Clean Renewable energy is an important need in today’s world with fossil fuels getting scarcer daily. In this research, we aim to use a small wind turbine and a simple wind tunnel to measure the efficiency of a wind turbine. To do this, we custom-printed a three-blade turbine and a base and tested its efficiency in a wind tunnel.
The model wind turbine consists of a propeller attached to a motor that is attached to a stand that places the motor in the center of the wind tunnel 15 centimeters in height from the base.
The wind tunnel we used is a low-speed open-circuit wind tunnel (ELD, model 402B) that can be operated in a range of wind speeds from 3.0 - 48.7m/s. A five-hole probe (AeroProbe Inc., model # P-C05C03B-SX-S) is used to measure the magnitude and direction of air velocity in the wind tunnel. It measures the static pressure and stagnation pressure in the axial, vertical, and horizontal directions and then Bernoulli’s principle can be used to calculate the flow velocity in three dimensions. A digital multimeter is used in this experiment to measure the output voltage of the motor and a slow-motion camera is used to measure the angular velocity of the propeller.
To conduct this experiment, we first installed the model into the wind tunnel by screwing the base of the model to the bottom surface of the tunnel – after which the tunnel was closed. Then, the room temperature and air pressure were collected from the barometer and thermometer and input into the five-hole probe LabView program. Next, the probe was zeroed according to the origin of the model (center and front of propeller). With the probe zeroed, the wind tunnel could be turned on and the air velocities were recorded by setting the wind tunnel VFD (frequency) to three different values. After setting the VFD input for each wind speed, a 15 seconds wait-time was given to ensure the flow in the tunnel had reached steady state flow. At steady state the free-stream velocity, voltage generated, and slow-motion videos were recorded with the five-hole probe, multi-meter, and phone respectively. Then, the five-hole probe was moved behind the propeller to measure the downstream air velocity. Finally, the wind tunnel was turned off and the data was checked for accuracy.
Results
During the experiment, the speed of the air 70 mm in front of the propeller and 35, 70, and 140 mm behind the propeller is recorded when the frequency of the wind tunnel is 15, 20, and 25 Hz. The average speed at both positions is then calculated. Based on the average wind speed in front of and behind the propeller, the energy consumed by the system is calculated based on the ideal gas law. The voltage and current readings in the multimeter are also recorded, allowing us to calculate the power output of the motor. By comparing the ideal power output and the measured power output, we calculated that the efficiency of our wind turbine is between 0.25% and 0.334%.