EET-216_Lab_7_FINAL

Electrical Engineering Electrical Engineering Technician AMAT/ SETAS Course: EET-216 DRAWINGS & INSTALLATION 3 Names: 1. _________________________________________ 2.________________________________________________ 3. _________________________________________________________ Lab # 7 Title: Wind Turbine Make sure that you are wearing appropriate protective equipment when performing the tasks. You should never perform a task if you have any reason to think that a manipulation could be dangerous for you or your teammates. Introduction The production of energy using renewable natural resources such as wind, sunlight, rain, tides, geothermal heat, etc., has gained much importance in recent years as it is an effective means of reducing greenhouse gas (GHG) emissions. The need for innovative technologies to make the grid smarter has recently emerged as a major trend, as the increase in electrical power demand observed worldwide makes it harder for the actual grid in many countries to keep up with demand. Furthermore, electric vehicles (from bicycles to cars) are developed and marketed with more and more success in many countries all over the world. This Introduction to Wind Power lab, covers how a permanent magnet wind turbine produces electricity from wind power, and how Maximum Power Point Tracking controllers are able to adjust the blade velocity of variable-speed fixed pitch wind turbines. The Discussion of this exercise covers the following points: ● Air density ● Kinetic energy in the wind ● Calculating wind power ● Relationship between wind power and wind speed ● Relationship between torque, rotation speed, and rotational mechanical power ● Conversion of wind power into rotational mechanical power and electrical power ● Typical torque-versus-speed curve at the wind turbine rotor ● Variable-speed, fixed-pitch Wind turbines. ● Wind turbine generator efficiency

The air density, symbolized by the Greek letter 𝜌 (rho), is an important parameter to know in wind power applications. Air density is the mass of air per unit volume: 𝜌 = 𝑚/? Where: ρ is the air density, in kilograms per cubic meter (kg/m3) 𝑚 is the mass of air, in kilograms (kg) ? is the volume, in cubic meters (m3) The air density varies with atmospheric pressure, temperature, humidity, and altitude. In SI units, ρ = 1.225 kg/m3 under standard sea level conditions, which are: a temperature of 15.5°C, an atmospheric pressure of 101.325 kPa, and a relative humidity of 36% Kinetic energy in the wind Any object or fluid in motion has kinetic energy. For example, wind, which is a mass of air in motion, has kinetic energy. The faster the speed of the wind, the higher the kinetic energy of the wind. The kinetic energy in a mass of air in motion can be calculated by using the following equation: ? ? = 𝑚V 2 / 2 Where: ? ? is the kinetic energy, in joules (J) or [feet-pound force (f lbf)]. ∙ 𝑚 is the mass of air, in kilograms (kg) V is the velocity of the mass of air, in meters per second (m/s) 2 is a constant. ? ? = 𝑚V 2 / 2 ? ? imperial unit version of the above SI unit equation. Where ? ? is equal to 32.174 lbm/lbf s ∙ 2 . Calculating wind power The Figure 1 below shows wind of constant speed passing through a cross-sectional area ? . This area could be, for example, the area swept by the blades of a wind turbine. In SI units, the power of the wind passing through the cross-sectional area is: ? ? = 𝜌A V 3 / 2 Where: ? ? is the power in the wind, in watts (W, or kg m ∙ 2 /s 3 ). 𝜌 is the air density, in kilograms per cubic meter (kg/m 3 ). ? is the cross-sectional area, in square meters (m 2 ). V is the wind speed (m/s). Cross-sectional area A Wind Velocity V Figure 1, Wind flowing through a cross-sectional area A

