Hydrogen Carriers for Bulk Storage and Transport of Hydrogen Webinar: Text Version

You are here

Below is the text version for the "Hydrogen Carriers for Bulk Storage and Transport of Hydrogen" webinar held on December 6, 2018.

Eric Parker, Fuel Cell Technologies Office

Good day, everyone and welcome to the U.S. Department of Energy's Fuel Cell Technologies Office webinar. We've got a great presentation this month from both Argonne National Laboratory and Pacific Northwest National Laboratory on the Hydrogen Carriers for Bulk Storage and Transport of Hydrogen. My name is Eric Parker. I provide program support within the Fuel Cell Technologies Office here at DOE and I'm the organizer for today's meeting. We'll begin in just a minute but, first, I have a few housekeeping items to tell you about.

Today's webinar is being recorded. The recording, along with the full slide deck, will be posted online. We'll be sure to let you know. Additionally, all attendees will be on mute throughout the webinar. So, please submit your questions that you have about the presentation via the chat box that you see here in the WebEx interface. You can send them at any time and we'll make sure they get addressed before the end of the webinar during the Q&A session at the end. With that, I would like to introduce today's DOE webinar host, Ned Stetson, who is joining us at DOE Headquarters. Hi Ned. Take it away.

Ned Stetson, Fuel Cell Technologies Office

Thank you, Eric. Good afternoon or good morning, everyone. Thank you for attending this webinar on hydrogen carriers. This is an exciting time for the hydrogen community as more technologies that come to market and demand is definitely growing. Today, there were 5,600 fuel cell electric vehicles on the road in the U.S. There are 35 hydrogen fuel retail stations open in California. There's now one open in Hawaii and about a dozen expected to open soon in the northeast. In addition, there are over 23,000 hydrogen fuel support lifts in operation and hundreds of fuel cells being used for backup power such as use in cell phone towers.

On top of that, there's growing interest in the potential hydrogen to benefit in helping improve the resiliency of the power grid. This is especially important as a percentage of energy from intermittent resources such as wind and solar increase on the grid. Having the ability to store energy and to divert some of that excess energy to other [inaudible] is becoming very important. Hydrogen has the potential [inaudible] both, energy storage and to be a pathway to connect energy sources with high-value end uses.

So, to this end, the DOE's Hydrogen Fuel Cell Technologies Office has launched the new H2@Scale Initiative. The H2@Scale Initiative is looking at how we can couple the various sources and high-value end use applications through hydrogen. The initiative is organized around the areas of make, move, use, and store. The areas of use and store are critical in order to couple where and when hydrogen is made to where and when it's used, especially when these are being separated by both time and geography.

Conventional methods to move and store hydrogen mainly as either compressed gas or cryogenic liquid have limitations such as their low-energy density, low-energy efficiency, and high cost. Therefore, it's important that we identify and develop new and better ways to move and to store hydrogen. Hydrogen carriers is one of the technology areas that we're interested in looking at that may provide benefits for both moving and storing hydrogen.

So, today's webinar will cover both a preliminary baseline analysis comparing some potential hydrogen carriers with conventional methods for moving and storing hydrogen and some initial plans we have on hydrogen storage research from HyMARC. Just a couple of words on HyMARC. HyMARC is the Hydrogen Materials Advanced Research Consortium. They are a member of the Energy Materials Network, or the EMN. The EMN was launched – excuse me – as a way to make the national laboratory capabilities more accessible to address the critical needs of industry and technology development.

The HyMARC National Lab team is comprised of Sandia National Lab, National Energy Renewable Lab, Lawrence Livermore National Lab, Lawrence Berkeley National Lab, Pacific Northwest National Lab, the NIST Center for Neutron Research, and SLAC. This core lab team has two key roles first is carry out foundational research done as [inaudible] of hydrogen interacting with materials for both the uptake and release of hydrogen and to provide low-class capabilities for the synthesis, characterization, and computation for materials development. Innovator projects are selected from administering universities for, for example, funding opportunity announcements to work with the HyMARC core team to help accelerate the project's progress.

