Efficiency in Wind Energy Lab
Design:
The aim of this lab was to determine factors that would lead to a more efficient windmill.
More specifically, the optimal fan blade pitch was to be determined. Pitch has a significant
effect on the efficiency of energy produced by the wind powered turbine. The pitch of the fan
blade is the angle of the fan blade in relation to its base. This has such a dramatic effect because
it affects the direction of the force of wind on the fan blades. Wind powered turbines work by
having the fan blades move in a circular motion, therefore the direction of the forces upon the fan
blades plays a crucial role. The more wind force pushing in the direction of the moving fan
blades will result in the fan blades spinning at a higher velocity and therefore produce more
energy with the same amount of wind. Through research, it was found that the optimal pitch of
the fan blades that would result in the most efficient fan would be between 15 and 30 degrees. It
was hypothesized that if a pitch of 25o was used, then the turbine would produce the most
amount of power. This was hypothesized because the pitch of 25o was between the optimal
range of 15-30o.
A Kidwind ALTurbine Kit was used as the wind powered device. Additionally, two
multimeters, a 2400 ohms resister, a circuit board, a meter stick, and a fan were required. First,
the windmill was assembled according to the Kidwind ALTurbine Manual (See Figure 1). A 4:1
gear ratio was used. Next, three corrugated plastic sheets were used as the fan blades and were
placed in the hub equally distanced from one another. After that, a circuit will be created on the
circuit board. The turbine served as the power source. The resistor and one of the multimeters
were placed in series in the circuit. This multimeter was used to find the current and was set at
200mA. The second multimeter was placed at either side of the resistor to measure the voltage
drop along the resistor. This was set at 2000mV. Finally, the windmill was placed exactly 1
meter from the fan and the voltage and current produced was observed and recorded. This was
done three times for each pitch. The pitch of the blades was the independent variable and was
changed for each trial. It was set at 0o, 14o, 25o, 30o, and 45o. The dependent variables were the
voltages and currents that were used to determine the power produced by the windmill. The
controlled variables included the windmill device, the gear ratio, the material used in the fan
blades, the size and shape of the fan blades, the position of the fan blades, the resistor used, and
the distance from the fan. The windmill device was controlled by having it be identical for each
trial and not changing, adding, or removing parts. The gear ratio was controlled by keeping the
4:1 gear ratio for each trial. The material, size, and position of the fan blades were controlled by
using the same blades in each case only adjusting the angle of the blades. The resistor used was
controlled by using the same resistor and circuit set-up for each trial. The distance from the fan
was controlled by using a meter stick to ensure the windmill was exactly one meter away for
each trial.
Figure 1: Kidwind ALTurbine
Data Collection and Processing:
Table 1: Windmill-Generated Voltages and Currents Observed and Power Calculated for Various
Pitches
Pitch Voltage (mV) (±5)
350
420
370
0°
1395
1296
1436
14°
1330
1350
1379
25°
1410
1368
1386
30°
10
400
380
45°
Current (mA) (±0.5)
2.2
2.3
1.8
7.6
7.4
7.8
7.4
7.2
7.5
7.9
7.7
7.8
0
2.5
2.1
Power (W)
0.000770±0.000187
0.000966±0.000224
0.000666±0.000196
0.010602±0.000785
0.009590±0.000710
0.011201±0.000706
0.009842±0.000728
0.009720±0.000719
0.010343±0.000765
0.011139±0.000713
0.010534±0.000674
0.010811±0.000692
0
0.001000±0.000212
0.000798±0.000202
To calculate power generated:
Ex.) 0° Trial 1
P= V*I
V= 350 ±5mV  Convert to Volts
V= 0.350±.005V
I= 2.2±0.5mA  Convert to Amps
I= 0.0022±0.0005A
P= (0.350±.005V) * (0.0022±0.0005A)
P= (.350V ± 1.4%)*(0.0022A±23%)
P= .000770 ± 0.000187W
Figure 2: Graph of Power Generated at Each Pitch
Power Generated By Pitch
Watts of Power Generated
0.012000
0°
0.010000
14°
0.008000
25°
0.006000
30°
0.004000
45°
0.002000
0.000000
Pitch
Conclusion and Evaluation:
According to the data from above, it can be seen that the fan blade pitch of 30° produced
the most power with each trial producing over 0.001 Watts. No other pitch had all trials over
that value. This finding refuted the hypothesis that a pitch of 25° would be the most efficient
because the pitch of 30° produced more power with the same amount of wind. It can therefore
be determined that a pitch of around 30° would be the most efficient pitch in this environment.
This is supported by the researched optimal pitch range which said that the optimal pitch was
between 15° and 30°. This optimal pitch range was clearly evident in Figure 2 which showed
that when the pitch went lower than 14° or higher than 30°, very little power was produced. By
changing the environment, the results may have varied for the atmospheric pressure, temperature
of the air, and movement of the air may have all changed the values to some extent. A fan was
used to generate the wind and this wind moves differently than actual wind, which may have had
an effect on the results. Some weaknesses can be found in the material used in the fan blades.
The fan blades were slightly flimsy and therefore the wind may have had an effect on the pitch
the blades were at while the wind was pushing on them. Also, sometimes the fan blades would
spin too rapidly causing the hub, which held the fan blades in place, would fall off. Also, the
first trial in the 45° pitch did not spin correctly greatly skewing that trial’s results. These could
be improved in the future by using another method of securing the fan blades or using fan blades
of different material to prevent it from being flimsy ensuring that it stays the same pitch. Also,
the hub can be secured to the rest of the windmill unit with some sort of strong adhesive such as
hot glue. This will prevent it from falling off. Further investigations can be taken in seeing how
the different wind motion affects the optimal pitch.