Eric Parker, Hydrogen & Fuel Cell Technologies Office: Hello, everyone, and welcome to another H2IQ Hour, our monthly educational webinar series that highlights research and development activities funded by the US Department of Energy's Hydrogen and Fuel Cell Technologies Office, or HFTO, within the Office of Energy Efficiency and Renewable Energy, or EERE.
Just a reminder, if any of you are active on social media we definitely encourage you to share anything interesting or surprising you hear on today's webinar – I know we've got some cool topics lined up – and to use the H2IQ hashtag in your posts. And as always, we'll be announcing more topics like these soon.
As you heard, this webinar is being recorded, and the full recording, in addition to the slides you'll see today, will be posted on DOE's website. All attendees will be on mute throughout the webinar, so if you do have a question you think of please submit it through the Q&A box you should see in the WebEx panel in the bottom right – the Q&A box, not the chat box – and we'll do our best to cover as many of those as we can at the end of the presentations today.
And so with that I would like to turn it right over to our DOE host, Jesse Adams, to introduce today's topic and speakers. Thank you, Jesse.
Jesse Adams, Hydrogen & Fuel Cell Technologies Office: All right. Thanks, Eric. Welcome, everyone, to this month's H2IQ Hour presented by the Department of Energy's Hydrogen and Fuel Cell Technologies Office. For those that don't know me, again, my name is Jesse Adams. I've been with the Office for over 15 years, working mostly in the Hydrogen Storage Program on a variety of projects focused on increasing the capacity and reducing the cost of hydrogen storage.
So one of those options to increase capacity is to reduce the hydrogen temperature, and thus we have funded several prior projects related to cold and cryo-compressed, as well as cryogenic insulation. And we're also starting to look more and more at liquid hydrogen storage.
So thus I'm excited today to introduce today's topic, which is focused on cryogenic storage of hydrogen. The first presenter is Dr. Kevin Simmons from Pacific Northwest National Laboratory. His project is part of the H-Mat Consortium, which focuses on material compatibility with hydrogen. But this project adds another element, which is cryogenic condition, so as you can imagine, material performance can be significantly different under hydrogen pressure at say 20° kelvin, especially under thermal mechanical cycling. So you'll hear a lot more about that during today's presentation.
Kevin is a long time PNNL scientist, focused on polymers and composites. He is one of 37 distinguished staff members at PNNL, with 17 US patents, 5 foreign patents, 2 magazine R&D 100 Awards, and numerous other awards at the laboratory there. So with that, Kevin, the floor is yours.
Dr. Kevin Simmons, Pacific Northwest National Laboratory: Thank you, Jesse, for that presentation – or that intro. Next slide, please.
I'd like to kind of lay out the outline of our presentation today and talk a little bit, just introduce everyone to the H-Mat Consortium for the H2@Scale Program at the Hydrogen Fuel Cell Technology Office, talk a little bit about the benefits of the cold gas, the cryo-compressed and liquid hydrogen storage that we see, as Jesse had described, what some of those technical challenges are. And our H-Mat Cryo objectives, the project that we have been working on. And some results of a lab meeting that we had with multiple federal lab groups coming together to have a discussion around cryo materials testing. And the materials testing that we we've been doing in these models that we've been developing to input these materials' properties into these models to help us predict performance. Next slide, please.
So the H-Mat Consortium for the H2@Scale Program in the office is a combination of five national labs: Pacific Northwest National Lab, Oak Ridge National Lab, Sandia, Savannah River, and Argonne National Labs. And this group, we focus on the hydrogen compatibility of, in our case of polymeric materials. And I lead that effort on the polymeric side, and my colleague, Chris San Marchi at Sandia, he leads the effort in metallic materials. Next slide, please.
And within that group we have a core team here of what we call our cryo team. I want to give a shout out to my colleagues here at the different national labs; the data and the information they're presenting is a combination of all of our work together; I just have the privilege of sharing this great work that these individuals do. Dan Merkel from PNNL and NPWN, our modeling person. Chris Bowland and Amit Naskar from Oak Ridge, Chris San Marchi from Sandia, and Hisak Rowe from Argonne doing the modeling with _____ PNNL. And our focus is on addressing these material technical challenges, you know, the kind of testing requirements that we need to have for data to input into the models that we have been developing. Next slide, please.
So one of the benefits that you see of cryo-compressed, which is this is why it's an important thing to consider, is that you can increase the storage capacity – the storage density by 90-percent when you compare it to gaseous hydrogen. So over the years we've looked at I've been involved in both the 700-bar and the 500-bar cold gas work. And as you can see, the volumetric capacity goes down here on the third line from the bottom, and it continues to increase, and the gravimetric capacity increases as you get colder in temperature, as you condensify that gas.