So, this webinar today is being presented by Dr. Tom Autrey of the Pacific Northwest National Lab and Dr. Rajesh Ahluwalia from Argonne National Lab. Tom is a chemist and has been a scientist at PNNL for around 30 years and has worked extensively in hydrogen storage materials for at least the last 15 or so, including the leader role and the former Chemical Hydrogen Storage Center of Excellence. Rajesh has over 20 years of experience doing analysis on hydrogen for transportation and has led Argonne's efforts on hydrogen storage system analysis for [inaudible]. So, it's a background experience related to this topic and I'm sure will provide a very informative webinar. So, with that, I'll turn it over to you Tom.

Tom Autrey, Pacific Northwest National Laboratory

Thanks, Ned. Good morning, everybody. As Ned said, this is a pretty exciting time, looking at new concepts, looking beyond vehicles. So, I was asked to help organize this and got some help from our group here in the HyMARC team. So, this outline will give you kind of a breakdown of what we hope to accomplish here today, give you some high-level definitions, concepts definitions, objectives, and goals. Argonne then, I'm going to pass it on to Rajesh and Dennis, and they're going to talk about some of their preliminary analysis then we'll get into more of the definitions of what we talk about one-way carriers, round-trip carriers, and making carriers without hydrogen, give you some examples of that.

Then, Rajesh will pass it back to me. Then, I'll kind of give you more specifics, as Ned mentioned, of what HyMARC has plans to do, specific objectives to HyMARC, some examples that we've pulled together. Trying to identify gaps in knowledge, this is one of our big driving forces. Some of the tools, scientific tools that we're using and using foundational research to kind of help enable rational design. I hope I can get to kind of explain to you what I mean by that. Summarize that and then have an opportunity for questions and answers.

Next slide. So, as part of the H2@Scale, there are these new opportunities, as Ned mentioned, looking at intermittent sources of electricity. As one of those, how do we store this? Can we store it in chemical bonds in hydrogen? So, bulk storage and transport of hydrogen is of critical importance and that's a big part of H2@Scale. So, these storage needs may range from daily to seasonal and duration. And transport distances may exceed hundreds of kilometers. So, you may want to store it – make your – store your electrons and chemical bonds in one place and then you may want to transport that somewhere. So, trying to understand these issues and what materials will help you do that.

So, the hydrogen carriers research effort is seeking new concepts and materials that have potential to provide advantages over compressed and liquified hydrogen storage and transport. So, I think Rajesh will give a nice, kind of a benchmarking, if you will, of these other carriers, these hydrogen carriers that will compare to compressed hydrogen gas.

Next slide. So, some definitions. These might seem a little redundant, but hydrogen carriers are going to be hydrogen-rich materials. So, it's not necessarily the same requirements that will be for onboard. So, they may or may not be the same materials. But it could be liquid or solid phase. It's not just liquid phase but solid phase materials could have some real specific applications. It may need to be liberated on demand, putting it through a reactor, getting the hydrogen off. So, ideal carriers will have high densities at low pressures and near ambient temperatures.

So, the formation of the carrier and the release of the hydrogen should be as energy efficient as possible and to minimize the energy penalty associated with the use of hydrogen to carry and transport that. So, you can get a lot more hydrogen density in there, but you have to weigh in how much – what's the economics of getting that hydrogen on and hydrogen off again. So, it's not just how much – not just gravimetric and volumetric as – for vehicles, it's also the whole thing. How do you get hydrogen on? How do you get hydrogen off?

Next slide. So, just some real high-level starting objectives for this. We want to investigate pathways that is going to optimize these hydrogen carriers to realize the most efficient, safe, and economical approaches to just generally transport hydrogen from a production facility to a city gate. Rajesh will have a really good example of what we mean by that. Then we want to be able to facilitate geographically agnostic hydrogen storage. So, the goals, to kind of high-level goals here, we want to look at novel materials and new concepts in liquids and solids. Then, kind of open this up to think about alternate approaches to prepare and release hydrogen from hydrogen carriers. Are there alternatives to just heating this up? So, then, the next slide.

