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A forest of turbines? Prof Peter Cobbold explains why plans for 100 giant wind turbines in Clocaenog would destroy a quarter of the forest.

Byline: Prof Peter Cobbold

IN late July the Welsh Assembly Government used its web site to publish draft instructions to council planning departments: in essence these will facilitate the installation of hundreds of giant wind turbines in the Welshcountryside. One of the locations identified by the Assembly as a Strategic Search Area (SSA) for wind power was Clocaenog Forest. It was chosen because of ``. . . positive siting factors (defined as Forestry Commission woodland, due to single ownership and the presence of existing access tracks. . . )''.

The perimeter of the SSA, the only one in North Wales, encompasses a vast area. Wind turbine development, if it takes place here, will affect numerous places: Bylchau, Nantglyn, Prion, Bontuchel, Pwllglas, Gwyddelwern, Maerdy, Toe Nant, Cerrigydrudion, Glasfryn, Llyn Aled and the Sportsman's Arms.

How many turbines will be needed? The Assembly gives no detailed plans (those are left entirely to the private sector) except to stipulate that the SSA's generating capacity should be ``200MW minimum capacity''.

This implies at least 100 giant turbines, each of 2MW capacity.

To describe these machines as big is a considerable understatement. The blades of 2MW turbine reach up to 117m (380ft) and sweep out 1. 1 acres at 140mph tip-speed.

The diameter of the rotor is bigger than the wingspan of a jumbo jet. These are gigantic machines, twice the height of those near Cerrigydrudion, but the electrical output, averaged over a year, from a machine in cleared forest, would be worth just 73p per minute.

Quite where these 100 turbines would be sited in Clocaenog Forest can only guessed at. But there are several important clues.

Wind speed is of paramount importance. The best site, for maybe 10-12 machines, is the ridge to the west of the Alwen Reservoir. Many more machines would be sited on the long ridge in the centre of the forest that runs north-to-south from Tir Mostyn (where 25 smaller turbines are already approved), past Foel Frech to beyond Craig Bron-Banog, with an extension to exploit the escarpment overlooking Pentre-Llyncymmer.

The third large site is Cefn Du, which runs from the centre of the forest eastwards to the monument at Pincyn Llys, above the villages of Clocaenog, Cyffylliog and Bontuchel.

The simulated photograph of Cefn Du (right) shows 27 2MW turbines placed in three rows in accordance with wind engineering principles.

The turbines are shown on 80m towers, of which 20m is hidden by conifers (80m towers enable 7% more production than 60m towers).

What the photograph does not show is that very few of the trees on Cefn Du will remain after the turbines are installed.

The array of turbines in the photograph is 3km (2 miles) long: why? Wind engineers separate each turbine by four rotor diameters (ie. 300m for 2MW machines) and seven rotor diameters (ie. 500m) along the direction of the prevailing wind.

This is because of efficiency-sapping wake turbulence: a 2MW turbine extracts 2, 600hp from winds of 45-60mph, leaving a wake of three vortices spiralling around one another. One hundred machines will therefore require the felling of at least 11 sq km of forest, or approximately 3, 000 acres.

Engineering principles demand that the land surrounding turbines should be free from raised obstacles which might impair wind flow. In fact clear-felling the trees between the turbines, and up-wind from the edge of a group of machines for several hundred metres, will increase power production from 500KW to 660KW, or 32%.

That translates into a 32% increase in profits. One hundred turbines require an investment of over pounds 100m, so every percentage point of productivity is important.

It is therefore inevitable that all the trees in the photograph of Cefn Du (and more off-picture to the west) will be clear-felled to raise the retail value of the electrical power from this 27-turbine ``farm'' from pounds 15 to pounds 20 per minute.

An additional 500 acres of clear-felling will enhance wind-flow into the periphery of turbine arrays, so the total clear-felled area required for 100 turbines will be approximately 3, 500 acres. As the total area of Clocaenog is about 14, 000 acres, it follows that wind ``farming'' will destroy and industrialise one quarter of the forest.

Dividing the forest into isolated fragments will be ecologically very damaging, especially as engineers will dictate which sites will be used, not the Forestry Commission's ecologists.

The forest has a thriving colony of red squirrels. Pine marten, an even rarer, endangered, forest-dwelling mustelid, may well be present in the forest. Pine martens are agile, arboreal animals that travel miles, particularly around dawn and dusk, feeding mainly on voles and small birds.

It is important to update our knowledge about Clocaenog Forest's population of pine martens: look for the bushy tail, darkchestnut/black pelt, and the distinctive cream throat (and do not confuse with a young fox which is similar in size).

Information relating to this rare and important animal will be useful not just for turbine opponents, but also to the wider conservation community. To report sightings, please send details to my em ail address (treesnotturbines@fsmail. net).

For those people horrified at the prospect of Clocaenog Forest being ripped apart in the pursuit of wind energy, time is fast running out to do something about it.

Assembly consultations on the plans, which are outlined in its TAN8 consultation, end on October 8. Campaigners against proposed wind-farms across Denbighshire and Conwy have organised a series of meetings.

In fact several campaign groups have now come together over wind farm issues in North Wales. People Against Corwen and Cerrigydrudion Turbines (PACT), which is attempting to block plans for 65 giant turbines along a 10-mile corridor of the A5, has linked up with other organisations to create the North Wales Energy Group. There are many reasons why these groups oppose wind turbines, but Clocaenog Forest is a special case. Destruction of large areas of trees would ruin its ecology and landscape and will inhibit any attempts to diversify the local farming economy. The Assembly's plan runs until 2010. It fails to give serious consideration either to other forms of green energy, or to economising on energy consumption. So even more turbines would be needed here to reach its 2020 target, thereby completing the utter destruction of the forest and the landscape for miles around.

Peter Cobbold is an emeritus professor at the University of Liverpool with degrees in zoology. He has made significant discoveries in cell biology and is senior author of five papers in Nature, the world's pre-eminent journal of scientific research. Email: treesnotturbines@fsmail. net

Talks by Prof Cobbold

Friday Sept 17, 7. 30pm: Clawddnewydd Community Centre. Friday Sept 24, 7. 30pm: Ruthin School. For a talk in your community, please contact him for details (to be given before October 5). Details of the Assembly's TAN8 proposals are at: www. wales. gov. uk/subiplanning/ content/tans/tan08/mipps-index-e. htm


Prof Peter Cobbold says destruction of large areas of trees would ruin the forest ecology; Two- Meg a Watt turbine drawn to scale with mature conifer, cottage and 6ft person. Tower height 80m. Blade length 37m. Swept area 1. 1 acres; Total height to vertical blade tip: 117m = 380 feet. Drawing by George Hartley; The pine marten and the red squirrel, both rare species, are just some of the wildlife in Clocaenog Forest; Cefn Du photographed from Craig Bron Banog, with Moel Famau on the far horizon, showing a `wind farm' of twenty-seven 2MW turbines, all depicted to scale. All the trees on the ridge (and beyond the photo to the west) would be clear-felled in order raise power production from the entire wind `farm' from pounds 15-worth per minute to pounds 20
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Publication:Daily Post (Liverpool, England)
Date:Sep 16, 2004
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