Author: Liam Lyng, construction projects manager, Mainstream Renewable Power
Mainstream Renewable Power is a global wind and solar company that was founded by Eddie O’Connor in 2008. It employs over 160 people and is developing, building and operating wind and solar farms across four continents. Mainstream’s first Irish project, the Knockaneden Wind Farm in Co Kerry, will complete its first year in operation this November.
The wind farm, which is located near Caherciveen in Co Kerry, was delivered into commercial operation on budget in November 2012. It produces 9 megawatts of electricity that feeds into the Irish grid, which is enough to power over six thousand houses.
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Fig 1: Blade delivery at O'Connell Bridge[/caption]
The nearest load centre, Caherciveen town, is tail fed from the Irish grid and has an approximate load of 5 megawatts. Previously, the power required by the town had to be transferred from the national grid via a long 38kV radial overhead line. Much of the power was being lost along the way in the grid system components, including the upstream 110/38kV transformer substation and the 50km long 38kV overhead line.
After construction of the wind farm, the power is now provided locally from the wind farm via a new 38kV substation looped into the pre-existing 38kV overhead line. The result is an offset of the power required to be imported, thus reducing the power loss in the national grid. The town is now supplied with power locally from the wind farm, with any excess generated injected back into the national grid. The carbon footprint of the town is therefore reduced. When this wind farm produces over 50 per cent output at any given time, Caherciveen town is consuming 100 per cent renewable energy.
The construction of the wind farm was split between four main construction contracts:
- Turbine supply agreement with Enercon GmBh,
- Civil balance of plant engineering, procurement and construction (EPC) contract with Moriarty Civil Engineering Contractors,
- Electrical balance of plant EPC contract with Kirby Group Engineering Ltd,
- Grid connection agreement with ESB Networks.
ENGINEERING CHALLENGE
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Fig 2: Transporting the turbine blade[/caption]
The biggest challenge identified by Mainstream was the transportation of the wind turbines to the wind-farm site. Given the nature of wind projects’ locations in Ireland, narrow, winding roads are always a challenge for the construction phase of wind farms. The longest wind-turbine component deliveries to the site were both the bottom tower sections and the blade. The vehicle length in total was 51 metres in length.
The hairpin junction at O’Connell Bridge in Kerry was of particular concern, in terms of the length of the haulage vehicles and the physical constraints that were present at the bend. In planning such activities, it was recognised that co-operation between all parties was critical to the success of the delivery including designers, civil contractors, haulage companies and turbine suppliers.
Local consultants Malachy Walsh and Partners were commissioned to undertake a transport route survey for the project. The survey examined the entire route from Shannon Foynes Port in Limerick to the site in Knockaneden, Co Kerry. All stakeholders such as Kerry County Council and landowners were identified and contacted. Easement agreements were signed with property owners to allow for the widening of the road at the entrance and exit of the bridge.
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Fig 3: Turbine swept path analysis by Paul Nealon and Cormac Murphy, Malachy Walsh and Partners (click to enlarge)[/caption]
Local authority staff, such as Kerry County Council roads engineer, were contacted and notified of the project’s intentions and all requirements from the area roads engineer were taken into account in the design. Key stakeholder engagement at an early stage in the project’s conceptual designs was key to the success of the delivery.
The civil contractor, Denis Moriarty Civil Engineering Contractors, appointed Malachy Walsh and Partners as the designers for the project. A full topographical and services survey was undertaken at the bend of O’Connell Bridge. The survey was undertaken due to the critical nature of this bridge.
A second AutoCAD Swept Path Analysis using AutoTrack was undertaken for the delivery of all the major turbine components. The extensive surveying was undertaken to minimise the amount of modifications required to both private and public property. The results of the survey enabled the designers to undertake detailed planning of extendable trailer movements (Fig 3).
CROSSING THE BRIDGE - THE BIGGEST HURDLE
The biggest challenges of crossing the bridge were transporting both the extended platform trailers for the blades and the clamp bogies for the top tower section, in terms of both length of the vehicle and width of the components.
The analysis identified how best the delivery should navigate the hairpin bend. Delivery routes were assessed using the automatic and manual steer feature built into the AutoTrack algorithms.
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Fig 4: 3D AutoCAD modelling of turbine delivery by Malachy Walsh and Partners[/caption]
The civil works identified included:
- Modification of an embankment to the left of the road;
- Lowered Bridge parapets on the right hand side; and
- Widening of the road at the exit.
3D AutoCAD modelling was undertaken to visualise the movements of the trailers following the modifications, as shown in Fig 4.
To undertake the construction works, approval from the National Roads Authority via a road opening licence was obtained. The civil contractor undertook all the construction works including reducing the embankment on the left, temporally decreasing the size of the parapet and widening the road at the exit of the bridge, as per the designs, design risk assessments produced by Malachy Walsh and Partners and the method statements approved by the project supervisor – construction stage (PSCS).
As with any design package, an independent verification was required. Martrain Haulage undertook a trial run of the route with an extendable platform trailer. Only a slight modification was identified at the bridge, with a few extra bricks on the bridge parapet to be temporarily removed. The route was verified and made ready for delivery.
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Fig 5: Turbine delivery was undertaken overnight[/caption]
Turbine delivery was undertaken by Martrain Haulage during the night, with garda escorts at both the front and rear of the convoy in order to minimise disruption to road users and ensure safe delivery of all components to site. O’Connell Bridge was one of the last sections of the route and the task was undertaken around sunrise. This improved the visibility for both the driver and the operative who steered the rear of the extendable platform with a remote device. All components successfully navigated the O’Connell Bridge junction. In total, more than 60 components were safely delivered to the wind farm.
Mainstream is now in the process of building the 7.65 megawatt wind farm in Carrickeeny in Co Leitrim, which will be purchased by IKEA upon operation. Mainstream will continue to operate the project for its 20-year lifecycle. The company is also developing the large-scale Energy Bridge project in the Midlands. Phase 1 will export 1,200 megawatts of surplus wind energy to the UK, which will generate an exciting new industry in the midlands.