And the cost is also a factor. At 350-bar it goes down, but it's still lower because you're reducing the amount of carbon fiber on the tape, which is a huge driver. Some preliminary estimates in work as you look towards liquid hydrogen it shows it could be even a further benefit. It might be similar in gravimetric capacity and volumetric capacity, but with the lower pressure we believe you can drive the cost down further on there. So that's of interest also. But when you're really talking about 70-percent savings in carbon fiber, those are key drivers that you have to be aware of on there, since that's the main effect. Next slide, please.
But there are technical challenges with the cryo-compressed. You need to have a good insulator around the outside of the take. That's typically done with a vacuum-insulated insulation – vacuum layer insulation around the outside of the tank. You can see here in the image this BWM tank is a yellow insulation and the black is the carbon fiber overwrap of a metallic layer on the inside, and then you have a shell around the outside. So that increases that volume on there, so that volume that you're increasing takes away from volume of hydrogen that could be stored. So anytime we can come up with better insulating options that's good.
The other challenge is a wide temperature range. So you're always going to have a first spill from ambient temperature down to a cryogenic condition, and how does that affect the take, or you're going to have some maintenance in which you might have some excursions from room temperature and back down to cryogenic conditions again on their install. So those temperature ramps and changes that the take undergoes can have an effect on the materials and they're a challenge to materials.
And then there's these design objectives that are kind of competing. You've got the – for the storage system that is a continuous-use tank or does it need to have long-term dormancy? And so as we think about light duty versus medium duty vehicle versus heavy-duty vehicles, each one of those has a different storage requirement from a dormancy standpoint. As you can imagine, a heavy duty vehicle for long-hauling is more of a continuous use versus a light duty that might have to sit for a week as you're on vacation, you know, how does that dormancy play into that? And those all impact insulation designs.
And then the other one is the combination of hydrogen exposure and thermal cycling, especially in metallic compounds, is we need to understand the hydrogen impact of metallic compounds and their low temperatures on their end. And is there any long-term effect of hydrogen in the thermal cycling and the fatigue life of the material aging. Next slide, please.
So our objective of our project is to come up with a material acceptance process as we look at these different materials and do some testing on there, how can we screen the materials easier for the program and for people who are looking into trying to reduce cost and come up with pressure vessel designs without having to build pressure bustles every single time you want to evaluate it. And so between the material acceptance process that we go through and how those inputs into models so we can screen out most _____, establish some of these methods of evaluated resonance fibers in the composites together and in the liners prior to constructing a full-size tank. So we can take a look at a numeric modeling at the tank level from these inputs in there to help pre-predict how we could actually do sensitivity analysis if we're changing the resin performance or composite layup and how that might affect the take. And then you can go take these new models and go and build tanks and test them. Next slide, please.
So one of the things that you do is step back with these models and you deconstruct the pressure vessel for its constituent property inputs. So the composite layer is made of a resin with the fiber to make into a composite, and with that composite you have interfacial adhesion that you need to deal with. And that composite overwraps a liner, and if you're talking cold gas that liner could be a polymer liner; if you're talking cryogenic that means the liner is most likely a metallic liner. And then how do those stresses and gas forces interact through the wall of that vessel? Next slide, please.
So when we got together at a lab meeting and just had a lot of discussions with different technical folks from across the different federal labs; we had NIST, we had NASA, we had other DOE labs there in the materials area. And we just took a look at, okay, what testing do we know that we commonly do that's out there in the data that's available? And we know that the ambient temperature testing is pretty well understood and there's lots of information out there, but when you start going sub-ambient, to 77° kelvin to 4° kelvin the non-information really drops off. And you can get some data that says "Here's the strength of a material" or "Here's the yield stress of a material," but the modelers really want the profile, the stress strained profiles. They want those inputs directly into their models to be able to run their models. So really our focus has been on trying to get some of this data, this difficult data down at these cold temperatures. And we've found that it's really deficient, so that's the area that we've been focusing on. Next slide, please.
One of our outcomes of this was a summary of really a focus on composite materials, needing more data for composite materials, you know, down around 20° kelvin temperature. More information on resins and what we can do to monitor – to alter the resin systems to get higher strength, lower CTEs on there. More information on metal liner materials in combination with hydrogen, that have been hydrogen treated at those temperatures, and what those fatigue lives might look like down there.
And then on the cold gas side, better understanding of polymer liners and just what is the limit for polymer liners. And this information is also valuable for looking from the infrastructure side for the office of hoses, flexible hoses, and what the limitations might be on those for fueling. Next slide, please. There we go.
And so this model that we have is a multi-scaled model from the constituents to the tank structure on there. So we can look at these down to the individual resins, resins combined with fibers, interfacial properties on there if you're looking at the coupon-level performance. And then roll that up into a finite element model using our EMTA, NLA, and ABAQUS routine in combination with finite element. So that's where I'm going to take a look at some of the data that we've got and how we're using that data into the models that have been developed. Next slide, please.
