A double-edged blade

Climate change’s presence becomes more and more difficult to dismiss each year, as people witness once-in-a-lifetime weather events breaking out with increasing regularity. Parts of the US are already witnessing heatwaves and forest fires that have grown more frequent and severe as time goes on.

The battle, then, is not something that needs preparing for in the future, but is very much taking place today. Wind energy is one of the cheapest and most efficient ways of producing green energy, and has become the cornerstone of many governments’ carbon neutrality plans. 2020 was a record-breaking year for wind turbine installation – spurred on in part due to the deadlines for feed-in tariffs and subsidies in China and the US – with 114GW of new wind capacity added globally, representing an 82% increase year-over-year according to Wood Mackenzie. Such rapid development brings many challenges, most recently supply chain robustness and, now, sustainability – especially given the nature of renewables and the expectations around them. As many turbines start reaching the end of their lifespan, the industry is only just coming to terms with their recyclability problems.

About 85% of turbine components – including steel, copper wire, electronics and gearing – can be recycled or reused, but turbine blades present a number of challenges. During the early years of turbine production, balsa wood or PVC foam were, essentially, the only component choice for blade cores. The core sits within a skin of resin, fibres and core, leading to one of the main issues with recycling: that there are at least three different materials to separate – although, often, it’s just a mixture of different types of resins and fibres, making the recycling process very difficult.

Tens of thousands of ageing turbine blades around the world are coming to the end of their life cycle, and questions are being raised over exactly what to do with them. In the US alone, about 8,000 will be removed each year between 2020–24. Europe, meanwhile, has about 3,800 coming down annually from 2020–22. This will only increase as most of these blades are coming from turbines built over a decade ago, when installations were less than a fifth of what they are now. Today, there are a number of initiatives under way to address this. Some of these blades are being burned in kilns to create cement or as fuel in power plants, and some original equipment manufacturers (OEMs) are finding innovative ways to reuse them. More needs to be done, however, to prevent turbine blades from ending up in landfill. Looking at future designs, OEMs are searching for more sustainable alternatives by experimenting with more easily recycled fibres, resins and PET foam core.

In the case of PET, this is increasingly seen by parts of the industry as a strong, light, recyclable option over incumbent materials. The latest version can help to reduce resin uptake by the foam during composite manufacture, resulting in a lighter blade and lower total cost.

Many, however, continue to hold on to the more traditional core materials for a variety of reasons. China, which makes up around 40% of the global wind energy market, initially purchased designs from Germany, the Netherlands and other parts of northern Europe when it started investing in wind energy – designs that typically relied on balsa and PVC.

Since its introduction to specific applications in wind, PET has increased its market share, initially at the expense of other foam core types such as PVC, SAN and, most recently, balsa, as the material iterates and improves on its offerings compared with alternatives.

“With balsa wood, it’s typically a six-year growth cycle,” explains Ray Lewis, market segment manager of wind energy at Diab, which has caused issues when demand has been prone to fluctuation and rapid spikes in recent years. “If you suddenly want them tomorrow, unless there’s plenty that happens to be available because someone planned them five years ago, you really have a bit of a problem – or, conversely, you build excess stock.”

In recent years, political drivers, Covid-19 and the 2020 demand rush have challenged balsa supply. The latter, driven mainly by the looming deadline for Chinese feed-in tariffs at the end of the year, has been most heavily felt in Ecuador, supplier of 75% of the world’s balsa. Local communities were underpaid for their labour and illegal logging became widespread as the nation’s balsa resources were stripped away. As supply got scarcer, the prices doubled or tripled, which, in turn, led to parts of the industry designing blades that have alternative builds requiring different materials, so that they have supply chain flexibility to mitigate risks. Such disruption has occurred before, but as today’s volumes are so much higher, the consequences have had a greater impact. At the same, PET suppliers had been building capacity, so the opportunity to switch had become possible.

“OEM’s constantly seek to improve their quality, and a synthetic material is seen as having less variables in volume production,” Lewis says. “With such production globalising, often near to OEM blade hubs, the benefits of localisation on sustainability and cost is clear.”

However, to match the strength of balsa, PVC would need to be present in a much higher density, which would be very expensive. PET has similar disadvantages, except the cost is a lot lower. “In the past year or two, some blade designer OEMs have been coming up with the heavier weight PETs to replace balsa,” Lewis says. “Which is a really big paradigm shift – from wood to foam.”

