Will wind work for you? Look beyond average wind speed

Will wind work for you? Look beyond average wind speed

Though the basic mechanics of the old-fashioned windmill are still present in the engineering of a personal wind turbine, time and technology have created a more efficient and effective machine. In our “How does it work?” series, we will discuss the ins and outs of how wind turns into watts.

Contrary to popular belief, average wind speed should not be a deciding factor in figuring out if wind is right for you. To determine what turbine model, if any, is most appropriate for your needs, there are two questions you should ask:

Is the site good?

When it comes to average wind speed “good” is a relative term. Whether the site has an average wind speed of 10 or 100 mph this static information does not tell you much. For example, let’s look at a potential scenario:

At site A the wind blows at 20 mph 50 percent of the time and doesn’t blow at all the other 50 percent of the time. At site B the wind always blows at 10 mph. Both sites claim an average wind speed of 10 mph.

Will they produce the same energy over time? No.

Even though both sites have the same average wind speed, they have different wind speed distributions.

In order to determine the appropriateness of a site, “good” should be defined by what you want to get out of your wind system. A good site is one with enough wind energy potential to satisfy some acceptable proportion of the total electricity used at the site. Depending on your site and electricity situation you are looking for a unique amount of power to be offset, or supplied for your site.

Some people like chocolate, some like strawberry. Which is good? It depends on your personal taste, and there is no hard and fast rule.

How does the site compare to other sites?

We already know comparing average wind speeds is inaccurate. Let’s set up a comparison scenario:

Turbine A generates a maximum rated power of 400 W at 12.9 mph. In this turbine's perfect world, the wind would always blow at 12.9 mph, which would allow the turbine to always perform at its peak. In this perfect world, the turbine would produce 3,504 kWh per year (0.4 kW x 24 hrs x 365 days). However, this perfect windy Shangri-La doesn't exist. The wind will always fluctuate. In fact, this turbine is only expected to produce 525 kWh per year, not the 3,504 kWh originally projected.

Turbine B has a maximum rated power of 1.2 kW at 13.1 mph, and generates 1,367 kWh annually.

So who has the better site? In this case we use "capacity factor" which is the actual energy produced divided by the theoretical maximum. Turbine A’s capacity factor is 15%, whereas turbine B has a capacity factor of 13%. Therefore, turbine A is more efficient compared to turbine B.

To find out if a personal wind turbine is right for your home or business, visit our Sitelook tool for a free evaluation and estimate.

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