The height of success7 December 2018
GE is designing and building the tallest-ever wind turbine, the Haliade-X, which at 260m will dwarf the current biggest turbine, at 187m, built by Vestas. There are plenty of advantages to upping the scale and height of turbines, but what are the hurdles of ever-increasing size and altitude? Molly Lempriere talks to GE engineering and product development leader Vincent Schellings.
GE Renewable Energy announced in March that it will build the world’s largest wind turbine, a towering structure that will reach 260m above sea level. It is expected to take three to five years to design and construct, and more than $400 million in investment.
Each of the three rotor blades, designed and manufactured by Danish company LM Wind Power, will be 107m long – that’s longer than a football pitch. This size means it will produce 45% more power than any wind turbine previously built, with a capacity of 67GWh annually. These turbines will, therefore, be able to power 16,000 European homes.
GE’s Haliade-X is the latest in a line of turbine expansions that have mirrored the growth of the wind power industry itself. “The offshore wind market is set to grow dramatically in the next couple of decades,” says GE engineering and product development leader Vincent Schellings.
“With a projected industry growth of 17–90GW in the next 12 years, offshore wind is expected to account for 15% of the global wind industry going forward, according to Bloomberg New Energy Finance. In 2017, offshore represented 8% of global wind installed capacity, and by 2025, it will represent more than 15% of global wind annual installed capacity.”
“Last year, 4GW of additional offshore wind power was installed and the offshore segment is moving towards 8GW per year,” Schellings adds.
An increase in the size of turbines comes with a multitude of benefits, in particular helping drive down the cost of wind energy. But despite the benefits, GE has lagged behind competitors in the race to create the biggest turbine, with Danish company Vestas earning the top spot, with its V164, with a height of 187m, and 80m-long blades, the equivalent of nine double-decker London buses. But Vestas’s turbine has a power rating of just 9.5MW, meaning it is to be dwarfed by GE’s 12MW Haliade-X.
But new technology brings new challenges, so what trials will these gargantuan turbines face?
More wind, more power
Wind speeds increase with altitude, thus the taller the turbine the faster it spins and the more energy it can generate. Furthermore, the wind is generally steadier higher up, easing power peaks and troughs, and increasing reliability.
“A higher capacity factor makes Haliade-X less sensitive to wind speed variations – meaning better predictability and the ability to generate more power at low wind speeds – and can capture more annual energy production than any other offshore wind turbine,” says Schellings.
Variability has been one of the main criticisms of renewable technologies, especially wind and solar power. The problem of downtime when the sun isn’t shining or the wind isn’t blowing has led many to deem such technologies unreliable, and to highlight the need for baseload generation through coal or nuclear.
So the increased capacity of the Haliade-X goes some way to alleviating this criticism. Taking advantage of all the wind available by harnessing the characteristically stronger and less variable winds higher up reduces the need to rely on expensive backups, such as batteries, adding to its cost-effectiveness.
By increasing the size of the turbines and not the wind farms, maintenance and operation costs will also remain comparable with previous offshore projects. “With fewer machines and foundations to install, in addition to reduced cycle times and a simplified operation, Haliade-X generates robust savings on overall project cost over the life of a wind farm,” says Schellings.
This is based on wind conditions on a typical German North Sea site, although the final location for the Haliade-X demo is still uncertain.
The greater the height at which the turbine operates, the longer the possible blade length, which disproportionately increases the energy capacity. As blade length doubles, the amount of energy it can produce is four fold, allowing for dramatic increases in capacity. GE predicts that a 750GW wind farm of Haliade-X turbines could power one million homes.
While onshore turbines struggle with wider clearances, space out at sea is less of a premium. Therefore, despite being five times the size of the Arc de Triomphe, land costs do not hamper the cost-effectiveness of the turbines.
Surviving the storm
Although bigger seems to be better in many ways, GE will undoubtedly face difficulties in the construction and installation of the monstrous Haliade-X. “The dimensions of a wind turbine of this size will be a first time in many ways, so we are getting prepared for that,” says Schellings.
