|Table of Contents
Sources of Error
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
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
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.