A vertical wind turbine has one real trick: unlike a propeller, it never has to rotate to face the wind. That makes it tempting wherever the wind is messy, but messy wind is usually slow wind too, so how much power you get depends far more on the spot than on the model.
What Is A Vertical Axis Wind Turbine (VAWT)?
It's a wind turbine whose blades spin around an upright shaft, like a merry-go-round, instead of around a flat one like a fan. The blades are fixed to the top and bottom of a vertical rotor, and that upright design allows it to catch wind from any direction.
The best-known design is the Darrieus, which looks like a giant egg beater. Scientists call the propeller kind a "horizontal axis" turbine, and that's the one you see on wind farms. In both, the wind turns the blades, the rotor shaft turns a generator, and the generator changes that mechanical energy into electricity.
The catch: very few vertical axis turbines are in use, because they don't perform as well as horizontal axis wind turbines. More on how a vertical axis wind turbine works and the advantages of vertical axis wind turbines.
Can A Vertical Wind Turbine Work On A House Roof?
It can, but it usually disappoints. Wind close to town roofs is slow and full of turbulence, and both kill output.
Residential roofs are the job VAWTs are most often sold for, because urban wind bounces off buildings and keeps changing direction. But in a big UK field trial by the Energy Saving Trust, most building-mounted turbines made very little power, while free-standing turbines on open, windy sites did much better. A roof installation also shakes the house.
So only consider a roof after you have:
- Measured the wind at turbine height for months, and compared it with a free-standing pole in an open spot.
- Had a structural engineer check the roof for the weight and the shaking.
- Checked the local permit, height and noise rules.
Choosing The Right Vertical Wind Turbine Site
The ideal conditions are open sites where the wind is strong but keeps changing direction: a coastal hillside, an open ridge, a farm field. A farm shed, a workshop or an off-grid cabin on a windy slope are all good applications for small wind power. A wooded valley is a different story: trees and hills lower the wind speed, often too much for any home wind turbine. In a sheltered spot, check whether there's enough wind on your site first. Often solar does more there for the money.
Vertical Axis Wind Turbines In Cities
Cities like them because they catch wind from any direction. The most famous example sits on the Eiffel Tower. In 2015 two vertical axis turbines went in above its second level, about 400 feet up, expected to provide about 10,000 kWh a year for the shops on the first floor.
That's a tiny slice of what the tower uses. Projects like this, and proposed rows of VAWTs along bridges and highways, are often as much about showing off renewable energy as about the kilowatt-hours.
Why Most VAWT Setups Are Hybrids
The most common setup isn't a vertical turbine alone. It's a VAWT plus solar plus a battery.
In much of the US, wind is weak in summer and strong in winter, when solar is at its weakest. A typical hybrid includes a battery bank for the gaps when both are quiet, a charge controller to protect the battery and an inverter to make house power. Set up like that, a vertical turbine can help keep a cabin running through winter.
Before you pick sizes, work out your yearly kWh with our calculator.
Sources
- U.S. Energy Information Administration, Types of wind turbines
- U.S. Energy Information Administration, Electricity generation from wind
- Energy Saving Trust, Location, location, location: small-scale wind field trial (2009)
- ASME, The Eiffel Tower goes green
- U.S. Department of Energy, Hybrid wind and solar electric systems (archived)
Hard Words
| Term | What it means |
|---|---|
| VAWT | Vertical Axis Wind Turbine. The egg-beater style turbine that spins around an upright shaft. |
| Darrieus | The best-known VAWT design, with curved blades that look like a giant egg beater. |
| Horizontal axis turbine | The propeller kind you see on wind farms. It has to turn to face the wind. |
| Charge controller | The box between the turbine and the battery. Stops the battery from being damaged by sudden gusts. |
| Inverter | The box that turns the battery's DC into AC for the house. |
Common Questions
Where do VAWTs work best?
On open, windy sites like coastal hillsides and ridges, usually with solar and a battery. City rooftops and sheltered valleys are usually too slow.
Can I put one on my house roof?
You can, but it usually disappoints. Measure the wind at turbine height for months and have the roof checked before you buy.
Why pair a VAWT with solar?
Because they cover each other's weak spots. Wind is often strongest in winter, when solar makes the least.