So here we take a look at liner materials that are the polymeric kind. We've got the sub-ambient MTS chamber that goes down to -130° C and we've looked at several different materials. This kind of gives you polymers are much more sensitive to temperature changes than the metallic counterparts on there. So you can see that all of the materials increase in stiffness, they increase in strength, but they also decrease in their elongation, and so they become much more brittle and fail at a much lower temperature. So there's some real limit to just how far that you can take a polymeric liner on there.
The most common ones in pressure vessels and the gaseous – the high-density polyethylene or nylon liners. So you can kind of see where the limitations can be to go very cold in temperature there. Next slide, please.
So then when you get into the resins, looking at cryo – in the testing resins its cryogenic conditions becomes very, very challenging. Most resins, the epoxy resins, for example, are glassy. Their glass transition temperatures are relatively high or well above ambient condition. And so one of the approaches we've been taking is looking at model resin systems. We have two base resin compounds for from EPON. And then looking at the cross-linking systems of different cross-linking chemistries to look at how those effects in the structure of the epoxy changes with the cryogenic conditions and testing those.
This is one of just our base model example over here on this side. You can see it becomes more and more brittle as it you go colder in temperature, increases in stiffness, increases in strength, and when we see the -183° temperature there, I left that in there so you can see there's a flaw. These things have become extremely flaw-sensitive from any kind of notch or bubble or scratch on the surface. And also we found early on that when you have your extensometer attached to the specimen the stress from just clamping the extensometer on there can also cause it to fail. So there's a lot of challenges in testing these materials down in these cryogenic conditions on there, so we had to work through some of those challenges.
What we do is we take these model resin compounds that we've got the data from and make up composite materials as to our T700 and fiber with these model resins and pregnate them in there and laminate unidirectional, and we have a couple of 0-90 laminate systems and the Short Beam Shear, tensile, and then some cracking investigation.
And just an image share on the bottom right-hand corner. This is a cryo stat for doing mechanical testing. This has the capability of going down to 1.9° kelvin, 1.7° kelvin. We typically operate it at 20° kelvin for the materials testing that we're doing, and it controls to 50° millikelvin in temperature; it's got a temperature-controlled atmosphere down on the bottom so we can dial it in, using both liquid helium and liquid nitrogen as we need for the temperature ranges. Next slide.
So one of the areas that our partners at Oak Ridge National Lab has been working on is surface modifications for sizing the fibers and how that can change the interlaminar shear strength on there. One of the things that was quite interesting is oftentimes we had found some initial work to increase the interlaminar shear strength at ambient condition, and then when we went to sub-ambient the strength at that interface is not there; it didn't translate to colder, it translated more to higher temperatures. And so Chris got to thinking and so he changed his direction and now in one of the things that he found is when he was making a change and he wasn't seeing any change in ambient conditions, but he said, "We should be seeing some changes in _____ what colder and colder in conditions and testing conditions," he started to see the noticeable change of some of the surfaces that he's modifying, to the point that at -75° he seen an 11-percent increase in interlaminar shear strength.
So now our next step is to take it down to these next lower temperature conditions to see if that trend can continue. But there was – we are now seeing an improvement in the interlaminar shear strength with sizing modifications. Next slide, please.
And working with Chris San Marchi, some materials testing we're doing in the cryostat is on some metals. So we're looking at 304L and Nitronic 50, and as you can see, the yield strength and the ultimate strength continues to go up. But you can see there's different behavior changes that go on in the materials as you go down in temperature. So for example, you see martin site formation in 304 stainless as you get colder and colder in temperature down to 20° kelvin.
And then what was also interesting is the Nitronic 50 down to -80 was seeing an increase in the elongation, and then once you get past -80 it shifts and goes in the other direction and lower. So there's quite some changes that go on in the metallics on there.
So our next phase that we're doing, we have samples that have been hydrogen-treated, and we will test the samples at the same conditions after being soaked in hydrogen to look at the hydrogen effect at these lower temperatures. Next slide, please.
So what do we do with all this information we've been testing? Well, we pick this information on the composite side and we put this into this EMTA NLA software that was developed at PNNL, and we can look at all these constituent-level properties and put them into the EMTA NLA software. And that software homogenizes the composite properties into this sub-user routine, and the ABAQUS can do structural analysis. And we've also – there's some techniques that we have to translate it over into some other software as well on there.
But this unique software really helps us understand what goes on in the composite and in the combination of the other tool that Argon has been using. Next slide, please.
So we'll take these properties of epoxies, _____ thermal expansion, the different mechanical properties and the temperatures, and those all get input into the thermo mechanical properties all get input into the software model and homogenized and it develops this subroutine – material subroutine in ABAQUS. And we can take that subroutine and put it into the FE model that we've developed with Argon. Next slide, please.
