海角社区

 

Higher power densities could transform future, green travel鈥攊ncluding by air鈥攁nd Louisiana is poised to lead in zero-carbon and low-carbon chemical fuel manufacturing.

Fuel cells are maturing as an environmentally friendly technology to power electric cars and trucks. It also holds advantages over battery-driven vehicles. Fuel cells do not have to charge for several hours, and recent research is enabling higher power densities, making the technology lighter, cheaper, and more portable鈥攚ith more room for people and cargo. Companies, such as Airbus and HyPoint, are even exploring fuel cells for planes, including commercial passenger airliners for up to 200 passengers鈥攁 mode of transportation long thought impossible to decarbonize. While taking a single long-haul flight on today鈥檚 jet-fueled airplanes generates more carbon emissions than the average person in many countries around the world produces in a whole year (or some do in a lifetime), fuel cell-driven travel emits nothing but water. Since transportation alone represents close to 40% of U.S. energy consumption (25% worldwide), it鈥檚 easy to see how fuel cells aren鈥檛 鈥渇ool cells,鈥� as Tesla CEO Elon Musk has joked, but a valid and complementary alternative to battery-driven electric vehicles鈥攅specially when those vehicles are large and have to go far, and the batteries that would be required to do so鈥攂ased on today鈥檚 technology鈥攚ould get too big, heavy, and expensive to be practical. Just as we have both gas and diesel engines, batteries and fuel cells meet different needs. Together, these green technologies could power almost all transport in the future.

Fuel cell vehicles began hitting the road in recent years. Toyota, Hyundai, and Honda now sell or lease fuel cell vehicles in California, and fuel cell buses are transporting people in several cities around the globe. General Motors has demonstrated the fuel cell truck prototype Chevrolet Colorado ZH2 Concept, which is powered by its Hydrotec fuel cell technology, and recently announced that it also will supply fuel cells for Nikola Motor鈥檚 Class 8 trucks.

海角社区 researcher Christopher Arges, an assistant professor in the Cain Department of Chemical Engineering, is helping to make fuel cell technology even more powerful. Today鈥檚 commercially available fuel cell vehicles, such as the Toyota Mirai, use low-temperature polymer electrolyte membranes (PEMs). Assembled into stacks, they need to be cooled with a radiator and sometimes also hydrated by a humidifier to work. To address these limitations, Arges and his team have invented a new type of extreme-temperature PEM that requires neither. This discovery holds great promise in increasing the power density in vehicles where multiple fuel cells could be stacked close together without the heat they produce turning into a performance problem. Arges鈥檚 PEMs actually perform better in the kind of heat you鈥檇 need to bake a pizza (200-250 C) than near the temperature of boiling water (100 C)鈥攖he current limitation of low-temperature PEMs. They also perform at very low temperatures, down to -70 C, about as cold as it ever gets in Siberia.

鈥淔uel cell technology is well suited to the future of clean, green travel and the impact of Chris鈥� research is huge.鈥�

Yu Seung Kim, fuel cell research team leader, Los Alamos National Laboratory

鈥淔uel cell technology is well suited to the future of clean, green travel and the impact of Chris鈥� research is huge,鈥� said Yu Seung Kim, a team leader of fuel cell research at Los Alamos National Laboratory, which has been working on the technology since the 1970s. 鈥淟ow-temperature fuel cells still have critical issues and the innovative concept of running fuel cells under hot and dry operating conditions will solve many of them.鈥�

In October 2019, representatives from Toyota came to 海角社区鈥檚 main campus in Baton Rouge, Louisiana to visit Arges鈥檚 lab and learn more about his work. Toyota recently announced plans to build heavy-duty fuel cell trucks for the U.S. market and both Toyota and General Motors attended a Department of Energy workshop Arges moderated last September.

鈥淚t鈥檚 critical for researchers like Chris to be working with someone like us who鈥檚 an integrator,鈥� said Craig Gittleman, engineering group manager for fuel cell materials and analysis at General Motors. 鈥淵ou cannot develop new technology in a black box. You have to look at membranes in combination with other things as far as performance, durability, and overall cost.鈥�

Gittleman has been working on fuel cell development at General Motors for 21 years. He sees opportunities for high-temperature PEM fuel cells in large trucks and heavy-duty applications where lots of low-temperature PEM fuel cell stacks would require large and expensive radiators to keep them cool enough to operate. He also sees advantages in using membranes that can perform at below-freezing temperatures, such as Arges鈥檚 PEMs, since General Motors is 鈥渘ot interested in developing a product we can only sell in certain parts of the world,鈥� such as in temperate California.

Operating fuel cells at high temperatures comes with challenges of its own, however. Going from cold to very hot and then back to cold again can cause stress for gaskets and seals and other materials in the fuel cell stack that would expand and shrink, changing the amount of compression in the stack and causing the materials to grow weak over time. This could be solved with better and more expensive gaskets and seals, Gittleman noted. Meanwhile, there are also inherent advantages to operating at higher temperatures. The platinum-based catalysts General Motors and other companies use actually degrade less rapidly in dry conditions enabled by high temperatures, and the fuel cells would be less sensitive to contaminants. Finally, the water within the fuel cells, which is generated as part of their normal operation, would remain in a vapor state at high temperatures rather than a liquid that can flood the system and jeopardize fuel cell performance.