Ultimately, lessons need to be learned from the past as we plan for the future. The industry has never been as focused as it is today, whether it’s dealing with old blades, moving from balsa to PET, or manufacturing recycled resins and fibres. However, while the quest for a fully recyclable wind turbine is a worthy one, the real game changer lies in going bigger and in maximising a turbine’s benefits over its lifetime, according to Lewis.

Harness the breeze

Rather than going bigger, however, some companies are looking at different ways to alter the design of wind turbines. Some, like the Madrid-based Vortex Bladeless, have come up with designs that completely remove the turbine blades, creating a vertical cylinder that waggles back and forth in the breeze, producing electricity by harnessing the vibrations. Alpha 311, on the other hand, manufactures a small vertical wind turbine that can generate electricity without relying on wind. Instead, the 2m-tall turbine, made from carbon fibre or recycled plastic, is designed to fit on to existing street lights and generate electricity as passing cars displace the air. The company’s CEO and co-founder, Barry Thompson, explains how he and fellow co-founder John Sanderson came up with the idea behind the turbine.

They had started working together on different projects, travelling up and down the UK on motorways, and would often get stuck behind trucks. “You can see the airflow that’s coming off the truck just by the movement of the trees and the foliage that it goes past,” he says. “If you’ve ever stood next to the road as trucks come passing, you feel the impact. [The project] grew from there.”

The company’s goal was to simply generate enough electricity at a low cost in order to power a street light. However, rather than proving capable of producing the 150W per day needed to power a street light, the turbines Thompson and Sanderson developed could churn out 1kW an hour, comparable with 20m2 of solar panels according to independent research commissioned by the company.

By using the infrastructure that was already in place – namely, the lighting columns themselves – Alpha 311 was able to massively reduce the cost of installing each turbine. Its initial prototypes were carbon fibre, but the Covid-19 pandemic caused problems with production, so the company went looking for alternatives and made new prototypes out of correx plastic. From there, Thompson says, they started looking at recycled plastic as a potential option.

He is quick to state that the technology his company came up with isn’t new – adamant about it, even – but instead the real genius in this product was achieved through the implementation of well-known science. “If you want to increase the amount of electrical energy for wind turbines, you’ve got to make it bigger. You increase the blade size, you increase the swept size, and that’s why we now have 850ft-tall wind turbines – because the blades are so long,” he says, laying out the route his company went down instead. “Or you double the airspeed impacting upon it. You can’t do that naturally, but you can if it’s in the middle of a road.”

By placing a turbine in the central reservation between two dual carriageways, with cars travelling in opposite directions on either side, you can double the airspeed impacting the wind turbine. And by doing so, the volume of air available to be converted into electricity is increased by up to a factor of eight, according to Thompson.

The power these turbines generate can be used elsewhere, of course. A 5G microcell with a 1km broadcast, for example, uses between 5–7kW of electricity per hour. However, Alpha 311 could have 28 turbines inside of a kilometre – what happens to the rest of the energy? Ideally, it’s fed back into the local grid, which helps to lower the transmission costs in the area, thereby lowering the cost of electricity. “The bulk of electricity generated by offshore wind, or even onshore wind, tends to be in more remote places, which means you’ve got to transmit it further [and] keep stepping it up to get it to where it’s needed,” Thompson explains. “But if you produce it where the demand is, you don’t have to do that – so the cost comes down.

“Energy generation itself isn’t particularly expensive to do, but transmitting it can be very expensive. If you can provide lower-cost electricity to low-income communities, you can help lift those people out of poverty.”

Thompson notes that he doesn’t see Alpha 311 replacing big energy producers in any real shape or form. Instead, he wants to work alongside them, generating electricity locally in communities where it’s needed, helping the local grid and clearing congestion. This, then, could free up the bigger energy producers to serve bigger industry, which tends to have the biggest draw on local communities in any case.

On the right track

In terms of sustainability, however, Thompson is hoping that the company’s new thermal plastic prototypes will prove to be a winner. These turbines will be a lot cheaper to produce than the company’s original carbon fibre models, made instead with recycled plastic waste and strengthened with glass fibre from recycled glass. The cost of the materials, then, goes from hundreds of pounds for carbon fibre to only £4. At the end of its life cycle, unlike its larger cousins, these turbines can simply be put into a chipper and the waste material used to produce parts of other turbines.

“The great thing is that companies are now looking at the impact,” says Thompson. “We can’t bury these [blades] in landfill. We can’t come up and burn them – it’s ridiculous.”

Initiatives like Alpha 311 may be able to help drive the effort towards greater sustainability in their own way, but it’s the larger, multinational turbine manufacturers that will need to provide the solution. But, as both Lewis and Thompson have stated, many of these companies are being proactive about this issue, and actively searching for an answer.