The sharp white blade stretches more than 80m back from the lorry cab, weighing heavily on a trailer almost comically far back.
Engineers, interested members of the public and irate drivers hold their breath, and finally the wind turbine blade is around the corner. The lorry continues at its stately pace.
Later, the blade is lifted high above the ocean and carefully fitted into the hub of the turbine’s nacelle, the tower previously fitted into a foundation that was loudly pounded into the seafloor by a hydraulic ram. It is a long, slow, complicated and staggeringly large-scale process that is increasingly familiar around the world. Some companies hope to simplify it – but others offer a completely different vision of wind power.
Lighter than air
Airborne wind power includes several different technologies in various permutations. A kite, drone, or inflatable is attached to a tether and flown – either under its own power or lifted by the wind – high above the ground. When it is in position, one of two things generally happens. Either propellers turn into turbines to generate electricity in flight, or the craft moves carefully on its tether, which turns a generator on the ground. Average deployment times could be one-hundredth of those for familiar horizontal axis wind turbines.
The airborne devices are not yet widespread but that could all change in the coming years according to Dr Peter Harrop, chairman of market research organisation IDTechEx, which has published his new report Airborne Wind Energy 2019-2039. After more than a decade of development, several companies are reportedly preparing to enter the market this year.
Sales “will happen,” Dr Harrop tells Professional Engineering. “Maybe not this year but next year. You’re talking $100,000 for something that might be 30kW, so three-times the cost of solar.”
Glasgow-based airborne wind company KPS hopes to sell a much more powerful 500kW unit by 2025. Founded seven years ago, the firm first developed a ‘yo-yo’ style design with two soft kites flying simultaneously before focusing on a larger concept, as backer Shell was joined by E.ON and Scottish Enterprise.
Despite KPS’ ambitious energy generation aims, head of engineering David Stewart tells Professional Engineering that the company is not aiming to muscle in on the traditional turbine market.
“If you’re a big investor we can say we’re a lot cheaper, but who’s going to believe that? We are going to go after areas that horizontal axis arrays haven’t penetrated.”
Those areas – small islands and remote locations – can be targeted because of the KPS device’s clever engineering. Instead of a ‘soft wing’ inflatable or a rigid drone-style unit, the concept has an ‘air beam’ wing that inflates to become rigid.
KPS hopes to sell a 500kW unit by 2025 (Credit: KPS)
“We are striving to build as light a structure as possible, but something that is maintainable and repairable,” he says. “If we were going to get any holes, we’ve got multi-layered structures… so it’s only going to be a slow leak.”
He adds: “Because it’s a fabric wing, we should be able to fold it up and fit it easily in a standard shipping container and then inflate that where needed. That is completely different to a horizontal axis wind turbine.”
With no 80m+ lorry load, specialised ships and hydraulic rams in the KPS air beam’s deployment, it could also be particularly suited to rapid roll-out.
“If you can get it in to an area… we would be able to set up. It’s certainly a possibility that in some areas that have been ravaged by a natural disaster, we could provide local power while they get their national infrastructure back online.”
Flexibility and easy transportation makes airborne wind turbines ideal for other remote or hard-to-reach areas in future, says Dr Harrop. Opportunities include replacing rural diesel generation for the new generation of farming robots, powering army frontlines to replace dangerous fuel supply missions and providing electricity for offshore fish farms or subsea robot charging points. And although companies are not targeting horizontal wind turbines’ slice of the market, they could jump in to follow them.
Traditional turbines have lifespans of 20-25 years and when operators close offshore wind farms, they face leaving behind sparse forests of huge concrete and steel pillars. Firms such as KPS hope to offer the sites new life by flying their 5-6m wingspan devices from abandoned towers. “It’s probably cheaper than decommissioning these sites and you get an extra 20 years of operation,” says Stewart.
Up where the air is clear
With the most powerful horizontal axis turbines offering up to 8.8MW, airborne turbines will not compare for energy generation and the applications suggested by both Stewart and Dr Harrop are decidedly small-scale. That is no issue for the nascent sector, claims the report author, as it will fill numerous niches in the new, decentralised energy system.
“I think that’s more intelligent and has a better chance of success, but there’s a weakness at the moment. While wave power is taking orders of maybe $200m… [airborne developers] need to prove the reliability,” he says. “Will they work most of the time?”
KPS is confident its design is resilient and maintainable, and much bigger companies are showing intent by backing their own versions of the technology. Google X’s Makani project uses kite-mounted turbines to generate electricity in-flight.
One key aspect of airborne wind could also lift it higher in years to come – with long tethers, kites and drones can fly much higher than traditional turbines, where the wind is stronger and more consistent. The KPS website mentions a potential altitude of 450m, while the world’s tallest horizontal axis installation is less than 250m. “The ability to fly at the altitudes we’re flying at gets you out of an awful lot of turbulence,” says Stewart. “We get a better wind resource up there.”
Consistent wind means airborne wind systems could operate without batteries, sidestepping one of renewable energy’s biggest issues. Such a proposition could be very tempting for energy companies, and they might find themselves echoing Dick Van Dyke’s iconic chimney sweep in the coming years.