IN DEPTH: GE's technology focus
The drone of chainsaws drifting across the fields in rural New England last summer did not sound uncommon, yet what was being sliced in half was not timber, but turbine blades at an operating wind farm.
On the other side of the US, six months later, high in California’s Tehachapi mountains, prototype steel trusses and architectural fabric panels were arriving in a dozen freight containers on the back of flatbed trucks.
The two scenes share a connection: both are central to GE’s strategy of developing technologies that can ratchet up turbine power output and help enlarge the company’s share of the global onshore market.
“Our philosophy is to continue to focus on driving toward the lowest CoE [cost of energy] and that means driving technology to ever-better economics to get to a subsidy-free position in wind,” says GE vice-president for renewables Anne McEntee. “We continue to see technology as the enabler going forward.”
The chainsaws at work on the wind farm in New England, which the developer does not want identified, were not being destructive: GE was testing an innovative method of lengthening the blades to increase the energy-capturing sweep of the rotors.
At this underperforming wind farm, two sets of 37-metre blades were brought down from two 1.5MW turbines and cut in half. A seven-metre fibreglass insert was then bonded onto each segment before the longer blades were bolted back on, increasing the rotor diameter from 77 metres to 91.
Results from the nine-month trial that followed have been “very encouraging”. The two retrofitted turbines saw an average increased output of almost 25%, bringing their sagging production levels “into profitability”.
“The extended blade programme... will provide a solution for all the turbines — from every manufacturer in the installed base — that have been performing below expectations,” says Keith Longtin, GE’s wind product-line general manager.
“Segmentation, if it offers life-cycle savings, has to be right. For land-based turbines the only way you are going to get rotor diameters of 140 metres and more cost-effectively is with a segmented blade.
“And because it is an insert, the blades are customisable for the full range of site conditions — the full seven-metre insert for a low wind speed site, other lengths and dimensions for other wind regimes.”
GE first explored the concept of a segmented blade over five years ago at the Netherlands’ ECN testing facility with trials of a 2.5MW machine outfitted with extended versions of the company’s 48.7-metre blades.
Following the success of the two prototypes in the US Northeast, further tests of the modular blade concept — which uses overlapping scarph joints to interlock the three blade sections — are planned for the Massachusetts Wind Technology Testing Center, along with more in-field trials.
Back on the West Coast, the contents of the containers have been pieced together to form a 97-metre space-frame tower —an “Eiffel-tower-like” lattice structure clad with high-tensile architectural fabric panels. The prototype structure, now topped with a 1.7-100 GE turbine, is part-way through a three-month testing programme.
For an industry moving towards taller towers — to get above the forest canopies in many wind-rich regions — the savings from the new-look tower will be substantial. According to GE’s calculations, 130-150-metre space-frame towers will be 20-30% cheaper than existing technologies, while 100-120-metre units will offer savings of up to 40%.
The tower will be launched to the market as a 139-metre version with a 2.75-120 GE turbine. It will use 30-50% less steel than conventional tubular designs and can be boxed up and trucked “pretty much anywhere in the world” for on-site assembly.
“It is a leap forward for the industry,” says Longtin. “It shows clearly there is great potential for cost-effective scale-up of wind turbines with much taller towers.”
McEntee adds: “The space-frame tower is an example of a technology that will get us into sites where we couldn’t go before [due to the size of traditional tower sections], while changing the economics for the better of the overall turbine.
“This tower will drive more usage of land that might not have been considered in the past for wind turbines.”
In particular, it is seen as being a “perfect fit” for the emerging markets of heavily forested sites in Scandinavia and the rest of Northern Europe, says Longtin.
“The next round of permits going out in these regions, they are looking for 140 metres,” points out Longtin. “And our design can be extended in 12-metre sections, so we can go still higher, as required. The physics aren’t limiting.”
The first commercial outing for the space frame tower will be in Germany next year, for an as-yet-unidentified developer.
The new blade and tower designs are being fine-tuned against the backdrop of GE’s campaign to move from “turbine-centric” thinking towards a holistic “industrial internet” view of wind farms as integrated power plants with sensor- and battery-fitted “brilliant” turbines sharing data to boost performance and production and levelise volumes of electricity flowed on to the grid.
“Having more intelligent control systems means we can both optimise power output and better manage the loads — and if we can do this, then we can put bigger rotors on these same turbines,” says Longtin.
“It is a natural evolution to move from controlling a single turbine to controlling — and so optimising — a whole wind farm.”
Buoying a targeted doubling of market share in Europe, from 6% in 2012 to 12% in 2015, GE recently announced a series of deals, including 110MW of orders for its “brilliant” 2.5-120 turbine in Germany, to developers Juwi, Abo-Wind, Max Bögl Wiesner and Pfalzwerke.
In the US, a trio of the “intelligent” machines — which use data-driven, turbine-to-battery communication to predict power production in 15-60-minute intervals — is being wired into developer Invenergy’s 86-machine Goldthwaite wind farm in Texas.
GE sold 59 of the 1.7MW version of the turbine to NextEra Energy last year for a development in Michigan.
The company’s recently unveiled “Japanese” model turbine, a 2.85MW machine designed for low wind speeds but with “typhoon-proofing”, will feature the same technology as the “brilliant” 2.5-120 turbine.
“This new marriage of battery storage and advanced software within a wind turbine allows forward-thinking producers to shift the winds in its favour by increasing wind power’s efficiency and short-term predictability,” says Longtin. “It is also about tailoring turbines for specific regions and even sites.”
McEntee concludes: “Ten years ago, wind turbines in the US were producing at a CoE of $0.15 per kWh; today they are $0.05-$0.07/kWh, so we have dropped the overall cost of energy by 60% and that has been done through investment in technology.
“We are continuing to invest in new technology because we believe there is more progress still to be made in RoI [return on investment].”