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Wind Turbine Blade Design, Flat Blades or Curved Blades

Time:2018-01-12 14:27Turbochargers information Click:

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Wind Turbine Blade Design, Flat or Curved

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Should wind turbine blades be flat, bent or curved

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The wind is a free energy resource, until governments put a tax on it, but the wind is also a very unpredictable and an unreliable source of energy as it is constantly changing in both strength and direction. To produce useful amounts of power, wind turbines generally need to be large and tall, but to work efficiently they also need to be well designed and engineered which makes them expensive too.

Most wind turbines designed for the production of electricity have consisted of a two or three bladed propeller rotating around a horizontal axis. It’s obvious to say that these propeller like wind turbine blade designs convert the energy of the wind into usable shaft power called torque. This is achieved by extracting the energy from the wind by slowing it down or decelerating the wind as it passes over the blades. The forces which decelerate the wind are equal and opposite to the thrust type lifting forces which rotates the blades.

wind turbine blade design

A Typical Wind Turbine Blade Design

Just like an aeroplane wing, wind turbine blades work by generating lift due to their curved shape. The side with the most curve generates low air pressure while high pressure air beneath pushes on the other side of the blade shaped aerofoil. The net result is a lifting force perpendicular to the direction of flow of the air over the turbines blade. The trick here is to design the rotor blade in such a way as to create the right amount of rotor blade lift and thrust producing optimum deceleration of the air and therefore better blade efficiency.

If the turbines propeller blades rotate too slowly, it allows too much wind to pass through undisturbed, and thus does not extract as much energy as it potentially could. On the other hand, if the propeller blade rotates too quickly, it appears to the wind as a large flat rotating disc, which creates a large amount of drag.

Then the optimal tip speed ratio, TSR, which is defined as the ratio of the speed of the rotor tip to the wind speed, depends on the rotor blade shape profile, the number of turbine blades, and the wind turbine propeller blade design itself. So which is the best blade shape and design for wind turbine blades.

Generally, wind turbine blades are shaped to generate the maximum power from the wind at the minimum construction cost. But wind turbine blade manufacturers are always looking to develop a more efficient blade design. Constant improvements in the design of wind blades has produced new wind turbine designs which are more compact, quieter and are capable of generating more power from less wind. Its believed that by slightly curving the turbine blade, they’re able to capture 5 to 10 percent more wind energy and operate more efficiently in areas that have typically lower wind speeds.

Wind Turbine Blade Design

So which type of blade shape would produce the greatest amount of energy for a wind turbine? – Flat blades are the oldest blade design and have been used for thousands of years on windmills, but this flat broad shape is becoming less common than other types of blade design. The flat blades push against the wind, and the wind pushes against the blades. The resulting rotation is very slow because the blades that are rotating back on the up stroke after generating power are in opposition to the power output. This is because the blades are acting like huge paddles moving in the wrong direction, pushing against the wind giving them the name of drag-based rotor blades.

However, flat blade designs offer significant benefits for the DIY’er compared to other wind blade designs. Flat rotor blades are easy and cheap to cut from a sheets of plywood or metal ensuring that the blades have a consistent shape and size. They are also the easiest to understand requiring less design and construction skills, but there efficiency and the ease of generating electrical power is very low.

Curved blades are very similar to a long aeroplane wing (also known as an aerofoil) which has a curved surface on top. The curved blade has air flowing around it with the air moving over the curved top of the blade faster than it does under the flat side of the blade, which makes a lower pressure area on top, and therefore, as a result, is subjected to aerodynamic lifting forces which create movement.

These lifting forces are always perpendicular to the curved blade’s upper surface which causes the blade to move rotating around the central hub. The faster the wind blows, the more lift that is produced on the blade, hence the faster the rotation. The advantages of a curved rotor blade compared to a flat blade is that lift forces allow the blade tips of a wind turbine to move faster than the wind is moving generating more power and higher efficiencies. As a result, lift based wind turbine blades are becoming more common now. Also, home made pvc wind turbine blades can be cut from standard sized drainage pipes having the curved shape already built-in giving them the best blade shape.

Curved Blade Air Flow and Performance

wind blade design

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