So the first thing we did with the ABAQUS model using the EMTA NLA is just like picking a cellular section and looking at different loading scenarios. And I think this particular one we did an aluminum liner in this particular case. But here's four different loading scenarios for the pressure vessel. In loading scenario one, where we cooled down from ambient condition down to 77° kelvin and then pressurize. So you're cooling down the tank and then pressurizing the tank. And then number two, you're cooking down and pressurizing at a rate that's consistent with being cooled and pressurized to the final together. And then the third one is you're cooling, but you're pressurizing faster than you're cooling. You pressurize up to a fixed pressure and then you continue to cool down. And then the fourth one is you cool the tank down to 77° kelvin and then you pressurize even colder, down to 50° kelvin during that last step. Next slide, please.
So when we take a look at, okay, these different loading scenarios, do any of them exceed the cellular criteria that might cause the tank to fail? And so basically a bottom line is is in the right-hand corner, and all those different scenarios on there, you can see that the 6060 1T6 and the 6016 T4 material, in any of those loading scenarios of temperature and pressure never exceeds the equivalent stress that would cause a failure. So the liner wasn't predicted to fail. If you go to the next slide, please.
Then we take a look at the composite side, looking at whether it's a hoop layer or a helix layer on there. Basically you want to make sure that you don't exceed the Failure Criteria of one. Once you hit the Failure Criteria of one then your ply fails. And as we've gone through these different scenarios what we've found is as you increase the strength of the epoxy as it gets colder it helps mitigate the matrix cracking as it cools down. So the bottom line is it's critical to produce a high-strength epoxy, is what we've found to mitigate the cracking in the composite. Next slide, please.
So that's the material model that had been developed, and using ABAQUS to do some initial evaluations of it. So then we wanted to go into a 3-D model of a hydrogen pressure vessel. And so Argon and PNNL are working together with materials information in the model for there that Argon had been using for a couple of years, a finite element model. We developed this tank model at 500-bar operating conditions between 34° and 80° Kelvin, and they both have a 2-D asymmetric model. And there's no bonding between the liner and the composite.
And so what they did is they looked at cooling this thing down to 80° kelvin from room temperature, and then the burst pressure is applied at 2.25 over 500-bar. And looking at the strains of maximum fiber strains or strains along the fiber directions. Next slide, please.
So when you think about if you have a metallic liner with a composite overwrap and you're going to have a mismatch between the composite overwrap and the tank liner on there, we looked at the difference between aluminum and then stainless steel. When that pressure is relieved and that tank is cold at 80° kelvin there's a gap that forms between the composite and the tank liner, and that shrinkage from that liner forms a lot of stress up in that neck area from the composite overwrap as well as on the aluminum. So you can see the stress increasing there on the composite in that upper right-hand corner image. So you've got stresses on the composite. And then when you take a look at the bottom left-hand corner, the aluminum liner on the left, you can see the high stress concentration down in that neck area, that corner on there from that stretching and pulling on that liner against that composite. And when they put the steel liner in there the stresses are lower; you can have a higher strength.
So you have to really be careful of the design and the thumb on this matches that might be going on in your design. In this particular case the stress was high enough that we actually were able to see a plastic deformation occur in that design. Next slide, please.
So also looking at fatigue loading. So there's thermal cycling as well as pressure cycling that we have to consider. So if you look at a fueling cycle and a discharge cycle, you've both got temperature and pressure that you have to deal with on that composite and on that tank, you know, between 5-bar and 500-bar and down to as cold as 35° kelvin. Next slide, please.
And so the PNNL and Argon together have been working on a failure prediction for hydrogen tank, and so we've got these 3-D finite element models, and we've been putting the inputs of the mechanistic damage model as a user material option in there. And looking at how to account for the different constituent thermal mechanical properties on the pressure vessel there. Next slide, please.
So matrix cracking is one of those damage mechanisms that can influence the performance of the material properties on there. And it's been found that depending on whether there's an internal or external layer positions can influence the matrix cracking on there. So you see the bottom two images of some previous work, and the EMTA model predicting, you know, that matrix crack density on there. So taking that matrix crack density model at the NLA and put it into that finite element model. So next slide, please.
So we've taken that finite element model and we actually have this at a half-scale now. This is an eight-scale, but we have it at a half-scale. And then looking at if you autofrettage it to 70 MPa and then ramp it up to bursting pressure, what happens? What's the effect of the matrix cracking on there? Next slide, please.
So when you take a look at the horizontal section or the vertical section you can see the matrix cracking actually goes – can be pretty significant. The hoops, the internal composite layers on there are under severe – from an autofrettage standpoint. Burst pressure can have a significant damage to the composite on there. And in this particular case it burst through the dome, as you can see the spot on the right-hand side where the high stresses in that dome region. Next slide, please.
