A renewable energy system is a big investment. It's either an investment you have already made, or an investment you would like to make. In either case you need to make sure that your investment is going to pay off.

Before installing a wind generator it is important to log wind speed data in order to properly select the best wind generator for your site. Wind generators have different power curves. Some wind generators work well for high wind areas and others are more efficient in lower wind speeds.

Traditionally wind speed for a site was determined by less-than-accurate techniques. In some areas there is average wind speed data available from a local airport or weather station - but this airport is most likely miles away, at a different elevation, and surrounded by different topography. It measures wind speed at 30 feet above ground, not at the heights where you would want to put a wind generator. Even worse then airport data are the "wind maps" of an area. Often times a single graduation shows thousands of square miles of area and has little regard for local topography.

A wind data logger is the key to determining how much wind you have at a site. A wind speed data logger measures the actual wind at YOUR site and at the elevation YOU choose. The data logger provides real data that you can analyze to make the best choices for your renewable energy installation.

If you already have a wind generator then a wind data logger is essential to make sure that your generator is performing as well as it can. Some wind generator failures are gradual and past data to look at it becomes impossible to locate a problem and fix it.

Why average wind speed WON'T work

It is all in one simple equation.

P=p*A*V³

where P is the theoretical power available, p is the air density, A is the swept area of the generator blades, and V is the velocity of the wind. Since the V term is cubed it is the dominant variable in the equation, so we can simplify the equation to P=V³.

This principal means that average wind speed does not very well represent the power available at a given location. Let's try an example: You live in a coastal location where the wind blows 10 MPH for half of the day and 20 MPH for the other half of the day. The average wind speed for your location would be 15 MPH and your power equation would look like:

P = hours * velocity³=24 * 15³ = 81,000 units of power per day

If we use the real wind data we can use the following equation:

P = hours * velocity³ = 12 * 10³ + 12 * 20³ = 108,000 units of power per day

That's 1/3 more power at your site than the average wind speed would suggest! That could mean a smaller wind generator or less solar panels could be used - and that is money saved.