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April 2011 Technologies: A Need for Research and Development in Improving VAWT’s Characteristics Rigoberto Chinchilla Eastern Illinois University, [email protected]

Samuel Guccione Eastern Illinois University

Joseph Tillman Eastern Illinois University

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Recommended Citation Chinchilla, Rigoberto; Guccione, Samuel; and Tillman, Joseph, "Wind Power Technologies: A Need for Research and Development in Improving VAWT’s Airfoil Characteristics" (2011). Faculty Research & Creative Activity. 9. http://thekeep.eiu.edu/tech_fac/9

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Wind Power Technologies: A Need for Research and Development in Improving VAWT’s Airfoil Characteristics By Dr. Rigoberto Chinchilla, Dr. Samuel Guccione, & Mr. Joseph Tillman

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The Official Electronic Publication of The Association of Technology, Management, and Applied Engineering • www.atmae.org © 2011 Journal of Industrial Technology • Volume 27, Number 1 • January 2011 through March 2011 • www.atmae.org

Rigoberto Chin- chilla, PhD in Integrated En- Wind Power Technologies: gineering, Ohio University, is an Associate Pro- A Need for Research fessor of Applied Engineering and Technology at and Development in Eastern Illinois University (EIU) since 2004. His teaching and re- Improving VAWT’s Airfoil search interests include Quality design, Biometric and Computer Security, Clean Technologies and Automation. Characteristics Dr. Chinchilla has been a Fulbright and a By Dr. Rigoberto Chinchilla, Dr. Samuel Guccione, United Nations scholar, serves in numerous departmental and university committees at EIU & Mr. Joseph Tillman and has been awarded several research grants in his career. Dr. Chinchilla can be reached at Wind is a vast energy resource which [email protected]. ABSTRACT Straight bladed fixed pitched verti- is clean and renewable. By its inherent Dr. Sam Guccione cal axis wind (VAWTs) offer nature, wind power has the potential is an Associate several potential advantages over the to reduce the environmental impact on Professor of Ap- wildlife and human health. Improve- plied Engineering standard horizontal axis wind turbines and Technology in which are now in common use world- ments in power electronics, materials, the Eastern Illinois wide. The purpose of this study was to and wind designs allow produc- University (EIU) determine the need for further research tion to continually lower the cost of School of Tech- wind generated electricity making it nology. He has and develop on improved airfoil or been coordinator blade characteristics for use on straight today economically viable compared of the School’s bladed fixed pitched VAWT. This need with most other fossil fuels. Automation and Control labora- was demonstrated by the design and tory for the past construction of an airfoil that was phys- Most wind turbines are installed in 10 years where he taught robotics, automated ically modeled and field tested. The test locations where the minimum annual processes, industrial computers and human showed that asymmetric would average wind speeds are between 14.3 machine interface in process control. Prior to his and 15.7 mph. This range is known as appointment at EIU, Dr. Guccione was depart- enable SBVAWTs to self start. ment chair of Engineering Technology and an Class 3 winds. The consistency and occasional assistant dean for 26 years at Dela- INTRODUCTION speed of these breezes are major factors ware Technical and Community College, Dover. in locating farms. Before his teaching career, he worked for 10 Wind is an abundant energy resource years at McDonnell-Douglas (now Boeing) and ultimately powered by the Sun. It is other companies as an electrical engineer in the estimated that approximately 3% of the MODERN WIND TURBINES US space program. He has degrees in Electrical Engineering from the University of Illinois Urbana- Sun’s thermal energy is transformed AND THEIR LIMITS Champaign and a doctorate in education from into wind energy. Recent studies show The majority of Temple University, Philadelphia. that current wind technology operat- currently focuses on the horizontal axis ing only in Class 3 wind locations is wind turbines (HAWTs). Today, more M r . J o s e p h capable of producing approximately T i l l m a n , P E than 90% of wind turbines in use are of serves as Direc- 72 terawatts of electricity (Stanford HAWT design (Vieira da Rosa, 2009). tor of Sustainabil- Report, 2005). This is forty times the Modern HAWTs are currently favored ity and campus amount of electrical power annually for electrical generation for several engineer at Lake Land College in consumed worldwide and this clean reasons. First, the arrangement of the Mattoon, IL. He power source is just beginning to be blades allows nearly their full area earned his BSEE tapped on a large scale. swept to always be interacting with from Southern Il- the breeze. This maximum exposure linois University at Carbondale Wind energy is developing into a to the wind improves the coefficient of and is a licensed major alternative energy source. Over performance (Cp) of modern HAWTs. Illinois profes- 159,000 megawatts of wind generation Modern HAWTs have low blade solid- sional engineer. He is extensively involved in alternative energy projects and is completing were operational by the end of 2009 ity which is the ratio of blade area to graduate studies at Eastern Illinois University in with 38,312 megawatts added in 2009 the actual swept area. This aids the Charleston, IL. alone (World Wind Energy Association, blades or airfoils in the production of 2010).The reasons for this growth are lift. Though very successful, the mod- straightforward.

