Vertical Axis Wind Turbines – Proficient Or Deficient?
Vertical Axis Wind Turbines, also called VAWTs, are turbines that spin on a vertical axis as opposed to the more standard Horizontal Axis Wind Turbines (HAWTs). There are two main types of these VAWTs, usually referred to as the Savonius and Darrieus turbines.
There seems to be a lot of vigorous debate about these types of wind turbine. They certainly have their detractors but also their ardent fans.
So let's dig a little deeper.
The Ardent Fans
The field of vertical axis wind turbines seems to attract a lot of diy enthusiasts who build a variety of designs and write about their products with great enthusiasm. These turbines fascinate many people, more so than do the horizontal axis turbines (HAWTs). This is probably due to the greater variation in designs than one finds with HAWTs.
However, it's not confined to amateurs – there are commercially produced models as well. Many of these have been placed on public buildings as well as on private homes.
Enthusiasts argue that they spin regardless of the wind direction that they are bird and bat friendly and that they make less noise. It is hard to find any reliable performance data.
The fact is that vertical axis turbines draw a lot of attention, but for all the wrong reasons. You won't find anyone extolling the virtues of how much electricity they produce in line with their rated capacities. And that's because their performance lags well behind that of horizontal axis wind turbines.
The laws of physics work against them because a portion of their area is not producing at any given time and this lowers the efficiency of the performance.
Also the VAWT design is subject to stresses and forces that impose greater strain on the overall system.This means using stronger materials and likely increased maintenance costs. In essence, they cost more to produce than a HAWT of similar size and capacity.
These two facts alone, inferior performance and higher manufacturing costs are the primary reasons why you don't find many vertical axis wind turbines in commercial use. After all, the market weeds out what works and what doesn't in terms of design and cost of production.
Unfortunately, many VAWTs have been placed in prominent places with great fanfare but more often than not, have failed miserably, often remaining inactive for long periods.
Unfortunately, a lot of the advertising hype associated with these turbines is quite misleading.
For a detailed critique, using a specific example, please visit our Vawt page.
It is a tragedy for the small wind industry when manufacturers and marketers make claims that are simply not true or not achievable in practice. Their major aim is to sell units and they fail to realize, or simply choose to ignore, the damage they do to the industry in terms of disenchanted consumers.
Vawt's are popular with the DIY population and some creative designs and experiments have emerged over the years. However, anyone wanting to seriously use wind power for their home is far better off with a HAWT.
It will be interesting to see if the Small Wind Certification Council in the USA receives any application to certify a VAWT and if they do, whether or not certification is achieved.
Technology in the wind industry is always advancing and it may be that ways will be found to produce vertical axis wind turbines at a more competitive cost, but the biggest challenge will be in the design area where the efficiency lags behind that of a HAWT. It is hard to envisage how that gap will ever be bridged.