● The blades of the wind turbine convert a portion of the power contained in the wind they intercept (linear mechanical power) into rotational mechanical power that makes the wind turbine rotor turn. ● The rotational mechanical power produced at the wind turbine rotor drives an electric generator. The electric generator converts the rotational mechanical power into electrical power. Wind, rotor, and rotor efficiency coefficient ? ? As already mentioned, the power contained in the wind passing through the area swept by the blades of a wind turbine rotor is: ? ? = 𝜌A V 3 / 2 Where: ? ? is the power in the wind, in watts (W, or kg m ∙ 2 /s 3 ). 𝜌 is the air density, in kilograms per cubic meter (kg/m 3 ). ? is the cross-sectional area, in square meters (m 2 ). V is the wind speed (m/s). Not all the power in the wind passing through the swept area is transferred to the wind turbine rotor. Only a fraction of the available wind power is extracted by the blades and transferred to the rotor. This fraction indicates the efficiency of the wind turbine rotor in converting linear mechanical power into rotational mechanical power. The fraction of wind power extracted by the blades and transferred to the rotor is called the rotor coefficient efficiency ? ? . The rotor efficiency coefficient depends on the design (shape) of the rotor blades. The rotor efficiency coefficient is sometimes expressed as a percentage (rotor efficiency coefficient multiplied by 100%). The rotor efficiency coefficient ? ? is generally between 0.4 and 0.5 for most blade designs. The rotor efficiency coefficient ? ? must be taken into account to determine the fraction of wind power ? ? that is transferred to the wind turbine rotor. The formula used to calculate the mechanical power ? 𝑚 at the wind turbine rotor is therefore: ? 𝑚 = ? ? ∙ ? ? = ( 𝜌A? 3 / 2) ∙ ? ? Three-blade wind turbine rotor F Wind turbine generator F T F Figure 4: A fraction of the power in the wind intercepted by the blades of the turbine is converted into rotational mechanical power to drive the electric generator of the turbine.

The rotor efficiency coefficient ? ? of a wind turbine is virtually constant over the normal wind speed range of the turbine. Therefore, the mechanical power at the wind turbine rotor varies in the same way as wind power, i.e., with the cube (the third power) of the wind speed. Typical torque-versus-speed curve at the wind turbine rotor Figure 5 shows a typical torque-versus-speed curve at the rotor of a wind turbine obtained for a given wind speed. As the rotor speed increases, the torque produced at the rotor increases until a point is reached, beyond which the torque gradually decreases to zero. Consequently, the mechanical power produced at the rotor also increases up to a certain maximum value, and then gradually decreases to zero, as Figure 5 shows. The point at which the mechanical power is maximum is referred to as the maximum power point (MPP) . A wind turbine must be operated as close as possible to the optimum speed to maximize the mechanical power developed at the rotor and thus obtain the maximum amount of electrical power. This is performed by setting the rotor torque to the optimum value, through adjustment of the current drawn by the electrical load at the wind turbine generator output. Note that the rotor speed at which the maximum amount of power is produced varies with the wind speed. Therefore, to operate the wind turbine at the maximum power point (MPP) and maximize the energy produced at any wind speed, the rotor speed must be continuously monitored and changed, by adjustment of the rotor torque. This is generally performed automatically by an MPPT controller in the wind turbine. Variable-speed, fixed-pitch Wind turbines . Variable-speed wind turbines are generally characterized as having higher efficiency than fixed-speed wind turbines and hence are becoming more popular, particularly for small wind turbines. Typically, variable-speed wind turbines are controlled, usually by using power electronics, to regulate the torque and speed of the turbine in order to maximize the output power. Variable-pitch controlled wind turbines Figure 5. Typical torque-versus-speed curve and mechanical power- versus-speed curve at the rotor of a wind turbine, for a given wind speed. Mechanical power at rotor ?? Rotor torque ? Optimum torque Maximum power Maximum power point (MPP) Optimum Velocity Rotor speed ? Rotor speed ?

1. OBJECTIVE Students will set up a circuit containing a solid magnet wind turbine, a prime mover (hand crank or coupled motor) three phase rectifier and variable resistive load. Then, with the measuring equipment, study the behavior of the wind turbine (frequency, output current, and generator torque) as the prime mover speed and load are varied. 2. MATERIALS REQUIRED Data Acquisition and Control Interface Prime mover Variable resistive load Three phase power rectifier Diodes and Bread Board Multi-function tester Clamp-on ammeter Miscellaneous wire and tools NOTE: Do not install any improper or damaged components. Have instructor review finished connections PRIOR to applying power. High voltages are present in this laboratory exercise. Do not make or modify any banana jack connections with the power on unless otherwise specified. 3a. Effect of Velocity and Load on Wind turbine. 1. Set up the six diodes to form a three phase full wave bridge rectifier. /3 2. Make sure that the AC and DC power switches on the power supply are set to the O (off) position, then connect the Power Supply to the three-phase AC power outlet. Connect the Power Input of the Data Acquisition and Control Interface to a 24V AC power supply. Turn the 24V ac power supply on. 3. Connect the USB port of the Data Acquisition and Control interface to a USB port of the host computer. 4. Turn the host computer on, then start the LVDAC-EMS sofware. In the LVDAC-EMS Start-Up window, make sure the Data Acquisition and Control Interface is detected. Select the network voltage and frequency (60Hz, 120V ) then click the OK button to close the LVDAC-EMS Start-Up window. 5. Connect the equipmnet as shown in the figure Below. Using you’re the rectifier that you constructed and the three phase resistor bank (all resistors in parallel)