鈥淚 see several potential benefits in Chris鈥檚 work,鈥� Gittleman continued, having recently invited Arges to give a virtual talk to his research group. 鈥淚 like his approach to performance and appreciate that he鈥檚 looking at different materials to meet specific needs.鈥� 

鈥淚 see several potential benefits in Chris鈥檚 work.鈥�

Craig Gittleman, engineering group manager for fuel cell materials and analysis, General Motors

A major challenge for the proliferation of fuel cell cars is the requirement to build a vast new infrastructure. In order to operate, fuel cells need oxygen and hydrogen. Oxygen is in the air, so that supply is free and readily available, while hydrogen (as H₂)鈥攁lthough the most abundant molecule in the universe鈥攎ust be made here on Earth by pulling H atoms from water or fossil fuels. This can happen with a zero-carbon footprint through water electrolysis driven by wind or solar power, or by steam-reforming methane, the primary component of natural gas. In the latter process, methane (CH₄) reacts with steam (H₂O) to produce hydrogen (H₂) as well as carbon monoxide (CO) and small amounts of carbon dioxide (CO₂). Steam-reformed methane generates over 80% of the hydrogen used today, and although this process produces carbon emissions, it鈥檚 much less than from gasoline production and combustion (and the carbon dioxide could be prevented from going into the atmosphere).

As the third-largest U.S. producer of natural gas, after Texas and Pennsylvania, Louisiana is a leader in hydrogen production and use in chemical manufacturing. Every seventh job in Louisiana is in the chemical industry and having that workforce, knowledge, and experience in the state matters to large companies such as CF industries, the world鈥檚 largest ammonia producer, which is building a new electrolysis-based green ammonia plant in Donaldsonville, Louisiana.

Ammonia, the third-largest chemical manufactured globally and used in fertilizers, requires hydrogen as a feed stock, or raw material. Water electrolysis plants, like the one CF Industries is building, can generate the hydrogen fuel needed for fuel cell vehicles in addition to meeting demand for ammonia production.

鈥淟ouisiana is very well positioned to 鈥榡ump start鈥� a broader, more integrated hydrogen economy," said David Dismukes, executive director of the 海角社区 Center for Energy Studies. 鈥淭here is role for Louisiana to play since we have considerable natural gas reserves that are still very economic.鈥�

Not only are fuel cells poised to transform the transportation sector, they can also be used to generate power for buildings, homes, and manufacturing facilities. They can power forklifts in large distribution centers, such as Walmart and Amazon, that don鈥檛 have time or patience for battery recharging but also cannot tolerate emissions from combusting fossil fuels. CF Industries expects hydrogen to provide 20% of the world鈥檚 energy by 2050, compared to less than 1% today.

鈥� As the third-largest U.S. producer of natural gas, after Texas and Pennsylvania, Louisiana is a leader in hydrogen production and use in chemical manufacturing. 鈥�

While some companies, such as CF industries, GM, Toyota, and the aircraft company ZeroAvia are eager to reduce their carbon footprint as much as possible and are looking to hydrogen derived from water-electrolysis, Arges believes hydrogen from steam-reformed methane will be an important and practical bridge to wider adoption of fuel cell technology.

鈥淚f we were to move to all hydrogen-based vehicles, it would cost something like 15 trillion dollars to build the necessary infrastructure from scratch,鈥� Arges said. 鈥淲hile California has been a leader in terms of refueling stations, we have a clear chicken-and-egg problem. What came first, the vehicle or the refueling station? In Japan, the government is actually building hydrogen refueling stations. And Tesla understands this problem鈥攖hey鈥檙e building charging stations for their own vehicles. This infrastructure challenge isn鈥檛 unique to fuel cells, but we need solutions that are pragmatic and near-term to make it possible for a lot more people to buy and drive fuel cell vehicles. And running fuel cells on hydrogen from natural gas seems to fit the bill.鈥�

Another possible bridge technology would be to put onboard reformers on trucks that could 鈥済as up鈥� on methanol and make hydrogen en route鈥攖his would also take up less room on the truck than a pure hydrogen system.

鈥淲e make methanol in Louisiana and you could take a gasoline station and retrofit it to pump methanol whereas you can鈥檛 really modify a gasoline station to pump hydrogen gas,鈥� Arges argued. 鈥淢ethanol is cheap, and you鈥檇 still be reducing carbon emissions, so this could be another bridge to fuel cell proliferation and reduction in greenhouse gas emissions.鈥�

Arges and his 海角社区 team hold a $500K award from the Department of Energy鈥檚 Advanced Manufacturing Office to figure out how to make more efficient and durable fuel cells in a shorter period of time using machine learning, or artificial intelligence. The researchers have already proven that it鈥檚 not just possible; their system is already working and suggesting reasonable solutions鈥攊n theory鈥攖hat Arges and his team can aim for and test in their lab. What makes their project unique is that they鈥檙e not only developing new materials for fuel cells (membranes and electrode binders), they鈥檙e also validating them in actual fuel cell devices. The machine learning is helping on every level鈥攎olecular, material, and in terms of device performance. It鈥檚 basic and applied research at the same time.

