‘It’s a nuclear power plant in the sea’ – GE’s DolWin3 offshore converter

‘It’s a nuclear power plant in the sea’ – GE’s DolWin3 offshore converter

RGN editor Jack Kennedy went to visit the site where the Dolwin3 grid connector is being built in Northern Germany and sat down with General Electric’s general manager for power electronics Patrick Plas to discuss the impact this technology could have for offshore wind energy in the future.

DolWin3 is a 900MW-capacity grid connection which will convert alternating current (AC), a form of electricity which travels inefficiently over long distance, to direct current (DC) in order to effectively transmit clean energy from a cluster of wind farms in the Southwestern part of the German North Sea to the mainland.

The AC-DC converters inside DolWin3

A high voltage direct current (HVDC) transmission line will connect DolWin3, which will sit 80km off the German coast, with an onshore converter located in Dörpen where it will then be converted back to AC carrying enough energy to power a city the size of Hamburg – or roughly a million households.

General Electric’s Grid Solutions division is leading the construction of this deeply technical project, contracted by German energy company Tennet which will use the system to supply energy across Germany.

Plas said it is DolWin3’s technical and transformative nature which attracted GE to participate in the project.

“It is in the genes of GE to do something complex. GE loves doing things that are difficult and also it is helping Germany go through an energy revolution. It’s complex, it’s difficult and it’s meaningful,” Plas explained.

“It is [the equivalent of a] nuclear power plant in the sea, bringing power to a million people. That’s why it is significant and meaningful for the environment.”

Arriving at the Nordic Yards ship building site in Warnemünde, where Dolwin3 has been constructed and is undergoing final preparations before being towed out in mid-June, the first thing that strikes you is the sheer size of the HVDC system.

At 76 metres tall and painted in a distinct yellow, DolWin3 towers over the shipyard. The platform is the length of an American football pitch and weighs a gargantuan 18,450 tonnes.

As this technology develops, Plas says the two primary objectives are to reduce both the size and cost of building and installing a platform like DolWin3.

He said: “We need to make this technology easier to implement and the easiness means the price because it’s not cheap and it has an impact on the electricity bill at the end.”

DolWin3’s ‘jacket’ being towed into position

The supporting structure for DolWin3, known as the ‘jacket’, has already been shipped out to location and when this platform is towed out, there won’t be much room for error in placing the huge construction on its pillars. Despite the size and weight of the platform there is only 50cm of leeway when it is attached to the supporting legs.

Plas noted that as wind farms continue to bring down the cost of energy generation – with recent auctions seeing cost-parity with conventional grid electricity – making sure that energy can be delivered at the same cost throughout the supply chain is crucial.

For this technology to continue to change the way offshore renewable energy is delivered to mainland grids it has to be refined to make it easier to install, cheaper and with multi-faceted applications – Plas hopes it will also lead to an increase in the number of wind farms being built.

“It’s in all the technical economical studies, it’s about making the business case fly in a lot more cases. If you lower the entry barriers then suddenly you have opportunities which are much more likely than before,” Plas asserted.

Currently there are cases of wind farms which are not economical as they are too far away from shore to have an easy, efficient connection without the use of HVDC. At the moment it is more expensive, but Plas says if you lower the price then suddenly many new wind farms are possible.

He added: “This is a way to develop more wind farms and more connections beyond Germany. Can we have cases in the US, the UK? Can we help these business cases fly in these two countries? – That is what we are trying to do.”

The future for GE and HVDC is already underway. Plas is already busy going forward with bids for future projects, for example DolWin6 – another project for Tennet, and he is aiming to continue to reduce the size and cost of offshore converters as the technology matures.

“The next one we are bidding for is a little smaller and lighter but it’s not going to be half the size of this one,” Plas predicted. “We also need to be cautious with how we introduce new technologies, you can’t just introduce something brand new without testing it when you are 80km offshore in the middle of the sea. This is why you need to go step by step and have a progressive approach on this technology evolution.”

Jack Kennedy was speaking to Patrick Plas at the GE/Tennet press event for the launch of DolWin3 in Warnemünde, Germany.

Make sure you read the next issue of RGN to get the full feature on DolWin3 and GE’s Grid Solutions visions.