vertical axis windmills need to be reoriented with respect to the wind direction continuosly
Answers
Fewer components – Obviously, the main rotor shaft of a VAWT is oriented vertically rather than horizontally. The advantage here comes as a reduction in parts. A conventional HAWT must first be generally oriented into the wind before the blades can rotate. In contrast, the blades of a VAWT catch wind in any direction without directional orientation. This makes it ideal for gusty conditions. What’s more, there is no need for components to control yaw and pitch.
Safety – Keeping workers from climbing tall turbine towers also makes VAWTs a safer alternative. Maintenance costs are further reduced because gearboxes, generators, and most electrical and mechanical components are at or near ground level, avoiding the need for climbing gear, lifts, and danger-pay compensation.
Scaling down – the design has potential to scale down and remain fairly efficient in dense urban areas or on rooftops where other renewable technologies might not be feasible. The residential possibilities of the VAWT model seem promising in reducing energy consumption from hydrocarbon sources.
Despite the plusses, there are good reasons that many are skeptical of VAWTs’ potential to ever be adopted on a wind farm. For instance:
Efficiency – When the wind blows on the blades of a HAWT, all of them contribute to energy production. When wind blows on a vertical-axis turbine, only a fraction of the blades generate torque while the other parts merely ‘go along for the ride’. The result is comparably reduced efficiency in power generation.
Simply put, because power generation efficiency isn’t as good, VAWTs aren’t as good long-term investments. This is ultimately why wind-energy developers have stuck with the HAWT. An owner’s greatest concern is simply generating as much power as possible over 20 plus years. Until recently, no prototype VAWT was close to the long-term generating capacity of horizontal-axis designs. Conventional VAWTs have no such optimization control, not yet, at least.
Scaling up – There are a number of obstacles in scaling VAWTs to commercial size. The first is that they aren’t as sturdy, by design, as a HAWT. This is because of where a HAWT carries most of its stress compared to widely-used VAWT models.
A large VAWT must be secured with many long guy-wires, especially those of the so-called “egg beater” design (link here). Conventional wisdom says that a VAWT wind farm of commercial scale would require more materials and space to generate a comparable amount of power as a farm equipped with horizontal-axis turbines. It’s not that VAWTs can’t be scaled to commercial purposes, they can, but the number of distinct challenges in doing so come without advantages in terms of cost or efficiency.