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The current flat-plate solar collectors perform best when their absorbers rotate around their axis. However, with their concentrators, reflectors, and tracking mechanisms, they take up a lot of space and are thus commercially speaking, not the best solutions. This paper proposes a novel solar collector design which employs the (relative) rotation of absorbers, but strives to combine the benefits of fixed and (absolute) tracking solar systems, i.e. volume occupancy from the former and thermal performance from the latter. The findings of our numerical analysis show that, the solar irradiance efficiency of this novel design is 20% higher than that of a fixed flat-plate collector during clear-sky days, and it is equally lower than that of an absolute tracking collector. This paper also introduces a new criterion for describing single-axis tracking solar collectors which should be included in the classifications of solar collectors. Finally, the article, which represents a continuation of our research in the field of solar energy utilization, can contribute to the future development of solar technologies and solve some of the current challenges. [ABSTRACT FROM AUTHOR]

This paper presents two methods (theoretical and numerical) for the thermal analysis of the previously experimentally installed solar collector construction at the Faculty of Engineering in Kragujevac -- a fixed flat-plate solar collector with Sn-Al2O3 selective absorber and gravity water flow. The theoretical research was based on the application of a specific calculation algorithm with a triple iterative procedure, i.e. with a three-stage check of all important performance indicators of the fixed flat-plate solar collector. In the numerical phase of the research, simple linear regression was applied to experimentally measured values of solar radiation intensity and experimentally determine values of heat power to form simple equations that could be used to predict the thermal performance of similar solar structures in the future. The results of theoretical and numerical studies showed agreement with experimental studies, because in the first case, the absolute measurement error was less than 10%, while in the second case, the determination coefficient was greater than 90%, so the authors hope that this work will be useful to the wider scientific community. [ABSTRACT FROM AUTHOR]

To improve solar collector efficiency, a variety of designs and materials have been introduced into production practice. Studies describing solar collector specifics, therefore, are particularly valuable to the scientific community as they contribute to the overall body of knowledge and constant improvement the in the scientific field. In that regard, the study presented in this paper analyses the thermal performance of the fixed flat-plate collector with an Sn-Al2O3 selective absorber. The fixed flat-plate collector design utilizes gravity water flow in an open loop system. A two-month study was conducted to perform the analysis. The experiment was based on measurements of water flow in the fixed flat-plate collector, the water temperature at the fixed flat-plate collector inlet and outlet, and solar radiation intensity on a horizontal surface. Results for three randomly selected measurement days have shown that fixed flat-plate collector can achieve relatively satisfactory values for average daily specific heat power, thermal efficiency, and inlet-outlet water temperature gradient, respectively: June 29 (381.78 W/m2, 60.67%, and 9.06 °C), June 30 (364.33 W/m2, 59.43%, and 7.46 °C), and July 15 (373.06 W/m2, 59.85%, and 8.69 °C). Apart from the relatively good measurement results, this type of solar collector does not require circulating pumps for operation, which brings a double advantage: energy saving and energy production. [ABSTRACT FROM AUTHOR]

This paper presents a design, development and experimental verification of an active vibration control system of aluminum plate. The active structure consists of an aluminum rectangular plate as the host structure, strain gages as the sensor element and a piezoceramic patch as the actuation element. Based on characteristics of the integrated elements with use of the fuzzy optimization strategy based on the pseudogoal function the optimal orientation of piezoelectric actuator is found, and the whole active vibration control system is designed and developed. The active vibration control system is controlled by proportional-integral-derivative (PID) control strategy. Control algorithm was implemented on the PIC32MX440F256H microcontroller platform. In order to prevent it from negative occurrences from derivative and integral terms in a PID controller, the first-order low-pass filters are implemented in the derivative action and in the feedback of integral action. The experiment considers active damping control under periodic excitation. Experiments are conducted to verify the effectiveness of the vibration suppression and to compare the damping effect with different adjustment of PID gains. Experimental results corresponding to the developed active vibration control system are presented. The system suppresses more than 90% of vibration amplitude, which confirms the high level of effectiveness in vibration active damping at the proposed active structure. [ABSTRACT FROM AUTHOR]

This paper deals with active free vibrations control of smart composite beams using particle-swarm optimized self-tuning fuzzy logic controller. In order to improve the performance and robustness of the fuzzy logic controller, this paper proposes integration of self-tuning method, where scaling factors of the input variables in the fuzzy logic controller are adjusted via peak observer, with optimization of membership functions using the particle swarm optimization algorithm. The Mamdani and zero-order Takagi-Sugeno-Kang fuzzy inference methods are employed. In order to overcome stability problem, at the same time keeping advantages of the proposed self-tuning fuzzy logic controller, this controller is combined with the LQR making composite controller. Several numerical studies are provided for the cantilever composite beam for both single mode and multimodal cases. In the multimodal case, a large-scale system is decomposed into smaller subsystems in a parallel structure. In order to represent the efficiency of the proposed controller, obtained results are compared with the corresponding results in the cases of the optimized fuzzy logic controllers with constant scaling factors and linear quadratic regulator. [ABSTRACT FROM AUTHOR]