In this study, the air temperature inside a semi-arid greenhouse was investigated. The model database was built using greenhouse climatic data from a prototype greenhouse in Algeria's Ghardaia region. Over January month, external and internal climatic data were collected in order to develop and validate models for simulating environmental conditions inside the greenhouse, such as relative humidity (RHext), total radiation (GH), air pressure (P), and external temperature (Text). The main objective of this study is to compare three deep neural network models feed forward networks (FFN), Nonlinear auto-regressive network with exogenous inputs (NARX), and recurrent neural networks (RNN-LSTM) to see which one predicted temperature changes in the environment the best. The results showed that the NARX-predicted results agreed closely with the measurements; additionally, RNN provided satisfactory results, while FFN was the weakest of the three models.

This work reports two projection methods for the calculation of shadowing and blocking in the surrounding heliostat field of a Solar Tower Plant. The first one is the classical parallel projection which is widely used in the literature. The second one is the oblique projection which has been barely addressed in the literature. For the same solar altitude, the frames of two adjacent heliostats are not parallel in reality, and consequently, the projection of the shadowing and blocking areas is not parallel. Compared with raytracing methods, these two projection methods have been developed to reduce the computational cost without affecting efficiency accuracy. Therefore, they are suitable for heliostat field optimization. We have chosen a case study presented by Collado(1), that used parallel projection in the calculations. Differences between parallel and oblique approaches are shown. Shading and blocking factors by the more accurate oblique projection are compared with the parallel one. The maximum difference is 0.09% and 1.44%, respectively for parallel and oblique projection in calculating the shading and blocking factor of a circular field of 4550 heliostats.

In this study, the Iterative Artificial Bee Colony Algorithm (IABCA) methodology was proposed to perform optimisation of a heliostat field for the Solar Power Tower (SPT) system. In this respect, a complete mathematical model of annual unweighted optical efficiency considering cosine losses, shadowing-blocking losses, atmospheric attenuation losses, interception losses and mirror reflectivity was developed firstly. A simple and efficient method is adopted to identify the heliostats with the highest possibility to shade or block another heliostat. The use of this method allows us to reduce the processing time of the shadowing and blocking efficiency and avoid unnecessary calculations. A case study of PS10 situated in Spain was used to validate the mathematical model and the proposed IABCA approach. The proposed IABCA maximize the annual unweighted optical efficiency. In order to evaluate the performance of the proposed approach, seasonal investigation on four different days 21 March, 21 June, 21 September, and 21 December at solar noon time was carried out. The results show that the proposed IABCA methodology boost significantly the performance of the heliostat field compared to the original PS10 layout. Percentage improvement for each studied day in terms of efficiency is 3.46%, 1.05%, 3.2%, 1.98%, respectively.

The present study focuses on the optimization of solar tower power plant heliostat field by considering different heliostat shapes including rectangular, square, pentagon, hexagon, heptagon, octagon, and circular heliostat shapes. The optimization is carried out using an in-house developed code-based MATLAB program. The developed in-house code is validated first on a well-known PS10 Solar Thermal Power plant having rectangular heliostats shape and the resulting yearly unweighted heliostat field efficiency of about 64.43% could be obtained. The optimized PS10 heliostat field using different heliostat shapes showed that the circular and octagon heliostat shapes provide better efficiency with minimum land area. The yearly efficiency is increased from 69.65% for the rectangular heliostat shape to 70.96% and 71% for the octagon and circular shapes, respectively. In addition, the calculated field area (land area) is reduced for the case of circular and octagon heliostat shapes with a gain of about 11.10% and 10.93% (about 42.0436 x 10(3)and 41.4036 x 10(3)m(2)), respectively, in comparison with the PS10 field area.

ABSTRACT In this study, the Iterative Artificial Bee Colony Algorithm (IABCA) methodology was proposed to perform optimisation of a heliostat field for the Solar Power Tower (SPT) system. In this respect, a complete mathematical model of annual unweighted optical efficiency considering cosine losses, shadowing-blocking losses, atmospheric attenuation losses, interception losses and mirror reflectivity was developed firstly. A simple and efficient method is adopted to identify the heliostats with the highest possibility to shade or block another heliostat. The use of this method allows us to reduce the processing time of the shadowing and blocking efficiency and avoid unnecessary calculations. A case study of PS10 situated in Spain was used to validate the mathematical model and the proposed IABCA approach. The proposed IABCA maximize the annual unweighted optical efficiency. In order to evaluate the performance of the proposed approach, seasonal investigation on four different days 21 March, 21 June, 21 September, and 21 December at solar noon time was carried out. The results show that the proposed IABCA methodology boost significantly the performance of the heliostat field compared to the original PS10 layout. Percentage improvement for each studied day in terms of efficiency is 3.46%, 1.05%, 3.2%, 1.98%, respectively.

This paper proposes a regulation method of back-to-back connected two-level PWM rectifier-five-level Voltage Source Inverter (VSI) in order to reduce the torque ripple in induction motor. First part is dedicated to the presentation of the feedback control of two-level PWM rectifier. In the second part, five-level Neutral Point Clamped (NPC) voltage source inverter balancing DC bus algorithm is presented. A theoretical analysis with a complete simulation of the system is presented to prove the excellent performance of the proposed technique.

This paper proposes a regulation method of back-to- back connected three-level converters in order to reduce the torque ripple in induction motor. First part is dedicated to the presentation of the feedback control of three-level PWM rectifier. In the second part, three-level NPC voltage source inverter balancing DC bus algorithm is presented. A theoretical analysis with a complete simulation of the system is presented to prove the excellent performance of the proposed technique.

This paper proposes an implementation of boost converter for a resistive load using photovoltaic energy as a source. The model of photovoltaic cell and operating principle of boost converter are presented. A PIC microcontroller is used in the close loop control to generate pulses for controlling the converter circuit. To performance evaluation of boost converter, a variation of output voltage of PV panel is done by shading one and two cells.

In this work we present a design of a mathematical model used in the simulation of the behavior of a heliostats-tower optical system. The model permits the calculation of the orientation angles of a heliostat (two axes tracking system) in a solar tower system, it also allows to calculate the shading area of a heliostat on another. The reflected radiation to the target (the tower) is calculated from the incident radiation from the sun and calculated shaded area. For each heliostat, the cosine effect (angle of incidence) is included in the calculation of the reflected radiation, and then, the shadow effect is taken into account on reducing the radiation reflected by an amount which depends on the shadow area

This paper presents a comparison between two Pulse Width Modulation (PWM) algorithms applied to a three-level Neutral Point Clamped (NPC) Voltage Source Inverter (VSI). The first algorithm applied is the triangular-sinusoidal strategy; the second is the Space Vector Pulse Width Modulation (SVPWM) strategy. In the first part, we present a topology of three-level NCP VSI. After that, we develop the two PWM strategies to control this converter. At the end the experimental results are presented. Keywords—Multilevel inverter, Space vector pulse width modulation (SVPWM), triangular-sinusoidal strategy.

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. But the unbalance of these different input DC voltage sources constituted the major limitation for the uses of this power converter. This paper proposes the control and regulation method of input DC voltages of five-level voltage source inverter.