Posts Tagged ‘Turbine Efficiency’

This is a walk trough to build a blade for your home made wind generator.

Your choice of blade design and material greatly affects your home made wind generator’s overall efficiency and performance. Most modern factory produced wind energy blades feature a 3 blade design with very slender blades made from space age materials mostly. Three blades work best to avoid vibration.

Those slender blades catch every bit of wind energy coming by too. You would think that the blades would have to be large in order to do this. But the most important aspect of blade design is how big of a diameter they form.

You will need a blade with outside diameter, measured to the tips, of at least 8 feet in order to achieve about 1000 watts of power production. If you don’t feel comfortable with this big of a machine then scale it back accordingly. Read more…

A 3 blade design can capture up to 8 horsepower of energy while many of the old bladed design will have a hard time producing 2 horsepower! All those blades get in the way of the wind moving through the blades and actually slow down the spin. This is what we regard as turbine efficiency.

Thankfully, the new materials and new blade design are available for us to take advantage from. These modern designs feature a high tip- speed ratio.

What is Tip-Speed Ratio?

Simply put, this is a comparison between angular velocity of the tip of wind generator blade and the wind speed.

Tip-Speed Ratio = Tip Speed / Wind Speed

Most of the newer models available today have a tip speed ratio of between 5:1 and 8:1. That is really moving. In other words, modern blades can rotate faster at lower wind velocities. The larger the number, the better efficiency in capturing wind energy.

This compares to the old slow moving water pumping windmills that used to dot the landscape with a tip speed ratio of around 1:1.

The old style windmills were designed to pump water, and although less efficient, they provided higher torque (because of the large blade outside diameter) and better performance at low wind speeds which gave them a steadier pumping action (more water delivered) in low wind situations. They had to start pumping immediately so they had to catch the wind at the start very effectively.

Home made wind turbine

If you think of your wind generator blades as aircraft propellers you will gain a new appreciation for the intricate designs necessary to achieve this high overall efficiency at tip speeds that approach 125 miles per hour.

You do not need to replicate these technical advances to have an efficient machine. Just follow the simple directions for a smooth operating homemade wind generator.

Note that the most efficient aircraft propeller design is not the best design for a wind generator blade. The propeller is designed to move air, while the wind generator blade is designed to be moved by the air. Subtle differences exist which we will explain further.