Offshore Wind

Hollandse Kust (west Alpha) Offshore Wind Farm | OHVS
North Sea, the Netherlands
Hollandse Kust (west Alpha) Offshore Wind Farm | OHVS

Smulders and EQUANS are building the offshore substation for the Hollandse Kust (west Alpha) offshore wind farm for TenneT.


About the wind farm

The Hollandse Kust (noord), (west Alpha) and (west Beta) offshore platforms will be located in the North Sea along the Dutch coast. Forty percent of the Netherlands’ electricity needs will come from offshore wind farms by 2030. TenneT will realise 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 to be constructed and operated by TenneT. Further background information can be found on and and


Scope of work

The contract for Hollandse Kust (west Alpha) 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. The consortium was already selected by TenneT TSO B.V. to construct an offshore transformer station for the Hollandse Kust (noord) wind farm zone.

Iemants is responsible for the engineering, procurement and construction of the steel structures for both the topside and jacket. All works are performed inhouse, at the Smulders’ production facilities in Arendonk, Balen and Hoboken (Belgium). The final assembly takes place at the EQUANS yard in Hoboken. The jacket is being assembled at the yard in Vlissingen (the Netherlands).  

EQUANS is responsible for the engineering, procurement, integration, construction and testing (on- and offshore) of all LV, MV, HV and auxiliary systems for the jacket and topside of the Hollandse Kust (Noord) offshore transformer station. The engineering, procurement, construction, integration and onshore testing for the topside systems will take place at the EQUANS yard in Hoboken (Belgium). For the jacket, these activities will take place in Vlissingen.


Key figures and planning

TenneT's transformer substations are an essential part of the offshore grid. Standardisation of these 700MW platforms will substantially reduce the costs of development, construction and maintenance. The jacket is 49 metres high and consists of 1,930 tonnes of steel. This steel structure is firmly anchored to the seabed with piles at a depth of 28 metres. The topside with three (inner) floors and an outer deck will be placed on top. This topside weighs approximately 3,600 tonnes and is 47 metres long, 35 metres wide and 25 metres high (excluding the antenna tower and the upper deck crane).

On 5 July 2022, the substation jacket was successfully loaded out at the Heerema yard in Vlissingen. The jacket was installed offshore in August 2022.