To produce wind power, all you need is a turbine and a temperature differential that causes, you guess it, wind. Power is produced on-site by turbines that can last some 20-25 or so years. This makes wind power pretty darned sustainable, right?
According to the National Clean Technology Conference and Exhibition, a wind farm with 80 turbines will generate about 53 million MW and 7 grams of carbon dioxide per kilowatt-hour in it 25 years lifespan. Fossil fuels generate about 865 g of carbon dioxide per kilowatt-hour, or approximately 45 million tons of carbon dioxide in its lifetime.
To be truly sustainable, though, wind turbines need to be designed to be recyclable and/or with recyclable materials.
This goes for home wind turbines too.
What is a wind turbine made of?
According to a report from the National Renewable Energy Laboratory, wind turbines are predominantly made of:
- Steel (71-79% of total mass)
- Fiberglass, resin, or plastic (11-16%)
- Iron or cast iron (5- 17%)
- Copper (1%)
- Aluminum (0-2%)
Many of these components are sourced in the United States and turbines are often manufactured domestically, which dramatically reduces their overall environmental footprint. The 2017 Wind Technologies Market Report found that turbine towers are 70-90% domestically sourced, blade and hub components are 50-70% domestic, and nacelle assemblies are over 85% domestically sourced. Other parts are more likely to be imported, such as the pitch and yaw systems, bearings, bolts, and controllers.
A single 60 m long fiberglass blade weighs about 17 tonnes. This means that just one 5 MW wind turbine contains at least 50 tons of plastic composite in the blades alone. Core materials in the blade include polyvinyl chloride foam, polyethylene terephthalate foam, balsa wood (in the fibers and epoxy) and polyurethane coatings.
Up until the 1980’s, though, wind turbines had long been made with wood, steel, aluminum, and other recyclable and repairable materials. The fiberglass blades and plastic components began to show up with the invention of larger wind turbines. These take advantage of the fact that wind increases with height, and power output quadruples when you double the rotor radius. From the 1990’s, turbine blades increased from around 50 m to 120 m a decade later. Off-shore wind turbines now frequently have rotors measuring a staggering 160 m in diameter, and a 220 m rotor diameter is being built in Holland.
This brings us to the fun irony that as wind turbines get more efficient and powerful, they also become less sustainable. And, even the substitution of fiberglass for wood or flax fibers, which sounds great in principle, means more petroleum-based epoxy resin is used overall as the natural fibers soak up more of it.
Wind turbine recycling and lifecycle sustainability
Around 84-90% of a wind turbine can be recycled as this is made up of steel, copper, and electronics, which can be salvaged at end of life. The blades are a different matter. These can stretch up to 100 feet and are made of uncrushable fiberglass that can’t be easily recycled. Instead they have to be cut up on site using a diamond saw and are then packed onto flatbed trailers and sent to landfill.
Turbine blades are, unsurprisingly, built to be strong and hard to cut. They’re also incredibly smooth and, of course, huge, which makes them difficult to handle (trash compactors and saws slip off the surface of the blades) and impossible for smaller recycling facilities or landfill operators to take on.
While the fiberglass or resin is usually inert and non-toxic, these blades take up a lot of space in landfill and represent a huge waste of resources that could, ultimately, be reused to make other products. Not to mention, these blades are so huge that big rigs can only carry one blade at a time, which translates to huge transportation costs and associated carbon emissions.
Turbine blades can last up to 20 years, but a 10-year lifespan is more standard as they are often replaced with bigger, more efficient and powerful blades. In the U.S. alone, about 8,000 wind turbine blades are now removed annually. In Europe, where wind power was adopted far earlier, about 3,800 blades are expected to be decommissioned annually through at least 2022. And because there are strict restrictions on what can go into landfill, some blades are burned for energy, even though this emits pollutants and is a very poor and inconsistent source of power. In fact, because fiberglass isn’t combustible, around 60% of the scrap remains as ash (the rest becomes air pollution).
Some companies are working on recycling facilities that can process these blades and use the fiberglass to make parts for vehicles and agriculture and sports equipment. Scientists are also working on ways to turn the blades into pellets or boards for using in flooring and walls. One company, Global Fiberglass Solutions, claims to be able to recycle 99.9% of a blade and handle 6,000-7,000 blades a year per plant. They already have a year’s worth of accumulated blades to process though and are hoping demand increases for the products, so they can increase how many blades they can take in.
