Performance Comparison of A Small Scale Vertical Axis Wind Turbine

The 3rd National Graduate Conference (NatGrad2015), Universiti Tenaga Nasional, Putrajaya Campus, 8-9 April 2015.

Performance Comparison of A Small Scale Vertical Axis Wind Turbine Koo Hui Yee, Chua Yaw Long College of Engineering, Universiti Tenaga Nasional, Malaysia. Email ([email protected], [email protected])

Abstract: The demand for wind energy is on the rise due to the tremendous increase in fossil fuels. Also, there are areas which do not have electricity supply and these places coincided with the poorest as well as isolated countryside areas. These people are not able to afford a wind turbine, neither small nor big. Hence, this research is focused on the design and performance of a small scale vertical axis wind turbine (VAWT) that anyone with common workshop materials could build as to harvest the wind energy to produce small scale electricity. In this research, the parameters such as rotational speed of turbine and voltage acquired are measured. The turbine built featured interchangeable part for blades that allows blades made of different type of material to be inserted for finding the material that could provide higher turbine’s efficiency. The performance of the turbine is studied and discussed. The VAWT built is economical and affordable as it could be built using simple and easy to get material. This small scale turbine could have great real-life application in rural areas to improve the people living condition by low cost small scale electricity generation. Keywords- Wind Energy; Vertical Axis Wind Turbine; Low Cost; Small Scale; Efficiency; Electricity Production

I.

INTRODUCTION

Wind energy is the kinetic energy from the movement of atmospheric air caused by uneven heating and cooling of the earth’s surface. It is a renewable energy source as well as a well-known form intended for extracting power for humankind. Wind energy is a potential clean energy source which can be used to produce energy at present and will for sure continue to be the same in the future. Wind energy contrasts with other forms of energy like biomass or fossil fuel which have constraints, particularly significant carbon dioxide emissions, threats to the environment and so on which in turn leads to a loss of their acceptability for utilization in energy generation [1]. Wind energy that originates from air moving across the earth's surface is a source of renewable power. Wind turbines harvest this particular kinetic energy and transform them into electrical power for households, institutions or even organizations purpose either on small or large scales.

People all over the world are now aware of wind energy which in turns contributes to the fastest growth and development of wind market. This wind energy is really a supply of renewable energy which offers an excellent and firm investment decision in the energy economy field. Additionally, this particular wind energy is needed by the wind turbine to generate clean energy which will not give rise to the greenhouse effect or environmental pollution. Technological breakthroughs provide low expenses for electrical power generation using wind energy harnessed by wind turbines and bring to an amazing financial savings. People from urban areas in various places totally count on wind turbines installed in their local areas that allow them to lower down their reliance upon electricity generated from some other resources. Making use of wind energy to generate electricity also plays a role in the growth of the world economy and growth of the career industry. 6 billion people, 80% of them which are living in SubSaharan Africa and South Asia, do not have supply of electricity. This particular humankind made use of kerosene and batteries for their households and diesel generators for their businesses [2]. Access to energy tightly correlates along with poverty. Not enough access to electrical energy or various other energy resources also means that wellness services, access to clean water and sanitation as well as education all suffer [3]. With shortage of sources, initiatives on grid extension are aimed to serve large population in cities while rural areas are viewed as to have excessive amount of electrification costs to serve few people. A small wind turbine design with minimal maintenance, available spare parts and with local users trained could possibly fulfill the needs for a long operation in the developing countries [4]. Developing countries around the world possess potential demand for small wind systems since they usually would not have electricity grid in non-urban areas. People require financial support to acquire small wind systems but government assistance nowadays is usually focused to subsidizing extension of the grid and installation of diesel generators [5]. The usage of batteries and subsequent charging is started to become common as the strategy used for the lack of electricity in small rural regions. Households in Sri Lanka utilized

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automobile batteries to power radio and TV sets. However, recharging the battery takes both time and money [6]. Technical requirements or standards should be considered within the design as to assure basic safety, reliability as well as durability of the wind turbine. However, standards pertaining to vertical-axis wind turbines are yet to be created and full qualification need to be performed by recognized institutions, which could be costly [7]. In this work, a small scale Vertical Axis Wind Turbine (VAWT) is designed and built. The wind turbine built is to be high in efficiency and is made locally with available and easy to get workshop materials. Additionally, it is constructible with normal and non-electrically driven workshop tools. A generator is also attached to the wind turbine for voltage generation and a circuitry to store the voltage produced is also constructed. Then, blade made with different type of material are inserted for testing as to find the material that could contribute to higher turbine’s efficiency. II.

