Windfarm may take half its 25-year lifespan to pay off carbon dioxide emissions caused by its construction
By JOHN ROBERTSON
The windfarm could take more than half its lifespan to pay back the carbon pollution it causes if more peat bog becomes dried out during its construction and operation than the developers expect. Viking Energy has come up with a worst-case scenario of 14.9 years to pay back the carbon dioxide emissions resulting from 25 years in operation.
The scenario has emerged because Viking Energy is not confident about the so-called floating roads over deep peat in the hills which it would build on top of a plastic membrane instead of digging down to hard rock. It is considered “highly likely” roads will sink over time and require drainage ditches, greatly increasing the amount of peat which would dry out. Roads cut into the hill could also lower the groundwater level, increasing peat erosion.
The uncertainty means Viking Energy cannot predict whether it will take as little as 2.3 years to pay back the carbon or up to 14.9 years. In its environmental statement it deduces from its study results that the most likely payback time will be 3.7 years. It concluded: “The results indicate that it is crucial that the peat bogs on site are disturbed as little as possible to prevent extensive loss of peat.”
The chairman of Sustainable Shetland, Billy Fox, said it was a major concern for objectors. “The jury is seriously out on whether or not we should be building windfarms on peat. There is a huge body of scientific opinion globally now that says we should not be touching it.”
The average depth of peat across the proposed windfarm site is around 1.5 metres but it reaches up to six metres deep in places. The floating road technique would be used for stretches of over 75 metres where the peat is more than one metre deep, which could amount to 53 miles of the total of 73 miles of new roads required for the turbines.
One plan for preserving the vast quantities of peat which will have to be excavated is to remove it in large clumps to prevent it drying out and releasing carbon then reinstating it again as soon as possible.
However, because of the amount of erosion and drying out of the peat that is already taking place on the hills, Viking Energy has said that more carbon could be released naturally if the windfarm is not built because the partnership intends carrying out a range of measures to preserve the moor.
The environmental statement concludes: “The overall effect of the Viking windfarm on climate change is determined to be beneficial for the best and intermediate scenarios and neutral for the worst case scenario. Overall … it would reduce carbon dioxide emissions associated with electricity generation in Scotland by between 2.8 per cent and 6.3 per cent and in the UK by between 0.29 per cent and 0.65 per cent respectively.”
Campaigners against the Viking proposal have also warned about the dangers of a catastrophic peat slide. Viking Energy said it had avoided areas of deepest peat or risk of peat slide and it has had 54 “locations of concern” assessed. It considers a peat slide due to windfarm construction “unlikely” but the impact of one happening would be significant due to the high sensitivity of the soil and watercourses.
Where there is considered a potential risk of peat slide Viking Energy pledges to have measures put in place to reduce the danger “to an acceptable level”.
As well as the 150 turbines, three substations will have to be built to step up voltage from 33 kilovolts to 132kv. They are proposed for Wester Scord, near Voe; Moo Field in the Nesting hills; and at Upper Kergord, which will be part of a large central converter station joined to the underwater cable from the head of Weisdale Voe to Scotland.
Electricity from the substations in Delting will be taken to the Kergord converter station by wooden poles whereas the power from Nesting will travel by underground cable to Kergord.
The converter station and the high-voltage direct current seabed cable are separate projects to the windfarm with their own planning applications and environmental impact assessments, although without either the windfarm could not go ahead. Equally, the cable would not be economically justifiable if there was to be no windfarm to produce power to send through it.
The windfarm is likely to cost £40m a year to run plus £65m a year in charges paid for transmitting the power down south.
As well as the network of roads in the hills to build and service the turbines, improvements will be needed to existing public roads, which will be paid for by the Viking Energy Partnership. These will include improving road junctions at Firth, Voe and Sand Water to enable abnormally long loads to navigate the corners. The turbine nacelles and other heavy components will be imported to Sullom Voe and Sella Ness.