As the turbine size increases so must its strength, to ensure the strong winds higher up are not its undoing. LM Wind Power has 50 years of experience building and testing turbine blades. At its testing and validation centre, storm conditions are simulated to put them through their paces. For its previous blades, this has included pulling a blade to and fro with the weight of 16 elephants, simulating wind forces of 100km per hour and conducting millions of bends to test for fatigue.
LM Wind Power has produced a fifth of all turbine blades in the world, at 205,000 already, and Haliade-X will mark its biggest project yet.
Beyond the physical problems to be faced by the Haliade-X project, there are broader issues going on in the energy industry. “With growth come challenges, specifically the challenge to compete with traditional sources of power generation, such as natural gas and coal, on a nonsubsidised basis in auctions and RFPs around the world,” says Schellings. “The development of the Haliade-X 12MW wind turbine will contribute to offshores challenges of decreasing the cost of energy in upcoming projects. Haliade-X will also contribute to offshores growing momentum.”
Despite the successes seen in the development and deployment of wind power, it must constantly fight with other power sources to secure a market share. This may be hampered as countries, such as the UK, withdraw subsidies. In 2017, the UK Government announced there would be no further green energy subsidies beyond 2025.
And while it seems the benefits outweigh the hurdles of Haliade-X and, more broadly, larger turbines, just how big can they get? “Two decades ago we didn’t get much further than a 3MW machine with a 100m rotor, and that seemed too big at the time,” says Schellings. “Through technology development, growth is always possible, but you need the right technology in order to do it cost-effectively.”
Haliade-X is set to be the tallest turbine in the world, but there are already plans to top it. A team led by the University of Virginia and funded by the US Department of Energy’s Advanced Research Projects Agency– Energy, for example, is currently designing a turbine that would be capable of producing 50MW worth of energy. The two-bladed turbine, designed to mimic a palm tree’s ability to bend in the wind, could be an incredible 500m tall.
GE is hoping to have its first demonstration unit installed by 2019 and to begin shipping the Haliade-X by 2021.
An industry of giants
ABB has been selected to deliver its pioneering WindSTAR transformers, specifically designed for floating wind turbines, to MHI Vestas Offshore Wind, a joint venture between Vestas Wind Systems and Mitsubishi Heavy Industries.
The transformers will be installed in each of the three turbines on WindFloat Atlantic, a floating, offshore wind farm, comprising the world’s largest and most powerful wind turbines ever installed on a floating foundation. The 8.4MW wind turbines are 190m tall to blade tip, more than double the height of the Statue of Liberty. Just three of these turbines will provide enough electricity for over 18,000 households in Portugal.
The WindFloat Atlantic wind farm will come into operation in 2019. It will be positioned 20km off the coast of Viana de Castelo, Portugal, in a location where the sea is 100m deep. Traditional offshore wind turbines are secured onto the seabed and can only be used in depths of approximately 40–50m. This floating solution opens up large regions of previously unusable ocean to renewable offshore wind power generation.
ABB will supply WindSTAR power transformers that are specifically engineered to be extra resilient against strong vibrations and extreme and sudden movements encountered on floating wind farms. The compact transformers are all designed to fit into the tower of offshore turbines. These 66kV transformers for floating applications present an important opportunity to facilitate offshore wind farms installed in deeper water. Traditional wind turbines are not viable in deeper waters and require expensive and difficultto- install subsea infrastructure. The 66kV voltage level is the highest wind turbine rating in the industry, allowing for significant reduction in transfer losses and enabling higher efficiency.
In its recently published energy transition outlook report, DNV GL, the world’s largest independent energy advisory and certification body, forecasted that, by 2050, 12% of the worlds primary energy supply will come from wind energy, of which 20% will come from offshore wind. In relative terms, offshore wind is growing 85-fold (2050 versus 2016), which is the same growth rate as for Solar PV. As electricity consumption accelerates, bottom fixed and floating offshore windfarms will play an increasingly important role to ensure that society can meet this demand.