Design and Implementation of a Horizontal Wind Turbine with ...

Design and Implementation of a Horizontal Wind Turbine with Circulating Airfoil Blade Design Utilizing Magnus Effect Abstract The world today faces a continuous looming threat of limited resources and energy, the burning of fuel can no longer be viewed as the only means to obtain energy. Renewable, safe and sustainable ways of generating energy must be developed and it lies as always on engineers to make that possible. The project discussed within this report utilizes wind energy as a source of renewable energy, since wind power plays an important role in tackling climate change, and through new design and concepts allows for greater yield and efficiency of energy in its application. The project utilizes Magnus effect as a lifting force on circulating airfoil blade attached on a horizontal wind turbine design. The different components of the wind turbine to be implemented are identified and specifications obtained in order to acquire during the implementation phase. The circulating airfoil shape discussed in this report is a new concept developed theoretically and has not been implemented. The circulating airfoil design was scaled to match that of a NACA0021 airfoil which shows high aerodynamic quality. Design criteria in this report was based on the following; the speed ratio of Magnus speed to air stream speed was maintained at 3. Based on these design criteria yielded from theoretical articles [1] [2] and the optimization carried out to reduce the weight of the rotor system, the dimensions and force calculations were obtained in order to produce a working prototype. The circulating airfoil was designed to have a 0.13m diameter driver cylinder with a 0.04m free rotating cylinder attached 0.18 apart. The rotor radius was found to be 0.7m. At a lift coefficient of 1.2 and a calculated wind speed of 12m/s a lift force of 26.46 N was achieved, the torque generated due to that lift was found to be 12.35 N.m. At a power output design assumption of 500Watt the angular velocity of the rotor was found to be 387 rpm.Further weight reduction for the rotor system through manipulation of cylinder material and dimensions can aid in obtaining better results during implementation.

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1. Objectives •

Produce energy through renewable sources.

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Build a working prototype for testing

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Understand the technology and engineering behind wind turbine generators

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Better understand fluid engineering through considering the Magnus effect

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Produce a project that develops mechanical engineering skills and provides innovation and creativity.

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Obtain appropriate efficiency rates to match those of regular wind turbines.

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Harvesting enough energy from working prototype.

2. Sustainability As the world’s desire for cleaner energy continues to build, we are confident that wind energy has the potential to maintain and even exceed the dynamic growth rate of the past several years. This growth will be tied to the fact that wind is the most cost effective and scalable renewable source of energy. Because of the small size of the existing installed base, the offshore wind sector will see higher growth percentages while the number of onshore turbines will continue to outpace those installed offshore. Strong, supportive policy and government support is key. It remains important for governments worldwide to establish policy frameworks that will provide the market stability required to maintain long-term growth. The EU’s 20-20-20 directive is a good example of policy that is driving action. But, implementation of these targets is different in every European country. Countries with the most attractive support schemes will see the most installations. Continued investment in grid infrastructure is critical for growth as well as wind turbine technology investments that improve efficiency and reliability while driving down emissions. 2|Page

Countries with the most efficient and flexible permitting processes will benefit by realizing the installation of the most advanced technology. No single solution will meet the world’s growing energy demands, but renewable sources, and in large part, wind energy, have an extremely important role to play. [3]

3. Design and Component Analysis The final design based on the analysis below will be a typical horizontal axis wind turbine with a direct generator rather than a gear box assembly. The blade design will be the new circulating airfoil blade design consisting of two different sized PVC cylinders, one of which is connected to a DC motor to circulate the airfoil surface and one rotating freely and maintaining the airfoil shape. The hub of the proposed wind turbine will house the two DC motors connected to two circulating airfoil blades. The rotor diameter which is the length of the blade and hub radius will be 0.7m based on dimensional analysis discussed below. The lift, torque and angular velocity of the wind turbine are also calculated below.

