Quick Answer
Horizontal axis turbines have an average efficiency of 45% to 50%, while vertical axis turbines typically achieve 20% to 30% efficiency, although some designs claim up to 45% efficiency.
Horizontal Axis Turbines (HAT)
Horizontal axis turbines are the most common type, resembling traditional wind turbines. They have a horizontal shaft that rotates as the water flows over the blades. This design is well-suited for high-flow, low-head applications, with optimal performance at speeds above 1.5 meters per second. The efficiency of HATs depends on factors like blade design, size, and angle. A well-designed HAT with a diameter of 2 to 5 meters can achieve peak efficiencies of 45% to 50%.
Vertical Axis Turbines (VAT)
Vertical axis turbines have a vertical shaft that rotates as the water flows over the blades, often in a helical or spiral design. VATs are more versatile and can handle a wider range of flow rates and head pressures. However, their efficiency is generally lower than that of HATs, typically ranging from 20% to 30%. Some innovative designs, like the Darrieus turbine, claim to achieve efficiencies of up to 45%. VATs are well-suited for low-flow, high-head applications and can be more cost-effective for small-scale installations.
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