A Russian-American joint venture says its new “turbo air-cooled” fuel cell design will provide three times the power of a regular fuel cell and four times the life of a regular fuel cell, opening the door for high-speed, long-range, hydrogen-powered electric VTOL aircraft,media New Atlas reported. In the aviation industry, weight is everything, and when it comes to energy-intensive vertical take-offs and landings like the forthcoming electric vertical take-off and landing (eVTOL) competitors, weight is even more important. Almost all companies are using lithium batteries to build prototypes, but the fact is that there is still a lot of room for improvement in the energy density of lithium batteries.
Commercial aviation taxis require all-day flights rather than long-term connections to charging stations, so every company planning around lithium batteries is praying for a magical new chemical from the test lab that will have twice or three times the capacity of the best batteries available. This is likely to happen, but hydrogen is already becoming a good alternative. Hydrogen is a problem in ground transportation, but in electric aviation, it may be the perfect choice. It provides a higher energy density, promises excellent flight endurance, and it allows you to fill up with fuel in minutes, just as you can fill a car’s tank.
In fact, some companies are already betting on it. Skai, an east coast start-up, is scrambling to launch a six-rotor five-seater aircraft that can fly in the air for four hours or 400 miles (644 kilometers) before you need to hydrogen a hydrogen tank. But a Russian-American joint venture says the perfect eVTOL power train still lacks a piece of the puzzle: a lightweight, high-power fuel cell design.
The California-based start-up is called HyPoint. Starting in 2018, HyPoint will begin manufacturing low-temperature proton exchange membrane (LTPEM) fuel cell systems for industrial-grade uAV systems. But since moving to Silicon Valley and being enrolled in the Alchemist Accelerator program, the company has focused on bigger goals.
“When we came to the U.S., we saw a huge market for urban air mobility,” said Dr. Alex Ivanenko, the company’s chief executive. “The main drivers of this market are mobility, compactness and energy density. Today, the main power system is built on lithium batteries, which have a basic technical barrier. Existing lithium batteries have a lower energy density, while existing fuel cells have lower power ratios. The air transport market requires high ratio of power and high energy density. There is no single power supply that can meet both requirements. Lithium doesn’t work, and neither can fuel cells. “
It is predicted that the right lithium battery technology may be 15 years away, and the HyPoint team is beginning to focus on fuel cell designs specifically for eVTOL. In order to be lightweight, Ivanenko says, a wind-cooled design is necessary; liquid-cooled fuel cells work well in the automotive sector, but the associated coolant tanks and pumps increase parasitic quality and are simply unable to fly in aviation.
The current air-cooled fuel cell has limited power capacity and life, and can only operate at temperatures of -5 to 30C, he said. So the HyPoint team set out to develop faster, more durable products and proposed what they called a “turbine air-cooled fuel cell.”
“We increase the power of the fuel cell stack by placing the fuel cell stack in an air pipe and circulating pressurized, humidified and hot and stable air through a fan. Ivanenko said. “Through the compression system to maintain the compression of air at about 3 bar inside, oxygen content of reduced air through the control valve for filling, and then replaced with a normal oxygen content of fresh compressed air. “
The extra oxygen on the cathode side of the fuel cell reactor, combined with the new high-temperature proton exchange membrane (HTPEM) technology developed by HyPoint, makes the hydrogen consumption of fuel cells three times as high as conventional designs, and triples its specific power output without adding any parasitic cooling mass that could reduce the weight of the VTOL aircraft.
Considering the entire system, the HyPoint system provides 2,000 watts of power per kilogram (2.2 pounds). The best liquid-cooled fuel cells have a power range of 150-800 watts/kg, while other air-cooled fuel cells have a power of around 800 watts/kg. According to HyPoint’s own data, the energy density of the entire system is about 960 Wh/kg, while the energy density of lithium batteries is typically one-third that, while that of other air and liquid-cooled fuel cell systems is just over half that.
Ivanenko says the system has other huge benefits; it can accept “dirty” hydrogen with a purity of only 99%, which is much less expensive than the 99.999% purified hydrogen required for LPTEM systems. “This is a significant decline in operational parameters for a commercial eVTOL operation,” he added.
It can work more or less at any real-world temperature, from -50 to 50 degrees C (-58 to 122 degrees F) and higher temperatures. Although it is still in the lab at this stage, the team expects the fuel cells to last about 20,000 hours without maintenance, while LTPEM systems typically last about 5,000 hours — another important factor for commercial operators.
HyPoint has been in contact with some of the major players in the emerging eVTOL markets in the Us, Europe and Australia, Ivanenko said, but he could not mention the companies by name, with the exception of ZeroAvia and Bartini. “We’re seeing a lot of interest from a lot of companies, ” he said. “We believe we have found a solution for them. Many of them asked us to test our technology with prototypes, because so far we’ve only verified it in the lab. We also agree with that view. So our development plan this year is to do a 15 to 20 kW prototype to validate this technology. Then in 2022 to form a complete scale, such as 150-200 kilowatts of the system. “
Switching from a lithium-powered prototype to a hydrogen-powered system should not require a complete redesign of most eVTOL fuselages, he said, so if competitors are willing to move something inside the aircraft design, more or less any competitor will have a chance to achieve a long-range flight of fast refueling.
So what about security? Is there a risk of explosion in hydrogen-powered eVTOL?
“This is a common issue for consumers,” Ivanenko said. “That doesn’t matter, because I think most consumers’ technology will be hard to switch to hydrogen anyway. That’s one of the reasons we focus on B2B with large companies that care about efficiency. “
“But it’s like, ‘This is a hydrogen bomb! ‘Remember the Hindenburg! It was 1938. It was almost a hundred years ago. What people need to know is that hydrogen, oxygen, propane and natural gas all belong to the same class of dangerous flammable gases. The propane bottle you use on a barbecue oven has the same warning certificate, which is the same type as hydrogen. Hydrogen does not have a special hazard level. Moreover, hydrogen is the lightest gas in the universe, and it is impossible to concentrate in the field at that dangerous concentration, which could cause a big explosion. Of course, you have to follow special safety rules, but don’t be afraid of hydrogen. Oxygen is much more dangerous. “
He went on to point out that he was driving a Toyota Mirai Hydrogen Powered car. “It has been thoroughly tested for safety collisions. Any manufacturer of hydrogen power systems knows what steps need to be taken in a particular application to obtain the appropriate safety certificate, and we will not be an exception. “