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   hoseobyoon (2012-02-01 10:10:50 )
   Get Inspired by Nature' Project"

"JFS's 'Get Inspired by Nature' Project" (No. 4)Dragonfly Wing Design Pioneers the Future -- Development of the Micro Wind Turbine  When I visited an exhibition about nature-based technology held in Tokyoin November 2011, I spotted a display featuring a micro-sized windturbine with a diameter of only about 50 centimeters. It had four verythin plastic corrugated blades, and the center of its rotor was madefrom a plastic bottle. I saw that just by catching a slight breeze theblades were rotating, generating electricity, and illuminating thelight-emitting diode (LED) lights connected to the generator. It turns out that the design of this tiny, toy-sized wind turbine isinfused with wisdom learned from the dragonfly's wing structure andmechanisms of flight, and it has the potential to solve some majorenergy problems facing society. In this issue of the JFS newsletter, wefeature an article about this micro wind turbine -- and how it wasinspired by the dragonfly and the characteristics and possibilitiesunique to its design. Here we interview its developer, Professor AkiraObata of Nippon Bunri University. Micro Flying Robot Laboratory, Nihon Bunri University *-*-*-*-*-*-*- It was in 2005 when Prof. Obata, who majored in aeronautics, encounteredsome interesting research on dragonflies. Subsequently, he got involvedwith a five-year research project titled "Research and Development of anInsect-Type Micro Flying Robot" subsidized by Japan's Ministry ofEducation, Culture, Sports, Science and Technology. During this time heworked on developing a flying robot that employed the principles of thedragonfly's mechanisms of flight. As the first step in this research, Prof. Obata's laboratory developedspecialized experimental equipment -- the world's first large water tankdesigned to observe a magnified equivalent of how air would flow arounda dragonfly's wings, at rates as slow as dragonfly actually experienceswhile flying. Applying a principle which allows water to simulateairflow accurately under certain circumstances, this tank enables thevisualization of water flow lines and vortices, and helped to discoverthe principles behind how a dragonfly's wings create lift. Prof. Obata found that the dragonfly's wing structure held the key toits stable flight. Specifically, it was the fact that its very thinwings, with their corrugated surface, created a series of small vorticesabove the wing surface while in flight. This was the secret to allowingthe wings to create lift by making the vortices flow backward, like on aconveyor belt, and simultaneously reducing air resistance by alsosweeping backward any air that is trying to "cling" to the wing. Based on this research he succeeded in developing a micro-sized flyingrobot using the dragonfly's wing structure and flight mechanism as aninspiration, but one day one of his friends asked him, "So, can youactually create anything useful with this robot design?" The questionintrigued him. He replied, "That's a good point. I will invent somethinguseful using the technologies learned from the dragonfly." The dragonfly is good at maintaining stable flight even in a slight breeze,So he wondered if he could make use of this ability to keep stable atlow speeds as a nature-based technology, taking the opposite of theapproach usually followed by industrial society in pursuing high speedand high power. Later on, he came up with the idea of applying thetechnology to the blades of wind turbines, and after three to four yearsof trial and error he created the micro wind turbine. Most large-scale wind turbines in Japan have a mechanism that rotatesonly with the wind blowing from the same direction at a constant speed,like the ones used in Europe. These turbines do not rotate in lightwinds, so they are not so suitable for Japan where winds varydramatically in strength and direction. In fact, this micro wind turbinerotates even when it catches a slight breeze as light as 30 centimetersper second (about 1 kilometer per hour), even with a generator attached. It also costs a large amount of money to construct sturdy wind turbinestructures that can withstand gale force winds such as typhoons. In highwinds, the turbine blades curve into a conical shape -- instead ofrotating faster -- to adjust to the wind, and this lowers the electricityoutput automatically. The micro wind turbine can tolerate high windsbecause of its ability to avoid damage by adjusting its shape, and yetcan continue rotating even in a slight breeze, so it is better suited tothe variety of wind conditions in Japan. (Video) Many wind turbines in Japan generate electricity using blades thatrotate at a high speed to turn a shaft connected to a