Figure 1: Horizontal Axis Wind Turbine with Circulating Airfoil Blade Design Utilizing Magnus Effect

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4.2.12 Rotor Blade The blade design introduced in this report is a new design concept consisting of a circulating airfoil surface. The circulating airfoil is achieved through connecting a rotating driver cylinder to a free rotating cylinder which are at an offset of each other. The driver cylinder is rotated by a DC motor encased in the rotor hub and connected to the cylinder via shaft. Once the driver cylinder is rotated the surface of the blade is rotated along both the driver cylinder and the free rotating cylinder mimicking a treadmill like operation.

Figure 2: Circulating Airfoil Showing Blade Treadmill Motion

Figure 3: Circulating Airfoil Blade Design Showing Drive Cylinder and Free Cylinder

4.3 Design Dimensions and Calculations

4.3.1 Design Restrictions Where possible the design analysis has adhered to the following restrictions: 4|Page

1. Maintain design Shape of NACA0021 Airfoil. 2. Speed Ratio kept within the range of 1 to 3. 3. Material Selection should reduce weight as much as possible.

4.3.2 Rotating Cylinder Dimensions Assumptions: 1. Velocity Ratio,

assumed to be 1.

2. Angular Velocity of Magnus assumed to be 1800 rpm. 3. Velocity of Wind for design purposes assumed to be 12 m/s.

4.3.3 Circulating Airfoil Dimensions Assumptions: 1. Design to be similar in shape to NACA0021 airfoil design. 2. The diameter of the front circle is almost considered to be equal to 21 percent of the chord length to make an approximate similarity to NACA0021.

Figure 4: NACA0021 Airfoil Design Dimension

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Figure 5: Comparison between Shape of Circulating Airfoil and NACA0021

Figure 6: Dimension of Circulating Airfoil Blade with Cylinder Diameters

4.3.4 Cylinder Weight Calculations Since in HAWT the reduction of weight of the rotor system is a crucial factor in supporting the wind turbine. Therefore based on different iterations of cylinder diameter and minimum wall thickness whilst keeping the cylinder length constant, the weight of the cylinders were found for both PVC and Steel. Based on the calculated 13 cm diameter size of cylinder, and minimum wall thickness from the table, the weight for a selected PVC of density = 1400 kg/m3, of length 1 m can be found to be:

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Where, m: mass (kg) ρ: Density (kg/m3) R: radius of Cylinder t: Minimum Wall Thickness L: Length of Cylinder

4.4 Rotor Radius Assumptions: 1. Power output, P assumed to be 500 Watts. 2. Coefficient of Power, Cp taken to be 0.3. 3. Velocity, v taken to be Rated Velocity = 12m/s. 4. Density of Air, ρ = 1.25 kg/m3.

4.5 Lift Force Assumptions: 1. Coefficient of Lift, CL taken to be 1.2.

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4.6 Torque Assumptions: 1. Number of Blades taken to be 2.

4.7 Angular Speed of the Rotor Assumptions: 1. Power output assumed to be 500Watts.

5. Implemented Prototype 5.1 3D Drawings 5.1.1 Airfoil Blade Design

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Figure 7: Driver and Free Rotating Cylinder

Figure 8: Blade Bearing Cylinder Holder

9|Page Figure 9: Assembled Circulating Airfoil Blade Design

Figure 10: Circulating Surface Attached to Blade

5.1.2 Hub Design

Figure 11: Hub Design For Holding Motors

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5.1.3 Fully Assembled Prototype

5.2 Prototype Model Components 5.2.1 Airfoil Blade Component

Figure 12: Free Rotating PVC Cylinder

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Figure 13: Driver PVC Cylinder

Figure 14: Circulating Leather Surface Fabric

Figure 15: Polyamide Holders With Bearings Attached

5.2.2 Fully Assembled Prototype

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Figure 16: Assembled Porotype with Motors Connected

5.3 Motor Specifications

Figure 17: Motor with Gearbox 5000 rpm

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Manufacturer: ZHENG Motor

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Serial #: ZYTD-38SRZ-R1

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Working Voltage: 12V , Speed: 5000 RPM, Power Rating: 8W