And so the bottom line is autofrettage pressure can increase a matrix cracking on these internal layers. So between the cool temperature matrix cracking from the layers mismatching between them, the autofrettage pressure, adding additional matrix cracking in there. You can see on the right-hand side of that autofrettaging is increasing the matrix cracking failure indicator on the internal layers, which is the red that you see, versus the external layers, which is the green. And so once you autofrettage you operate between that one and two, and if it over-pressurizes you can see that internal layer are the ones that fell first on there. Next slide, please.
So in summary, the H-Mat program and the cryo team has been working on some materials testing protocol and getting some new data and applying that data into these pressure vessel models so that we can evaluate new material sets without going into expensive tank builds on there. We've been able to develop materials testing in some looking at model material compounds down to 20° kelvin and use those to input into the pressure vessel predicting the performance.
Looking at this new model, as these material failure criteria and in conjunction with the FE model to help us product these burst pressures, and the something new that's been added in there is these cracked densities, the addition of the effect of crack density in the composite from both thermal and pressure cycling, and how that affects the burst pressure of the tank.
Also important, autofrettaging conditions at cryogenic temperatures can impact burst pressure. We found that from the modeling higher-staked resin systems can improve their cryogenic composite tank performance. We found that there's these latex nano beads on the surface for sizing onto carbon fibers can increase the interlaminar shear strength in subambient conditions. And we see the effects of cold temperatures on yield and ultimate strengths on stainless steel and next is to look at the impact of hydrogen addition. Next slide.
I'd just like to thank Jesse Adams, Ned Stetson, and Nahar Astagi for their H-Mat program support and the Office of Hydrogen and Fuel Cell Technology for their support in this work. Jesse, back to you.
Jesse: All right. Thanks, Kevin. We're running a few minutes behind so I'm going to quickly introduce our next presenter.
So it's Eric Dirschka from NASA's Kennedy Space Center. He has a BS in Mechanical Engineering from the University of Central Florida and he has worked with NASA for over 30 years in a variety of positions, including systems engineering for the Space Shuttle. He currently is the lead engineer for NASA-wide Propellants Management Group. So Eric will provide a quick overview of liquid hydrogen work at NASA. And really this is a technology that the Hydrogen Fuel Cell Technologies Office is starting to investigate a lot more now for heavy-duty applications due to potential advantages related to capacity, cost, and fill time amongst others.
So with that, Eric, the floor is yours.
Eric Dirschka, NASA: All right. Thank you. Can you hear me okay?
Jesse: Yes.
Eric D.: Okay. Thanks for the introduction and thanks for inviting me to share some information about NASA. This is a high-level overview, but I'm open to questions on details if you have them.
This first slide is a picture of the SLS rocket. It's a Space Launch System rocket. Since the retirement of the Space Shuttle NASA has been helping commercial space flight companies achieve low Earth orbit, while NASA focuses on systems for deep space and long duration missions. This SLS rocket is a super heavy lift rocket that's needed for those deep space missions. Next slide.
There are ten NASA centers across the country, and my group at Kennedy Space Center is responsible for supplying all of them with bulk propellants. And when I say propellants, in general those are liquid hydrogen, liquid oxygen, liquid nitrogen, and gaseous and liquid helium, but just for convenience we can refer to them all as propellants. Of course, really only oxygen and hydrogen are propelling something.
Each of the centers specialize certain categories of work. Only four of them routinely use liquid hydrogen or LH2 as we call it. And I'll touch on each of the centers later. Next slide.
So why does NASA use liquid hydrogen, or LH2? This slide is just some Rocket Science 101 basically to help you understand why NASA uses it. So chemical rocket engines, which you see here; that's a picture of one, combust a mixture of fuel and oxidizer to produce thrust. That rocket engine performance is maximized when you use hydrogen as the fuel and oxygen as the oxidizer. That's the highest performing engines that exist are hydrogen-oxygen. In order to fit enough hydrogen and oxygen onboard a rocket, though, you have to refrigerate it to be a cryogenic liquid, or liquefied, and that enables you to fit much more onboard. There's a gas-to-liquid volume ratio of about 800:1, so in order to get enough onboard to launch the rocket.
The operations associated with these cryogenics, the storage, transfer, and loading have a multitude of complications, as you might imagine, but the high performance of the engine makes it worth it, so that's why NASA is doing it. Next slide.
You still may be wondering how the engine burns liquid hydrogen. The engines are designed to be chilled down to keep the hydrogen and oxygen in their liquid state and flow without cavitation through the pumps, and then vaporize to a gas just prior to combustion. In the center of the slide you can see the combustion chamber is just above the nozzle. Next slide.
So most of the liquid hydrogen work at NASA relates to rocket propulsion, rocket propulsion systems. At Glenn Research Center in Plum Brook Station that includes this cryogenic research component development and flight vehicle space environment simulation testing. That's a mouthful. This photograph, though, it shows an example, the SHIVER Project was a test tank aimed to develop technologies to reduce boil-off in the cryogenic storage tanks for those deep space missions. Next slide.
