Lillground Wind Power Plant, Sweden
Lillground Wind Power Plant
Contractor: Vattenfall AB
Customer: E. Pihl & Søn A/S
Calculation: Tech-Marine Consulting ApS
The project concerned transport of 48 foundations and a power station for the Lillground Wind Power Plant, at the time, the third largest in the world.
The foundations were produced onboard flattop barges at Ordra Port, Poland and towed to the Lillground, Sweden, South of the Oresund bridge, where the wind farm is located. The foundations diameter at the widest place were about 10 m with heights ranging from about 10.3 – 14.3 meters and weight in the 1300-1430 ts range.
Tech-Marine undertook the following consultancy / production tasks for the main contractor E. Pihl & Søn A/S:
Tech-Marine Consulting ApS
Environmental load calculation
Analysis of barge motion
On-Hire and Off-Hire survey support of barges
Required BHP calculations for the towing operation
Damage Stability investigation
Approval of loading manual from class and maritime authorities
Loading, Unloading sequence Operation guidance for the barges
Design and calculations of securing arrangements for foundations
Tech-Marine Construction ApS
Production of 49 Boat Landing & Access Ladders
Production of Hydraulic System, for lifting the boat landing free of ice in
case of icy winther
Production of 200 Twin horn bollards for tender boats
Production of 49 Davit Cranes
On behalf of E. Pihl & Søn A/S, Tech-Marine investigated the wind, current and wave impact on the mooring systems used for fixation of the barges during the loading & unload sequence of the foundations at the wind farm. Tech-Marine calculated minimum requirements for the anchoring system and proposed methods to ensure safe operation.
For production and transport four barges, one of them a semi submersible, of the Nordsø type and one smaller barge for transport of the transformer foundation were chartered. In addition one tugboat were chartered for towing of the transport barges.
For the unloading procedure one additional barge converted to a special crane barge were chartered.
Tech-Marine set the operational window for the crane barge based on accelerations determined on model test, wind and sea state information.
The concrete foundations were cast in large moulds placed onboard the barges.
During concrete casting it was important to maintain the same deck height above the pier. To achieve this, Tech-Marine produced a loading sequence for the ballast tanks during concrete casting.
Tech-Marine anticipate at the on-hire survey of the barges on behalf of E. Pihl & Søn A/S, to ensure that the barges were in working condition and noted the general condition of the barges. Furthermore stability calculations were carried out as basics for the loading & unloading operations.
Barges for transport:
Tech-Marine made stability calculations for the barges to be used for transportation of the foundations, from the production site to the site of the wind farm.
Three of the barges carried 4 foundations during the trip to the site and one barge carried 5 foundations..
Stability calculations were made for the voyage and separate calculations for the unloading procedure. During unloading it were of great importance that the stability of the barges always was sufficient to ensure safe operations.
Ballast operations were carried out using fixed and portable bilge pumps. Therefore the sequence of the ballast operations were carefully planned to minimize shifting of water.
The arrangement and cargo distribution onboard the barges were of such an unusual character that approvals from the class and the maritime authorities were required. All documentation produced by Tech-Marine Consulting ApS were approved by the Classification societies and maritime authorities in respect of strength and stability.