Renewable Energy Resources and Technologies
Reza Roohi; Masoud Akbari
Abstract
The design of novel and effective receivers is one of the most challenging aspects of solar energy harvesters, especially for Parabolic Dish Collectors (PDCs). The variation of solar flux due to the solar time and sky clearance index can affect the output thermal energy of the collector. One of the major ...
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The design of novel and effective receivers is one of the most challenging aspects of solar energy harvesters, especially for Parabolic Dish Collectors (PDCs). The variation of solar flux due to the solar time and sky clearance index can affect the output thermal energy of the collector. One of the major approaches to producing a uniform performance for the PDCs is the utilization of Phase Change Materials (PCMs). The PCMs can absorb the solar flux at its peak instances. Subsequently, due to the thermal buffering effect, excess energy is released in cases with lower solar flux. In the present study, a novel design of receiver with multiple layers of thin PCM inserted between the passages of the working fluid is numerically simulated. The simulations are designed to determine the effect of operational parameters on the performance of the examined novel receiver. According to the results, by increasing the Heat Transfer Fluid (HTF) flow rate from 60 to 90 kg/h, the system efficiency is increased from 53.8 to 66.4 %.
Renewable Energy Resources and Technologies
Amir Hossein Zare; Esmail Mahmoodi; Mohsen Boojari; Ali Sarreshtehdari
Abstract
Significant growth of the wind power market has led to a dramatic increase in the scale and capacity of wind turbines over the past decades. As these extreme-scale structures are expected to pose a wide range of challenges, an innovative concept which both lightens blade's mass and improves their aerodynamic ...
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Significant growth of the wind power market has led to a dramatic increase in the scale and capacity of wind turbines over the past decades. As these extreme-scale structures are expected to pose a wide range of challenges, an innovative concept which both lightens blade's mass and improves their aerodynamic performance, is vital for the future of rotor's design. In the present study, modeling and evaluating of an innovative pre-aligned rotor design based on SANDIA SNL100-00 wind turbine blade were accomplished. To evaluate the aerodynamic performance of the proposed rotor, CFD simulation was used as a well-developed technique in fluid mechanic. In the new rotor design, the swept area was increased using an equal blade length and the blade sections were more appropriately aligned with the wind flow compared to the reference model. This enhancement attained due to transferring the bending position from the root to a certain point alongside the length of blade. According to simulation assessments, this modification led to the overall improvement of main performance parameters in terms of the mean power and the applied torque on the blades. The simulation revealed that the novel concept is capable of increasing the mean power coefficient by 13.21 % compared to the conventional rotor designs. Analysis of the axial induction in front of the rotor plane displayed a greater drop in the flow velocity streaming up to the rotor, which could lead to have a more efficient configuration for harnessing the upcoming wind's power.
Renewable Energy Resources and Technologies
Reza Roohi; Alireza Bahramian; Sepideh Samghani
Abstract
Ground thermal energy as a clean and sustainable energy source has received significant attention lately. Several strategies and hybrid configurations have been proposed to harvest geothermal energy for air conditioning and industrial purposes. The possibility of moist soil freezing in the vicinity of ...
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Ground thermal energy as a clean and sustainable energy source has received significant attention lately. Several strategies and hybrid configurations have been proposed to harvest geothermal energy for air conditioning and industrial purposes. The possibility of moist soil freezing in the vicinity of borehole tubes is known to be the source of several benefits and difficulties. The high storage capacity during the freezing process and the structural damage are the major advantages and disadvantages of the thawing phenomenon, respectively. In the present study, the numerical simulation of the freezing process around the U-tube configuration of boreholes accompanied by the solar energy injection as the auxiliary heat source is investigated. Lower values of cold stream temperature result in the higher amount of recovered heat, while increasing the injected heat temperature intensifies the heat regaining. Moreover, the energy absorbed by the ice layer around the tube is directly related to the cold stream temperature.
