|Table of Contents
Sources of Error
The purpose of this project is to determine if multiple rotors will
increase the electrical energy output of a horizontal axis windmill. Torque, the
force created by the rotating horizontal axis, will be used to turn the axle of
various sized DC motors and generate electricity. A digital multimeter will be
used to measure mAmps and mVolts and electrical energy output in mWatts
calculated. Revolutions per minute (RPM) and wind speed measurements will be
used to calculate tip speed ratio. Various sized motors were used to assess the
ability of the rotor variation to start and continuously turn larger motors.
Opposition to the production of electricity from fossil fuels is
rising and the earth's non-renewable resources are being depleted. Twenty
percent of all greenhouse gases released in Ontario in 2001, were produced by
five coal fired power plants. Wind power offers a pollution free, electricity
generating alternative, using a renewable energy source. The cost of wind
generated electricity is declining, in comparison with other energy sources.
Wind power is currently one of the fastest growing sources of electricity
generation in the world, growing an average of 25% per year.
Most wind turbines are the single rotor, classic Danish three-blade
design. Although there has been a large amount of research on windmill design,
there appeared to be none published on the use of multiple rotors.
Results from Phase 1 of this project (Torque it Up!), indicated that
multiple rotors did increase the torque of a horizontal axis windmill and could
potentially produce more electrical energy. Subsequent to my initial research, I
did find that researchers in California have been testing a multiple rotor
This research could impact on the construction of wind turbines.
Multiple small rotors weigh less, are easier to produce and transport and are
less subject to fatigue. Multiple rotors turn at lower wind speeds and produce
more torque. Increased torque may permit increased turbine size and produce more
electricity than that of a single rotor wind turbine.
The use of multiple rotors could result in lower construction costs
because rotor blades would be smaller, fewer support towers would be required
and the overall efficiency of wind turbines would increase.
My engineering objectives were to design and build a multiple rotor,
horizontal axis, laboratory scale windmill that could be coupled to the axle of
various sizes of DC motors. The scale model was used to determine the effect of
different rotor attributes (number, size, distance apart and orientation of the
rotors) and size of DC motor on the resulting mAmps and mVolts generated. The
rotor arrangement and motor that produced the most electrical energy output was
If a three-blade rotor on a horizontal axis windmill generates a given
amount of electrical energy, then adding additional three-blade rotors will
increase the amount of electrical energy output.
I predict that the
distance between the rotors will affect the amount of electrical energy produced
and that there is an optimal distance.
I predict that the orientation of the rotors (i.e. blades off set or
in line) will affect the amount of electrical energy produced.
I predict that the size of the rotors will affect the amount of
electrical energy produced.
I predict that single rotors will be able to start and continuously
turn smaller DC motors but will be unable to start turning larger DC motors.