The Wells turbine is a type of low-pressure air turbine that has garnered significant attention in the field of renewable energy. Developed in the late 1970s by Prof. Alan Arthur Wells of Queen's University Belfast, this turbine has found applications in wave power plants, specifically in oscillating water column wave power plants.
Background on Wave Power Plants
Wave power plants harness the energy from ocean waves to generate electricity. The process involves converting the kinetic energy of the waves into electrical energy. In oscillating water column wave power plants, the rising and falling water surface creates an air compression chamber, producing an oscillating air current. The Wells turbine is designed to work efficiently with this type of air flow.
Characteristics of the Wells Turbine
The Wells turbine is a low-pressure air turbine that rotates continuously in one direction, regardless of the direction of the air flow. Its blades feature a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream. This unique design allows the turbine to function without the need for rectifying the air stream, eliminating the requirement for expensive check valve systems.
Efficiency of the Wells Turbine
The efficiency of the Wells turbine is lower than that of a turbine with a constant air stream direction and asymmetric airfoil. One reason for this lower efficiency is the higher drag coefficient of symmetric airfoils, even under optimal conditions. Additionally, the symmetrical airfoil runs partly under high angle of attack, which occurs during the air velocity maxima of the oscillating flow. This high angle of attack causes a condition known as "stall," where the airfoil loses lift. As a result, the efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.
History and Development
The Wells turbine was developed in the late 1970s by Prof. Alan Arthur Wells of Queen's University Belfast. Since its inception, the turbine has been used in various wave power plants around the world. While its efficiency may not be as high as other turbines, the Wells turbine's unique design makes it an attractive option for applications where rectifying the air stream is not feasible.
Applications and Examples
The Wells turbine has been used in several wave power plants, including the famous EMEC (European Marine Energy Centre) in Scotland. This turbine's ability to function with oscillating air currents makes it an ideal choice for wave energy conversion. While the efficiency of the Wells turbine may be lower than other options, its unique design and ability to operate in challenging conditions make it a valuable asset in the field of renewable energy.
FAQ
What is the typical efficiency range of a Wells turbine in oscillating flow? The efficiency of the Wells turbine in oscillating flow typically ranges between 0.4 and 0.7.
How does the Wells turbine's design differ from other turbines? The Wells turbine features a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream, making it unique compared to other turbines with asymmetric airfoils.
Can the Wells turbine be used in any type of wave power plant? The Wells turbine is specifically designed for use in oscillating water column wave power plants, where the rising and falling water surface creates an air compression chamber.
What is the primary advantage of using a Wells turbine in wave power plants? The primary advantage of using a Wells turbine in wave power plants is its ability to function without the need for rectifying the air stream, eliminating the requirement for expensive check valve systems.