the hybrid system. For a given load and a desired loss of power supply probability, an optimum number of batteries and PV modules was calculated based on the minimum cost of the power system     

Optimal design of linear switched reluctance motor for sea wave power generation

The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment; thus, it is a feasible solution for the generator of a sea wave power generation system. However, the corresponding thrust density and efficiency remain insufficient. This study focused on a new type of flat linear switched reluctance motor(LSRM), using the finite element software to establish a structural model, and optimized the design with the goal of improving the e...