Performance Assessment of Darrieus Turbine with Modified Trailing Edge Airfoil for Low Wind Speeds

Kumar, Palanisamy Mohan; Kulkarni, R. V.; Srikanth, Narasimalu; Lim, Teik‐Cheng

doi:10.4236/sgre.2017.812028

Cited by 12 publications

(8 citation statements)

References 19 publications

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“…Flow separation was controlled especially at lower TSRs and Reynolds numbers (Re), where a maximum of 50% performance enhancement was reported at a freestream wind velocity (V ∞ ) equal to 3 m/s. Kumar et al [23] utilized truncated NACA 0018TC-39 airfoils to enhance the start-up characteristics and performance of a SB-VAWT with three blades. Wind tunnel measurements showed a substantial performance improvement for the turbine with truncated airfoils at lower Re, mainly due to manifested lift characteristics.…”

Section: Of 21mentioning

confidence: 99%

A Dynamic Rotor Vertical-Axis Wind Turbine with a Blade Transitioning Capability

2019

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This work presents an optimized design of a dynamic rotor vertical-axis wind turbine (DR VAWT) which maximizes the operational tip-speed ratio (TSR) range and the average power coefficient (Cp) value while maintaining a low cut-in wind velocity. The DR VAWT is capable of mimicking a Savonius rotor during the start-up phase and transitioning into a Darrieus one with increasing rotor radius at higher TSRs. The design exploits the fact that with increasing rotor radius, the TSR value increases, where the peak power coefficient is attained. A 2.5D improved delayed detached eddy simulation (IDDES) approach was adopted in order to optimize the dynamic rotor design, where results showed that the generated blades’ trajectories can be readily replicated by simple mechanisms in reality. A thorough sensitivity analysis was conducted on the generated optimized blades’ trajectories, where results showed that they were insensitive to values of the Reynolds number. The performance of the DR VAWT turbine with its blades following different trajectories was contrasted with the optimized turbine, where the influence of the blade pitch angle was highlighted. Moreover, a cross comparison between the performance of the proposed design and that of the hybrid Savonius–Darrieus one found in the literature was carefully made. Finally, the effect of airfoil thickness on the performance of the optimized DR VAWT was thoroughly analyzed.

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Section: Of 21mentioning

confidence: 99%

A Dynamic Rotor Vertical-Axis Wind Turbine with a Blade Transitioning Capability

2019

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“…A dense fin pattern will generate too much restriction to airflow, preventing the warm air from rising out of the heat sink efficiently. Natural convection is employed in devices such as wind turbines, where wind velocity is higher [14][15][16][17].…”

Section: Natural Convection Heatsinksmentioning

confidence: 99%

Thermoelectric Materials—Strategies for Improving Device Performance and Its Medical Applications

Mohankumar¹,

Babu²,

Subramanian³

et al. 2019

Sci

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Thermoelectrics, in particular solid-state conversion of heat to electricity and vice versa, is expected to be a key energy harvesting and temperature management solution in coming years. There has been a resurgence in the search for new materials for advanced thermoelectric energy conversion applications and to enhance the properties of existing materials. In this paper, we review recent efforts on improving figure-of-merit (ZT) through alloying and nano structuring. As heatsink characteristics dictate the performance of thermoelectric modules, various types of heatsink designs has been investigated. Several reported strategies for improving ZT are critically assessed. A notable increase in figure-of-merit of thermoelectric materials (TE) has opened up new areas of applications especially in the medical field. Peltier cooling devices are widely employed for patient core temperature control, skin cooling, medical device and laboratory equipment cooling. Application of these devices in the medical field both in temperature control and power generation has been studied in detail. It is envisioned that this study will provide profound knowledge on the thermoelectric based materials and its role in medical applications.

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“…Initial investigation with trapped vortex airfoil [24], followed with wind tunnel tests [25] shows promising results on low Re. Airfoils with modified trailing edges have also been studied for their ease of manufacturing [26]. With the constraints on thickness and lift coefficient genetic algorithm optimization has been carried out to generate the new airfoil profile that can accommodate standard shapes of carbon fiber material from NACA 0018 surface pressure distribution.…”

Section: Ntu-20-vmentioning

confidence: 99%

Strategies for Enhancing the Low Wind Speed Performance of H-Darrieus Wind Turbine—Part 1

et al. 2019

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Small wind turbines are key devices for micro generation in particular, with a notable contribution to the global wind energy sector. Darrieus turbines, despite being highly efficient among various types of vertical axis turbines, received much less at tention due to their starting characteristics and poor performance in low wind speeds. Radically different concepts are proposed as a potential solution to enhance the performance of Darrieus turbine in the weak wind flows, all along the course of Darrieus turbine development. This paper presents a comprehensive review of proposed concepts with the focus set on the low wind speed performance and critically assessing their applicability based on economics, reliability, complexity, and commercialization aspects. The study is first of its kind to consolidate and compare various approaches studied on the Darrieus turbine with the objective of increasing performance at low wind. Most of the evaluated solutions demonstrate better performance only in the limited tip speed ratio, though they improve the low wind speed performance. Several recommendations have been developed based on the evaluated concepts, and we concluded that further critical research is required for a viable solution in making the Darrieus turbine a low speed device.commercially exploited for large scale power production [2]. The VAWTs are preferred for small scale power generation due to their unique advantages such as Omni directionality [3], lower manufacturing cost, the benefit of a generator on the ground level, and low noise. As VAWTs are preferred for roof top installations, the skewed flow must be accounted for. Wind tunnel test on both HAWT and VAWT shows that VAWT perform better than HAWT in skewed flow, even up to 30 • . Among VAWTs, the turbines are categorized as lift and drag based. The Savonius turbines are based on the drag difference between the rotating blades. Despite its lower efficiency and maximum power coefficient of 0.18 [4], these types of turbines are preferred for low wind conditions due to high dynamic moment as demonstrated in a recent study [5]. The lift based Darrieus turbines are preferred for moderate wind speeds with the power coefficient of 0.35~0.38 [6]. Since the small wind turbines are often installed in the locations of power demand [7] rather than optimum wind speed condition. As high wind sites are exploited to the fullest, these turbines find their locations that have an average wind speed of 4~6 m/s. Darrieus turbines are notoriously bad performers in these wind speeds due to their non-self-starting nature and very low torque due to the aerodynamics that are associated with the Darrieus rotor configuration.The search for a feasible solution to enable a Darrieus turbine to generate optimal power at low wind speed continue for decades. Over these years, countless efforts have been made through experimental, computational and field tests to achieve significant progress in understanding self-starting physics of Darrieus turbine. These at tempts substantially improv...

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Performance Assessment of Darrieus Turbine with Modified Trailing Edge Airfoil for Low Wind Speeds

Abstract: Darrieus wind turbines are simple lift based machines with exceptionally high efficiencies in terms of power coefficient compared to similar drag based vertical axis turbines. However, in low Reynolds numbers, a notable performance loss was reported. As a potential solution, truncated NACA

Cited by 12 publications

References 19 publications

A Dynamic Rotor Vertical-Axis Wind Turbine with a Blade Transitioning Capability

A Dynamic Rotor Vertical-Axis Wind Turbine with a Blade Transitioning Capability

Thermoelectric Materials—Strategies for Improving Device Performance and Its Medical Applications

Strategies for Enhancing the Low Wind Speed Performance of H-Darrieus Wind Turbine—Part 1

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