New battery technologies for eVTOLs: “We are trying to figure out the limitations”


Oak Ridge Laboratory

The Holy Grail within the emerging eVTOL industry is a major breakthrough in battery power. To discover a new technology that can radically improve the duration of batteries and lessen their need to be constantly recharged. Whoever makes this quantum leap and successfully patents it, is looking at riches beyond imagination.

Typical of the verve to find that Grail is U.S Oak Ridge National Laboratory (ORNL) based in Tennessee, “where researchers are working on more improved, longer-lasting batteries for eVTOLs,” reports sciencedaily.com. Their aim is “to figure out the limitations.”

To design this ultimate battery, the team is developing new energy-dense materials and learning how they degrade under extreme conditions. The researchers are also developing battery control systems. Not surprisingly, one thing the scientists have learned so far is that performance demands for electric air taxis can significantly reduce their longevity and durability.

This means such aircraft cannot rely on the same batteries that power a Tesla Model Y or Chevy Bolt, for example. That is because EV batteries usually drain at a steady rate, while eVTOLs require varying amounts of power for different flight stages like climbing, hovering and descent.

Marm Dixit

Marm Dixit, a ORNL lead researcher told sciencedaily.com, “Now we know more about what is required of the eVTOL battery, we’ll need to engineer systems differently to achieve that. Our focus is fundamental: What happens to the materials under these specific loads and operating conditions?” Adding, “Therefore, we are trying to figure out the limitations of the battery chemistry we have now, and then tune the battery to bridge that gap.”

Llias Belharouak, an ORNL Corporate Fellow who guides the research, remarked, “The eVTOL program presents a unique opportunity for creating a brand new type of battery with very different requirements and capabilities than what we have seen before. This requires us to answer questions about the interplay of battery safety, cycle life and stability at high temperatures, while balancing the need for short bursts of high power with energy reserves for longer-range flight.”

The first major takeaway from the study is that the power and performance demands for eVTOL batteries can significantly reduce their longevity and durability.

“The team made lithium-ion batteries at the DOE Battery Manufacturing Facility located at ORNL and ran them through simulated climb stages of eVTOL aircraft,” writes sciencedaily.com. “Scientists studied what happened inside the battery during cycling, including how much energy was rapidly accessible during the demanding takeoff phase, then tested the battery materials afterward for corrosion and other chemical or structural changes.”

The website goes on, “Systematic investigation linking actual flight profiles to real-time physical battery operation is rare. However, it is key groundwork for developing new battery chemistries to achieve safe flight performance. The study incorporates testing of a new ORNL-developed electrolyte, a material through which electrodes exchange ions against the current state-of-the art version used in lithium-ion batteries. Using the eVTOL mission profiles, the ORNL electrolyte performed better, retaining more capacity during the most power-demanding flight phases.”

Dixit points out, “Your battery is not just capacity at the end of 1,000 cycles. It’s what’s happening within a cycle that tells you whether your system is going to work or crash. And the stakes are much higher here because you’re asking how safe it is to go up in the air. This is a question we don’t know the answer to… yet.”

Energy Storage Area at Oak Ridge Laboratory

What drives researchers on toward the Holy Grail is also, of course, global climate change. “There is a strong incentive,” continues Dixit, “as during a period of such change, eVTOLs can help curb planet-warming. At present, the global transportation sector is responsible for contributing 14 percent of all air pollution.” One recent study found that only 10 countries and territories out of 134 are meeting air-quality standards.

The current Tennessee research is one of many strategies aimed at greening up air transport. For instance, another group of scientists are working on a new generation of biofuels to power planes that may contribute significantly less harmful pollution to the atmosphere.

Meanwhile, a growing number of major airlines, including American, Delta, and United, have pledged to achieve net-zero carbon pollution by 2050.

(News Source: www.sciencedaily.com)

  
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