In this study, the improvement of the turbine performance of Savonius, one of the vertical axis Wind turbines, was carried out numerically. The numerical approach used in the improvement studies was supported by experimental results and was confirmed. Within the scope of this improvement, a Wind collector was placed in the turbine front zone to decrease the negative moment on the counter-rotating blade of the Savonius turbine. To obtain the highest turbine performance, all of the changes in the design parameters of this Wind collector, such as the Wind inlet width, Wind outlet width, collector length, and collector height, were examined, and ideal design parameters of the collector were specified. The geometric parameters of the investigated Wind collector were taken depending on the circular dimension of the Savonius turbine used. Unsteady simulations for different geometric parameters using the sliding mesh approach were performed in the CFD program. According to the numerical analysis results, the power-coefficient of the conventional turbine was increased to 0.23 levels by using the Wind collector with the ideal geometric parameters. Thus, with the use of a Wind collector, the power coefficient of a conventional Savonius Wind turbine was improved by about 54%.

In this study, the effect of Wind speed on the energy and exergy efficiencies of the LS-2 parabolic trough solar collector have been studied. The Wind speed on the reflector and receiver has been considered between zero and 27 m/s. Three working fluids of Therminol VP-1, Syltherm 800 and Dowtherm A have been used. The inlet temperature of the working fluid and volumetric flow rate are assumed to be in the range of 300-650 K and 50-600 L/min, respectively. In order to solve the governing equations, a developed thermal model in the engineering equation solver has been used. The results showed that at the inlet fluid temperature of 650 K and volumetric flow rate of 50 L/min, if the Wind speed increases to 27 m/s, the energy efficiency decreases using Therminol VP-1, Syltherm 800 and Dowtherm A are 0. 87%, 1. 16% and 0. 85%, respectively and the exergy efficiency decreases are 0. 88%, 1. 18% and 0. 86%, respectively. Also the results showed that the variations of energy and exergy efficiencies for Wind speeds greater than 10 m/s are negligible. The results indicated that although Wind speed increase has little effect on the energy and exergy efficiencies of the collector, but the rate of these decreases are comparable with the rate of efficiency increases observed in previous studies using different efficiency enhancement strategies such as turbulators and nanofluids, so Wind speed is important. The performance evaluation study revealed that using Therminol VP-1 and Dowtherm A are more suitable than Syltherm 800 to be used as working fluids in parabolic trough solar collectors

Distance relays calculate the path impedance between the fault point and the relay location by sampling the voltage and current at the relay location. By using the ratio of the impedance estimated by the relay to the impedance of the line where the relay is installed, the location of the fault can be estimated by a distance relay. However, several factors influence the estimated impedance and proper operation of distance relays. The most important of these factors is the resistive fault occurrence, which results in an increase in the impedance and deviation of the impedance estimated by the relay as well as causes relay under-reach. Therefore, in the present study, an adaptive method is proposed to modify the protection zones of distance relays settings under different operating conditions and resistive single-line-to-ground (SLG) fault occurrence. Furthermore, the adaptive distance protection of transmission lines, Wind farm collector lines and the protection coordination of the relays in these lines are investigated. In this method, an adaptive coefficient is added to the conventional characteristics of distance relays to improve the accuracy and coordination. The proposed adaptive method can also maintain the coordination of different protection zones of primary and backup relay pairs. In addition to analytical verification, the numerical results obtained from simulation show the efficiency of the proposed method. The proposed method is implemented on a power system with transmission lines and Wind farms and simulated in MATLAB/Simulink environment.

This paper deals with the performance of a heat pipe solar collector. The solar collector consisted of an interconnected heat pipe so as to reduce the production cost by using an interconnected heat pipe because all the heat pipes can be evacuated, sealed and tested at once. Performance of a prototype of the heat pipe solar collector was experimentally examined, and the results were compared with those obtained through theoretical analysis. The results shown in this paper seem feasible.