5.4 Generator Selection A research been done to be familiarized with types of generators which could be used in wind turbine and to know the advantages and disadvantages of each type in order to choose the proper generator for the project. Wind turbines may be designed with either synchronous or asynchronous generators, and with various forms of direct or indirect grid connection of the generator. Direct grid connection mean that the generator is connected directly to the (usually 3-phase) alternating current grid. Indirect grid connection means that the current from the turbine passes through a series of electric devices which adjust the current to match that of the grid. With an asynchronous generator this occurs automatically. [13] 13 | P a g e

5.4.1 Types of Generators: There are many different kinds of generators that could be used in a wind turbine and they can be grouped into three different types: Induction Generator An induction generator is a type of electrical generator that is mechanically and electrically similar to an induction motor. Induction generators produce electrical power when their shaft is rotated faster than the synchronous frequency of the equivalent induction motor. Induction generators are often used in wind turbines and some micro hydro installations. Induction generators are mechanically and electrically simpler than other generator types. They are also more rugged, requiring no brushes or commutator. Induction generators are not self-exciting, meaning they require an external supply to produce a rotating magnetic flux, the power required for this is called reactive current. The external supply can be supplied from the electrical grid or from the generator itself, once it starts producing power or a capacitor bank can be used to supply it. The rotating magnetic flux from the stator induces currents in the rotor, which also produces a magnetic field. If the rotor turns slower than the rate of the rotating flux, the machine acts like an induction motor. If the rotor is turned faster, it acts like a generator, producing power at the synchronous frequency. The common down side of using an induction generator in a wind turbine is gearing. Typically, you need an induction motors to run 1500+ RPM to meet the synchronous so a gearing is almost always needed. So one of the major disadvantage of induction generators is that they take quite large amount of reactive power. [14] Permanent Magnet Alternators Permanent magnets alternators (PMA) have one set of electromagnets and one set of permanent magnets. Typically, the permanent magnets will be mounted on the rotor with the electromagnets on the stator. Permanent magnet motor and generator technology has advance greatly in the past few years with the creation of rare earth magnets (neodymium, samarium-cobalt, and alnico). Generally, the coils will be wired in a standard three phase wye or delta. Permanent magnet alternators are can be very efficient, in the range of 60%-95%, typically around 70% though. As a generator they do not require a controller as a typical three phase motor would need. It is easy to rectify the power from them and charge a battery bank or use 14 | P a g e

with a grid tie. Car alternators are not PMA but actually have a field coil instead of permanent magnets, and are typically very inefficient around 50%. They typically need to be spun 1500+RPM to get any real power out of them, but with a belt or gear arrangement can still do a decent job. [14] Brushed DC Motor Brushed DC Motors are commonly used for home built wind turbines. They are backwards from a permanent magnet generator. On a brushed motor, the electromagnets spin on the rotor with the power coming out of what is known as a commutator. This does cause a rectifying effecting outputting lumpy DC, but this is not an efficient way to “rectify” the power from the windings, it is used because it’s the only way to get the power out of the rotor. A good brushed motor can reach a good efficiency, but are typically at most 70%. There are many great advantages to using a brushed motor. One of the biggest reasons is because typically you can find one not requiring any gearing and still get a battery charging voltage in light wind. They are also quite easy to find can find them on different things that might get thrown away or given away (like a treadmill). [14]

5.5 Wind Tunnel Testing A wind tunnel test was conducted for the airfoil blade design. Due to restrictions on the wind tunnel setup available in the Mechanical Lab it was only possible to test a stationary surface blade rather than a circulating surface. Data was obtained from the available wind tunnel load cell by substituting the 4 mm support bar with a 4 mm screw bar to fix the blade design in the wind tunnel. The blade can be installed in the measurement section vertically and by this way the flow forces at the model are measured electronically in the wind tunnel. For this purpose the wind tunnel is provided with a permanently installed electronic two-component force transducer beneath the measurement section.

