Work begins on Horns rev 3

In a few years' time, the turbines of a new 400MW wind farm will be producing power in the North Sea. The Danish Energy Agency is well underway with the tender process for the Horns Rev 3 wind farm, and work on the project has already started at Energinet.dk.

From his office in Fredericia, Energinet.dk's senior project manager Søren Juul Larsen is supervising the work to establish the infrastructure for the huge new wind farm. The project deadline is 31 December 2016. That is when the so-called 'landing facilities' that will transmit the 400 MW of wind power from the North Sea to the mainland are scheduled to be ready, so the turbines can be installed and connected to the national grid in Denmark.

The landing facilities will consist of a transformer platform in the North Sea, to be placed near the site of the wind turbines, a 34 kilometre submarine cable that will transmit the power from the platform to the mainland and the new onshore transformer station facilities and cables.

“Right now, we're mainly working on the design, procurement and regulatory approvals process. By the end of the year, we will have made all the major purchases and also expect to have EIA approval for the project. That's when we'll start the construction process,” explains Juul Larsen.

160 square kilometres of seabed mapped

The first step will be to lay the land cables, a project scheduled for early 2015. Next will be the work to construct the platform to feed the power from the wind turbines to the mainland from its position 34 kilometres off the Jutland coast. As for the wind farm, tenders have been invited for the platform, which will be constructed in a shipyard somewhere in Europe and from there transported to Esbjerg.

Energinet.dk was also in charge of the wind farm EIA, or environmental impact assessment, which was completed in August. In an EIA, all parties are consulted, according to the senior project manager.

“When constructing a DKK 1.5bn landing facility, there are a lot of factors – or stakeholders, if you like – to consider, spanning all the way from the common field mouse to people's summer houses in the vicinity. That's why it was so important to have two public hearing phases, so everyone could raise their doubts and concerns,” he said.

“Some people might think this is annoying and time-consuming, but it's actually a very important part of the process. And, compared with other countries, our public hearing process actually runs quite smoothly.”

In addition to the EIA, extensive geological surveys have been conducted of the seabed covering the 160 square kilometre area, of which the new wind farm will cover 88 square kilometres.

Turbine sizes from 3 to 10 MW

Four energy companies – DONG Energy (Denmark), Statoil (Norway), Vattenfall (Sweden) and E.ON (Germany) – have pre-qualified for the project, and the decision as to who will be selected to construct the wind farm will not be taken until early 2015. Only when that happens will it be clear which turbines are to be erected, and that makes for a complex design process, Juul Larsen explains.

“As yet, we have no information on the number or size of wind turbines to be built. All we know is that it will be a 400MW wind farm. In designing the landing facilities even before we know the name of the concessionaire and the turbines to be erected, we've had to set up some guidelines. For example, the turbines must have a capacity of between 3MW and 10MW.”

These guidelines illustrate the speed of innovation in offshore wind technology over the past decade. When the Horns Rev 2 wind farm was built in 2008, it featured what were then state-of-the-art 2.3MW turbines; two years ago, 3.6MW turbines were installed for the Anholt Wind Farm. Today, 3MW is relatively small for a wind turbine, and 10MW turbines are still in the development stage.

Very stringent coordination

The four pre-qualified candidates have until 16 September to submit their preliminary tenders to the Danish Energy Agency, after which there will be another round of discussions and negotiations. The final tenders will not be submitted until next year, and the company awarded the tender, the concessionaire, will be selected in February 2015. Transport and installation of the foundations and turbines is scheduled to begin in late 2016 or early 2017.

“Due to the many parties involved in the tender process, we have to make sure that there is very stringent coordination across commercial players and regulatory authorities,” says Juul Larsen.

“Clearly, the most challenging part of the process is to connect the interfaces of all the parties involved, so we can coordinate timetables and align expectations on all matters. It is essential that all parties – the municipal authorities, the Danish Nature Agency, the Danish Energy Agency, the concessionaire and us – openly discuss all issues and raise any problems or concerns so there won't be any surprises.”

Strong international connections essential

The Horns Rev 3 wind farm also involves an upgrade to the existing electric power infrastructure in Denmark while, at the same time, the country is expanding its international grid connections. The new Skagerak 4 connection strengthening the link between Norway's and Denmark's grids is scheduled to open later this year, and in 2017 work will begin on a new undersea HVDC (high voltage direct current) interconnector to the Netherlands: the so-called “COBRA” cable. In addition, Energinet.dk is looking at the possibility of establishing a grid interconnection to Germany via Kriegers Flak, even though the wind farm planned for that location has been postponed.

“We're strongly expanding our grid connections to our neighbouring countries so we can send power where it’s needed. If there's no wind blowing here at home, then we need to source energy from somewhere else, and when we have too much energy available here, we need to be able to sell it to countries that have a shortage,” he said.

Horns Rev 3 is due to be completed and fully installed by 2020.