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Chasing the promise of cheaper and less obtrusive wind power generation

Bill Gates has just invested in Airloom, a US business that promises quieter wind power generation closer to the ground

The wind energy market is a very strange paradox. On the one hand, wind energy is almost universally accepted as a critical pillar to decarbonise the planet. It enjoys the stability of long-term policies and commitment by governments worldwide.

On the other hand, the entire wind energy industry seems to be in a deep crisis, with cancelled projects, financial losses and diminishing investor support. Industry observers note rising interest rates, materials costs and challenging issues across the industry’s supply chains.

Denmark’s Ørsted, a big wind energy player, has seen its stock price fall by more than 50 per cent since the start of the year to just one-quarter of its high point of €180 back in December 2021. Siemens lost nearly €1 billion in its wind energy division last year. Vestas, another Danish wind turbine supplier, saw its operating margins decline by over 360 per cent - from €428 million in operating profits in 2021 to a €1.15 billion loss last year.

The UK, striving to be a world leader in wind farms, received no bids at all in its most recent auction round for 15-year fixed-price contracts. It is expected to try again at double its original guide price (to over €80 per megawatt-hour).


Here in Ireland, multiple planning challenges are reducing the momentum behind several proposed wind farm projects, both onshore and offshore. Objectors point to potential damage to marine environments, visual impact to upland amenities and noise.

The combination of predictable certainty of demand, but stumbling suppliers and challenges in public acceptance would seem to be a perfect opportunity for innovators and new entrants.

The industry norm is “horizontal axis wind turbines”, the familiar blades spinning around a central generating hub at the top of a tall mast. Some turbines now have towers over 100 metres in height, with rotor diameters almost as long as the pitch at Croke Park. If such blades rotate at about 20 revolutions per minute, the blade tip speeds can approach 500km/hour.

The energy density at the blade tips far exceeds that at the central hub and the high rotational torque can generate three megawatts (MW) of energy or more. The huge machines benefit from more stable wind flows at height rather than at their tower base but they are complex to design and awkward to transport and assemble – as well as being a highly visible intrusion in our landscapes and maritime horizons.

An alternative design, a “vertical axis wind turbine”, has blades that spin merry-go-round style around a vertical shaft. These can position their generators at the mast base for easy access. However, they are relatively rare in part due to wind stress variation from ground level to the top of their blades, potentially leading to shorter lifetimes.

Ideally, we need a new turbine design with its generating equipment placed away from a central shaft and close to the dense energy at the blade tips, but also near to ground level for ease of access and maintenance, with smooth and uniform wind stress.

Bill Gates thinks a Wyoming-based start-up, Airloom Energy, has a solution and he has just invested $4 million (€3.65 million) in the business.

Airloom uses aerofoil-shaped blades, each about 10 metres long. They are vertically mounted and equally spaced apart on to a shared horizontal track, held in place typically about 25 metres above the ground. The blades power the track in a loop, changing direction around the loop much like a yacht sail can tack across the wind.

The wind stress across the length of each aerofoil is uniform since the blades are relatively short, thus overcoming the fatigue challenges of vertical axis turbines.

Instead of rapidly spinning blade tips powering a central rotating hub generator. Airloom places multiple generators around the track loop, in principle one on each of the small masts which support the track. The generators are thus close to the ground and easily accessible for maintenance.

The key insight is that the design is highly scalable because the track loop can be extended horizontally. Airloom’s current prototype track is short, but their test results and modelling show that 50kW could be generated from a 45-metre track with 10 blades; 250kW from a 72-metre track, and 1.3MW from a 400-metre with some 90 blades. Installed Airloom systems could even be upgraded, simply by extending an existing track and adding more blades.

The entire system is readily manufactured, and transported. Airloom asserts that an entire 2.5MW system would fit into a single standard cargo container. The “levelised cost of energy”, an energy industry-standard metric, is expected to be around €12 per MW, which is substantially less than current wind turbine systems.

The Airloom system is designed to be quieter than most existing wind turbines. Given its low height, it is not particularly visually intrusive and less dangerous to birdlife than traditional turbines. It is currently designed for flat ground, but an elevated track could conceivably be run above uneven or sloping ground should a flat site be unavailable.

Airloom potentially could disrupt the global wind energy industry.