Table of Contents



Literature Review

Experimental Design


Test Station Construction




Statistical Analysis

Sources of Error


Glossary of Terms




The overall efficiency of a windmill is the amount of electricity that can be generated over time on a cost basis. Two important factors that determine overall windmill efficiency are the ability to use low velocity wind and the ability of the windmill to convert the kinetic energy of the wind into electrical energy (conversion efficiency).

The results show that multiple rotors operated at lower wind speeds and had a higher conversion efficiency.

1. Adding a second 28 cm rotor, coupled to the 1.5 - 3 V motor, increased the amount of electricity generated by 4500% at medium fan speed and 2324% at high fan speed.

2. A single 28 cm rotor did not produce enough torque to start and continuously turn the larger motors (9-18 V and 12 V) at either fan speed.

3. Adding a third rotor increased the amount of electricity generated by two rotors an average of 28 %.

4. Three 28 cm rotors, with 0 cm distance between the rotor hubs and with the nine blades offset 40 degrees generated the most electricity for all three motor sizes.

5. This rotor combination also produced the highest tip speed ratios.

6. There is an inverse relationship between rotor spacing and electricity generation. As the spacing between the rotors increases, electricity generation decreases.

7. Interestingly, three 28 cm rotors, spaced 3.5 cm apart, with the blades of rotor one and three inline and the blades of rotor two offset 60 degrees, produced more electricity than the same rotor spacing with all blades offset 40 degrees.

A summary of all calculated means of wind speed, mWatts and tip speed ratio can be seen below.

The highlighted data below displays a summary of five rotor variables, including those that produced the highest mWatts and tip speed ratios.

To view the graphs of all results, please click on the "Graphed Results" link.

Graphed Results

Statistical Analysis/Conclusions