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Wind turbines inaugurated in Borssum

Challenging island location confidently handled

Lots of water, moorland, a motorway directly adjacent and bridge-only access: logistically speaking, the location of the two wind turbines operated by the municipal Stadtwerke Emden GmbH is effectively an island. Riep Paulusma, Head of Project Development at IFE, reports on the challenges encountered throughout this project in this exposed location.

The first issue was the geological quality of the soil: underneath a 1.5-metre thick top layer came a 3-metre thick layer of peat containing 600% water. This necessitated a complex deep foundation and water drainage. Secondly the island location required extremely careful logistics planning. The site could only be accessed over 5 bridges, only one of which could and was allowed to be used, and correspondingly reinforced, for heavy loads. And it was precisely this bridge that was to be demolished at a predetermined time before which all heavy equipment had to have left the site again.

Each of the foundations for the two turbines was constructed on 60 piles and the location for the crane was also piled. Additional water drainage measures had to be put in place to keep the excavation dry. “Apart from three deep wells and powerful pumps, we also used a data logger on the motorway,” explains Riep Paulusma. “It monitored the groundwater level during construction of the foundation to prevent any subsidence of the motorway.”

With the approval of the Emden Water and Shipping Office, a bridge was reinforced by steel beams, to aid site logistics. The crane, concrete mixers and up to 140-tonne trucks, among other vehicles, crossed this bridge. Time played an even greater role than normal during construction. The construction of a Tennet TSO GmbH electrical substation in Emden-East lies ahead, as part of which the bridge is to be demolished and replaced by a new one. “We therefore had to rely on concentrated deliveries to site,” explains Riep Paulusma. However, it did not end there. Ultimately the crane had to be removed from the site after installation. “The construction speed is always dependent on the wind. As this location is seriously exposed to the wind, we had to factor in additional downtimes just to be on the safe side.”

Moreover, Enercon signalled during the construction phase that a new type of generator and revised rotor blades would soon be ready for operation. The client, Stadtwerke Emden GmbH, decided to wait to install this generator in the research and development systems.

The gondola and rotor blades were finally installed in August, with the blades featuring trailing edge serrations (TSE), fine teeth on the edge of the rotor blade that reduce sound emissions by 1.5 decibels.

The official inauguration of the turbines took place on 12 November 2015. This was a special event for Stadtwerke Emden GmbH, not just as the client but equally as a sustainable energy supplier. Physically the wind turbines now regeneratively generate 100% of the electricity needs of all households in Emden.

“A new era has begun for us,” continues Pascal Habakuck, CEO of IFE. Following the planning and construction management phase, supported by IFE surveyors, the takeover now means that IFE is also responsible for technical and commercial operational management of the turbines. “Good planning pays off. I am convinced that this will be confirmed again by this project.”

Project facts and figures
Type of installation: E-115, upwind turbine with active blade adjustment
Manufacturer: Enercon
Hub height: 139 metres
Nominal output: 3 MW
Rotor diameter: 115 m

Concrete volume: 958 m³
Steel reinforcement: 149 tonnes

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