STX offers modular offshore substations

FRANCE: Maritime construction group STX France has launched a new modular design for offshore substations it said could cut energy costs by reducing delivery times, capital expenditure and operational costs.

STX's modular substation design can even be placed on floating foundations

The SeeOs (scalable, efficient, evolutive offshore station) is based on a standard 200-300MW module with all the features necessary to meet 90% of cases, STX said.

Two or three modules can then be joined together to meet power requirements up to 900MW, and various features added, such as shunt reactors, back-up generators, accommodation units and workshops.

The modules can be installed on monopile, jacket or floating foundations, depending on the site.

"With its efficient design, SeeOs decreases delivery time by 20%, reduces project Capex costs by 20%, and optimses operations and maintenance costs by up to 20%," the company claimed.

STX came up with the idea based on its experience designing and manufacturing offshore substations (OSS).

So far, it has supplied the OSS for Westermost Rough (210MW) in the UK and is currently building units for Arkona (398MW) in Germany and Rentel (309MW) in Belgium.

While all OSS are currently designed as one-off units, they are basically doing the same thing: taking the voltage from the wind turbine, transforming it into a higher voltage and sending it to the export cable, explained Frederic Grizaud, director of STX's marine energy business unit.

By analysing customer requirements, STX came up with a standard design using 80% of common features across all modules, while also "fully compliant with the strictest requirements and regulations," the company said.

Among other things, this saves on development and commissioning costs and cuts around four to six months off delivery times.

The modules, which weigh less than 1,000 tonnes apiece, can be installed by the same vessels as the foundations – vessels that are already on site and significantly cheaper than the heavy-lift vessels usually required.

Operational costs can be reduced because the modules are fully enclosed, which means a longer lifespan and allows easier access and better working conditions for maintenance crews, Grizaud added.

Standardisation also improves reliability, and all modules will be able to benefit from software upgrades.

The concept also takes account of expected market evolution.

"The SeeOs has enough space and other requirements to accommodate the move to 66kV in the near future," Grizaud said. Modules can also be installed on floating platforms for deep-water sites.

In addition to Europe, STX is also optimistic for SeeOs's prospects in the emerging offshore markets such as the US and China.

"New markets will be looking for a track record and proven solutions," Grizaud noted. And to save on transport costs, the standardised modules can be manufactured locally.

Feedback from the industry has been "very good", Grizaud said. The arrival of zero-support projects means "there is a real interest in new ideas and anything to help get prices lower," he added.