Lightning No Match for Wind Turbine Blade Protection System
Standing hundreds of feet above ground, wind turbines — like tall trees, buildings, and telephone poles — are easy targets for lightning. Just by virtue of their height, they will get struck.
Lightning protection systems exist for conventional wind turbine blades. But protection was needed for blades made from a new type of material—thermoplastic resin composites — and manufactured using an innovative thermal (heat-based) welding process developed by scientists at the National Renewable Energy Laboratory (NREL).
Thermoplastic materials, like plastic bottles, can be more easily recycled than the thermoset materials commonly used to make wind turbine blades today. While thermoset materials need to be heated to cure, thermoplastics cure at room temperature, which reduces both blade manufacturing times and costs.
NREL’s patent-pending thermal welding process for thermoplastic blades allows for these benefits and even adds to them by replacing the adhesives currently used to bond blade components. The use of welding instead of adhesives eliminates the downsides of added weight and cracking potential.
While thermal welding offers benefits, it also requires adding within the blade a metal heating element — which can attract lightning. As a result, a team of NREL researchers led by Robynne Murray and supported by General Electric (GE) and LM Wind Power (a GE subsidiary) invented a new lightning protection system to keep the novel thermoplastic materials safe.
Thermal Welding Goes for the Patent
In 2018, Robynne Murray, an NREL engineer who specializes in advanced manufacturing methods and materials for wind turbine blades, received a two-year NREL Laboratory Directed Research and Development award to research thermal welding of thermoplastic wind turbine blades.
To make one of these new blades, a vacuum pulls liquid thermoplastic resin into the fiberglass material that is placed in a mold for each blade half. To weld the blade halves together, scientists sandwich a conductive material — such as an expanded metal foil or carbon fiber — between the two blade components and attach a wire to a power source. This creates the heating element. As current flows through this element, the thermoplastic materials melt. Once they are melted, the current is switched off and the bond cools under pressure.
Murray’s research demonstrated that thermal welding can effectively bond thermoplastic wind turbine blade segments. She submitted a patent application on the process in 2018.
A Pathway for Lightning
Thermal welding works. But it leaves the conductive heating element, which can attract lightning, within the blade.
“Thermal welding is an important step in the progression of commercializing thermoplastic materials for wind blades, but what happens when lightning strikes a thermal-welded blade? That was an unanswered question and a big concern,” Murray said. “For thermal welding of thermoplastic blades to become commercially viable, it is critical that the conductive bond lines be protected from a lightning strike.”
Partnering with GE and LM Wind Power, Murray submitted a research proposal to the U.S. Department of Energy’s (DOE’s) Technology Commercialization Fund (TCF). TCF awards are designed to advance technology developed at national laboratories toward commercialization while encouraging lab-industry partnerships.
“With our partnership with GE, a company that can take the thermal welding process to commercialization, our TCF was a strong proposal,” Murray said. “Together, we wanted to determine whether we can protect these blades from lightning strikes and eliminate a big reason to stop us from using the technology.”
In 2019, the team received $150,000 in TCF funding; GE matched that amount.
The research partners set up shop in NREL’s Composites Manufacturing Education and Technology (CoMET) Facility to demonstrate that thermoplastic blades sealed using thermal welding can be protected from lightning strikes.
The team infused an expanded aluminum foil into the blade skin to divert lightning current away from the metal heating elements. They then completed experiments using a simulation that showed that a lightning strike would not cause blade failure with the lightning protection system in place.
Lightning protection To build a lightning shield for their innovative wind turbine blade design, the research team added an expanded aluminum foil layer (left) and a carbon-fiber heating element at the bond lines (right) to enable thermal welding of the blade parts. Photos by NREL
Lightning strike. Researchers used a lightning simulation technique to see where lightning might strike the blade and found that, typically, electricity hit the tip of the blade or one of the edges—but not inside the blade or welded seams where it could cause excessive damage. Photo by NREL
Physical damage tests — which subject the blades to high currents of electricity — demonstrated that about 80% of the electric current went into the expanded aluminum foil layer for lightning protection and not into the blade skin. The carbon fiber beneath the damaged area of the tip was also unscathed.
The research confirmed the design can protect wind turbine blades against failure caused by lightning strikes.
“LM Wind Power and GE Research were excited to work with NREL on the development of this technology and appreciated the support by DOE’s Technology Commercialization Fund. Thermal welding technology for thermoplastic, recyclable wind blades offers a significant opportunity to impact the sustainability and carbon footprint of wind blade structures,” said James Martin, director of blade platform deployment for LM Wind Power. “NREL’s focus on mitigating the lightning damage risks associated with the electrically conductive elements in the welded bond is a key challenge to be overcome, and their work has helped mature the technology toward potential commercialization.”
Still More Questions To Answer
The project has already delivered two strikes against lightning. Murray’s work developing a market-ready thermal welding system, however, is still at bat.
