In June 2021, the Department of Energy (DOE) Small Business Innovation Research (SBIR) grant was awarded to The Protium to further promote the development of its cryogenic tank technology. Protium’s storage tank technology is usually used to store cryogenic liquids, or liquefied gases stored at a deep freezing temperature of -150 ⁰C or lower, and will surely play an important role in the development of renewable liquid hydrogen economy.
Storing hydrogen as an energy source is tricky. There are two methods: it is stored in a gaseous form at room temperature under very high pressure, or it is stored in a liquid form at very cold temperatures. In order to maximize the energy density of hydrogen, both extremes of high pressure and low temperature are necessary.
Today, most hydrogen fuel cell vehicles use hydrogen in storage tanks at pressures up to 10,000 psi [pounds per square inch]. However, because liquids are denser than gases, it is more advantageous to store industrial gases such as hydrogen at low temperatures to better maximize their energy density.
However, when these cryogenic liquids are distributed to an environment higher than these deep freezing temperatures, the refueling process becomes complicated. Therefore, Protium will channel their SBIR funds, totaling US$178,039, specifically to reduce so-called “evaporation” losses, which represent this general challenge in the liquid hydrogen fuel sector.
Eli Shoemake, Chief Commercial Officer of Protium, said: “When you fill one of these cryogenic liquid hydrogen tanks at room temperature, it’s like putting water on a hot stove, it will flash and boil immediately, and then all the steam will evaporate. “Usually, you have to fill the water tank for a long time before it becomes cold enough to actually contain and store liquid. But when you do this, basically all the boiling hydrogen is wasted, and you can’t It is in the car because it will only be emitted into the atmosphere.”
It is dangerous to not allow gaseous hydrogen to be discharged from tanks containing liquid hydrogen. Protium aims to better control emissions and allow the discharged hydrogen to play a role in the fuel cell.
“So basically, what happens is that [the tank] is full of liquid, and when the heat enters the liquid, the liquid will boil, which means you will produce gas. Basically, you have to let the gas leave the tank, otherwise, you will let you If you have too much pressure in the tank, it will explode. So basically, what you do with these liquid tanks is that if you don’t want them to explode, then you will take the hydrogen out of the tank at any boiling rate,” Schumacher said . He added that ideally, the vaporized gas is then used in fuel cells instead of wasted.
An unrefrigerated liquid hydrogen tank slowly discharges hydrogen – Photo: Courtesy of Protium
Therefore, Protium has developed a heat exchanger built into its fuel tank to reduce the amount of evaporation loss during refueling. By transferring the liquid hydrogen in the tank through this heat exchanger, it is heated to a gas before being distributed to the fuel cell at a steady rate. Protium hopes to maximize its cryogenic tank by isolating the heating process from the rest. s efficiency. Storage tank.
“We 3D printed the heat exchanger on the wall of the tank so that when the hydrogen passes through the heat exchanger channel, the hydrogen heats up before it leaves the tank and enters the fuel cell,” Shoemake said. “This kind of heat usually heats up the liquid hydrogen in the tank and makes the evaporation rate worse. So we have been using this boil-off gas from the tank to intercept the heat, otherwise the heat will enter the tank. It’s like an extra layer of insulation. This allows us to use less insulation in the fuel tank, making it more performant and lighter. This is the real benefit.”
Installing this heat exchanger into a fuel tank is a new method of hydrogen fuel technology that has existed since the “space race” of the Apollo era.
“All these cryogenic storage tanks are from the Apollo era and the space race, when people asked the question,’How do I keep liquid hydrogen forever?’ In these vacuum insulated containers,” Schumacher said. “[Traditional model] has very good insulation, can keep hydrogen at a low temperature indefinitely, and there is little loss from evaporating from the tank. If you want to store hydrogen for days, weeks, or months, that’s great NS.
“But for most vehicles, when you just want to use it and burn it in a fuel cell, it really doesn’t make sense to try to retain hydrogen forever. So we said,’Let’s not just design a hydrogen tank, let hydrogen Evaporate and leave the canister, but leave the canister at the speed that the fuel cell wants to use.’”
According to Shoemake, the general consensus is that cryogenic tank technology always has an evaporation loss of 0.5% to 1%. Therefore, Protium’s storage tanks are ready to increase the efficiency of traditional cryogenic storage tank technology by converting liquid hydrogen into hydrogen at a measurable but stable evaporation rate through a heat exchanger. But in order to take their innovative technology further, they are also exploring how to improve the cooling of the cryogenic tank system in an attempt to further reduce the evaporation rate to zero.
“We will look at creating a liquid hydrogen tank with virtually zero evaporation, because not all of this heat goes into the liquid and evaporates your hydrogen. We basically wrap the entire tank in this heat exchanger and connect it to a huge refrigerator. It can keep the entire water tank cold,” Shoemake explained. “Then you can connect the storage tank to a refrigeration system that can store liquid hydrogen indefinitely without loss. This is a big problem when you talk about transporting liquid hydrogen or storing liquid hydrogen for long periods of time. Time Therefore, if we can eliminate the 1% loss by installing this kind of refrigerator in the storage tank, it may make the entire liquid hydrogen chain more efficient.”
Considering these technological advancements, Protium mainly envisions their tanks for use in unmanned aerial vehicles [UAV] or unmanned aerial vehicles.
“The scale and scale we are focusing on now is in the aerospace field, especially because it makes sense,” Shoemake said. “One of the main advantages of using our technology is that it is really light compared to traditional technology, and it also has the advantage that using liquid, you can get more [hydrogen] in a smaller space. The combination of these two things is very important for the aircraft.”
However, although the application of drones and drones is the current focus, Shoemake does not rule out that their technology will be extended to other vehicles in the future.
“Marine vehicles are another type of vehicle that we look for a lot for our cryogenic storage tanks, where it makes sense to try to keep your tanks small and you might want to be liquid,” Shoemake said. “It may also be road trucks and vehicles, but it may not be a passenger car, because our tanks are designed to refuel it, and then the fuel will be distributed at a certain speed anyway. If you have a passenger car, you may not want to Parked for a week and then come back without fuel. But things like long-distance semi trucks that are often driven from one warehouse to another on the road, maybe this makes sense.”
Top photo description and credit-Dr. Ian Richardson and his team tested the 3D printed liquid hydrogen tank, which was then used to power a fixed version of the Insitu EagleWorX drone fuel cell. On Monday, July 13, 2020, Jeff Knapp (blue jacket, wide-brimmed brown hat), chief engineer of the Insitu EagleWorX department at Washington State University’s Outdoor Research Facility (ORF), conducted the test-Photo: Bob Hubner, WSU News .
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Post time: Sep-14-2021