Written by Bernadette Ballantyne
Supported by Fugro
It was the year 2000. The Y2K bug, which was predicted to create a software meltdown and bring global economies to a standstill, led to nothing more than a few minor temporary IT issues. JK Rowling’s fourth Harry Potter book “Harry Potter and the Goblet of Fire” became the fastest selling novel of all time; a 24 year old Tiger Woods becomes the youngest ever golfer to win four grand slams; and American and Russian astronauts became the first ever inhabitants of the International Space Station.
Meanwhile, in the UK engineers were taking the first steps towards an energy revolution which would see our reliance on coal power become a thing of the past. In the North Sea, near Blyth in Northumberland a crane driver called Bobby Hazel was about to do something that no crane driver had ever done before and his actions would herald the start of the UK’s journey to becoming the world leader in offshore wind.
The UK’s First Offshore Turbines
“I think the actual nacelle only weighed about 50 tonnes,” says Bobby who works for Fugro and 20 years later is still out at sea, talking to us from a lifting barge. “I think the towers were about 30 tonnes apiece,” he says explaining that they started with the foundation – a monopile. “And then we just built it up from there which was one tower followed by another tower then the nacelle on the top.”
The blades were picked up as a pair, called bunny ears, which were connected to the nose cone, followed by the final single blade. “And that was it, job done. It was all over then,” says Bobby who had no idea that this pilot offshore wind project of just two Vestas V66 turbines, each with a capacity of 2MW, would become the start of a massive expansion in wind generation for the UK.
“I believe we now account for 40% of the world’s operating offshore wind projects,” says Bazhad Ayoub, a senior analyst at Renewable UK, who tracks offshore wind data for projects all over the world. He explains that after this pilot project at Blyth, it was the UK government’s introduction of the renewable obligation in 2002 that really kickstarted the industry. “What it did is it place an obligation on retail electricity suppliers to source a gradually increasing percentage of electricity from renewable sources,” he says.
In return the power producers received a fixed price for each unit of electricity that they generated over the next 20 years. This was critical. Offshore wind was new and came with risks and uncertainty, which investors did not like. But they did like the guaranteed 20 year income stream introduced through the new renewables obligation. Around the same time the body responsible for the UK Coastline, Crown Estates, gave permission for windfarms to be built on the seabed, each site allowing up to 30 turbines.
Much was learned from these early wind farms, which were concentrated around the north coast of Wales from the Rhyl Flats, up to Barrow and up as far as Robin Rigg in Scotland. On the east coast these early sites were located as far south as the Kentish Flats and Gunfleet Sands and then further north at Scroby Sands, Lynn and Inner Dowsing off the coast of Lincolnshire.
For the next raft of projects Crown Estates made larger sites available. As the size of the sites grew so did the turbines. On the pilot project at Blyth each turbine produced 2MW of power – enough for around 3000 homes every year. But by the time the second round of windfarms were launched, the turbine size had almost doubled to 3.6MW.
Offshore Wind Electricity Price Plummets
Since then the turbines have just kept on growing. Wind farms being planned today consist of enormous 12MW turbines. At six times the capacity of the earlier technology they are more than treble the height as the turbine blades have grown to create more energy than ever before.
One of the side effects of this growth was the economy of scale that comes with expansion. But it was over another decade before the industry really saw the price of electricity generated by offshore wind plummet. “In 2015 the CFD auctions were a bit of a game changer because it made developers compete with one another and help bring prices down,” says Bazhad.
Developers were pitted against each other, bidding for government guarantees of a price per MWh. The winners were those that could deliver the offshore wind energy at the lowest price. As a result of this competitive arrangement prices have nosedived from £114 per MWh to £39per MWh as developers and their supply chains worked hard to deliver projects more cost effectively than ever before.
Today the CfD auctions and the early rounds of offshore wind have resulted in around 8.5GW of power capacity being installed in the UK, and more recent awards through the second round of contracts for difference auctions are set to see another 5.1GW come online by 2024. The third round is bringing even more and this is not all. In March 2019 the government announced a landmark agreement called the Offshore Wind Sector Deal calling for industry to install a total of 30GW by 2030. In return for guaranteeing future subsidies through contracts for difference rounds, the industry agreed to continue reducing costs and investing in the supply chain. But as we will hear in part two Boris Johnson’s new government has just set an even higher target and challenged industry to build 40GW by 2030, which won’t be easy. “So, at the moment, I think the UK has about a potential of 37 gigawatts overall if all projects are built,” says Bahzad.
North East Origins
And it all began with two wind turbines in the north east. “So at the time they were the largest and most powerful offshore wind turbines in the world,” says Patrick Rainey, offshore logistics manager with RWE Renewables, which was part of the consortium that originally developed the Blyth Offshore Wind Farm.
For any offshore wind turbine, the starting point is to collect data about the site, a site survey, and this is where Fugro came in. “Fugro worked in the oil and gas industry right from its early days in the 1970’s, where we developed a number of seabed operated devices for pushing our cone penetrometer technology into the seabed,” says Tony Hodgson, regional strategic sales manager for Europe and Africa, and the cone penetrometers that he mentions have been used for soil investigation since the 1950s. These steel rods with a conical tip are pushed into the ground to gather geotechnical information, first measuring the resistance of the ground to the insertion of the penetrometer giving the soil bearing capacity. Today’s penetrometers can measure a range of properties from pore water pressure to magnetometry giving a range of information about the seabed.