generator. Incontrast, the micro wind turbine rotates efficiently at low speed, anddo not make any low-frequency noise, one of the problems with large-scalewind turbines. At the same time, thin plastic plates or even cardboardcan be used for micro turbine blades, as well, making it safe forsomeone to even stop the spinning blades by hand. Micro wind turbines have many possible applications. For instance, indeveloped countries they can be used to generate basic householdelectricity -- at least enough to charge cell phones and batteries -- byinstalling them on the balconies of apartment buildings. Whereas incountries where blackouts often occur, they can supply basic electricitydemands, such as for lighting at night, without the need to constructlarge-scale power plants or expanding power grids. Prof. Obata intendsto conduct more research toward the design's practical use for supplyingelectricity safely and inexpensively in rural areas. His research laboratory has two objectives for achieving the practicaluse and promotion of the micro wind turbine. The first is to achieve aconstant output of electricity amounting to up to 20 percent of theactual power of the wind. Although there are challenges getting actualelectricity output from a generator, an output of between 15 and 20percent appears achievable at this time with the speed of 2.5 meters persecond (nine kilometers an hour), the average wind speed in Japan.However, if the developers can attain high rotation under the averagewind speed and an electrical output of nearly 30 percent of the power ofthe wind under various conditions on electric loads on the generator,this new invention could be the perfect compact wind turbine, usable byanyone. Prof. Obata says, "I want to review the theory of the windturbine right from square one, and achieve 30 percent output bycombining the latest electricity generation technologies." Another challenge is production cost. This wind turbine is produced insmall numbers at the moment, as the manufacturing process requires timeand efforts. When considering mass production, the labor cost could beexpensive. Thus, there is no option but to produce it in developingcountries with lower labor costs, although, it may be a challenge tomaintain high quality and product performance. He still hopes to be ableto manufacture the turbines while maintaining high quality at a low cost,even in a country like Japan where labor cost is high, and estimates themanufacturing cost per unit could be kept as low as 10,000 yen (aroundU.S.$130). At the end of our interview we asked Prof. Obata for his currentthoughts and what he wants to pass on to the younger generationregarding the key philosophy of learning from nature, looking back athis past studies -- specifically when he started to observe dragonflies,then develop a flying robot, and finally created the micro wind turbine. Reflecting on his past research and inventions, he answered, "Certainly,research based on field work to study nature is important. But I believealso that engineering studies to produce things that mimic naturalsystems are as important as field studies, and this approach of studyingnatural systems holds new meaning for science. It will contribute to thedevelopment of more environment-friendly things, and is available foranyone, anywhere to try -- regardless of age, sex, or academicbackground. People get a good feeling about this approach, which makesit easy to attract more and more people. And I've found that this goodfeeling actually brings us the good fortune of new discoveries."  In the end he left us with this message for younger generations: "Natureis wonderful and gives us much to learn from infinitely. But it does noteasily open the doors to its mysteries, nor does it usually tell us evenwhere the doors are. So we need to ask, what can we do to learn fromnature? When we keep humbly coming up with questions about the wondersof natural phenomena and observe them, then we can sometimes find thosedoors." "From my own experiences, I would say that developing a visualizationtool is the key to success. Try to create your own visualization tool tofind the doors to answer your questions. Once you find the doors, youwill see a new world. Finally, I believe that the idea of learning fromnature is highly compatible with the mindset of the Japanese people, andthis is one of the things we should pursue." *-*-*-*-*-*-*- Epilogue: When we look at nature around us from different perspectives,we might be able to see new possibilities for the future. JFS's "GetInspired by Nature" project will introduce a broad range of discoveriesinspired by nature in Japan and the world. If you have ideas orsuggestions, please share them with us.  Written by Noriko Sakamoto

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