DESIGN OF WIND TURBINE

The design of the vertical axis wind turbine starts from simple to complex. Few aspects are being reviewed and modified on the sketching before finalizing the preliminary design as to enhance the performance. Finalized design is then drawn using the drawing software known as SketchUp before proceed to the fabrication. Fig. 1 shows the components of the wind turbine which comprised of top nut, support arm, blade, blade shaft, center shaft, bottom support, stand and generator support.

A. Stand The material for the stand is stainless steel as this material has larger mass and density compared to the other component material, thus able to provide more stable base structure to the wind turbine. B. Bottom Support The material for the bottom support is plastic as this material is flexible, easy to fabricate yet has enough strength to act as an extension of the stand in order to support the rotor part. C. Generator Support The material for the generator support is plastic as this material is flexible, easy to fabricate yet has enough strength to act as a support to the generator. D. Center Shaft The material for the center shaft is plastic as this material is light in weight, thus able to minimize the weight of rotor part and contribute to make the rotor part to have more rotation. E. Support Arm The material for the support arm is plastic as this material is easy to fabricate, strong yet light in weight, thus able to support the blades while minimizing the weight of rotor part and contribute to make the rotor part to have more rotation. F. Blade The material used for the blade is polyfoam, plastic and paper cardboard respectively as these material are easy to fabricate, light in weight yet can be used for comparison in determining the efficiency of wind turbine, while minimizing the weight of rotor part and contribute to make the rotor part to have more rotation G. Top Nut The material for the top nut is plastic as this material is flexible and light. It acts as a lock to the rotor part by preventing the support arm holding the blades from moving out from the center shaft. H. Voltage Storage Circuit The function of this circuit is to store the voltage generated by generator while the wind turbine is working.

Figure 1. Exploded View of VAWT III.

MATERIAL SELECTION FOR COMPONENTS

Different material is used for different components based on their own properties and suitability.

Fig.2 shows the schematic diagram of the circuit which comprised of components such as a dynamo as generator, a 1N4001 diode, a 4700 microFarad capacitor, a 470 ohm resistor and a red LED. When the button is not pressed down, which is not closing the circuit connected to the LED, the generator task is to charge the capacitor up with voltage. The generator is left to run on for some period of time as to allow the capacitor to store up efficient amount of charges or voltages. After that, when the generator is stopped, the push button is pressed so that the circuit connected to the LED is now closed. The LED now lights up using the voltage stored

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in the capacitor due to the fact that capacitor now acts as the power source for the circuit, giving power to the LED. However, a capacitor does not act like a battery because it dumps its charge quite fast, so the LED will only receives power for some time. Hence, larger capacitor can be used as greater charge can be stored and the longer it can power a device, though it takes longer to charge.

Figure 4. Base Structure with Semi-Assembled Rotor C. Step Three Fig. 5 shows the blade being inserted into the support arm accordingly, forming the complete rotor part.

Figure 2. Schematic Diagram for Voltage Storage IV.

WIND TURBINE SET UP

The setting up of the VAWT involved four simple steps. A. Step One Fig. 3 shows the support arm is inserted into the center shaft as to form the rotor part of the wind turbine.

Figure 5. Base Structure with Fully-Assembled Rotor D. Step Four Fig. 6 shows the generator with the storage circuitry being inserted to the center shaft of the turbine, forming the full model of the wind turbine.

Figure 3. Semi-Assembled Rotor B. Step Two Fig. 4 shows the semi-assembled rotor part being inserted into the base structure.

Figure 6. Voltage Storage Circuit Installation

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V.