At Marshall Space Flight Center they do component and integrated system testing. This is a picture of the ICPS, the Interim Cryogenic Propulsion Stage for the space launch system, that SLS rocket I was talking about. The liquid oxygen – liquid hydrogen-based stage, you can see the big tank on top is a liquid hydrogen tank and the smaller tank on the lower part is the liquid oxygen tank. That's the stage that will propel NASA's Orion spacecraft, which is basically the new capsule, and it will provide the propulsion needed to fly beyond the moon and back to Earth. Next slide.
At the Stennis Space Center they do operational rocket engine testing, and they're the largest user in NASA. Over the years Stennis usage varies from a low of about 2 million pounds of hydrogen a year to a high of up to 10 million pounds per year. And that picture is the space launch system, again, the SLS. That's the core stage with the four engines on the bottom of it, and that's got 539,000 gallons of liquid nitrogen will be onboard that rocket. That picture there is where they're loading that stage onto a test stand at Stennis, where they'll do the green run, it's called, where they'll run the engines in a full duration flight simulation basically, but they run the engines fully for eight minutes and make sure that it's truly ready for flight before it's shipped to the Kennedy Space Center. Next slide.
Kennedy Space Center is where the rocket and spacecraft ground support systems are – there's development done for that and for the rocket launch itself is done at Kennedy. Of course, that picture there is the Legacy 850,000 gallon liquid hydrogen tank that was used for Apollo, the Space Shuttle, and now it's going to be used to support the SLS space launch system. Next slide.
And this is the big picture shot of the entire launch complex, Launch Complex 39B, which is where the Apollo and Shuttle launch from. And for scale, the lightning towers, they are 600-feet tall, and the two white spheres that look small in this picture, are the liquid oxygen and liquid hydrogen storage tanks. Each of them are approximately 850 gallons, and there's a new 1.2 million gallon liquid hydrogen tank that's not shown here, but it's under construction, adjacent to the existing liquid hydrogen tank. The larger quantity is required for the SLS rocket. Next slide.
So how do we get the liquid hydrogen? We purchase it as a bulk liquid as a commercial item delivered by semi truck tankers, and we get up to 15,000 gallons per truck. That's pretty important, because there's few production plants in the US, so they're long haul deliveries. The nearest plant is a roundtrip of over 1,000 miles from Kennedy Space Center. So to minimize the delivery transport losses and also scheduling impacts at the launch pads where there's a lot going on, we want to get a large quantity delivered at one time as possible. And that's the same for Stennis Space Center as well, and they require between 5 to 12 tankers delivered in one day. That picture you see there, it's showing four trucks, but there's actually five that are hooked up to a manifold at the launch pad there and five trucks are offloaded at one time. Next slide.
Agency-wide the usage does vary from a low of 3 million to a high of 10 million pounds a year. And historically only two suppliers have been able to meet our requirements to be able to keep up with the demand in these large quantities trucks at one time: Air Products and Chemicals, and their closest plant is New Orleans; and Praxair, with their plant in Macintosh, Alabama.
There's four new plants, liquid hydrogen plants announced, so that should help the competition and supply reliability. And NASA is planning to solicit and award our new supply contracts starting in 2021, after these plants come online. Next slide.
This last slide illustrates that NASA's exploration to the moon and Mars will continue, and so the need for liquid hydrogen propulsion will also continue.
So thanks for your time and attention. That's all I….
Eric P.: Thank you, Eric. This is now the Q&A portion of the webinar. And before I turn it over to our host, Jesse, to run the Q&A with our presenters, I just want to let everyone know a couple of people have asked where they can find this presentation, and we will be uploading the full slide deck along with the entire recording of today's webinar to the DOE HFTO website. And if you navigate to the webinar section of our website you'll find both the archive of all previous webinars as well as all upcoming webinars. So be sure to head there soon for this presentation.
With that I'll turn it over to Jesse to start our Q&A.
Jesse: All right. Thanks, Eric. Thanks to the other Eric; that's a really interesting presentation, lots of crazy awesome capabilities there at NASA, I mean 850,000-gallon hydrogen storage tank is pretty awesome.
So we'll get to the Q&A here. So again, everybody put in their questions in the Q&A chat box there. We have a lot of people online. We don't have a lot of questions so far, so feel free to send them in. But we'll get started.
I think first one, send this off to Kevin. So question is what is the difference between liquid hydrogen and cryo-compressed hydrogen?