2 Journal of Industrial Technology • Volume 27, Number 1 • January 2011 through March 2011 • www.atmae.org ern HAWT is not without criticisms or Finally, there are three technical issues Figure 1: A Homemade Savonius Wind weaknesses. that demonstrate the limitations point Turbine (Courtesy of authors) of HAWT design. First, HAWTs cannot A very common objection to operate in high winds. Generally, the development is the rhythmic noise from large turbines must yaw or turn their the rotation of the blades. Sources of blades out of the wind and apply a this noise can vary from trailing edge brake when wind speeds reach above blade noise relating to turbulence to the 25 m/s or about 55 mph. Unfortunately, effect of unsteady loading noise caused the power available in any wind is di- by the change in wind velocity which rectly proportion to the velocity of the is due to the presence of the tower and wind cubed so many large turbines are mechanical noise from the gearbox and unable to harness this power. HAWTs yawing mechanism (Wagner, Bareib, operate best on rolling hills, in moun- and Guidati, 1996). Empirical evidence tain passes, or offshore where there are shows that common large commercial few obstructions. HAWTs are not de- HAWTs can output sound pressure lev- signed for the turbulent winds found in els ranging from 58 dBA to 109 dBA urban environments. Finally, the size of (Rogers, Manwell, and Wright, 2006). the HAWT is reaching an upper limit. The lower end of the range is often Massive 5 MW wind turbines with just above ambient noise sound pres- blade diameters of 126 m (over 400 ft) sure levels in some rural environments currently hold the title as the largest generally less than 1. Figure 1 shows a and the sound pressure level drops off wind turbines. Though this is not the student built . rapidly with distance. maximum structural or material limit, an end is in sight (Marsh, 2005). It is According to Johnson (1985), a well A second common objection concerns doubtful that reliable 10 MW HAWTs built Savonius style wind turbine has the aesthetics of large HAWTs. Though will ever be built. In light of all these a coefficient of performance of around this topic is subjective by nature, it is criticisms and disadvantages, a renewed 0.30 which is considered useful and often a very important issue during the interest has been shown in vertical axis reasonably efficient but its low tip planning stage of wind farm develop- wind turbines, VAWTs. speed ratio makes it better suited for ment. Many landowners fear that their the operation of mechanical pumps. property values will decrease if a wind VERTICAL AXIS WIND Savonius VAWTs have two advantages farm is built near their property. Part TURBINES in that they are simple and inexpensive of this fear is reduced by the $3,000- Vertical axis wind turbines (VAWTs) to construct and are self-starting, even $5,000 annual lease that many rural are the lesser known type of wind tur- in low wind speeds. landowners receive per turbine installed bine. In VAWT designs, the air scoops upon their property. or airfoils rotate perpendicular to the In 1931, Georges Darrieus patented his direction of the wind. As Gipe (2004) VAWT in the United States (Bernhoff, Some criticism has been brought about notes, there are two principle designs Eriksson, and Leijon, 2006). Instead of wind technology and the danger to avi- of VAWTs, the Savonius type and the cups catching the wind, the Darrieus an species. Much of this concern stems Darrieus type though there are several model uses either two or three curved from early wind farm construction in configurations of the Darrieus type. or straight blades which have a cross California. During the late 1970s and Some of these Darrieus configurations section similar to an airplane wing. Be- early 1980s, some farms were unfortu- are the focus of current research. cause of the wing profile, the Darrieus nately sited in migratory bird paths. In turbine is a lift producing machine. The light of these past mistakes, guidelines VAWTs were first recorded about 2,200 blades of a traditional Darrieus turbine have already been developed by most years ago in ancient Persia and were are curved and joined together at the states (Association of Fish and Wild- primarily used to grind grain (Cher- top and bottom while being bowed life Agencies, 2007). Current statistics emisinoff, 1978). In more recent times, outward in the middle. This shape is shows that avian deaths due to wind the Finnish engineer S. J. Savonius called a troposkein, which is Greek for turbines are approximately 0.02% of all created his first VAWT in 1922 (Peace, turning rope (Johnson, 1985). the avian killed by other human built 2004). A typical Savonius design uses structures in the nation (Sagrillo, 2003). two S-shaped blades or cups for the ro- There are other forms of Darrieus wind Massive construction of wind turbines tor though some versions often incorpo- turbines, notably the H-rotor design. nevertheless, have to be done carefully rate more blades. Johnson (1985) writes The H-rotor Darrieus is the most com- in order to protect wildlife. that Savonius rotors are primarily drag mon configuration of a straight bladed turbines since their tip speed ratio is vertical axis wind turbine (SBVAWT). The “H” rotor received its name due to