EXPERIMENTAL TESTING

Testing of the vertical axis wind turbine model is performed in a self-constructed wind tunnel to ensure more stable wind flow and wind speed during the testing process. Then, anemometer is used to determine the wind speed. Wind speed is set to be at 1.2, 1.8, 2.4, 3.0 and 3.6 m/s. Three types of blade material are being tested throughout the experimental testing. The experimental testing is divided into two parts, which are Part I testing on the aerodynamic performances and Part II testing on the circuitry for the voltage storage. Fig.7 shows the wind turbine being placed in the model wind tunnel for testing.

Figure 9. Graph of Rotational Speed vs Wind Speed

Figure 10. Graph of Voltage vs Wind Speed Figure 7. Experimental Setup in Wind Tunnel Fig.8 shows the different types of blade material used for testing, which are polyfoam, plastic and paper cardboard blades.

Figure 11. Graph of Efficiency of Wind Turbine vs Blade Material Figure 8. Blade made of Polyfoam, Plastic and Paper Cardboard VI.

RESULT AND DISCUSSION

A. Experiment Part I: Testing Aerodynamic Performance In this part of experiment, parameters being determined are rotational speed (rpm), voltage (V) and efficiency of wind turbine. Graphs are plotted to show the relationship among the parameters.

From Fig.9, it is noted that as wind speed increases, rotational speed increases. From Fig.10, it can be seen that as wind speed increases, voltage also increases. In short, both graphs show that as wind speed increases, rotational speed and voltage also increases. Moreover, it is noted that for both graph, blade made of polyfoam records the highest rotational speed and voltage value followed by blade made of plastic and cardboard. This shows that with lighter density material, wind turbine will be able to spin faster, creating greater force on the shaft and thus making the generator to turn faster and generate more voltage for electricity production. Efficiency of the wind turbine can be found through formula using the results obtained. The power output (electrical) can be calculated as in equation below:

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(1)

where Po is the power output, V is the generator’s voltage and R is the generator’s resistance. The power input (mechanical from wind) can be obtained using equation below:

(2) where PI is the power input, ρ is the air density which is equal to constant value 1.23 kg/m3, A is the swept area which is equal to πr2 and v is the wind velocity. Therefore, the efficiency can be calculated by comparing the output and input values and computing through equation (3), which is:

(3)

From Fig. 11, it can be seen that polyfoam blade has the highest efficiency compared to plastic and cardboard blade. This shows that material with lighter density will have better performance as they are able to produce higher rotational speed and higher voltage. B. Testing Voltage Storage for Run Time One Minutes In this experiment, parameters being determined are voltage stored in capacitor (V) and LED lights up time using voltage stored in capacitor (sec).

Figure 12. Graph of Voltage Stored vs Wind Speed

Figure 13. LED Lights Up Time vs Wind Speed From Fig.12, it is noted that as wind speed increases, voltage stored increases. From Fig. 13, it can be seen that as wind speed increases, LED lights up time also increases. In short, both graphs show that as wind speed increases, voltage stored and LED lights up time also increases. Additionally, it is noted that for both graph, blade made of polyfoam records the highest voltage stored and LED lights up time followed by blade made of plastic and cardboard. This shows that with lighter density material, wind turbine will be able to spin faster, creating greater force on the shaft to make the generator to generate more voltage and thus more voltage can be stored and LED lights up time can be longer. In short, experiment for part I and part II are conducted by varying the blade material of the wind turbine to observe on the aerodynamic performance of the wind turbine. From all data obtained and analysis, it is noted that blade made of polyfoam works better than blade made of plastic and cardboard. This is proven through the relationship found through the few parameters determined. It is shown that, polyfoam material with the lightest density compared to plastic and cardboard, able to make the blade spin faster, creating greater force on shaft, thus making the generator to generate voltage for electricity production. Also, from the efficiency found, blade made of polyfoam shows the highest value followed by blade made of plastic and cardboard. From the efficiency, it is also proved that the prototype worked properly and results obtained are trustable. In addition, circuit proposed also has the ability to store the voltage produced. C. Cost Analysis A preliminary budget has been set at RM400.00. However, all the materials and tools are obtained at as low price as possible to fulfill one of the aim, that is to produce a low cost and affordable small scale vertical axis wind turbine. All the materials used are cheap workshop material that can be easily accessed. Moreover, not much electrical driven tools are needed for constructing; only hot glue gun and hot glue sticks are being used for all the major joining joints. Fig. 14 shows the full expenses used in building this vertical axis wind turbine.