The construction is expected to pump £70m into the Shetland economy alone over its five years with the first four spent preparing the sites and roads and the final year for erecting the turbines. VEP estimates on average 221 workers will be needed in Shetland during each year of building the giant complex, bringing in £5m a year in wages, although workers will be recruited from outside Shetland as required. The peak workforce will be over 400 for the third year and may require an accommodation barge to be brought in to house them.
Little or none of the turbine manufacture will take place in Shetland with the construction jobs limited to labouring, road building, civil engineering sub-contract work, accommodation and other services.
During the construction period eight compounds will be needed of around 100 square metres each to provide offices, workers’ canteens, toilets plus areas for mixing concrete and keeping materials and equipment. Three of the compounds are proposed for Delting, the biggest being at Sella Ness to include a laydown area where turbines and their gigantic blades will be brought ashore from ships at Sullom Voe and stored along with other farm components.
The other seven compounds are at Houb, Scatsta; Fili Field, near Brae; Susetter Hill; Hamarigrind Scord, Nesting (one on either side of the road); one across the main road from Sand Water; and Scord of Sound near Kergord.
Concrete mixing for the turbine foundations will be done on the windfarm sites using water from lochs and burns to avoid heavy ready-mix lorries hammering up and down the public roads.
The environmental statement envisages no major damage to tourism and recreation although some income could be lost. A moderate impact is expected on visitors’ perceptions of the landscape character and visual amenity during construction and, during operation, the visibility of the turbines will lead to a loss of landscape value and visual amenity.
“The effects of these impacts could lead to a loss of tourist income in Shetland as well as a loss of recreational amenity to the local residents. The creation of recreational amenity by increased access provision was perceived to have a positive impact.”
Viking Energy is undertaking to promote Shetland as a sustainable community and green energy tourist destination. It will also develop walking routes and mountain biking routes as well as encouraging public access on the new roads and organising tours.
There has been controversy across the world about bird deaths from windfarms, particularly from flying into turbine rotors. During the investigation stage for the Viking project, Viking Energy moved turbine sites to help provide flightpaths for bird colonies. Its studies now conclude “non-significant long-term adverse effects of negligible or low magnitude on all species except whimbrel”. It is estimated that about 10 whimbrel will die in the rotors each year and there are only about 40 breeding pairs in or near the windfarm site, which represent 7.5 per cent of the UK breeding population.
Among other issues considered in the statement published this week are the effects on television signals. With the analogue switchover taking place in 2010/11, only the digital signal which will be of concern, which is stronger and less prone to interference. Viking Energy accepts there will still potentially be issues and it has committed itself to monitoring reception and sorting out problems, perhaps by improving digital reception equipment. Noise from the working windfarm is not expected to be an issue.
After 25 years if there is no extension to planning permission the windfarm will be decommissioned. All the bits above ground would be removed but the foundations, roads and buried cables would be left in place to avoid more disturbance to the environment.
Giant windfarm – big numbers:
£800m price tag to build over a period of at least five years.
£37m income to the Shetland community each year including £23m for Shetland Charitable Trust.
£3m a year for the four private investors from Shetland Aerogenerators who would own five per cent of the project.
221 jobs a year in Shetland during construction.
150 turbines of 3.6 MegaWatts each in four quadrants referred to as Delting, Collafirth, Nesting and Kergord.
145 metres is the height from the ground to the tip of each rotor blade at its highest point.
700 cubic metres of concrete poured into each of the 22-square metre bases for the turbines and set 1.5 metres into the hillside.
11permanent wind monitoring masts will be erected of up to 90 metres in height to ensure the windfarm is efficient.
3 substations to step up voltage from 33 kilovolts to 132kv at Wester Scord, near Voe; Moo Field in the Nesting hills and at Upper Kergord, which will be part of a large central converter station joined to the underwater cable from the head of Weisdale Voe to Scotland.
73 miles of new 6-12 metre wide roads which, in areas of deep peat, will be so-called floating roads built on top of a geotextile membrane.
8 construction compounds of around 100 square metres each needed during construction to provide offices, workers’ canteens, toilets plus areas for mixing concrete and keeping materials and equipment.
14 quarries or borrow pits needed to avoid trucking in stone over public roads. They will be reinstated afterwards.