THE extent of Scotland's push to become the green energy leader of the world is revealed today as figures show 2700 new onshore wind turbines are in the pipeline, taking the potential total number stretching across the country to more than 4000.

However, experts warned space is running out for the often controversial developments, with claims from one leading wind-farm developer there are only three to four years of "serious" onshore development left as the number of suitable sites disappear.

Analysis of the energy map from RenewableUK indicates an unprecedented surge in proposals for wind turbines, with 56 applications lodged for new sites compared to 28 the year before, with a total of 530 new turbines proposed in a single year.

There are 1349 turbines in operation and a further 2738 turbines are either in the planning process, under construction or with consent for building work.

However, Colin Anderson, development director for Banks Renewables, the company behind a development at Ard Ghaoth, near Gartmore in Stirlingshire, warned that time was running out for future projects. "There are about three to four years of further new serious development," he said. "Accumulative impact is an issue and we do take it seriously."

The warning came as it emerged a 100ft underwater turbine destined to form part of a major tidal energy project has been installed in the sea around Orkney. First Minister Alex Salmond said the project was a "fitting end" to an exceptional year for renewable energy in Scotland.

He said: "This year projects were switched on representing £750 million of investment in renewables, and a staggering £46 billion of investment is in the pipeline."

However, Brendan Turvey, policy officer for Scottish Natural Heritage (SNH), said public protest against wind farms had become more organised at a time when the mood in the industry was "very much" moving from onshore to offshore developments.

He said: "There is also an increasing difficulty in gaining consent for onshore developments and I think we are reaching the point where we are almost at capacity in some areas. There are some areas in the south-west of Scotland where there are significant amounts of development in the system and we are near the capacity of the landscape to absorb further wind-farm development."

The figures from RenewableUK show 722 wind turbines have received planning consent in Scotland but have yet to be built. They range from single-turbine developments to a large-scale farm of up to 33 wind turbines at Strathy North, in the Highlands.

There are 550 turbines, or 22 wind farms, under construction, with developers putting a further 151 sites into the planning process in the past year.

SNH said the continued appetite for onshore wind power would make a significant contribution to meeting the challenging SNP target of producing the equivalent of 100% of Scotland's electricity consumption by 2020. The current rate is around 30%.

Mr Turvey said: "We have worked out the target of 100% translates to around 16GW of installed capacity. When you look at what is already installed consented we are actually halfway there already. When you look at everything in the system, including offshore, from consented projects to those in the early planning stages, it adds up to around 29GW. A substantial amount of this is from offshore wind, as well as wave, tidal and onshore."

A breakdown of planning applications shows Aberdeenshire has the highest level of potential development, with 33 separate applications entering the planning system in 2011, the majority of which are small-scale

developments by landowners and farmers looking to diversify income.

In contrast, 43 turbines are proposed for Glenmorie in the Highlands by Wind Energy, a company which is a majority-owned subsidiary of AES Corporation, one of the largest power companies in the world.

As the number of non-contentious site continue to be snapped up, concerns have been mounting about a drive to build in more sensitive locations, with councillors last week postponing a decision on the Allt Duine wind farm, one of 11 such developments proposed for the area surrounding the Cairngorms National Park.

A separate application is shortly due to be lodged for 10 turbines at Ard Ghaoth, close to the boundary of the Loch Lomond and Trossachs National Park.

Mr Anderson said: "If we genuinely feel there are too many (turbines) in the area, we won't go there. I think most developers feel the same. Bad schemes shouldn't go through and just because policy is supportive of renewables it shouldn't mean bad schemes are getting through the system."

Jenny Hogan, policy officer at Scottish Renewables, which represents the interests of the green energy sector, agreed the "easy" sites for onshore wind power had been used up. She said: "There is only so much space in Scotland. Look at hydro power, where all the suitable sites have been used in Scotland. It can't keep going exponentially. Of course we are using up easier sites and we are moving into more difficult areas of onshore development."