3 Journal of Industrial Technology • Volume 27, Number 1 • January 2011 through March 2011 • www.atmae.org the single horizontal arm supporting its Figure 2: A Modern H-Rotor Darrieus Wind Turbine two or more blades (Berg, 1996). The (Courtesy of Shaghai Aeolus Windpower Technology, LTD.) H-rotor may play a central role in de- veloping wind energy. Figure 2 shows a modern H-rotor Darrieus wind turbine.

VAWT ADVANTAGES VAWTs have several advantages which are just now beginning to be utilized. Islam, Fartaj, and Carriveau (2008) note that fixed pitch SBVAWTs are among the simplest types of wind turbines in existence. The airfoils of a SBVAWT are often uniform in cross section and do not require the extensive machining associated with HAWT blades. This simplifies airfoil design and construc- tion. Most VAWTs have a low cut-in speed so that they produce at least a little electricity in low wind speeds. Many VAWTs have a tip speed ratio of only 2 to 3 which equates to some useful power production but with less noise generation. VAWT DISADVANTAGES SELF-STARTING Because VAWTs can intake wind from Efficiency still is a major drawback to The (Darrieus) VAWT is not self-start- any direction, they can operate in the use of VAWTs in commercial pow- ing and typically uses the generator as a turbulent and variable wind conditions er production. State of the art HAWTs motor to spin the blades up to operat- far better than HAWT designs (Berry, can realize coefficient of performance ing speeds (Berg, 1996). Exceptions do 2009). In fact, VAWTs can often oper- (C ) values approaching 0.50 while the exist as Darrieus turbines can self-start ate in higher wind speeds than their p best VAWTs see Cp numbers a little under certain conditions. The principal HAWT counterparts which equates better than 0.40. Johnson (1985) notes issues affecting self-starting capabilities to greater energy generation under that most VAWTs average Cp values are the electromechanical load upon the these conditions. These advantages in the 0.30s. Secondly, VAWTs have VAWT and the shape and number of have led both designers and politicians traditionally have not been located on airfoils. to consider adding VAWTs to urban towers. This often limits the turbine’s environments (Ragheb, 2008). VAWTs access to higher winds and thus higher Darrieus wind turbines have difficulty often have their gearbox and electri- electrical production. Historically, in self-starting in most normal wind cal alternator located near the ground VAWTs cost more to operate and regimes. However, evidence shows that which facilitates easier maintenance. maintain than HAWTs. The Flo Wind a Darrieus turbine using fixed geom- Some new VAWT designs have a coef- Company supplied a fleet of several etry symmetrical airfoils can self-start ficient of performance approaching 0.40 hundred VAWTs located in the Cali- in the field during atmospheric gust- and allow for greater turbine density fornian mountain passes of Altamont ing (Dominy, Lunt, Bickerdyke, and per parcel of land (Allan, 2007). Marsh and Tehachapi which operated for 20 Dominy, 2006). Evidence shows that (2005) notes that new H-rotor VAWT years before maintenance costs caused lightly loaded VAWTs equipped with designs may also break the 10 MW the machines to be retired (Sagrillo, symmetrical, NACA (National Advi- barrier as the orientation of the blades 2005). Finally, traditional Darrieus sory Committee for Aeronautics) 0012 coupled with modular manufacturing rotors are not self- starting under most airfoils will self-start in wind speeds techniques allow VAWTs to be con- wind conditions and the manufacture under 10 m/s, 22.4 mph (Dominy et al., structed larger than HAWTs. However, of their blades is a challenge because 2006). there are reasons why VAWTs have of the complex shape which adds not seen more widespread use in wind expense to the turbine. Research and As Tangler (2000) notes, the constant farms. development of H-rotor Darrieus mod- chord VAWT blades adversely affect els is seeking to overcome both the blade efficiency and self-start capabil- self-starting and manufacturing issues ity. Darrieus type VAWTs have histori- of the traditional “eggbeater” style. cally used symmetric airfoils from the

