Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology

[tweetmeme] Yuji Ohya  and Takashi Karasudani of the Research Institute for Applied Mechanics, Kyushu University have issued a new article titled „A Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology.“

The introduction to this interesting analysis reads:

We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine, for a given turbine diameter and wind speed. This is because a low-pressure region, due to a strong vortex formation behind the broad brim, draws more mass flow to the wind turbine inside the diffuser shroud.

For the application of an effective energy resource in the future, the limitation of fossil fuels is clear and the security of alternative energy sources is an important subject. Furthermore, due to concerns for environmental issues, i.e., global warming, etc., the development and application of renewable and clean new energy are strongly expected. Among others, wind energy technologies have developed rapidly and are about to play a big role in a new energy field. However, in comparison with the overall demand for energy, the scale of wind power usage is still small; especially, the level of development in Japan is extremely small. As for the reasons, various causes are conceivable. For example, the limited local area suitable for wind power plants, the complex terrain compared to that in European or North American countries and the turbulent nature of the local wind are pointed out. Therefore, the introduction of a new wind power system that produces higher power output even in areas where lower wind speeds and complex wind patterns are expected is strongly desired. Wind power generation is proportional to the wind speed cubed. Therefore, a large increase in output is brought about if it is possible to create even a slight increase in the velocity of the approaching wind to a wind turbine. If we can increase the wind speed by utilizing the fluid dynamic nature around a structure or topography, namely if we can concentrate the wind energy locally, the power output of a wind turbine can be increased substantially. Although there have been several studies of collecting wind energy for wind turbines reported so far, it has not been an attractive research subject conventionally. Unique research that was carried out intensively in the past is the examination of a diffuser-augmented wind turbine (DAWT) by Gilbert et al., Gilbert and Foreman, Igra and others around 1980. In these studies, there was a focus on concentrating wind energy in a diffuser with a large open angle, a boundary layer controlled with several flow slots was employed to realize a flow that goes along the inside surface of the diffuser. Thus, the method of boundary layer control prevents pressure loss by flow separation and increases the mass flow inside the diffuser. Based on this idea, a group in New Zealand developed the Vortec 7 diffuser augmented wind turbine. They used a multi-slotted diffuser to prevent separation within the diffuser. Bet and Grassmann developed a shrouded wind turbine with a wing-profiled ring structure. It was reported that their DAWT showed an increase in power output by the wing system by a factor of 2.0, compared to the bare wind turbine. Although several other ideas have been reported so far, most of them do not appear to be reaching commercialization. The present study, regarding the development of a wind power system with high output, aims at determining how to collect the wind energy efficiently and what kind of wind turbine can generate energy effectively from the wind. There appears hope for utilizing the wind power in a more efficient way. In the present study, this concept of accelerating the wind was named the “wind-lens” technology. For this purpose, we have developed a diffuser-type structure that is capable of collecting and accelerating the approaching wind. Namely, we have devised a diffuser shroud with a large brim that is able to increase the wind speed from approaching wind substantially by utilizing various flow characteristics, e.g., the generation of low pressure region by vortex formation, flow entrainment by vortices and so on, of the inner or peripheral flows of a diffuser shroud equipped with a brim. Although it adopts a diffuser-shaped structure surrounding a wind turbine like the others, the feature that distinguishes it from the others is a large brim attached at the exit of diffuser shroud. Furthermore, we placed a wind turbine inside the diffuser shroud equipped with a brim and evaluated the power output generated. As a result, the shrouded wind turbine equipped with a brimmed diffuser demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 4–5 compared to a standard micro wind turbine. Furthermore, for the practical application to a small- and mid-size wind turbine, we have been developing a compact-type brimmed diffuser. The combination of a diffuser shroud and a brim is largely modified from the one with a long diffuser with a large brim. The compact “wind-lens turbines” showed power augmentation of 2–3 times as compared to a bare wind turbine. The application examples for a few projects are introduced.

Read the full article here in PDF format.

Citation: Ohya, Yuji; Karasudani, Takashi. 2010. “A Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology.” Energies 3, no. 4: 634-649.

2 Responses to “Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology”
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  1. […] more here: Shrouded Wind Turbine Generating High Output Power with Wind-lens … By admin | category: KYUSHU University | tags: applied, KYUSHU University, new-article, […]

  2. […] and Grassmann developed a shrouded wind turbine with a wing-profiled ring … Read more:  Shrouded Wind Turbine Generating High Output Power with Wind-lens … Share […]

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