鈥淭his is important because a device has many different materials and components in it,鈥� Arges explained. 鈥淚t鈥檚 got a membrane, two electrodes, two bipolar plates, and lots of different operating parameters and variables that all depend on each other. Machine learning tools can help streamline and accelerate development in this large design space鈥攏ew materials to formulate that would turn out to be better for an actual fuel cell device.鈥�

Fuel cells are a bit like batteries in that they contain two electrodes (an anode and a cathode). While the electrodes in batteries are separated by a porous separator with liquid electrolyte, in fuel cells, the 鈥渕eat鈥� in the electrode sandwich is the non-porous membrane, or PEM. Part of the reason fuel cells are expensive is that the electrodes are 鈥渄usted鈥� with platinum, which acts as a catalyst and drives the reactions that create the electrical current. The platinum particles require a binder to hold them in place. The binder acts like a glue and also moves ions鈥攁toms or molecules with an electrical charge鈥攂etween the electrodes and the PEM.

鈥� By using artificial intelligence, Arges expects to cut a total development time of 15-20 years down to 1-5 years. 鈥�

Arges is quick to point out that promising materials don鈥檛 always yield better device performance, depending on how they鈥檙e manufactured, combined, and integrated. By using artificial intelligence, Arges expects to cut a total development time of 15-20 years down to 1-5 years.

鈥淥ften, new good materials discovered in the lab completely flop once we put them into fuel cell devices,鈥� Arges said. 鈥淲hat really excites me about the machine learning aspects of this project is that these tools can do things that aren鈥檛 so intuitive from the human experience and identify relationships that are often hidden and difficult to find. They can suggest solutions and tell us which experiments to prioritize. 鈥業f you want to get to this point in performance, you need a material with this property and you need to integrate it this way鈥攏ow, go do it.鈥� That鈥檚 what we鈥檙e working on right now.鈥�

After recently filing a patent on a high-temperature PEM, Arges鈥檚 team has made great strides in developing new electrode binders also. They鈥檝e managed to increase the power density in a fuel cell by a factor of 10 by switching to a new binder. They also anticipate 50% in additional improvement.

鈥淭he new binder is working brilliantly, just awesome,鈥� said Arges.

In the low-temperature PEM fuel cells used today, the membrane chemistry and the binder chemistry are the same even though they have different requirements鈥攖he membrane has to be mechanically robust, so as not to rip under gas pressure, and only conduct protons (positively charged ions)鈥攏ot electrons鈥攐r the fuel cell shorts out, which could be dangerous鈥攅ven catastrophic. Also, while the membrane shouldn鈥檛 let gas through, which Arges describes as 鈥渄on鈥檛-cross-the-streams Ghostbusters bad,鈥� the binder needs to be permeable and let gases through quickly. A better binder leads to more efficient use of the platinum catalyst and more functional electrodes, and thus lower fuel cell costs.

By making membranes and binders that can operate efficiently and remain intact at extreme temperatures, Arges is excited about 海角社区鈥檚 current foothold on the frontier of fuel cell technology.

鈥淚鈥檓 happy to have Toyota鈥檚 support,鈥� Arges said. 鈥淲hen they flew into Baton Rouge and shared their vision for high-temperature systems, it not only validated some of our working hypotheses, but it motivated us further and honed our focus. The high-temperature direction is now garnering more and more interest in the fuel cell community.鈥�

Arges predicts his lab will double fuel cell power density within a year. This would be important for vehicle manufacturers such as Toyota, which hopes to improve their Mirai from 3 kW to 9 kW per liter. A three-fold increase in power density would be transformative and allow fuel cells to go up to 700 miles before filling up on hydrogen again. This would alleviate the burden of building numerous hydrogen gas refueling stations and also lower the manufacturing cost of fuel cell vehicles.

鈥� By making membranes and binders that can operate efficiently and remain intact at extreme temperatures, Arges is excited about 海角社区鈥檚 current foothold on the frontier of fuel cell technology. 鈥�

The 海角社区 researchers have partnered with Xergy, a membrane manufacturer in Delaware, to scale up their extreme-temperature PEMs. Those membranes will be evaluated independently by Los Alamos National Laboratory and Toyota, which will be testing both performance and durability under relevant automobile conditions.

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Arges鈥檚 work has so far clinched research grants from the U.S. Department of Energy (both the Basic Energy Sciences and the Advanced Manufacturing Office), the 海角社区 Board of Supervisors LIFT² program, the Louisiana Board of Regents, the National Science Foundation, and others.

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