Final answer:
The greatest efficiency for wind turbines is achieved using a three-bladed design, which has been proven to harness about 50% of the wind's energy while also being safer for birds.
Step-by-step explanation:
Research has shown that the greatest efficiency for wind turbines is achieved using three blades. The blades of a wind turbine, which can be likened to long airplane wings, are designed to rotate on an axis which allows them to engage the wind at different angles, thereby affecting the efficiency of the turbine.
According to figure 12.4, the most common and efficient modern wind turbine configuration is the 3-blade design, which can harness about 50% of the wind's energy. This design not only provides optimal efficiency but also poses less risk to birds due to its lower tip speed compared to turbines with one or two blades.
Furthermore, the 3-bladed rotor operates within the theoretical and practical limits of wind turbine efficiencies, which are restricted by the Betz and Glauert limits.