“We answered the question about lightning. But there are more questions to answer and more work to be done,” Murray said. “The next step for us is to do structural validation of thermally welded blade bond lines and blade tip segments. I hope we can do this in the next year or so.”
Read more about this project in Wind Engineering.
Article courtesy of NREL.
According to a Tesla Semi customer, the electric truck program is suffering more delays and a price increase that is described as “dramatic.”
Tesla Semi has seen many delays, more than any other vehicle program at Tesla.
It was initially unveiled in 2017, and CEO Elon Musk claimed that it would go into production in 2019.
In late 2022, Tesla held an event where it unveiled the “production version” of the Tesla Semi and delivered the first few units to a “customer-partner”: PepsiCo.
More than 3 years later, the vehicle never went into volume production. Instead, Tesla only ran a very low volume pilot production at a factory in Nevada and only delivered a few dozen trucks to customers as part of test programs.
But Tesla promised that things would finally happen for the Tesla Semi this year.
Tesla has been building a new high-volume production factory specifically for the Tesla Semi program in a new building next to Gigafactory Nevada.
The goal was to start production in 2025, start customer deliveries, and ramp up to 50,000 trucks yearly.
Now, Ryder, a large transportation company and early customer-partner in Tesla’s semi truck program, is talking about further delays. The company also refers to a significant price increase.
California’s Mobile Source Air Pollution Reduction Review Committee (MSRC) awarded Ryder funding for a project to deploy Tesla Semi trucks and Megachargers at two of its facilities in the state.
Ryder had previously asked for extensions amid the delays in the Tesla Semi program.
In a new letter sent to MSRC last week and obtained by Electrek, Ryder asked the agency for another 28-month delay. The letter references delays in “Tesla product design, vehicle production” and it mentions “dramatic changes to the Tesla product economics”:
This extension is needed due to delays in Tesla product design, vehicle production and dramatic changes to the Tesla product economics. These delays have caused us to reevaluate the current Ryder fleet in the area.
The logistics company now says it plans to “deploy 18 Tesla Semi vehicles by June 2026.”
The reference to “dramatic changes to the Tesla product economics” points to a significant price increase for the Tesla Semi, which further communication with MSRC confirms.
In the agenda of a meeting to discuss the extension and changes to the project yesterday, MSRC confirms that the project went from 42 to 18 Tesla Semi trucks while the project commitment is not changing:
Ryder has indicated that their electric tractor manufacturer partner, Tesla, has experienced continued delays in product design and production. There have also been dramatic changes to the product economics. Ryder requests to reduce the number of vehicles from 42 to 18, stating that this would maintain their $7.5 million private match commitment.
In addition to the electric trucks, the project originally involved installing two integrated power centers and four Tesla Megachargers, split between two locations. Ryder is also looking to now install 3 Megachargers per location for a total of 6 instead of 4.
The project changes also mention that “Ryder states that Tesla now requires 600kW chargers rather than the 750kW units originally engineered.”
Tesla Semi Price
When originally unveiling the Tesla Semi in 2017, the automaker mentioned prices of $150,000 for a 300-mile range truck and $180,000 for the 500-mile version. Tesla also took orders for a “Founder’s Series Semi” at $200,000.
However, Tesla didn’t update the prices when launching the “production version” of the truck in late 2023. Price increases have been speculated, but the company has never confirmed them.
New diesel-powered Class 8 semi trucks in the US today often range between $150,000 and $220,000.
The combination of a reasonable purchase price and low operation costs, thanks to cheaper electric rates than diesel, made the Tesla Semi a potentially revolutionary product to reduce the overall costs of operation in trucking while reducing emissions.
However, Ryder now points to a “dramatic” price increase for the Tesla Semi.
What is the cost of a Tesla Semi electric truck now?
Electrek’s Take
As I have often stated, Tesla Semi is the vehicle program I am most excited about at Tesla right now.
If Tesla can produce class 8 trucks capable of moving cargo of similar weight as diesel trucks over 500 miles on a single charge in high volume at a reasonable price point, they have a revolutionary product on their hands.
But the reasonable price part is now being questioned.
After reading the communications between Ryder and MSRC, while not clear, it looks like the program could be interpreted as MSRC covering the costs of installing the charging stations while Ryder committed $7.5 million to buying the trucks.
The math makes sense for the original funding request since $7.5 million divided by 42 trucks results in around $180,000 per truck — what Tesla first quoted for the 500-mile Tesla Semi truck.
Now, with just 18 trucks, it would point to a price of $415,000 per Tesla Semi truck. It’s possible that some of Ryder’s commitment could also go to an increase in Megacharger prices – either per charger or due to the two additional chargers. MSRC said that they don’t give more money when prices go up after an extension.
I wouldn’t be surprised if the 500-mile Tesla Semi ends up costing $350,000 to $400,000.
If that’s the case, Tesla Semi is impressive, but it won’t be the revolutionary product that will change the trucking industry.
It will need to be closer to $250,000-$300,000 to have a significant impact, which is not impossible with higher-volume production but would be difficult.
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