I think – so this is where I'm going to hand it over to Rajesh. So, he's going to give some examples of these hydrogen carrier pathways for three different options. So, Rajesh, it's all yours now.

Rajesh Ahluwalia, Argonne National Laboratory

So, for our initial study, we selected three liquid hydrogen carrier pathways, also abbreviated as LHC, to cover different classes of carriers. The examples here are liquid ammonia and liquid MCH/Toluene system. These represent class of carriers that require, for example, a steam method reforming plant for hydrogen production. On the other hand, liquid methanol represents a class of carriers that does not explicitly require a hydrogen production step. We also selected these looking at liquid ammonia and liquid methanol, which are one-way carriers, whereas MCH/Toluene is a two-way carrier. One would think that ammonia and MCH are easier to produce using our renewable hydrogen than methanol which would also require a source of CO2.

Our initial results are for a scenario in which LHC is produced centrally, transmitted via truck to city gate, located 150 miles away, where it is dehydrogenated. The gaseous hydrogen product is decomposed, purified to fuel cell quality hydrogen using PSA. The gas terminal here serves multiple functions including bulk storage of hydrogen, buffer storage of hydrogen and a facility to load and unload tube-trailers for hydrogen distribution to the fueling stations.

So, the table which is underneath that I don't have a control over, it shows – what's that? Yeah, so the previous one which is underneath here shows you some of the boundary conditions for producing and the processes for producing ammonia by [inaudible] process which is also decomposed catalytically at high temperatures. Methanol is also produced, in our study, by steam reforming to produce synthesis gas following commercial methods for synthesis of ammonia and purification. MCH is produced by hydrogenating Toluene over non-PGM catalyst and dehydrogenated at city gate using supported catalyst. As a reference, we also include a gaseous hydrogen pathway in which hydrogen is produced by SMR. The terminal now is at the production site, since there is no city gate to speak of.

So, in the next slide, we summarize – so if you go to the next slide, Eric, it summarizes [inaudible] assumptions. I only want to touch on a few of them. So, the first one is that the scenario that we've been looking at is for 50,000-kilogram hydrogen per daily production. So, this represents an entry-level or a transition-state scenario. It would represent, for example, about five to ten percent market penetration in a medium city, medium-sized city like San Diego, California.

50,000-kilogram hydrogen per day corresponds to 370 tons per day – this is bulleted here – ammonia production; 350 tons per day, methanol production; 890 tons per day, MCH production. So, as reference, commercial ammonia plants would have capacity of the order of 2,500 tons per day. So, that's about seven times as large. Some of the modern methanol plants that are being built would have capacity of 5,000 kilograms per day. So, that's 15 times per large. The MCH/Toluene being demonstrated by Chiyoda, so the pilot plant for that would have a fraction of the capacity that we list here. I also want to mention that we do have a ten-day geologic storage for plant outages. So, that's part of the GH2 terminal. Hydrogen is being distributed in 500 [inaudible] which typically have a payload of 1,042 kilograms or so.

So, in the next slide – so, whereas, ammonia and methanol production are – and decomposition are mature technologies, MCH production and decomposition technologies are at a pilot stage. So, in the next couple of slides, I talk about some modeling results on hydrogenation of Toluene and dehydrogenation of MCH. What our model shows – and this is consistent with what's happening at the pilot scale – is that one can get nearly complete conversion of Toluene to MCH in a catalytic reactor operated at 240° C and 10-atmosphere with a four-to-one hydrogen to Toluene ratio. We do need a makeup for Toluene, which is about two and a half percent. This is primarily due to the dehydrogenation losses that I'm going to talk about in the next slide.

This is - the dehydrogenation process is exothermic. There is potential for raising steam in larger capacity plants, but not something that we would consider at the scale of 50,000 kilograms per day, a hydrogen facility.

So, if you move on to the next slide, which is on dehydrogenation – so the hydrogenation step was conducted in a non-PGM catalyst. It is not considered a critical barrier. Dehydrogenation of MCH, however, is using a precious metal catalyst. In this case, platinum on aluminum. There has been quite a bit of research looking at selectivity and durability of these types of catalysts.

