TenneT and ENGIE Solutions/Iemants sign contract for offshore transformer substation Hollandse Kust (west Alpha)

December 11th '20

A joint venture consisting of ENGIE Solutions and Iemants (subsidiary of Smulders) and TenneT have signed a contract for the offshore transformer substation Hollandse Kust (west Alpha).  Earlier this year the consortium already won the contract for the construction and installation of the offshore transformer substation Hollandse Kust (north). Both contracts are the result of a European call for tenders issued by TenneT earlier this year. The transformer substation for Hollandse Kust (west Alpha) is scheduled to be commissioned in 2024. 

The contract includes the engineering, procurement, construction, offshore installation, connection and testing of the offshore transformer substation. The topside and the jacket will be built separately on land and installed at sea on site using a crane ship.

Standard design

TenneT's transformer substations form an essential part of the offshore grid. Standardization of these 700 MW platforms substantially reduces costs for development, construction and maintenance. According to the design, the jacket is 49 meters high and consists of 1,930 tons of steel. This steel structure will be firmly anchored in the seabed with piles at a depth of 28 meters. On top of this, the topside will have three (inner) floors and an outer deck. This topside weighs approximately 4,300 tons and is 47 meters long, 35 meters wide and 25 meters high (excluding antenna tower and upper deck crane). 


Marco Kuijpers, TenneT's Offshore Director: "The current collaboration with the ENGIE Solutions/Iemants consortium for the realization of the transformer substation for the Hollandse Kust (north) gives us confidence in the joint work for the next transformer substation; Hollandse Kust (west Alpha). By signing this contract, TenneT continues its strategy for cost-effective, standard offshore transformer substations to drive the Dutch energy transition."

About Hollandse Kust (north) (west Alpha) and (west Beta)

The offshore platforms Hollandse Kust (north), (west Alpha) and (west Beta) will be located in the North Sea along the Dutch coast. In 2030, 40 percent of the electricity demand of the Netherlands will be supplied by the electricity of offshore wind farms. TenneT realises the grid connections for these wind farms. These three 700 MW platforms will be the fifth, sixth and seventh large-scale grid connections for offshore wind energy in the Netherlands that will be built and operated by TenneT. The first high-voltage connections for the wind farms near Borssele will be operational in 2020, followed by the connections for Hollandse Kust (zuid) in 2022. TenneT will realise approximately 9.6 GW of high-voltage connections in the Dutch North Sea by 2030. More background information can be found on   


Picture: TenneT