Changing or modifying the blade design can also improve the efficiency of your turbine. It should be noted that blade changes are dependent upon the wind speed as well as the torque and rpm-rating of the generator. Lengthening the blades can generate greater torque while slowing down the rpm of the turbine. Larger blades also require greater sustained wind speeds to turn. Find the optimal number of blades for the tip-speed ratio, which is the ratio of the speed of the tips of the blades to the wind speed. Higher tip-speed ratios equal more speed for the blades, which is almost always preferred. You can also try different blade mediums, including wood, plastic or PVC pipes.
Assess the effectiveness of the generator-motor. If your blades are regularly spinning at a rpm that is faster than the motor can handle, remove the coiled wires from inside the motor and unwind the wiring. Replace the coils with thicker wiring that will generate more electricity at the higher rpm speeds. Use the reverse of the process if your rpm is slower than the motor is designed to handle, using thinner wiring.
Traditionally, excess electricity produced by turbines is directed by the charge controller to a dump load. The dump load is a specifically designed heat sink where electricity is turned into heat and dissipated into the atmosphere. As an alternative, your class could find a useful application for the excess heat, such as serving as an alternative heating method for certain parts of a building or integrating it with a hot water heater.
Other efficiency issues arise when the entire system is put together. Inspect the way that the turbine is mounted on a rooftop or other supporting structure for potential play occurring when high wind speeds interact with the turbine. Also inspect the attachment points of the blades to the blade hub of the motor. If the blades are not secured and tightened correctly, then they will degrade at their attachment points, causing a loss of efficiency when they interact with the wind.