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NACA 4-digit series, mostly NACA Figure 3: An Experimental H-Rotor Darrieus Wind Turbine 0012, 0015, and 0018 which were (Courtesy of the authors.) developed for aviation applications (Islam, Fartaj, and Carriveau, 2008). These airfoils were used because there is much performance data for them. However, the main problem with using these symmetric airfoils is their low starting torque at low speeds (Islam, Fartaj, and Carriveau, 2008).

Research into new airfoils for VAWT applications is increasing. The general direction for Darriues H-rotor design points to using asymmetric airfoils in place of symmetric airfoils. Islam, Fartaj, and Carriveau (2008) state that it is better to use a high lift and low drag asymmetric thick airfoil for low speed operation typically encountered by SBVAWTs. These thick airfoil shapes have several advantages for smaller SBVAWTs including improved perfor- mance and increase in starting torque (Islam, Ting, & Fartaj, 2007). Contin- ued research and development with thick airfoil shapes is warranted with a focus upon developing a self-starting SBVAWT.

MATERIALS Airfoil materials for SBVAWTs must be judiciously chosen because wind tur- bines operate under a variety of forces Wood is a better choice for VAWT them the material of choice. Fiberglass and weather conditions. Berg (1996) blades. Many smaller, homebuilt composites are another strong candi- states that wind turbines are fatigue HAWTs use wooden airfoils. As a date for small, experimental VAWT critical structures subjected to combina- building material, wood is readily avail- research. tions of wind, gravity, and gyroscopic able and has good fatigue properties loadings. At rotation rates of 30-60 as well as a relatively high strength-to- CONCLUSIONS AND rpm, the turbine blades must withstand weight ratio but has moisture stability 9 SUGGESTIONS at least 10 cycles during a 30 year life- issues (Islam, Ahmed, Ting, and Fartaj, time which is 100 to 1000 times more The superior capabilities of VAWTs 2008). It is easily shaped and wood can described have shown the need for ad- cycles than a typical transport aircraft is be coated to prevent moisture penetra- designed to withstand. ditional applied research in the design tion. It is a good candidate for small, characteristics of various VAWTs. In experimental VAWT airfoil research. Aluminum blades fabricated by extru- addition, the authors hope this research sion and bending have often been used will facilitate better SBVAWT designs Fiberglass composites or fiber rein- for future commercial applications. on VAWTs. Though reasonably inex- forced plastics are another possible pensive to manufacture, aluminum is material for VAWT airfoils. These A small working model of a SBVAWT not the best choice for VAWT blades. composites have low density, good me- The main problem with using alumi- outfitted with experimental airfoils chanical properties, excellent corrosion was constructed. This SBVAWT was num alloy is its poor fatigue proper- resistance and versatility of fabrication ties and its allowable stress levels in designed to produce an electrical output methods (Islam, Ahmed, Ting, and of about 100 watts. A review of the dynamic applications decrease rapidly Fartaj, 2008). Fiberglass composites al- at increasing number of cyclic stress current literature has shown a possible ready see widespread in HAWT blades design using thick asymmetric blades. applications (Islam, Ahmed, Ting, and where their strong performance makes Fartaj, 2008). Blades were manufactured using wood