Our modeling study shows that in order to obtain higher than 95 percent conversion, we would need to keep the pressure down to about two atmosphere or so. That would be a reactor operated at 350° C. The PSA typically operates at 10 atm. So, we'd need a four-stage compressor to raise the pressure of hydrogen from two atm to 20 atm. As I mentioned, there is about two and a half percent loss for toluene and MCH in this system, we end up using 11 percent of the hydrogen that we produce during the dehydrogenation step. This stale gas is used in the natural gas to supplement the heating value of the natural gas in the hydrogen burner.

In the next slide, we show you or we summarize the results about levelized cost of hydrogen distributed around to the stations. So, our baseline case, the gaseous hydrogen, the levelized cost is $4.80. This includes producing hydrogen, includes transmission and distribution to the stations. But it does not include the station cost. So, obviously, the very limited scenario that we looked at, production and decomposition of LCH are extra steps. They incur about 33 to 47 percent incremental cost over the baseline of the GH2 scenario that we talked about.

The production costs line up at ammonia greater than methanol, greater than MCH. The decomposition cost is – goes the other way. That is the methanol almost the same as MCH. So, methanol is being dehydrogenated by a steam method reforming step. This is a plain decomposition over MCH, is over a precious metal catalyst greater than ammonia. Transmission and distribution, we do save somewhat with MCH over the methanol that we – or rather it's more expensive for the MCH rather than the methanol.

I do want to mention that the scenario that we just described is for 50,000 kilograms per day. The DOE record is for very low production volumes, perhaps on the order of 1,000 kilograms per day. The cost there is into $16.00 per kilogram hydrogen dispensed at the station. Of course, we do not have the station costs included in our study. All four scenarios that I just described, they all use geologic storage, which is not available at all sites. So, the future studies will consider options taking advantage of liquid hydrogen carriers to circumvent the cost and non-availability of geologic storage at all sites.

So, in the next slide, some more results. These are available in Argonne's slides and were presented last year at the AMR. So, this one, again, looking at the levelized costs broken down in terms of capital operation and maintenance, fuel, and utilities. So, 70 percent of the incremental cost in the ammonia and in the methanol plant is because of the added cost of the – the capital cost of making ammonia and methanol and decomposing it. For MCH, the capital cost is lower and it's equally – the balance is equally divided between O&M fuel and utilities.

So, in the next slide, is energy efficiency. So, not too surprisingly, the energy inefficiency because of the additional production and decomposition of LCH is about – can be up to 50 percent. Here, we make the assumption about that all the electricity that's consumed in these processes can be – we can come up with a single metric of fuel and electricity assuming 33 percent efficiency and the energy efficiency that we calculate or the energy consumption lines up as MCH nearly the same as ammonia at 2.52 kilowatt hour per kilogram hydrogen, per kilowatt hour of hydrogen heating value greater than methanol, greater than the gaseous hydrogen step that we are looking at.

So, in the next slide, now we would like to look at scenarios in which the liquid carriers could be advantageous. So, one way, and I hinted on that earlier, was to look at larger plants and take advantage of the economy of scale. If you look at these two figures, this gives you an idea about where the recent methanol and ammonia plants have been built in United States. So, you will see a concentration of these on the Gulf Coast. Takes advantage of the critical energy infrastructure that's available over there. It also takes advantage of the differential in energy prices, natural gas price in the Gulf Coast, for example, that's low at $2.55 per million Btu versus California, which is at $6.80 per million Btu.

So, the scenario that we have looked at is a very large central production plant. So, I hinted off that, talked about that, that typically these plants can be for methanol, can be up to 5,000 tons per day. We look at even futuristic plants which might be at 10,000 tons per day in which a syngas is being produced by ATR. I will have something more to add to that. These are transmitted by railway across to California – that's about 2,250 kilometers away – stored and then transferred by trucks to the city gate. So, what we are doing here is we are producing 10,000 tons per day and we are syphoning off 350 kilograms of it because there's a limited demand right now. So, the balance of the city gate looks exactly like what was in the reference scenario.