Kevin: So the difference is that the level of pressure. So liquid hydrogen, it's less than 3-bar; I think it's right around a bar or two to just a little bit higher that. I think it's around 50 psi or something. And then the cryo-compressed you have the liquid in there, but you also have a gas phase that's in there as well, and so you're compressing that gas phase up to 500-bar, you know, with the liquid in there, and that helps keep it more towards the liquid phase side until you're ready to use it. And this helps with dormancy as well in there. And to increase the density of the gas to make sure you have more onboard storage capacity.
Jesse: All right, so next question. Again, for Kevin, will the polymers that are being investigated work as internal liners for natural gas pipelines?
Kevin: So I would say it depends on – and I would say in some of them yes, in some of them probably not. So it kind of all depends on the condition. There's a lot of natural gas pipelines now that are medium density to high-density polyethylene and some polyamide systems, and so I'd say yes on some of those cases. Others we'd have to consider the other conditions that they'd be subjected to.
Jesse: All right, next one. So this is coming – so the question is what has been done to assess the manufacturing time for cryo-compressed say 500-bar tanks, and how does that compare with kind of traditional 700-bar compressed hydrogen tanks?
Eric P.: Jesse, could you repeat that question again? You cut out just a little bit.
Jesse: Yeah. So what has been done to assess the manufacturing time for cryo-compressed tanks, like say 500-bar, and how does that compare with the more traditional 700-bar ambient tanks?
Kevin: Yeah, it's a good question. So I've been involved in looking at that in the past and the 700-bar tanks have, as you would imagine, more widening time on there to put more fiber down. And the 500-bar would have less, as you see, less widening time, 'cause there's less carbon fiber on there. But they've got to substitute that time, and the really difficult part of that is the insulation, putting the multilayer vacuum insulation around that take. And there is time-consuming. And then the pump down time to pull the vacuum down on the tanks also is a considerable amount of time. So there are some tradeoffs on there, which is why when you look at that cost difference on that table that I had was not substantially lower; it was slightly lower on there, about 20-percent. Most of that is because you make up that difference in that carbon fiber price back into a little bit longer time in manufacturing to take. So that's an area that I think needs to be worked on, and for medium duty and heavy duty do you really need that high a level of vacuum insulation performance with a continuous runtime? Can you get away with more of a physical insulation on there?
So those are all questions that I think need to be thought of on there to help reduce that cost further. Good question, though.
Jesse: All right. Thanks, Kevin. So we've got a couple of questions here that are related. So there's interest here in kind of this new liquid hydrogen supply that's coming online, so maybe this is a good one for you, Eric. What are the names of these other suppliers besides Air Products and Praxair? And then do you know what the capacity that's coming online is?
Eric D.: Yeah, let's see, Praxair, which has actually been merged with Linde, so they're building a plant I believe in La Porte, Texas. And Air Products is also building a plant in La Porte, Texas, if I remember correctly. These are online; if you Google them in the news you'll find them. And then in Air Liquide I believe is building one. I think that one's in Nevada, just over the line from California. And then a fourth one is being built in California, I'm not sure who's building that one.
Jesse: All right. Thanks.
Eric D.: And they're all _____ capacity. Yeah, it's interesting, when you look it up, the capacity, they're all just a little less than 30 tons a day. There must be some economy of scale or optimal efficiency there somewhere. It's in the high 20 tons per day, just shy of 30.
Jesse: All right. Thanks. Next question. Any interest in NASA using cryo-compressed in order to reach higher densities than liquid hydrogen to save space onboard?
Eric D.: With the launches, with space flight mass is everything. So because you have to accelerate – every pound that you launch into orbit you have to accelerate it to orbital velocity, so mass is actually critical, making everything as light as possible. So the tanks, the fuel tanks, fuel and oxidizer tanks on the rockets have to be made as lightweight as possible, so that precludes much pressure capability. They're pretty low-pressure tanks. If the pressures went up like cryo-compressed they would just get too heavy.
Jesse: All right. This one is for Kevin. Has PNNL identified particular polymer properties that become more important at cryogenic temperatures?
Kevin: Let's see. Yeah, the particular one is the brittleness, the elongation of break. So in some cryo absorbent work we've done in the past under the Hydrogen Storage Engineer Center of Excellence we looked at polymer liners down to 77° kelvin. And we did this work with Hexagon Link and we actually tested some high-density polyethylene liners at 77° kelvin. One of the things we found is you had to maintain a minimum, I want to say it was like 20 or 30-bar of pressure in there, because you needed to keep the liner pressed out against the wall of the pressure vessel. As soon as you release that pressure that liner starts to go into tension because of the CTE difference, and then you crack and your tensile fell because elongation at break will cause that thing to crack, that liner to crack. So those things are possible, but there's also technical limitations on there.
Jesse: All right, so next one probably for Kevin as well. So can a felt interlayer aid in differential strain between the bladder and the overwrap on a cryo-compressed vessel?
