A numerical Resolution of The Current-voltage Equation for a Real Photovoltaic Cell

AbstractSolving the characteristic equation of the real photovoltaic cell that contains two variables is to find for each value of the voltage of the cell the value of the electric current generated by this cell. Since the complex shape of this equation does not permit to resolve it analytically despite that we know the intervals of solutions, the interval of solutions of the electric current varies from the value 0 to the value Isc (the short-circuit current). The interval of solutions of the voltage varies from the value 0 to the value Voc (the open circuit voltage), from the advantage of knowing the intervals of solutions, we can solve this equation with a numerical model

Modelling photovoltaic water pumping systems and evaluation of their CO2 emissions mitigation potential

In photovoltaic (PV) water pumping design, the accurate prediction of the water flow is a key step for optimized implementation and system robustness. This paper presents a model to characterize the motor-pumps subsystems used in PV pumping installations. The model expresses the water flow output (Q) directly as a function of the electrical power input (P) to the motor-pump, for different total heads. The actual model is developed using the experimental results obtained by the use of several motor-pump subsystems of different types and technologies. This work details the investigations concerning centrifugal and positive displacement motor-pump subsystems. The experimental tests are used to validate the developed model. Based on the motor-pump subsystem model, a method is proposed to estimate the amount of carbon dioxide (CO2) emissions saved by the use of water pumping facilities powered by a photovoltaic array instead of diesel fuelled generators. This work shows that the dissemination of PV water systems not only improves the living conditions in remote areas, but is also environment friendly.Photovoltaic Water Pumping systems CO2 emissions Diesel Climate

Wind effect on full-scale design of heliostat with torque tube

Despite the importance of designing support structures for solar collectors, very little reliable work has been done to investigate the forces of the wind on heliostats of solar tower at real scale. Wind loads on heliostats are usually determined at low-speed wind tunnels scale, where the design full-scale Reynolds number cannot be reached. In the present study, measured data are used to validate the simulations at wind tunnel scale. Thereafter, by using the same method, three-dimensional numerical simulations of turbulent wind flow around a big heliostat of solar tower are performed. The obtained numerical results are presented for several elevation angles at normal operation and stow position. The results revealed that the known stow position (when the backside of the heliostat is facing the ground) is not the optimum position (other optimum elevation angles are discovered) especially with high wind speed, and the effect of torque tube is significant on heliostat mean wind loads

Combined Reconfiguration and Capacitor Placement for Distribution System Volt/Var Control through Opposition based Differential Evolution Algorithm

Power distribution systems must be very effective in power delivery. Utilities are continuously looking for recent technologies to enhance power delivery performance. The control of power loss is one of the most important issues directly related to system efficiency. Distribution system reconfiguration and optimal capacitor placement are the two most popular techniques adapted for the control of power loss. The techniques not only concentrate on power loss control but also control volt/var of the distribution system, and at the same time improve the system reliability and security. Former method is the process of changing the topology of distribution system by altering the open/closed status of switches to find a radial operating structure that minimizes the system real power loss while satisfying operating constraints. Later is the identification of optimal location and size of the capacitors with the objective of minimizing the power loss. This paper combines both reconfiguration and optimal capacitor placement for the effective optimization. Furthermore, it utilizes Opposition based Differential Evolution algorithm for efficient searching for the optimal solution. The effectiveness of the proposed approach is demonstrated by employing the feeder switching operation scheme to IEEE-33 bus Power Distribution systems. The proposed algorithm reduces the transmission loss and controls volt/var while satisfying power flow constraints.Distributivne energetske sustav mora biti vrlo učinkovit u prijenosu energije. Javni sektor neprestano traga za novim tehnologijama ne bi li povećao učinkovitost prijenosa. Upravljanje gubicima energije jedan je od najvažnijih problema koji je direktno povezan s učinkovitošću mreže. Rekonfiguracija distributivne mreže i optimalno pozicioniranje kondenzatora su dvije uvriježene metode koje su prilagođene za upravljanje gubicima energije. Navedene metode se ne koncentriraju samo na upravljanje gubicima već i upravljaju naponsko-reaktivnim prilikama distributivne mreže, i istovremeno povećavaju raspoloživost i pouzdanost sustava. Prva metoda uključuje postupak promjene topologije distributivne mreže promjenom stanja sklopki kako bi se našla radijalna operativna struktura koja minimizira gubitke radne snage u prijenosu uz zadovoljenje operativnih ograničenja. Druga metoda uključuje identifikaciju optimalne lokacije i veličine kondenzatora s ciljem minimizacije gubitaka snage. U ovom radu se kombiniraju obje metode, rekonfiguracije i optimalnog pozicioniranja, s ciljem učinkovite optimizacije. Za postupak optimizacije odabran je na opoziciji baziran genetski algoritam diferencijske evolucije s ciljem učinkovite pretrage optimalnog rješenja. Učinkovitost predloženog pristupa provjerena je primjenom komutacijske sheme srednjenaponske distributivne mreže na IEEE-33 sabirnici baziranim distributivnim energetskim sustavima. Predloženi algoritam smanjuje gubitke prijenosa i upravlja naponsko-reaktivnim prilikama mreže uz zadovoljenje ograničenja na tokove energije