So, I have a couple of slides talking about the economy of scale and how it affects. So, the next slide is showing what type of the dependence of the production plant technology on the scale of production at a low scale of 1,700 tons per day. The reference is one step steam method reforming. The modern plants almost invariably use SMR plus ATR for syngas production. So, this is a two-step process at an even larger scale of 10,000 tons per day. Something that's talked about in the literature but has never been built is a one-step ATR-based syngas production step.

So, if you go to the next slide, so you can look at the capital costs, how that depends. So, that's in million dollars per ton per day of methanol, how that varies with the plant capacity. So, going from 350 tons per day, which was the case that we were looking at, if we absolute could go to 10,000 per day plant, why there is almost a factor of two decrease in the capital cost. So, at the right, you see this involves our reference case, very low methanol production capacity. This is the intermediate case.

10,000 tons per day is what I want to present a few results. I just wanted to mention that about 50 percent of the total capital cost, regardless of the technology that we were using at is in the reformer air separation unit and our CO2 removal. So, that it counts for about 50 percent. I also wanted to mention, and that was an advantage that was discussed before, that the storage cost represents a small fraction of the total capital cost.

So, if you put all this information together in the next slide, so now we can look at the levelized cost of hydrogen for the scenario of a very large, centralized production of methanol in which a small fraction has been syphoned off for production of fuel cell quality hydrogen. This is a result that I presented earlier at the small scale where the cost was $6.70. Now we see that, with the new scenario, the levelized cost, is very competitive with the baseline GH2 scenario. So, where did the savings come from? The saving came from – 50 percent of the saving came from the economy of scale. Other 50 percent came from the lower cost of the feedstock.

So, in the next slide – so here is a summary of where we are going. The first block is to calibrate our initial results. So, we've been talking to the various experts, looking at the field data for ammonia and methanol plants of different capacity since the end refining our estimate. We are also talking to OEMs, looking at if you can verify, validate, and calibrate our results for MCH production and dehydrogenation. We will continue to look at scenarios that favor hydrogen carriers.

We are looking at different demand and supply scenarios, for example, with the byproduct hydrogen, where the LHC step can be particularly advantageous. We also want to look at renewable hydrogen. I had a couple of sentences about why ammonia and MCH may couple very well with renewable hydrogen production. The last one is to do reverse engineering and coordinate with HyMARC. On that note, I am going to hand the control back to Tom.

Tom Autrey

Thanks, Rajesh. Eric, let's move to the next slide and that number five will start to become apparent. So, what I wanted to do was give you some more specific objectives of HyMARC. I mean there's the objectives of the hydrogen carriers at a higher level. Then HyMARC really is going to continue their role as trying to leverage our capability and expertise for accelerating progress in carriers. So, we're looking to the community for development of new materials and ideas. We're available to help with accelerating the progress and doing research in that area.

But kind of beyond that, when we started to think about how we would define our roles, we want to look at, "What are the important properties of hydrogen storage materials beyond onboard vehicular?" So, determining advantages and limitations for materials and approaches to carriers for transport which the material could be different for transport than for long-term storage or even for short-term storage. So, all these different materials, what would be the advantages and disadvantages for different applications. We're interested in looking in trying to understand novel approaches to release or absorb hydrogen onto carriers. I'll try and give some examples of that to follow.

When characterizing novel approaches to preparing carriers that do not require the discreet step of making gaseous hydrogen. Can you take electrons and protons from water and store those in carriers is one example. Rajesh gave example of methane, the methanol formation. In both of those, you don't need to have – make hydrogen and store that in a separate step and then add that. Comparing approaches that can be used to prevent phase changes. I'll try and give some examples of that. It seems as though hydrogen-rich materials are soluble or stay liquid and then as they start to lose hydrogen, then they could start to solidify. So, how do we prevent that?

