Vertical wind turbines are seen as a more people-friendly way to harness the power of wind. Their major downside is that they produce a lot less electricity than their vertical counterpart. However, some power is better than none, which is why their market has grown substantially in the past few years.
Whether you’re looking to make one yourself or assemble a store-bought vertical wind turbine kit, these systems can be a great addition to any household. In what follows, you’ll find out the pros and cons of these products and whether they’re worth buying (or making).
How Does a Vertical Axis Wind Turbine Work?
Vertical axis wind turbines (VAWTs) date back to the 1980s, when their popularity experienced a significant surge due to their ease of use and urban friendliness. Unlike the traditional, horizontal turbine, these new rotary mechanical devices can operate regardless of the wind’s direction. As such, there’s no need for them to be turned towards the wind in order to work or improve efficiency.
More importantly, vertical wind turbines operate with much less noise, which makes them a great addition to any household. The fundamental principle behind these devices is identical to that of horizontal models, with the exception of the turbine blades themselves. Although not as deafening as the traditional, propeller-type framework, vertical axis wind turbines are also less efficient. Because of this, VAWTs are not usually built or used in large units.
Types of Vertical Wind Turbines
There are two common types of vertical wind turbines, the Darrieus model, which bears striking resemblance to an egg beater, and the Savonius rotor. The latter basically looks like a drum that’s been split in half and attached to the chute of the turbine. While their goal is the same – turning the middle shaft in order to propel the rotation of a turbine system, they achieve this goal using different principles. This is the reason why their design is so different. Their core advantage is being able to work regardless of wind direction.
The central downside of these vertical axis wind turbines is that they do not produce a constant flow of electricity. Unlike uninhabited locations, urban areas often have lower wind speeds due to trees and nearby buildings. Still, they are able to produce a noteworthy amount of energy even with low or constantly changing wind velocity. In what follows, we’re going to take a closer look at each model and see what makes them tick and turn.
The Darrieus Model
The appearance of the Darrieus rotor is unmistakable. The best way to describe it would be to liken it to a large egg-beater. Both in the industrial and the vertical wind turbine kits you can purchase off the web, the rotor is located at the bottom of the base. The blade(s) are mounted on top of a huge monopoly, whereas the top of the shaft usually has to be secured by means of several guy wires to keep it from being knocked down by the wind. The movement path of the blades is a circular one around the shaft.
The aerodynamic principle that helicopters rely on is very similar to the way in which this vertical wind turbine kit works. Basically, the incoming airflow is projected at greater velocity towards and past the middle pole by the blades, which keeps the mechanism spinning.
Although it’s been around for a fairly long time (the first patent was filed as early as the 1920s), the technology behind the Darrieus suffers from the same fundamental problems it did back when it was initially discovered. Its major disadvantages are:
- The turbine does not self-start. This means that it has to use its own generator to get the rotor spinning. Only when the wind velocity increases do the generator stop powering the system and the turbine generates electricity.
- The Darrius vertical wind turbine is fragile. There are major difficulties in protecting it from extreme weather conditions, which is why it’s not recommended in areas where wind speeds can be really high.
A version of this VAWT that is currently tested in the United Kingdom is the quiet revolution vertical axis wind turbine or the QR. Although this type of framework requires a three-phase electrical connection, which tends to be quite rare, it has the potential to silently generate enough energy to power a household or a small commercial site.
Instead of guy wires, the blades are secured to the shaft itself, while the aerodynamic features of their helical design make up for a nearly silent process of operation. Furthermore, there’s no need to worry about powerful wind resulting in unpleasant vibrations, as the aero-elastic blades are designed to counteract this effect.
The Savonius Rotor
Equally distinguishable as a turbine system is a Savonius rotor. Instead of blades, this vertical wind turbine uses cups or scoops to capture and harness the power of the wind. The problem is that the wind tends to strike both the front and the back of these scoops, which has a tendency to slow down the entire mechanism. On average, they tend to be less effective than the Darrieus type that uses lift forces to operate. For this reason, you won’t often find self-assembly vertical wind turbine kits with the Savonius framework.
On average, Savonius rotors are now considered outdated. With an efficiency that oscillates between 5 and 10 percent, but may go up to 15 as a result of numerous tweaks, the end result is just not worth the bother. The main reason for this is the fact that Savonius models use drag force in order to rotate the cups, which basically restricts the speed of rotation to that of the wind. These models are considered rudimentary and their commercial use is almost inexistent. Their advantage is their simple design and ultra-low cost.
Benefits of Vertical Axis Turbines
There are a series of advantages to using a vertical axis wind turbine, some of which we’ve already mentioned. In a nutshell, they are:
- Vertical wind turbines are much quieter than their horizontal counterpart. They also generate much less vibration, which is part of the reason why they’re so popular in the domestic segment.
- They are able to produce electricity even at low wind speeds and no mechanism is needed to operate the turbine itself.
- VAWTs do not need or have yaw controls because they can spin regardless of wind direction, so they don’t ever need to be turned.
- These turbines are shorter and more aesthetic. They can also be painted to match surrounding structures.
- Because the rotor is at the base of the framework, there’s no need for a crane when servicing a vertical axis wind turbine. The fact that they are much shorter than HAWTs further lowers maintenance costs.
Despite these noteworthy advantages, vertical wind turbines have their faults too. As mentioned in the Darrieus section, these propellers are not as efficient as the standard, horizontal type. On average, they can pull off around 30% efficiency, but the drag that occurs within the rotating blades usually prevents them from giving more. Aside from being prone to harsh weather conditions, they also need a jump-start.
More powerful winds occur at higher altitudes. This is the main reason why HAWTs are so effective at what they do. Because VAWTs have to be installed on a base closer to the ground and also due to the fact that they are generally shorter, the high-altitude energy of winds will remain largely out of reach. Generally, though, as can be noticed, the benefits far outweigh the drawbacks of these vertical turbines.
The Future is Green
Although upright turbines not as common as the horizontal propeller models, they are more urban-friendly, as well as less expensive overall. Despite an initial bout of Savonius-type systems, the majority of HAWTs are now built on the Darrieus framework because Savonius rotors have very low efficiency, whereas their blade counterparts can easily output anywhere from three to four times the amount of energy of a vertical wind turbine.
Overall, vertical axis turbines are still less efficient than the horizontal kind. While this is true from a strictly mechanical perspective, a modern, up-to-date Darrieus propeller system can easily provide enough electricity to power up a domestic household in the right conditions. For large-scale, commercial or governmental applications, vertical turbines may not be the best choice. However, for a household that in a remote area, they are incredibly effective at turning wind power into sheer electricity.
Over the past decade, the demand for renewable energy systems, like home wind turbine kits, has skyrocketed. On the one hand, this is due to increased awareness among consumers about the environmental impact of various sources of electricity, particularly coal and fracking. On the other hand, this trend is also motivated by an ever-increasing price of the kilowatt-hour. When considering long periods of time, such as a decade or more, these vertical wind turbines reimburse users the initial investment and help them save a lot of money.