Hornsea: world’s largest offshore wind farm
Hornsea Project One will be the world’s largest offshore windfarm when it goes ‘live’ in 2020. Located 120 kilometers off the English coast, Project One will generate 1.2 GW, providing electricity for approximately a million households. One, however, is modest compared to the other two sections of the Hornsea site.
^ Image of an existing wind farm of Ørsted, the Walney Offshore Wind Farm is located approximately 15 km from the coastline of Walney Island. The project was the first to deploy the Siemens Gamesa 3.6 MW 120m turbine in the UK.
Article by Lucien Joppen
The Hornsea-plot, consisting of three Projects (see box), is an enormous endeavour spanning almost one and a half decade. Establishing a wind farm of this size will undoubtedly push the United Kingdom’s ambition to use more renewable energy and cement its position as a front runner in offshore wind energy.
As Greg Clark, the current business and energy secretary of the UK, put it: “Our wind industry has grown at an extraordinary rate over the last few years, and it is a fundamental part of our plans to build a clean, affordable, secure energy system. Britain is a global leader in offshore wind, and we are determined to be one of the leading destinations for investment in renewable energy, which means jobs and economic growth right across the country.”
Despite Britain’s global leadership, the driving force behind Hornsea is Ørsted, formerly known as Dong Energy. The Danish energy company is the largest power producer in Denmark and the largest offshore wind farm company in the world, surpassing the mark of constructing and operating more than 1000 offshore wind turbines in 2016. The company is also very active in the UK, operating several offshore wind farms, such as Barrow and Burbo Bank. As it stands now, Ørsted has acquired the rights for Project One and Two. As stated, construction for Project One has begun in the first quarter of 2018. On Project Two, the company has yet to make a final investment decision and a spokesman stated it could be another two years before it is signed off.
High capacity turbines
Meanwhile, the first of the 174 monopiles in Project One has been installed. These are the cylindrical support structures for the turbines that are installed deep within the seabed. Each monopile, a commonly-used construction in offshore wind farming, is 65 meters long, has a diameter of 8.1 meter and weighs around 800 tonnes. The construction will be carried out in two stages: one vessel will handle the monopiles, the other will carry and install the wind turbines and turbine blades: four at a time. For Project One (and Project two), Ørsted has selected Siemens Gamesa as the supplier of the wind turbines (the SWT-7.0-154 model). The capacity per turbine is 7MW, total height of the turbine is 200 meters, the diameter of the rotor is 154 meters. The 7.0 model generates 10 per cent more power than its predecessor, Siemens Gamesa states. For Project Two, Siemens Gamesa will supply its latest model, the SG 8.0-167 DD turbine which will generate an additional 10 percent of power.
Because of the distance between Project One (and the other Projects) to the shore, Hornsea requires an offshore reactive compensation substation. This facility is needed for the wind farm(s) to conform with the UK grid code. This code demands that any power plant should support the electricity grid, not just in normal operation, but also in the event of voltage dips. The Hornsea One offshore reactive compensation substation will be standing at a depth of 23 meters. The main geotechnical challenge will be the extremely weak chalk layers. The topside and jacket design were conceptualized by Ramboll in close collaboration with Ørsted, with the focus on design optimization and steel weight reduction.
Cutting edge technology
The establishment of the aforementioned offshore station is only one example of the cutting edge technology required to make the Hornsea Projects work. A lot of the challenges are related to the location, the distance to the mainland and the depth, varying from 22 tot 73 meters. According to Benj Sykes, Vice President, Head of Programme Asset Management and UK Country Manager for Ørsted, several “exciting technologies” have been tried and tested in the Hornsea Project One. “There have been more challenges in the design than other projects because of the scale and that it is so far from shore.”
The Hornsea site will consist of three separate Projects, aptly named One, Two and Three and is located roughly 75 kilometers off the coast in the North Sea. In total, the Hornsea site spans an area of 4,730 square kilometers. Project One will form the ‘leftfield’ of the site, taking up 630 square kilometers. On the site 171 7MW turbines will be installed, divided into two subzones, generating 1.2 MW in total per year. Project Two will be located in the centre of the Hornsea site in an area of approximately 400 square kilometers. 300 turbines generating a total of 1.8 GW are planned and completion of the project is expected in 2022. Project Three will be the largest development on the Hornsea site, spanning an area of 696 square kilometers and generating around 2.4 GW. Construction will begin from 2022-2025.
Wind power is the most competitively priced technology in many, if not most markets worldwide, according to the Global Wind Technology Council. The GWTC mentions drivers such as the emergence of wind/solar hybrids, more sophisticated grid management and increasingly affordable energy storage.
GWTC’s statistics show that more than 52GW of wind power was added in 2017, bringing total installations to 539 GW globally. “Wind power is leading the charge in the transition away from fossil fuels, and continues to blow away the competition on price, performance and reliability”, said Steve Sawyer, GWEC Secretary General. “Both onshore and offshore, wind power is key to defining a sustainable energy future.” The projected growth of wind energy also has ramifications for the valve industry. Valves are used in turbines, transformer platforms, onshore grid feed and on jack-up vessels, etc. Equipment in general needs to be robust to withstand strong and changing wind pressures as well as fluctuating temperatures and salty seawater/winds.