I've had a couple people ask me what tip speed ratio is and why it's important in wind turbines. The tip speed ratio is simply a number from 0 - (theoretically a huge number, but usually 8 - 10) which tells you how fast the blades are moving in relation to the wind speed.

The formula for tip speed ratio is as follows:

TSR = Blade Tip Speed / Wind Speed

For example, if we have blades whose tips are moving at 80MPH and a wind speed of 10MPH that would give us a tip speed of 8 (which is what the windmax blades give).

In wind generators a higher tip speed ratio is better and here is why. We normally have 3 blades which are travelling through the air. A low TSR means that the blades aren't moving very fast and there is quite a bit of air that passes through the wind generator without even touching the blades. With a higher TSR the blades are moving faster which means that they 'touch' more wind during each rotation. This means that they are able to extract more energy from the wind which means they are more efficient. The wind generator blades we use have a TSR of 8 and an efficieny of about 49% (maximum efficiency is around 60%).

There is a downside to having that increased efficiency though... a higher TSR means that the blades are rotating faster which means that your wind generator will produce more noise. This could be a problem for you in a (sub)urban neighborhood. We've had people email us and say that they were forced to take down their turbine because people complained.

When trying to figure out what TSR you should use for your wind generator make sure to think about noise. When the wind really gusts you'll hear some chopping.

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