5 Journal of Industrial Technology • Volume 27, Number 1 • January 2011 through March 2011 • www.atmae.org and plastic film and the resulting airfoil nid=164BD5A4808122A70CC Marsh, G. (2005). Tilting at was field tested under various wind A59 FCA46F984D? purl=/432928- utility-scale VAWTs: Towards 10 speeds and electric loads. The results xZkiEJ/webviewable/ MW and beyond? Refocus, 6(5), of this test showed that under standard Bernhoff, H., Eriksson, S., & Leijon, September/October, 37-42. wind and load conditions the SBVAWT M. (2006). Evaluation of different Peace, S. (2004). Another approach self-started as needed to become a vi- turbine concepts for wind power. to wind. Mechanical Engineering, able VAWT design process. Renewable & Sustainable Energy 126(6), 28-31. Reviews, 12(5), 1419-1434. Ragheb, M. (2008). Wind turbines in It also appears that VAWTs equipped Berry, A. (2009). Small vertical axis the urban environment. Retrieved with the asymmetric airfoils optimized wind turbine technology ideal July 12, 2009 from https://netfiles. for self starting and particular aero- for urban settings. Retrieved July uiuc.edu/mragheb/.../Wind%20 dynamic regimes could be utilized in 12, 2009 from http://windguys. Turbines%20in%20the%20 regions of low or turbulent air. This com/2009/06/16/small-vertical- Urban%20Environment. pdf could create the opportunity for wind axis-wind-technology-ideal-for- Rogers, A., Manwell, J., & Wright, turbines in more urban areas. A VAWT urban-settings/ S. (2006). Wind turbine acoustic has more acceptable aesthetics and Cheremisinoff, N. P. (1978). noise. University of Massachusetts can operate in turbulent air that would Fundamentals of wind energy. Ann at Amherst, Department of exist in an urban environment. Though Arbor, MI: Ann Arbor Science. Mechanical and Industrial low wind speeds produce low power, Dominy, R., Lunt, P., Bickerdyke, Engineering. properly designed VAWTs show cut in A., & Dominy, J. (2006). The self Sagrillo, M. (2005). The myths & or start up at low wind speeds. Some starting capability of a Darrieus mysticism of vertical axis wind energy production at these low speeds turbine. Retrieved June 7, 2010 turbines. Windletter, 24(2), 1-3. adds to the attractiveness of the design. from http://xa.yimg.com/kq/ Sagrillo, M. (2003). Putting wind Figure 3 shows a small working model groups/24857016/256422458/name/ power’s effect on birds in of a SBVAWT constructed as part of DarrieusSelfStartingStudy.pdf perspective. Retrieved July 7, 2009 this research. Gipe, P. (2004). Wind power. White from http://www.awea.org/faq/ River Junction, VT: Chelsea Green sagrillo/swbirds.html Finally, the authors believe that in Class Publishing Co. Stanford Report (May 20, 2005). 2 (12.5–14.3 mph) wind locations, the Islam, M., Ting, D., & Fartaj, A. New global wind map may lead to small VAWTs researched here may (2007). Design of a special-purpose cheaper power supply. Retrieved become the choice as low speed wind airfoil for smaller capacity straight June 5, 2009 from http://news. turbines are adopted in urban residen- bladed vawt. Wind Engineering, standford.edu/news/2005/may25/ tial and commercial installations. 31(6), 401-424. wind-052505.html Islam, M., Ahmed, F., Ting, D., & Tangler, J. (July, 2000). The evolution REFERENCES Fartaj, A. (2008). Design analysis of rotor and blade design. Allan, S. (2007). Will TMA Wind of fixed-pitch straight-bladed American Wind Energy Association blow away the competition. Pure vertical axis wind turbines with Wind Power 2000, Palm Springs, Energy System News. Retrieved an alternative material. Retrieved California. June 19, 2007 from http://pesn. May 5, 2010 from http://www. Vieira da Rosa, A. (2009). com/2007/02/01/9500453_TMA_ ontario-sea.org/Storage/26/1801_ Fundamentals of Wind_going_commercial/ Design_Analysis_of_Fixed_Pitch_ processes. 2nd Ed. New York, NY: Association of Fish and Wildlife Straight_Bladed_Vertical_Axis_ Elsevier. Agencies. (2007). Existing wind Wind_Turbines.pdf. Wagner, S., Bareib, R., & Guidati, G. power siting guidelines. Retrieved Islam, M., Fartaj, A., & Carriveau, (1996). Wind turbine noise. Berlin, July 2, 2009 from http://www. R. (2008). Analysis of the design Germany: Springer. fishwildlife.org/agency_science_ parameters related to a fixed-pitch World Wind Energy Association Siting_wind.html straight-bladed vertical axis wind (March 10, 2010).World wind Berg, D. (1996). Vertical-axis wind turbine. Wind Engineering, 32(5), energy report executive report. turbines-the current status of an 491-507. Retrieved August 21, 2010 from old technology. Retrieved June Johnson, G. L. (1985). Wind energy http://www.wwindea.org/home/ 22, 2010 from http://www.osti. systems. Upper Saddle River, NJ: index.php gov/bridge/purl.cover.jsp;jsessio Prentice Hall.

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