Journal of Renewable Energy and Environment
Volume:3 Issue: 2, Spring 2016

Pitch control is one of major aspect of wind turbines control particularly in high wind speed and wind oscillations. General Electric model of wind turbine is practically compatible with the structure of the wind turbines. Simulation results using this model are closer to the actual case, compared to that of the other models.
At this end, results of application of Fuzzy, self-organized Fuzzy and PI controllers as well as the case with no controller in pitch control process are compared. With connection to the electrical power limit and converter cost, economical analysis of pitch controller application is carried out. It is shown that application of a self-organized Fuzzy controller result is around $142,646 saving.

This paper proposes an improved direct active and reactive power control (DPC) strategy for a grid-connected doubly fed induction generator (DFIG) based wind-turbine system under unbalanced grid voltage condition. The method produces required rotor voltage references based on the sliding mode control (SMC) approach in stationary reference frame, without the requirement of synchronous coordinate transformation, and therefore causes a simpler design for power control system. Under unbalanced grid voltage condition, two control targets obtained simultaneously, i.e., removing stator active and reactive power oscillations. Moreover this method reduces the THD of stator current. Also it is shown that the proposed control method not only has a high-speed dynamic response but is stable during wind speed and system parameters variations. Simulation results for a 2kw DFIG confirm prominence of proposed control strategy.

This study analyzes the thermal performance of solar thermal energy using double-pass absorber plate in Sanandaj, Iran. To this end, a mathematical model was encoded according to the energy and exergy balance equations and solved by MATLAB software. Given the environmental conditions and radiation intensity of a winter day in Sanandaj, the effects of external parameters such as radiation intensity and internal parameters such as canal’s height, inlet mass flow rate, absorber length as well as some physical parameters on the efficiency of the system were analyzed and the energy and exergy output of the system was studied. To validate the proposed model, the results obtained from numerical simulation were compared with experimental data, which showed an acceptable compatibility. Finally, the ability of the system to supply the thermal load of the building in the given day was examined and the roles of various factors in the area under thermal coverage of this system were analyzed. The obtained findings indicated that a system with an area of 3 m2 and mass rate of 250 kg/hr in radiation intensity of 619 W/m2 and temperature of 3.45° is capable of supplying the thermal load of a space with an approximate area of 14 m2.

Treatment of landfill leachate is challenging, due to its characteristics such as age, dumping place, composition and origin of wastes. For this reason, the application of hybrid processes is helpful for complete treatment of contaminants present in the leachates. The addition of membrane operations to biological treatment technology offers new advantages for this method. For this aim, a bench-scale integrated process based on submerged aerobic MBR has been designed and fabricated. Also, Nanofiltration process as a post-treatment was used to upgrade MBR effluent. The results showed that the submerged UF-MBR system effectively removed biodegradable trace organic compounds with the average removal rate of about 75% at optimum food-to- microorganism (F/M) ratio (BOD basis) of 0.2 gBOD/g.d under a HRT of 24 h. The addition of NF process increased the treatment efficiency up to 98%. The effluent COD was reduced from 3500 mg/l to below 50 mg/l. Further, the effect of PAC addition was studied. NH3 –N, TKN and Heavy metals removal efficiency were obtained 97 ± 2%, 96 ± 2% and 99 ± 2%, respectively.

The transesterification reaction of canola oil and methanol was studied with hybrid amino functionalized chitosan-carbon support, as the catalyst. It was observed that this hybrid was more active than parent polymer at the reaction condition. Furthermore, the reaction parameters, such as reaction temperature, molar ratio, amount of the catalyst and reaction time were studied and finally methyl esters was obtained with 95% yields at lower time (3.5 h). This novel heterogeneous catalyst offers several attractive advantages such as high catalyst activity, easy recovery and reusability of the catalyst.

In a 10-ton capacity pilot plant solar liquid desiccant air conditioner (LDAC) developed, dehumidification of the outside air is achieved through a honeycomb packed-bed heat and mass exchanger, using lithium chloride solution as the desiccant. The dry air obtained from the dehumidification process is evaporative cooled inside a cooling pad and directed into the conditioned space. The dilute solution thus produced is concentrated in a honeycomb packed-bed scavenger air regenerator using hot water from flat plate solar collectors. Carryover of the desiccant particles has been avoided by using eliminators. The air conditioner was installed on a 250 m2 area of the fluid mechanics laboratory of Babol University of Technology, a hot and humid location in the north on the Caspian Sea. The experimental data obtained were compared with the predicted results of a model developed for the air conditioner based on HYSIS and CARRIER energy soft-wares. The comparison reveals that good agreement exists between the experiments and the model predictions. The above tests further reveal that the unit has a satisfactory performance in independently controlling the air temperature and humidity of the conditioned space. The inaccuracies are well within the measuring errors of the temperature, humidity and the air and solution flow rates. An efficient heat recovery within the air conditioner resulted in a thermal COP of about 1.5 and an electrical COP of 7. A commercialization study reveals that the operating cost of an LDAC is significantly lower than its conventional counterpart. The costs would further reduce if a storage system was used to store the concentrated solution of liquid desiccant. A simple payback of five years was determined for the solar components of the liquid desiccant system in this study.