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materials. Moreover, tools needed for building it is also not complex. In short, the use of wind turbine should be emphasized to maintain the ecosystem stability and sustain the energy resource for future generation. Using renewable energy such as wind power can be said to be one of the best option to save the planet. VIII. RECOMMENDATION

Figure 14. Expenses for Vertical Axis Wind Turbine Prototype VII. CONCLUSION The vertical axis wind turbine with interchangeable part for blade is well designed and fabricated. The prototype is being tested with different types of blade material to analyze its aerodynamic performance. The results obtained are then being analyzed with proper graphical analysis and related equations. From the results, it is noted that material with lightest density, that is polyfoam, is able to produce better performance than the other two materials which are plastic and cardboard. Blade made of polyfoam able to spin faster, creating greater force on shaft and thus making the generator to produce more voltage. With these, polyfoam blade had contributed to higher efficiency of turbine compared to plastic blade and cardboard blade. In addition, polyfoam blade able to make the wind turbine spin faster and having higher voltage output, thus increasing the voltage stored in capacitor and LED lights up time can be pro-longed. The vertical axis wind turbine built is economical, low cost and affordable. It is built using very simple and easy get material. Also, the wind turbine is able to generate electricity at low wind speed. Although the power output was low at low wind speed, but by storing up the energy for some time using appropriate circuitry, it will still be able to use to power up some loads such as light bulb even though when the turbine is stop rotating. This can have great real-life application in which there is a very brief shut-down in power, for instance, if the power goes out for a few seconds and then turns back on. While the power is off, the LED or whatever desired load needs to be kept on can remain on with the presence of a capacitor acting as a backup power source. Also, this low cost vertical axis wind turbine can be then implemented at rural areas for the people that do not have electricity supply due to their poverty. It will be a very good choice as it is a cheap, simple design that can be made with available workshop

There are few imperfections occur throughout the project. If those errors can be eliminated or minimized, better results can be obtained. One of the improvement can be made is that testing the wind turbine in a proper wind tunnel to ensure more stable wind flow and wind speed compared to the model wind tunnel. Additionally, wind flow is quite significant in ensuring more accurate results. Therefore, this suggestion is valuable and should be considered in priority for future experimental testing. Generator with lower resistance is also suggested to be used as to increase the voltage output, so with higher voltage output can produce higher power supply. On the other hand, to store more energy generated, capacitor with larger value can be considered. With more energy stored, it can be used to power up loads anytime when the turbine blade stop turning at longer period. Lastly, this low cost small scale vertical axis wind turbine could then be implemented at rural areas to provide small scale electricity for the people that do not have enough access to electricity supply due to their poverty. Although voltage output is low especially at low wind speed, but by storing up the energy for some time using appropriate circuitry, it would still be able to use to power up some loads such as light bulb even though when the turbine is stopped rotating. REFERENCES [1]

[2]

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[7]

K.R. Dixon, "The Near Wake Structure of a Vertical Axis Wind Turbine Including The Development of A 3D Unsteady Free-wake Panel Method for VAWTs," Netherlands, Master Thesis 2008. G. Legros, I. Havet, N. Bruce, and S. Bonjour, The Energy Acces Situation in Developing Countries. New York: UNDP and World Health Organization, 2009. H. Cheikhrouhou. (2011) African Development Bank Group. [Online]. http://www.afdb.org/en/topics-and-sectors/sectors/energypower/ Winafrique. (2011) winafrique.com. [Online]. http://www.winafrique.com/index.php?option=com_content&view=artic le&id=92&Itemid=145 American Wind Energy Association American Wind Energy Association. (2002) AWEA.org. [Online]. http://www.awea.org/learnabout/smallwind/upload/US_Turbine_RoadM ap.pdf S. Dunnett. (2011) Practical Action. [Online]. http://practicalaction.org/docs/energy/wind_energy_battery_charging.pd f J. Cace et al. (2007) Urbanwind. Org. [Online]. http://www.urbanwind.org/pdf/SMALL_WIND_TURBINES_GUIDE_f inal.pdf

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