“We designed drilling systems to take samples from the seabed to test in our laboratories. This is really what the offshore wind industry needed,” he says.
Much of the work focussed on gathering data about the seabed conditions and the wind profile, what developers call site characterisation using geophysical and geotechnical surveys that identify the likely construction challenges. Having worked at Fugro for 43 years Tony remembers doing the site characterisation at Blyth which began with two 20m deep boreholes taken from the seabed. “And that enabled the foundation pile to be designed based on a drilled and grouted techniques,” says Tony.
So this single pile, or monopile that was buried 18m deep into the seabed, and measured 3.5m in diameter, became the foundation for the UK’s first ever offshore wind turbines.
Increasing Drilling Speed
Back in 2000 the drilling speeds for driving in the steel monopiles was much slower than it is now, and increasing drilling speed is a key objective for Fugro as it seeks to support developers in bringing down the cost of offshore wind. “The drilling speeds, at the time, were relatively modest, I would say probably in the order of 400 to 500 millimetres and hour during speed, so you know, to drill a socket down to 18 metres. It’s taking us, 9- 12 hours to actually drill into the seabed. We’re actually now doing things much faster and our new design drills are aiming at drilling speeds of maybe 10 times faster than that. So that’s really exciting for the future. So, but at that time, you know, the drilling speed was relatively modest.”
After the socket was drilled and the steel pile in place, it was grouted in and left for several days to achieve the required strength. Then it was time for Bobby and the construction team to come and build the 66m tall turbines, which were 66m tall.
And there they sat providing clean energy to the UK for almost 20 years.
But as Sir Isaac Newton said: “What goes up, must come down.”
“So in about 2017 we started to look at end of life, opportunities for the site. Was there repowering? Was there reuse? The life extension options. We also at that time were investigating the decommissioning sort of trying to plan for that,” says Patrick.
And in 2018 the decision was made to tender the contract to dismantle the UK’s first ever offshore wind turbines and it was won by Fugro, meaning that Bobby Hazel was back in the North Sea. He remembers the turbines being in good condition when he took them down.
“It came apart pretty good actually, the bolts weren’t rusty – nothing like that. Everything was good,” says Bobby.
But that didn’t mean it was going to be a breeze as as the team had to rocky seabed to contend with. This meant bringing in a special barge with pin pile legs rather than the traditional spud cans. It was a job for a 60mlong, 32m wide, 1000t capacity barge called The Excalibur.
“So we mobilised the Excalibur in Port of Blythe,” says Tony Stevens, Fugro’s project manager for the decommissioning project which began onsite in April 2019. “The biggest challenge we found was actually finding a company who has the correct tools – existing tools in their stock to be able to come to site. Otherwise we’re looking at quite an expensive design and fabrication of the new tools to remove the blades and the nacelle and the tower sections.”
Fortunately Fugro found a small specialist supplier based in the Netherlands that had the bespoke equipment needed to take apart the turbines. They began with the north tower and it happened within days. More difficult was removal of the monopile. “There were many lease conditions but quite an important one was that we had to take the turbines down to half metre minimum below the seabed,” says Tony Stephens. Previous projects had underestimated the force required to cut and lift the piles fighting against the considurable skin friction of the existing seabed. “I think one of the projects, they were stuck there for a number of days with a cut pile, but not enough crane capacity to remove it,” says Tony.
“So we spent a lot of time and effort during the preparation phase at looking at that those two options, those two processes, ensuring the cut is made. And then having plenty of crane capacity to take the cut pile back on board.”
The team then used rock to infill the head of the pile. “By backfilling it, we reinstated the seabed as close to its original condition as was possible,” says Patrick.
Having successfully decommissioned the two turbines Tony Stephens says the team were eager to do more. “We obviously got faster and we were all in the mood then to carry on and it would have be lovely if there were two or three more to carry on and take down but that was that, we had done the job.”
Fortunately for Tony there are going to be a lot more turbines to decommission in the future. According to Bazhad we currently have 2324 installed off the coast of the UK and if we reach the 40GW target this will be more than 5000!
For Patrick the lessons from the first ever offshore wind decommissioning in the UK were all about good data. “I think one of the things that that we found from my side at least was really understanding the site and really knowing what you have, knowing your documentation, your as-builts. Has anything changed throughout the course of the 20 years that the site’s been there? And also, what impact will any of those things that you find have on your decommissioning? So the one that I like to use is when we remove the nacelle all of a sudden the hook on point that we had, for when you come to the top of the ladder, that disappears with the nacelle so all of a sudden, you then have to have a you have to find a solution – this hook on point has disappeared.”
And Patrick says it is these small points that can create the real decommissioning challenges that could multiply as the number of turbines and the number of sites increases.
Of course the lessons from Blyth started over twenty years ago, and in the second episode on offshore wind we are going to explore how innovations in data collection, analysis and foundation construction are supporting this booming industry.
“You know, in the UK, we have the sector deal now and there’s emerging projects in the US and Taiwan, Europe,” says Bazhad from Renewable UK. “And then you’ve got what we call sort of the third sort of wave of countries now looking at offshore wind, such as Japan, South Korea, Australia. Overall for the UK and globally, the offshore wind sector, the future is very bright,” he says.
