Swiss researchers studying wind turbines as alternative energy sources say the bigger the turbine, the greener the energy it produces.

The findings, published in the journal Environmental Science & Technology, could accelerate a trend toward construction of ever-bigger turbines, the researchers said.

Marloes Caduff of the Institute of Environmental Engineering in Zurich and colleagues point out that wind power is an increasingly popular source of electricity, now providing almost 2 percent of global energy and likely to create 10 percent of worldwide electrical power by 2020.

The average size of commercial turbines has grown in last 30 years, from diameters of 50 feet in 1980 to nearly 500 feet today, and upcoming super-giant turbines could approach 1,000 feet in diameter.

The researchers said bigger turbines produce greener electricity for two main reasons.

First, they said, manufacturers now have the knowledge, experience and technology to build big wind turbines with great efficiency.

And second, advances in materials and design permit large turbine blades that harness more wind without proportional increases in their mass or that of the tower and the nacelle that houses the generator.

That suggests larger turbines can deliver more clean power without large increases in the amount of material needed for construction or fuel needed for transportation, the researchers said.