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Figure 18: Wind Tunnel Component Schematic

Figure 19: 4mm Screw Bar Attached to Wind Tunnel & Airfoil Blade

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Figure 20: Wind Tunnel Experimental Setup

5.5.1 Wind Tunnel Data Name: test1 Data Start t Time Index v Velocity p Pressure a Angle Lift Mz Torque x Distance U2 Voltage 2 h:min:s m/s Pa grd mm N N 2:50:42.1 PM 3.500 0.000 342.500 0.000 -0.100 2:49:59.1 PM 0.000 0.000 343.000 0.000 0.000 2:50:26.1 PM 3.400 0.000 343.000 0.000 0.000 2:50:49.6 PM 4.000 0.000 343.000 0.000 0.000 2:51:24.6 PM 5.100 0.000 343.000 0.000 0.000 2:51:40.1 PM 6.000 0.000 343.000 0.000 0.000 2:51:56.1 PM 6.900 0.000 343.000 0.000 0.000 2:52:20.1 PM 8.000 0.000 343.000 0.000 0.000 2:52:36.6 PM 9.100 0.000 343.000 0.000 0.005 2:52:55.6 PM 10.100 0.000 343.000 0.000 0.015 2:53:03.1 PM 11.000 0.000 343.000 0.000 0.020 2:54:35.1 PM 18.900 0.000 342.500 0.000 0.025 2:53:15.6 PM 12.000 0.000 343.000 0.000 0.030 2:53:23.6 PM 13.000 0.000 343.000 0.000 0.030 2:53:33.6 PM 13.900 0.000 343.000 0.000 0.030 2:54:02.6 PM 16.100 0.000 343.000 0.000 0.030 2:54:17.1 PM 17.000 0.000 343.000 0.000 0.030 2:54:26.1 PM 18.000 0.000 343.000 0.000 0.030 2:53:48.6 PM 15.000 0.000 343.000 0.000 0.035 4:32:15.2 AM 16.000 0.000 344.000 0.000 0.075

x Distance

Fy Drag

Fx

Nm 0.000 0.000 0.000 0.000 -0.010 -0.010 -0.010 -0.005 -0.010 -0.015 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 -0.005 0.045

V -75.580 -75.580 -75.580 -75.580 -75.580 -75.580 -75.222 -75.580 -75.580 -75.580 -75.580 -75.550 -75.580 -75.580 -75.580 -75.550 -75.580 -75.580 -75.640 -75.580

0.001 0.001 0.000 0.014 0.001 0.001 0.001 0.001 0.000 0.000 0.002 -0.001 0.001 0.006 0.002 0.001 0.000 0.001 0.000 0.000

mm -0.001 0.000 0.000 0.001 0.000 -0.001 0.000 -0.001 0.000 -0.001 0.001 0.001 0.000 0.001 0.001 0.000 0.000 0.001 0.001 -0.001

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4:32:27.7 4:32:38.2 4:32:47.2 4:32:55.2 4:33:02.2 4:33:09.2 4:33:23.2 4:33:30.7 Data End

AM AM AM AM AM AM AM AM

17.100 18.100 19.000 20.200 21.200 22.000 23.050 24.100

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

344.000 344.000 344.000 344.000 344.000 344.000 344.000 344.000

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.080 0.080 0.090 0.110 0.120 0.120 0.200 0.240

0.045 0.045 0.060 0.055 0.065 0.070 0.025 0.040

0.001 0.000 0.001 0.000 0.000 0.001 0.001 0.001

-75.580 -75.580 -75.580 -75.550 -75.580 -75.580 -75.580 -75.580

0.001 0.005 0.002 0.000 0.001 0.001 0.002 -0.004

8. Discussion & Conclusion In this report the planning and implementation of a horizontal axis wind turbine with circulating airfoil blade design that utilizes Magnus effect is discussed. The necessary components for implementation of a prototype are identified and their operating methods described. The dimensions of the wind turbine are then obtained through utilizing mathematical models concerned with rotor diameter and hub size, while restricting airfoil design to that of a NACA 0021 airfoil shape design. An iteration was then developed for PVC tubing at different diameters and internal thickness to find the weight of the cylinders which contribute the largest weight percentage of the entire rotor system. Finally, by calculating the total rotor radius which is the radius of the hub in addition to the length of the blade, the lift force, torque and angular speed of the rotor system was calculated. The implementation phase was then carried out by acquiring all necessary material and components. A prototype was developed to better understand the working mechanisms and limitations of the design phase in order to construct the real model. The airfoil blades developed for the prototype were used to experimentally obtain data by utilizing wind tunnel equipment. The wind tunnel results obtained were limited to stationary blade surface due to restrictions on wind tunnel equipment usage.

