A new study found wind farms may not be as efficient as we thought, and won't be reliable as an alternative energy source.

According to the research wind farms generate below 20 percent of their projected output for approximately 20 weeks a year; for nine weeks they are believed to generate 10 percent. On average these wind farms exceeded 90 percent of their supposed output for only 17 hours a year, the Adam Smith Institute reported.

The study also looked into the 30 to 90 minute variability of wind generation and found the variations in output are much greater than in conventional energy sources, such as gas and nuclear.  

The findings suggest a move towards wind-powered energy to reduce the world's carbon footprint is unrealistic, and nuclear and gas are better low emission alternatives.

To make their findings the researchers looked at 6.5 million recordings from 22 sites across the U.K.  and 21 in Ireland. They determined a Europe-wide power grid would not help solve this problem because the output situation of wind turbines is similar across the continent.

"Wind farms are a bad way of reducing emissions and a bad way of producing power. They are expensive and deeply inefficient and it seems like they reduce the value of housing enormously in nearby areas. We probably do want to reduce carbon emissions, because according to the IPCC global warming will begin to slow economic growth in one hundred years, but nuclear and gas power are our best ways of doing that until cheap and efficient energy storage options are available on a vast scale to smooth the highly variable output of renewables," said Ben Southwood, Head of Policy at the Adam Smith Institute.

Gordon MacDougall, managing director of wind farm developer Renewable Energy Systems and a member of the British Wind partnership believes the report overlooked "crucial facts, such as that onshore wind is cheaper than building new nuclear and coal plants, Business Green reported.

"Onshore wind farms produce significant amounts of energy even at low wind speeds," he told Business Green. "It is also supported by 70 [percent] of the public compared to 42 [percent] supporting nuclear and 29 [percent] fracking, according to the government's latest annual Public Attitudes Tracker of April 2014. If the facts are ignored it will be consumers who are left to foot the bill and security of supply that will be put at risk."

The study was conducted in partnership with the Scientific Alliance.