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Research Papers

J. Sol. Energy Eng. 2018;140(6):061001-061001-5. doi:10.1115/1.4039747.

This research document presents a new insulation material for solar thermal collectors. Tests were carried out in the laboratory, on an active solar energy demonstration system (ET 200), illuminated with a halogen lamp instead of sun. In this paper, the polystyrene used as insulation in the ET 200 flat plate solar collector was replaced by the cheaper natural material based on clay and straw. The polystyrene in the experimental device is placed under the absorber plate and along the edges of the casing containing the components of the solar collector. In this work, only the polystyrene of the four similar edges was replaced by the composite material. The use of the clay and straw as insulation material instead of polystyrene increased temperature difference (T2 − T1) between the inlet and the outlet of the absorber by 0.9±0.14 °C (p < 0.05); thus, increasing the useful power transmitted to water in the solar collector. Compared to polystyrene, tank water was well heated using the proposed material (p < 0.05). This latter also improved the performance of the solar collector by 5.77%. So, it is recommended to use the cheapest nonpolluting material based on clay and straw instead of synthetic insulation to improve the performance of the solar collector.

Commentary by Dr. Valentin Fuster
J. Sol. Energy Eng. 2018;140(6):061002-061002-7. doi:10.1115/1.4039776.

A street lamp with automatic solar tracking system can control the adjusting mechanism of azimuth and altitude so that the solar panel may adapt itself to the sunlight to improve the photoelectric conversion efficiency. In this work, we demonstrated the design of the adjusting mechanism of azimuth and altitude and verified the wind resistance. The method was realized by capturing the incident direction of sunlight using the photodiode array. The signal of the photodiode array can be processed by LM339N and then was sent to the single chip, which can deal with the signal to the motor of the adjusting mechanism of azimuth and the linear actuator of the adjusting mechanism of altitude, respectively. The hall sensors, embedded in the adjusting mechanism, are utilized to fulfill the feedback of the motion position to the single chip. These results clearly reveal the potential of the system in application.

Commentary by Dr. Valentin Fuster
J. Sol. Energy Eng. 2018;140(6):061003-061003-11. doi:10.1115/1.4039777.

This work is concerned with an experimental design for generating power from thermoelectric generator (TEG) and linear Fresnel lens collector with one-axis solar tracking system. Main purpose of this experimental design is to measure the performance of the TEG with linear Fresnel lens collector. This work also aims to create a mathematical model by using adaptive neuro fuzzy inference system (ANFIS) model so that the electrical production estimates of the constructed system can be made for a given data set. For this reason, two individual systems, selective surface adapted for achieving medium temperature scale and nonselective surface for low temperatures, were constructed. There are two different coolant systems, which are passive and active, to create effective open circuit voltage values. Experimental results show that the maximum open circuit voltages were obtained as 0.442 V and 1.413 V for experimental system with selective surface adapted, as 0.341 V and 0.942 V with nonselective surface adapted when the received radiated power on Fresnel lens was measured nearly 625 W/m2 on average in the noon time. Experimental values were collected for the selective surface adapted system on 11th and 12th of September, 2017 and for nonselective surface on 13th of September, 2017, respectively, in Samsun/Turkey with location 41°14′N and 36°26′E. The collected data such as solar irradiation, wind speed, ambiance temperature, and open circuit voltage were used for (ANFIS) modeling. Obtained result shows that experimental calculations and modeling are consistent with each other.

Commentary by Dr. Valentin Fuster
J. Sol. Energy Eng. 2018;140(6):061004-061004-9. doi:10.1115/1.4040534.

In this work, the exergy analysis of two configurations of hybrid solar–sugarcane cogeneration power plant is proposed in order to evaluate the overall efficiency enhancement of the cycle. Solar thermal energy was coupled to a sugarcane cogeneration power plant localized on the tropical region of Brazil, in order to preheat the feeding water supplied to the steam generators and to reduce the fuel consumption during the sugarcane-harvesting season in order to stock the unused fuel for its use during the off-season. The exergy analysis of the cycle was proposed based on a thermodynamic model, which considered real operational states, and allowed to quantify the main parameters of performance, such as the solar-to-electricity (STE) efficiency, the power generation increasing, the percentage of fuel saved, and the exergy destruction rates of the equipment. The results showed that, under design conditions, almost 10% of fuel was saved, and the overall exergy destruction decreased 11% approximately. Additionally, as a result of the hourly analysis of the annual operation, it was found that the power plant operated 331 extra hours, 8.50 GWh of electricity were generated, and due to this fact, it has attained economic benefits for the operation of the sugarcane cogeneration power plant.

Commentary by Dr. Valentin Fuster
J. Sol. Energy Eng. 2018;140(6):061005-061005-9. doi:10.1115/1.4040206.

Baking is an energy intensive unit operation. The thermal application of solar energy is getting attention in food processes by eliminating the facts of interrupted supply and fluctuated costs of nonrenewable energy sources. This study has been carried out for the design and development of solar bakery unit which comprises of a 10 m2 Scheffler reflector focusing all the beam radiations on a secondary reflector that further concentrate the beam radiations toward the heat receiver of solar bakery unit to heat up the air circulated through baking chamber employing a photovoltaic operated fan. Computational fluid dynamic (CFD)-based three-dimensional (3D) simulation was performed to analyze the design for uniform air distribution in the baking chamber. The system designed configurations gave quite good results for airflow distribution. The receiver temperature reached between 300 and 400 °C while temperature at the inlet of baking chamber was in the range of 200–230 °C, sufficient for most of the products to be baked. The maximum available solar power at receiver was calculated to be 3.46 kW having an average efficiency of 63%. A series of experiments were conducted for the baking of cakes and total energy available in baking chamber was about 3.29 kW and cake utilized 0.201 kW energy to be baked. The average value of energy utilization ratio was found to be 45%. As a base, the study would lead to the development of an appropriate and low cost solar baking units for the maximum retention of quality parameters and energy saving.

Commentary by Dr. Valentin Fuster
J. Sol. Energy Eng. 2018;140(6):061007-061007-17. doi:10.1115/1.4040290.

Radiation absorption is investigated in a particle curtain formed in a solar free-falling particle receiver. An Eulerian–Eulerian granular two-phase model is used to solve the two-dimensional mass and momentum equations by employing computational fluid dynamics (CFD) to find particle distribution in the curtain. The radiative transfer equation (RTE) is subsequently solved by the Monte Carlo (MC) ray-tracing technique to obtain the radiation intensity distribution in the particle curtain. The predicted opacity is validated with the experimental results reported in the literature for 280 and 697 μm sintered bauxite particles. The particle curtain is found to absorb the solar radiation most efficiently at flowrates upper-bounded at approximately 20 kg s−1 m−1. In comparison, 280 μm particles have higher average absorptance than 697 μm particles (due to higher radiation extinction characteristics) at similar particle flowrates. However, as the absorption of solar radiation becomes more efficient, nonuniform radiation absorption across the particle curtain and hydrodynamic instability in the receiver are more probable.

Commentary by Dr. Valentin Fuster

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