The European recycling facility Veolia has tried grinding the blades to dust to extract chemicals. Their aim is to make wind turbines truly sustainable.
Interestingly, many of the blades currently going into landfill are being marked with GPS coordinates, so they can be dug up and reused if recycling becomes easier and more economically viable.
New materials and wind turbine designs for sustainability
The waste generated from defunct wind turbines is minimal compared to the overall waste going to landfill in the U.S. It is an emerging problem, though, and, given its nascency, the industry has a good chance to nip this waste in the bud and create a truly circular economy.
The Danish company Vestas, which manufactures turbines in Colorado, has announced a zero-waste goal for 2040, for instance. More modern designs may also last 30 years or more and be able to be repaired rather than scrapped.
As for design, one option to make a fully recyclable wind turbine is to forego the resin and fiberglass altogether and use steel blades. For larger turbines, this doesn’t work as steel is too heavy. For smaller installations, however, steel blades may be a more sustainable alternative, for now at least. And there’s also a possibility that larger installations could look into using lighter steel alloys that are also fully recyclable. Steel is about 90% recyclable and making steel blades can cost about 90% less, is faster, and is more accurate than making similar blades with plastic resins and fiberglass. Although steel blade were talked about with excitement about five years ago, not much has happened since, and newer, lighter, technologies seem to have taken off instead.
A wood-carbon blade has also been proposed. These would contain less plastic overall, and because the plastic isn’t enmeshed with the wood, it can be separated out easily for complete reuse of all the materials. These wood-carbon blades still contain a lot of plastic though, with a three-bladed 5 MW wind turbine producing 7.5-18.4 tonnes of waste that can’t be recycled, compared to 50 tonnes for a conventional blade.
Current turbine blades are made with resins called thermosets that become solid during production as they react with heat. Like cooking an egg, this process is not reversable. The resins cannot return to their original liquid state, which means the fiberglass and core of the blade, usually made from balsa wood or foam, are trapped and unrecoverable. The problem, then, is to create thermoplastic resins that can be turned back into liquid under high heat, releasing the materials for reuse.
A team at Vanderbilt University’s Civil and Environmental Engineering department has been working on this kind of resin. Their creation, called Elium and now made by a company called Arkema, self cures, meaning it makes its own heat and cures at room temperature without creating flaws in the fiberglass. This reduces the overall energy demand for making turbines initially and allows the fiberglass blades to be recycled at the end of their life.
Last month, Arkema won the 2020 Pierre Potier Prize for its Elium liquid thermoplastic resin which allows the manufacture of 100% recyclable wind turbine blades. At end of life, the blades are first ground and then heated to depolymerise the resin. This allows it to be separated from the fibre filler. After purification and reformulation, the process yields a new liquid thermoplastic resin with the same characteristics as the virgin resin.
Wood wind turbines
One of the most interesting ideas, perhaps, as to how to reinvent wind turbines to be more sustainable is to go back to making them out of wood. While these turbines would need to be smaller, they could be almost entirely made of sustainable, renewable materials, and would be a carbon sink in themselves. If they were built on-site from materials gleaned from managed forests, this would represent the idea for a circular economy and significantly reduce manufacturing costs and associated transport emissions. Wood wind turbines may even be more visually acceptable and less of a danger to bats and birds.
One European company is now installing wooden wind turbines in unlikely places, such as small towns and on farms. EAZ Wind, founded by four windsurfers, aims, to provide green electricity for residents who otherwise wouldn’t be able to install a giant wind turbine. The turbines, when installed on 15 m tall towers, produce around 30,000 kWh of electricity per year, which could power around ten Dutch households. One of the turbines costs about 46,000 euro, and the payback time is about 7 to 10 years in windy spots.
The future of energy production
The wind power industry looks eager to figure out current design issues and make more sustainable choices, which will give wind power a real role in the future of energy production. In the meantime, if you’re looking to retrain for a new career, the Bureau of Labor Statistics projects that wind turbine service technicians will be the second-fastest growing occupation between 2018 and 2028, at 57% growth. The fastest? Solar photovoltaic installers. The future of work is green too!