Wind turbines come in different designs and sizes, and the primary distinguishing feature is the orientation of the axes; they can either be horizontal or vertical. In a horizontal-axis wind turbine, a vertical propeller turns horizontally in the direction of the wind, and in a vertical-axis wind turbine, blades rotate around facing the wind vertically as the turbine spins around its vertical axis.
Over the years of usage, it became evident that HAWTs, or horizontal axis wind turbines, work best in unobstructed locations, while VAWTs are less efficient but better suited for installation on hill tops or even rooftop in cities.
General Overview of VAWT and HAWT
When it comes to HAWTs, wind direction matters. The blades perform best when wind intersections at the correct angle. For this reason, they are often equipped with a rotation drive which automatically changes the direction of the blades to match the direction of the wind.
Vertical axis wind turbines are less reliant on the wind angle and can function at lower wind speeds than a typical HAWT. On the other hand, certain designs of horizontal axis wind turbines, like the ones made by TBHAWT Manufacturing, overcome efficiency loss and have their designed work effectively even when the wind speed is 8 m/s or below.
VAWTs or Vertical Axis Wind Turbines are designed to stand perpendicular to the ground, thus converting wind from every direction. These turbines are ideal for use in urban settings as they can be placed in rural areas too, where wind patterns are irregular.
Even though this makes VAWTs ideal for residential use, they are not as efficient as HAWTs. HAWTs have a higher operational speed and productivity, whereas VAWTs are less productive, but they are still a more economical choice for residences with turbulent winds.
Wind turbines which do not exceed 100KW in operational output are typically thought of as small and are used primarily for domestic purposes. However, there are some economically feasible designs of HAWTs which exceed 50KW that provide high profit margins owing to the cost and large customer base.
Small VAWTs are becoming increasingly popular for domestic and rural use because of the lower requirements for space and investent. These turbines can easily be installed in remote areas which are off the national grid, and can be easily disconnected from the national power lines.
Horizontal Axis Wind Turbine
Blades of horizontal axis wind turbines are parallel to the ground while the turbine itself rotates on a horizontal ground axis. HAWT are perpendicular to the wind, which causes the blades of the turbine to rotate easily, so that the wind turbine blades turn following an aerodynamic lift.
Horizontal-axis wind turbines (WTs) are dominant in the wind energy market as their design allows for obtaining more energy from the full revolution of blades for a constant wind stream. Additionally, horizontal axis wind turbines have resistance to backtracking, which is also advantageous in this type of power generation.
To achieve optimum performance, horizontal-axis wind turbines must be sited in the primary wind direction. If the horizontal-axis wind turbine requires a change in direction for a wind that is not constant, the efficiency of energy generation may drop significantly at times.
This limitation, however, is removed when a horizontal-axis wind turbine farm is established in an appropriately chosen site with good, constant unidirectional wind flow.
Small wind turbines generally have a wind vane to optimize the direction of the turbine toward the wind. On the other hand, large wind turbines come equipped with a yaw meter that rotates the wind turbine to keep its face to the wind stream. An operator trying to offer a more economical solution needs to ensure consistent, stable wind flow.
Vertical Axis Wind Turbine
The Vertical Axis Wind Turbine (VAWT) generates lift and drag to rotate its blades around a vertical axis to a vertical ground. While having less recognition compared to Horizontal Axis Wind Turbines (HAWT), VAWTs are able to accept and utilize wind from all directions making their use ideal for suburban and urban locales with chaotic winds.
The foundation approach allows benefits when it comes to costs of maintenance and noise, perfect for where people live. Customers of the wind turbine may install equipment closer to the ground, including the gearbox, which lowers the overall maintenance prices. Besides that, it is a less noisy construction which creates better co-living conditions.
Wind turbines with vertical axes capture energy from the wind effectively, however, they also experience difficulties when it comes to wind backtracking. With vertical axis turbines, the blades rotating along the wind direction have to rotate back into the wind stream before the blades are pushed around.
However, recent discoveries can indicate that vertical-axis wind turbines have a lot more in common with horizontal-axis wind turbines. The efficiency of the wind turbines highly varies depending on the corresponding parameters: the area wind conditions and the required power generation output volume.
Rotation
While rotating, HAWT blades experience changeable inertial forces and stable gravity. These effects lead to blade fatigue due to alternating, damaging loads placed on the blades.
In the case of rotation, the effects received by the vertical axis wind turbine are less complex due to the more stable inertial force and gravity’s contribution. Consequently, the energy expenditure is constant, and thus, the VAWT’s fatigue life is longer than that of HAWT blades.
Wind speed
It is now well-selling fact that horizontal axis wind turbines are among the best performers with regards to starting speed and wind flows because of the super necessary starting speed relatively high starting speed. One must also consider the fact that wind turbine effectiveness depends greatly on the construction design of the wind turbine.
To illustrate this point, China Aerodynamics Research and Development Center did an experiment concerning a miniature horizontal-Axis turbine with a starting wind speed of 5m/s and a maximum effective wind speed of 5.9m/s.
The experiment confirmed that the starting speed of 5m/s is not enough to exceed the turbine energy consumption and thus is not sufficient. However, for commercial purposes, other wind turbines with higher rated wind speed ranges as the WTW-55 TBHAWT Manufacturing wind turbine mentioned above are more favorable.
Wind vertical axis turbines generate electricity at a lower wind speed, but that results in lower productivity. Powering H-structure vertical wind axis turbines with reasonably expected costs is feasible, but an operator must ensure that the airfoil and optimal setting angle are accurately followed. This way, H-structured wind turbines will start at a remarkable 2 m/s.
Efficiency
Many horizontal-axis wind turbines are adopted in wind energy, whereas VAWT is less widely adopted when compared to HAWT. HAWT can be categorized into horizontal, large, and medium-scale wind turbine types. Big WTs require large open spaces where there is access to wind, particularly near the sea.
Little turbine generators are less restricted and can facilitate electricity for individual domestic consumers, as well as for a small commune or town. However, it all depends very much on the size of the wind farm. The larger the wind farm, the greater the number of households it can serve.
For commercial purposes, horizontal axis wind turbines are more efficient than VAWT in terms of scaling and productivity. Unlike VAWT, HAWT are larger, which raises the maintenance cost, but they more than compensates this by supplying on average ten times more energy than vertical axis turbines.
As a reminder, vertical-axis wind turbines can be exceptionally inefficient in high-speed wind flows because of their low starting torques and problems with dynamic stability.
Both types of horizontal and vertical axis wind turbines have their pros and cons. In order to get the most out of a vertical axis wind turbine, a developer must first decide if they want a self-procuring wind turbine, or if they want to monetize wind energy with a goal of creating a sustained long term income.