Using a VAWT at home

by Steve
(Canada)

I want to add a wind turbine to my home, it is a small lot, and I can't really go too high. Can I use a VAWT style turbine instead of a standard generator? Is it less noisy?

ANSWER:

Hi Steve and thanks for a great question. I say “great” because vertical axis wind turbines or vawt's, as they are commonly known, are a source of fascination for many people. I think that fascination is often due to the quite different designs, as opposed the more traditional horizontal axis wind turbines (hawt's).

Your question also gives me the opportunity to point out a number of different crucial factors that anyone contemplating a home wind turbine, particularly a VAWT, needs to take into account.

Having said that, let's move on to specifically addressing your question...

You say you have a small lot and can't go too high so I am assuming you are in an urban area. In a rural area, even on a small lot, you could probably go higher.

Urban areas present significant challenges for anyone wanting to install a wind turbine, irrespective of type. So let's look at these challenges.

The height challenge



Higher is always better when one wants to extract maximum power from the wind which is the whole point of putting up a turbine anyway. You want to generate as much electricity as possible to reduce your power bill.

The height challenge will be reflected in the actions of your local governing authority and your neighbors, who will probably combine to restrict the height. The authority may well have a set limit and even if they don't your neighbors may well lodge an objection that results in reduced height.

The turbulence challenge



The surrounding environment – your house, other buildings, trees, utility poles or towers will make it difficult for any turbine that lacks height. It is a significant part of the laws of physics that all those items will combine to create a turbulent effect. What this means is that the wind behaves differently around buildings and the resulting turbulence creates additional stresses on turbines, causing them to wear out sooner. There is also an issue with extracting less power from the wind in turbulent situations. A very general rule of thumb is that your turbine hub should be at 10 times the height of whatever is causing the turbulence. That is quite obviously out of the question in an urban area.

That is why rooftop turbines are not a good investment. At the best, they are probably only going to be about three meters above the roof and that's going to be totally inefficient.

Turbine type



Now let's look at your query about using a VAWT. The vertical axis wind turbines come in all sorts of shapes and sizes, which is part of their fascination. However, they suffer from considerable disadvantages when compared to horizontal axis wind turbines.

Steve, if you haven't yet seen our page on Vertical Axis Wind Turbines then it's worth visiting and reading the material presented there.

In short, they are not as efficient as a HAWT. In other words, all other things being equal, for example wind speed and swept area, then the VAWT will extract less power from the wind.

When you add that to your issues with height and turbulence, you can see that will not be a wise investment.

The noise issue is really irrelevant when placed against the other issues. Sometimes extravagant claims are made by the marketers of vertical axis wind turbines, such as “totally silent”. All wind turbines, irrespective of type, make a noise. There is no significant data that shows a VAWT makes less noise then a HAWT.

So is there anything one can say to urban dwellers who want to utilize wind power?

I think there is – investigate the concept of community wind. That's where people band together and set up a commercial HAWT. You can read more about this at our page on Community Wind Power.

Steve – maybe you could become a catalyst for setting up a community wind project in your area. Think about it!

Ian
BlueRam Group

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