For our final project for CS 59000: Embedded Systems, a partner and I implemented several tests on a small-scale wind turbine using the Texas Instruments MSP430 board. We use the Analog to Digital Converter (ADC) to gather information on voltage generated by the turbine and rotations per minute calculated with the help of an optical tachometer. We then send these values to a Java-based user interface to report in real-time on an attached computer.
For the final part of our project, we designed a wind turbine stand on springs that we can use, along with the MSP430, to measure accelerometer data from the wind turbine under stress. We also send the real-time data to the user interface on an attached computer.
Power Coefficient (Cp)
We measured the following characteristics of the wind turbine at LOW fan speed:
- AT = 0.134614 m2
- V3 = (2.101 m/sec)3 = 9.275
- ρ = 1.2041 kg/m3 at 20°C (from Wikipedia)
The average voltage reported by our program at LOW fan speed was 2.304 volts. Resistance was set at 330 Ω.
Using these values, we found the power coefficient, Cp, to be:
Cp = 0.00929 or 0.01
This part of the project required the use of the optical tachometer connected to the MSP430 board. The tachometer will output a high value when no blade blocks the beam, and a low value (close to zero) when a blade is in front. We read this information and convert the rate at which blades are passing in the beam to compute a rotations per minute (RPM) value.
The average RPM we measured at a given time was: 55 RPM
We measured the radius of a blade, and found R = 20.7 cm or 0.207 meters.
At LOW fan speed, the velocity of wind was recorded as V = 2.101 m/sec * 60 s= 126.06 m/min.
Using these values, we found the Tip-Speed Ratio to be:
λ = .567 rotations
We constructed a special stand for the wind turbine that allows the turbine and MSP board to move in unison, while still being flexible to allow natural movement due to the wind.
For this part of the project, we modified the provided Java program to also display accelerometer data in the X- and Y-axes. We track and record this data in real-time, which gives some insight into how the wind turbine is moving as the speed and direction of wind changes.
Although we are not able to give a unit for these values, the magnitude of change can indicate what is happening in the physical system. For instance, when we see X values change from near-zero to negative, we know that stress is being placed in the wind turbine in the negative X direction (see diagram below — blue values represent negative readings).