Kevin: So right now some pressure vessels are bonded on the liners and some are unbonded. There's different trains of thought related to that. On the gaseous side that's probably less of an issue if it's bonded or unbonded, but when you get to the cryo side and you have those differences, the unbonded – if it was bonded it might become unbonded after a certain period of time. If you put felt in there I'm not sure that it would, because what you're really doing is you're shrinking that liner down from the two ends of the tank and the strains and the stresses that go on are because the ends of the tank are captured on both ends of the composite, and so it's pulling that liner in tension on there, so that's where the stresses developed. Unless there's some other thinking behind that question, that's what I would say is an answer for you.
Jesse: All right. Another one for you, Kevin. So does PNNL or other national laboratories research anything related to hydrogen brittlement and metal, hydrogen expansion and metal, or hydrogen blister and non-metal, like tribology under hydrogen environment?
Kevin: I'm glad you asked that question. So that's the other part of our H-Mat program. On any of the metals related work, that's Chris San Marchi at Sandia, and he's done quite a bit of that work down there in Sandia on the metal side, to answer that question, looking at, you know, the swelling and brittlement and where that's happening at and certain types of metals. Chris is a plethora of knowledge in that space.
On the non-metallic side that is our current scope of work. So what we've found is there's not a lot of data or information out there on the polymer side on hydrogen effects of these polymers, so that's what our H-Mat program is, is scoped to look at. And so we've done quite a bit of elastomeric work and some thermoplastic work and we see blistering behavior, swelling, cracking in different types of materials under different conditions. So if you have a rapid gas decompression that changes the performance of that O-ring or gasket material to swelling on there. Or if you go slow you can mitigate some of the rapid expansion and reduce the damage in the materials. So some of the findings that we're having.
And we do – tribology, we have in situ tribology, where we can go up to almost 30 megapascals in hydrogen in looking at the wear on materials in polymeric materials, as well as up to 30 megapascals in an in situ DMA, where we can go into helium and hydrogen conditions in a DMA and look at the pressure effects on the polymeric materials.
Jesse: All right. Thanks, Kevin. Next I'm getting a couple questions here, I just want to I guess clarify a little bit when we talked about the difference between liquid hydrogen and cryo-compressed. So liquid hydrogen is what it sounds like, it's liquid hydrogen it goes on as a liquid. Cryo-compressed is very cold, but it goes on as a super-critical gas and the temperature can vary. We've looked at kind of different options there ranging from 300 all the way up to 700-bar, even higher. So kind of the difference there is dormancy. So cryo-compressed you get a lot better dormancy the higher the pressure you go to before you would have to vent due to the tank warming.
Liquid hydrogen is all low pressure, so you have to vent very quickly due to dormancy, but you can also fill very fast because essentially you're filling as a liquid and you don't need the compression. So there are kind of some pros and cons there, but wanted to clarify that.
Kevin: Thanks, Jesse.
Jesse: Yep. Going to the next question, again, for Kevin, is stainless steel generally going to perform better than aluminum as a liner for cryo-compressed in the presence of hydrogen?
Kevin: Not sure about that yet. We actually have the QE doing some 2219 aluminum on the testing at 20° kelvin and also in hydrogen soak. But right now the stainless steels are performing pretty well from that aspect on there. But we definitely want to see how we can reduce weight, right? And so aluminum is in the QE to do.
Jesse: All right. Next question is for Eric. So given the challenges with delivery, would NASA ever consider having their own hydrogen plant?
Eric D.: Yeah. Yes, we have looked at that, and there are requirements surge and then taper off, so it's feast or famine, so to speak, with our requirements. So with a liquid hydrogen plant, the plant operates steady state 24/7 producing liquid hydrogen. And because mass's requirements are feast or famine, that makes them almost incompatible, you know, just opposites there. Where we need a whole bunch, you know, we need 100,000 gallons this week and then we don't need anything for a month. So that just is incompatible with the steady state production of a plant. So we're better off just doing it like we are; we're buying it on the market. As long as the suppliers are able to keep up with our requirements, which so far they have, that seems to be the most efficient and reliable way.
Jesse: All right. Eric, do we have time for one more question here?
Eric P.: I think we can call it now. There's more than we could ever get to. So thank you, everyone, for submitting those. We're going to go ahead and be sure to capture all of these. And if you want, we definitely welcome you to reach out to our presenters and continue the conversation offline.
I think I skipped over Eric's e-mail, but I'll go ahead and throw it on the screen here and feel free to reach out to the rest of us as well on the webinar team here at HFTO. And so with that I'll definitely thank everyone for attending today and thank our presenters for an awesome dual presentation. And thank you, Jesse, for hosting. That is going to do it.
As I said earlier, we will be posting this full recording as well as the slides on the HFTO website under our webinars page. So please be sure to check back in a few days for those. And with that, also sign up for our newsletter to hear about more H2IQ Hour topics in the near future. And enjoy the rest of your week everyone, and goodbye.
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