Eskdalemuir Seismic Region News & Development
Background, important information & latest developments from the Eskdalemuir Working Group (EWG).
Eskdalemuir Seismic Region Latest News (Dec 2020)
Xi Engineering recently concluded Phase 3 of Eskdalemuir work for the Scottish Government. For those of you that have not been involved, the Scottish Government are aiming to maximise the potential of renewable energy generation within the Eskdalemuir Consultation Zone to assist with the current Climate crisis. The Eskdalmuir Consultation Zone extends 50km from the centre of the Eskdalmuir seismic array in which there is a restriction in the levels of seismic noise created by wind turbines. The available budget of 0.336nm has currently been exhausted which prevents any further deployment. Phase 3 work looked at the effect of using measured data as opposed to the conservative algorithm and quantified the effect of extending the exclusion zone from 10km to 15km. As a prime location for onshore deployment, this resource must be optimised. A single turbine at 10km is equivalent to 7000 turbines at 50km in respect to seismic budget or a seismic noise perspective. The report issued stated that to further optimise the deployment within the region, before and after seismic levels would be required. Developers commonly use this practise when it comes to audible Noise. The conclusions of this Phase 3 work showed that a combination of extending the consultations zone, using measured data as opposed to conservative planning algorithms and conducting before and after measurements would result in additional seismic budget, allowing for significant levels of deployment within the region.
Wind turbine development in and around the Borders region of Scotland and England has for a number of years been impeded by objections from the Ministry of Defence (MoD) because of the necessity to safeguard a seismic monitoring station near to the small village of Eskdalemuir. This Eskdalemuir Seismic Array (EKA) detects ground vibrations produced by unauthorised nuclear explosions and is part of the United Kingdom’s contribution to the International Monitoring System (IMS) network that is used to check that the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is being adhered to by its treaty members. As the UK’s designated national authority, the MoD must ensure that the UK’s responsibilities are fulfilled under the CTBT, by ensuring that the station’s detection capabilities are not compromised.
In response to wind turbine development on land near to the EKA the industry conducted a study into wind turbine vibration. The study’s findings showed that wind turbines could have an impact on the EKA and resulted in the introduction of a 10km radius Exclusion Zone and a 50km radius Statutory Consultation Zone for all Wind Turbine development. This consultation zone covers an area of almost 8000 km2 covering the South of Scotland and the North of England representing around 3% of the UK’s total land area. Within the Consultation Zone, a vibration budget was implemented with all existing, newly built Wind Turbines and signed in planning contributing to an overall vibration level acting on the EKA. That level has now been reached and without further algorithm development or mitigation to reduce vibration levels, there can be no further Wind Turbine development in the area.
Xi’s Involvement in Eskdalemuir seismic region
Xi Engineering was asked to stand as technical experts in the Newfield Public Enquiry where Xi showed that the algorithm used to define the budget required improvement. As a result, the Eskdalemuir Working Group (EWG), a body made up of industry, government and MoD representatives were tasked with reworking the budget calculations. Xi Engineering Consultants was the chosen company to perform this work due to their superior expertise in this field, in collaboration with AWE seismology experts from the AWE. The outcome of this substantive study lead to a revised safeguarding tool and the removal of planning objections for 1.1GW of on chore deployment. A suitably conservative algorithm was developed using a ‘worst-case’ turbine model representative of available scientific evidence in 2014.
During the following 6 years, both turbine technology and scientific understanding of seismic waves produced by wind turbines have improved significantly. Based on this improved understanding and ultimately evidence for the MoD, Xi Engineering is working with developers and the EWG to deliver more onshore deployment in the region.
As wind turbines are likely to produce less vibration than the conservative ‘worst-case turbine budget algorithm, providing evidence to show this fact allows sites to remove MoD objections. Where a development project shows that the turbines, they intend using have a lower vibration level than the worst-case turbine it may be possible to add additional wind turbines to a development, or even propose new sites. The measurement process to do this typically requires three stages of measurement.
- Measurement of an equivalent candidate turbine at a site with similar ground conditions to Eskdalemuir
- Background measurements of the proposed site prior to construction to establish the background seismic levels
- Verification measurement of a new site following construction to ensure the allocated seismic budget has not been exceeded.
“I’m delighted to see a Scottish SME, Xi Engineering Consultants Ltd, having been successfully appointed, then go on to undertake such ground-breaking scientific work in cooperation with the MoD’s own experts.” – Scottish Energy Minister, Fergus Ewing