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10. List of References 1. Ahmad Sedaghat, Magnus type wind turbines: Prospectus and challenges in design and modelling, Renewable Energy 62 (2014) 619-628 Dr. Ahmad Sedaghat. [ONLINE] Available at: http://www.sedaghat.iut.ac.ir/ahmad-sedaghatmagnus-type-wind-turbines-prospectus-and-challenges-design-and-modelling-renewable. [Accessed 14 November 2015]. 2. Kazemi, S.A.K, 2015. Aerodynamic Performance of a Manufactured Circulating Airfoil Section for Magnus Systems. Energy, 84156, 1-41. 3. David Appleyard, D A, 2010. Is Current Wind Growth Sustainable? Renewable Energy

World,

[Online].

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17-19.

Available

at: http://www.renewableenergyworld.com/articles/print/volume-13/issue-2/windpower/the-big-question1.html [Accessed 26 November 2015]. 4. Emrah Kulunk. 2011. Aerodynamics of Wind Turbines. [ONLINE] Available at: http://cdn.intechopen.com/pdfs-wm/16241.pdf. [Accessed 14 November 15]. 5. Manyonge, A W, 2012. Mathematical modelling of wind turbine in a wind energy

conversion system: Power coefficient analysis. Applied Mathematical Sciences, Vol. 6, 2012, no. 91, 4527 - 4536. 6. Magdi Ragheb and Adam M. Ragheb (2011). Wind Turbines Theory - The Betz Equation and Optimal Rotor Tip Speed Ratio, Fundamental and Advanced Topics in Wind Power, Dr. Rupp Carriveau (Ed.), ISBN: 978- 953-307-508-2, InTech, Available from: http://www.intechopen.com/books/fundamental-and-advanced-topicsin-windpower/wind-turbines-theory-the-betz-equation-and-optimal-rotor-tip-speed-ratio 7. MASSAGUER & MASSAGUER & PUJOL & COMAMALA & VELAYOYS, A & E & T & M & J, 2008. BLADE SHAPE INFLUENCE ON AERODYNAMIC EFFICIENCY OF

A

MAGNUS

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WIND

TURBINE

SHAPE

USING

INFLUENCE

PARTICLE ON

IMAGE

AERODYNAMIC

EFFICIENCY OF A MAGNUS WIND TURBINE USING PARTICLE IMAGE VELOCIMETRY, 1, 3.

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8. Siefert, J, 2012. Progress in aerospace sciences. A review of the Magnus effect in aeronautics, 1, 43 9. Eriksson, Bernhoff & Leijon, S, H & M, 2007. Evaluation of different turbine concepts for wind power.Evaluation of different turbine concepts for wind power, 1364-0321, 1-1432 10. Ackermann & Soder, T & L, 2002. An overview of wind energy-status. Renewable and sustainable energy reviews, 1364-0321, 1-119 11. Gear Ratios and Mechanical Advantage. 2016. Gear Ratios and Mechanical Advantage. [ONLINE] Available at: http://www.maelabs.ucsd.edu/mae_guides/machine_design/machine_design_basics/Mech _Ad/mech_ad.htm. [Accessed 13 February 2016]. 12. Wind Turbine Generator Technologies | InTechOpen. 2016. Wind Turbine Generator Technologies|InTechOpen.[ONLINE]Availableat:http://www.intechopen.com/books/adv ances-in-wind-power/wind-turbine-generator-technologies. [Accessed 28 March 2016]. 13. Types of Generators used for Wind Turbines. 2016. Types of Generators used for Wind Turbines. [ONLINE] Available at: http://centurionenergy.net/generator-types. [Accessed 29 March 2016].

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