6. Have your instructor verify your connections. /3 7. In the LVDAC-EMS , open the Metering window. Make the required setting in order to measure the output voltage and frequency from the generator, and rectified Voltage, Current supplied to the resistor bank. 8. In the LVDAC-EMS , open the Oscilloscope , then make the appropriate settings in order to observe the waveforms of the Generator. Before and afer rectification ( E1 and E2 ). Select the AC generator voltage (Input E1 ) as the trigger source of the Oscilloscope . 9. With all the resistors in the resistor bank disconnected, turn the turbine at a consistent low- medium speed. Record frequency and amplitude of the AC turbine output in Table 1 . 10. Observe the waveforms on the Oscilloscope , how are they behaving? (voltage, frequency) ● The amplitude of the voltage and the frequency values gradually grew as the turbine was turned at a constant low-medium speed, until they remained constant at a narrow range of values. /2 11. Change the settings on the Resistor bank so that the resistance is 1Ω. Observe the waveforms on the Oscilloscope , record frequency and amplitude of the AC turbine output in Table 1 . 12. How does this change effect the counter torque produced by the turbine. (i.e. are the blades more difficult to move?) ● The blades were more difficult to move at a 5 ohm resistor load than they were at the detached resistor bank. It is simpler to move the handle in an open load when there is no counter torque generated in an open resistance bank. /2 13. Change the resistor bank settings to 0.5Ω. Record frequency and amplitude of the AC turbine output in Table 1 . 14. How does this change effect the counter torque produced by the turbine. (Are the blades more difficult to move?) ● In comparison to the resistor load of 5 ohms, moving the handle at 2.5 ohms proved to be significantly more challenging. Considering that the resistance value was lowered. As a result, an increase in current was noticed, which raised the counter torque. /2 15. Change the resistor bank settings to 0.33Ω. Record frequency and amplitude of the AC turbine output in Table 1 .

□ Yes □ No /1 If one was to try, what could the complications be? /4 ● The frequency of the voltage varies along with the wind's speed and the rotor's speed. The AC power network cannot be connected to this directly. Alternatively, the frequency needs to be adjusted so that it remains constant. If this isn't done, there's no guarantee that the wind turbine frequency will match the network frequency. As a result, it might cause harm to the generator and the power system. 4. How would a Maximum Power Point Tracking controler manage a fixed pitch variable-speed wind turbine such that the blade speed could be controlled with respect to wind velocity? ● Knowing the wind-rotors fixed-pitch variable-speed wind turbine's performance. The generator's rotor speed and torque are modulated to maintain it operating at its maximum power point (MPP). The MPPT controller modifies the generator's current to alter the blades' velocity. /4 5. What kind of feedbacks could the MPPT controler use to ensure the blade speed is appropreat to the wind speed? /5 ● The rotor speed needs to be continuously varied and monitored by adjusting the rotor torque in order for the wind turbine to maintain its maximum power point (MPP) and maximize the energy produced at any wind speed. Usually, the wind turbine's MPPT controller does this automatically. /8 Table 1 Prime mover speed: 100 bpm refer 2 nf email Load (Ω) AC Voltage (peak) Frequency (Hz) DC Current DC Voltage OPEN (∞Ω) 6.90 10.16 0.00 6.02 5 Ω 4.80 10.69 0.60 3.13 2 .5 Ω 3.76 9.91 0.75 2.07 1 . 67 Ω 3.37 9.87 0.82 1.06

/8 Table 2 Prime mover speed: 120 bpm Load (Ω) AC Voltage (peak) Frequency (Hz) DC Current DC Voltage OPEN (∞Ω) 8.04 11.92 0.00 7.51 5 Ω 5.45 12.39 0.72 3.73 2 .5 Ω 4.67 12.95 1.05 2.93 1 . 67 Ω 4.33 13.72 1.27 2.45

For that reason, it is harder to move the turbine at low resistances because there is no current flowing through it. Whereas to shorted leads, it would be alot harder as there will be a rapid current increase. Lastly, the rotational speed has a direct relationship with voltage, frequency, and current as shown in the result tabulated above