Wind turbines are tall structures with large blades used to produce electricity. They are useful sources of low-cost, renewable energy. But they can also be deadly to birds and bats. The turbines' large blades turn quickly in the sky. Birds and bats sometimes fly into them and are killed.

But a new type of wind generator may offer an answer to that problem.

In 2002, Spanish inventor David Yanez saw a short film about the Tacoma Narrows Bridge in the U.S. Strong winds caused the bridge to collapse in 1940. That incident was an example of the powerful vibrations wind can create when it blows past a long pole, like a car antenna or a stick of light wood. It gave Mr. Yanez the idea for a new type of wind-energy generator. He said he wanted it to include all the desired qualities.

He said it should be as low-cost as possible and need as little maintenance as possible. He also said he wanted it to quick to set up.

Mr. Yanez and his friend Raoul Martin took the idea to an engineering business. But they were told their idea would never work. So, Mr. Yanez and Mr. Martin built a small wind tunnel to experiment on their own.

They built a large working model of the generator in a field near their workspace. They called the equipment Vortex.

Mr. Yanez described how the Vortex generator works.

He said there is a mast that serves like a blade on turbines. It is made from the same material as other generators. Wind causes the mast to oscillate, or move back and forth. It does not spin around. So it creates no risk to birds and bats.

The Vortex generator creates about 30 percent less energy than a wind turbine with blades. But it is lighter and less costly to build and maintain. It is made mostly of plastic and has very few moving parts. The generator also does not create noise.

The current prototype works at wind speeds ranging from 1.5 to 7 meters per second.

The inventors say the next step is building a 12.5-meter-tall bladeless generator that could power small businesses or individual homes. They add that the generator could also provide additional power to a larger power supply system.

Mr. Yanez expects the Vortex bladeless generator to be ready for general sale by 2017.

I'm Jonathan Evans.

VOA's George Putic reported this story from Washington. Jonathan Evans adapted it for Learning English. Caty Weaver was the editor.

blade – n. a flat long turning part that is used on some machines to push air or water

generator – n. a machine that produces electricity

vibration – n. a continuous slight shaking movement : a series of small, fast movements back and forth or from side to side

maintenance – n. the act of keeping property or equipment in good condition by making repairs, correcting problems, etc.

mast – n. a tall pole that supports or holds something

oscillate – v. to move in one direction and then back again many times

prototype – n. an original or first model of something from which other forms are copied or developed