Environmental, economic and energetic benefits from implantation of several modes of solar collector movements

In this research, the performance of a moving solar system on two axes was studied, the east-west axis, this axis represents the tilt angle of the solar collector. The other movement is the surface's rotation around the perpendicular axis on the surface in the east and west directions, which in turn represents the azimuth angle of the solar collector. All possibilities for these movements were also studied, in order to reach the optimal option, which in turn depends on the importance of alication and the available space on the one hand, and the economic conditions on the other hand. The maximum value of solar radiation intensity was adopted as a guide to compare the performance of six options for tracking systems. Despite the high costs of tracking systems, they often have a positive economic return, as these systems increase the efficiency of the solar system, whether it is electric or thermal twice, the first one by increasing the intensity of the solar radiation incident on the solar collector, and the second one by increasing the optical efficiency of the solar collectors and thus increasing the overall efficiency of the device. The percentage of increase in the sixth type of solar energy is about 38% compared to the fixed mode. The minimum optical efficiency of the dual tracking mode has been found as 84%, while for fixed mode is about 48%.

Thermal performance assessment of a cylindrical box solar cooker fitted with decahedron outer reflector

One of the important issues humankind globally faces in recent years is the scarcity of non-renewable energy resources. Solar energy is considered safe and renewable, which can fulfil the demand and supply chain requirements. Solar box cookers (SBCs) are popular in domestic cooking due to their ease of use and handling. The prime objective of the present work is to develop and test the performance of a cylindrical SBC fitted with decahedron-shaped reflector (CSBC-FDR). The CSBC is designed using minimum entropy generation (MEG) method. Through experiments, we observed that absorber plate attains peak temperature of about 138°C–150°C with the aid of decahedron reflector. The first figure of merit (F1) is found to be 0.13, indicating better optical efficiency and low heat loss coefficient for the SBC. The second figure of merit (F2) is obtained as 0.39, which indicates good heat exchange efficiency (F') and less heat capacity for cooker's interior. The average energy efficiency, exergy efficiency, and standardized cooking power values are 21.93%, 3.04%, and 25.28W, respectively. These results show that the present CSBC-FDR is able to cook food in a shorter period with better efficiency. The experimental and numerical values of overall heat loss coefficient of the developed SBC are in close agreement. The experimentally assessed performance parameters reveal superior performance of the present cylindrical SBC in comparison with many conventional rectangular and trapezoidal box solar cookers.

ASSESSMENT OF SOLAR ENERGY POTENTIAL FOR A RADIALLY STAGGERED HELIOSTATS FIELD USING SUN TRACKING METHOD

This article deals with the potential assessment of tower type solar thermal power system. An algorithm was developed to employ sun-tracking method, which provides the characteristic angles of the heliostats such that the incoming beams of sun rays are reflected to the receiver. A suite of MATLAB code was developed to implement the mathematical models for a quick evaluation of solar energy potential in a radially staggered heliostat field for the capital city of Kingdom of Saudi Arabia, Riyadh. An existing clear-sky model in the literature was used to compute hourly insolation. Optical efficiencies and heat collected by the receiver (from individual heliostat in the field on hourly basis) were computed and the monthly-averaged daily results were presented zone-wise and for the complete heliostat field. It was observed that the optical efficiency of the heliostat decreases with increasing distance from the receiver tower; this was due to increasing spillage of the reflected rays and decreasing cosine efficiency with increasing distance of the heliostat from the receiver tower. Results showed that annual average optical efficiency of the field is nearly forty-nine percent.

The influence of axial offset of fusion splicing on a large mode area fiber based oscillator

Fiber oscillators have the potential for achieving high power, high beam quality lasers with simple and compact structure, of which the fusion splicing point is an important aspect to the laser output characteristics. A model taking into account the axial offset of the splicing point and spatial mode competition has been proposed to analyze the mode interaction of a large mode area fiber based oscillator. The calculated results show that the axial offset of the output side fusion point has the main influence on the laser output beam quality, but the axial offset would not obviously reduce the optical efficiency, especially when the value is smaller than 2 μm. The influence of cavity parameters on the laser output characteristics under the existence of splicing point with axial offset has also been discussed. This model can provide a method for analyzing the mode dynamic that may be helpful for understanding the mode interactions in fiber oscillators.

High-power thin-disk lasers emitting beams with axially-symmetric polarizations

We present the intracavity generation of beams with radial polarization at an average output power of 750 W and an optical efficiency of 43% from a continuous wave thin-disk laser. Circular grating waveguide output couplers (GWOC) were used to select the radial polarization. The sensitivity of the polarizing function of the GWOC with regards to the fabrication tolerances is also analysed in details with a particular emphasis on the effect of the duty cycle and the geometrical profile of the gratings. Furthermore, we present the conversion of femtosecond laser pulses from linear to azimuthal polarization using a nanograting-based polarization converter. Azimuthally polarized beams with an average power of up to 850 W, a pulse duration of 400 fs and a pulse repetition rate of 1 MHz were generated in this way with a conversion efficiency of >90%.

Comprehensive Methodology to Evaluate Parasitic Energy Consumption for Different Types of Dual-Axis Sun Tracking Systems

A dual-axis sun tracking system is an essential strategy to maximize the optical efficiency of harnessing solar energy. However, there is no significant study yet to optimize the net performance of the photovoltaic (PV) or concentrator photovoltaic (CPV) system equipped with a dual-axis sun tracking system. Parasitic energy loss associated with the power consumption of the sun tracking system is one of the major concerns for the solar industrial players. To address this issue, a comprehensive methodology has been developed to evaluate the yearly cumulative range of motion for dual-axis sun tracking systems in the cases of with and without fixed parking positions across the latitudes ranging from 45°N to 45°S. The parasitic energy consumptions have been investigated for three selected types of dual-axis sun tracking systems, i.e., the azimuth-elevation sun tracking system (AE-STS), polar dual-axis sun tracking system (PD-STS), and horizontal dual-axis sun tracking system (HD-STS). The simulated results indicate that the dual-axis sun tracking system with the nonfixed parking (or stow) position has lower yearly cumulative parasitic energy consumption with respect to the sun tracking system with a fixed parking position. Lastly, our simulation result has shown that the parasitic energy consumption of the sun tracking is relatively smaller to that of the electrical energy generated by the concentrator photovoltaic system with the ratio between 0.15% and 0.29% for AE-STS, between 0.15% and 0.30% for PD-STS, and between 0.17% and 0.35% for HD-STS.

Electrodeposition of nano-Cu, Ni and binary Ni/Cu into nano-porous AAO layer for high-efficiency black spectrally selective coating

Background Anodic aluminum oxide (AAO) template is widespread due to its diverse metal nanostructures. Various solar selective black coatings on aluminum oxide template were investigated. Spectrally selective nano-coating of nickel, copper and nickel–copper on anodized aluminum was produced. Results The coatings were performed via electrodeposition and evaluated by measurement of coating thickness, hardness and optical properties. Also, these coatings were analyzed by scanning electron microscope, energy-dispersive X-ray spectroscopic and polarization studies in 3.5% NaCl solution. The anodized aluminum showed higher corrosion resistance (4.8284 KΩ) and lower corrosion rate (0.02189 mm/year). However, the electro-colored Al with Cu for 60 min showed the highest corrosion rate of 0.1942 mm/y, compared with other Al samples. The effect of anodizing time on the metal density and the optical efficiency of black copper coating was studied. Results The obtained solar panels exhibit low values of solar reflectance within the visible range and high solar absorption efficiency. These coatings are highly efficient and adequate for any solar system.