Then, catalysis is going to be important in trying to understand all the different things you need to consider in catalysis, the stability, the cost, the rates. The rates are going to depend, again, on how much hydrogen you need at any given time. So, all these different applications could have different needs that are more important for one application or another. Heterolytic versus homolytic activation of hydrogen for to putting hydrogen on or taking hydrogen off. Then validating concepts for rational design. I hope I can kind of explain what I mean by that.

Next slide, Eric. So, I want to move in to some examples. These are, by no means, the only examples or primary examples. I'm hoping to provide these as things that could seed new ideas. We do a lot of electrocatalysis at our laboratory. So, I have some colleagues that I like to listen to and learn from. So, can we do electrocatalysis? Just some simple examples of CO2 to [inaudible] or to formate or even onto methanol. What kind of – could you do electrocatalysis to do that? Are there advantages of electrocatalysis over thermal catalysis?

Taking a phenol to a cyclohexanol? Could you do that electrochemically without having to make hydrogen in a discreet step? So, then it becomes, can you run that backwards without having to generate hydrogen or can you use the – transport this around, release hydrogen and run this through some sort of fuel cell? So, lots of possibilities.

The next slide. Some other examples that I'm kind of fascinated by personally are aqueous mixtures of organics. So, here's an example I give of an alcohol where half the hydrogen comes from the alcohol and the other half comes from water. So, if we want to store something in a smaller amount of volume and transport it around, could you transport the water – not transport – I'm sorry. Transport the alcohol or store the alcohol and then, later on, wherever you need to get the hydrogen off, you then doubled your volume, but you get part of your hydrogen from water. So, this would be where water is readily available and there's cost to that. Water's not free.

But this is interesting chemistry. The reaction to make the acid, that's uphill. So, that's endothermic. But are there ways that you could tune the thermodynamics of the acid by stabilizing it as a base – with a base as a salt? So, the free energy for the reaction is going to be proportional to the PKB of the acid and the base pair that you choose. So, you could – this is kind of potentially an example of a rational approach to looking at designing some material. So, understanding how you can tune the thermodynamics.

On the next slide, this is – comes back to one off the things we started to talk with Rajesh and Dennis about is this formate by carbonate cycle. I find this – this is one of the perfect hydrogen storage, from a thermodynamic point of view. You can take a formate and dissolve it in water. If you throw in some catalysts and you wait long enough, you make bicarbonate and hydrogen. So, this is an example of some NMR studies we just recently did with some colleagues and coworkers where we just followed this reaction at 20 degrees.

So, it starts at the bottom where we start with formate. Then, having a catalyst in there, it releases hydrogen and makes this bicarbonate. The equilibrium constant is about 1 for this. So, this reaction is readily reversible. So, there are lots of things to ask good questions about this. Solid really again of the product versus the starting material. What kind of catalyst do you want to use? What do you do with the bicarbonate once it's formed? Do you get credit for taking CO2 out of the atmosphere? Or you can recycle this. So, that could all – all those sorts of questions could depend specifically on the application you want.

Formate is a pretty benign compound. Talk to other people working in the field, and they've pointed out to me that it's being looked at as a road deicer. So, there, it's kind of a non-toxic relatively, at least environmentally safe material. So, if you could store "hydrogen" on formate as a solid and add water later when you needed to get the hydrogen off – so half the hydrogen, again, comes from the carbon and half comes from water – you can minimize your volume density. So, is there advantages to that and when are there advantages to that?

Next slide, please. Another thing that I've been really fascinated by is I've been calling chemical compression. Chemical compression may have different meanings in different places, but what I'm talking about here is that if you have some compound like ammonia borane, it decomposes, and you can never regenerate it because the pressures you have to go to are so high that you can generate high pressure of hydrogen. But formic acid is really interesting because delta G is negative and delta H is positive. So, this is better than ammonia borane in that the reaction isn't going to have thermal runaway. So, you can – it's entropy controlled.

As it decomposes, you make hydrogen and CO2. You can generate pretty high pressures. And so, how do you compare apples and oranges to figure out, "Is there some way we can minimize physical compression? Can we use do – use formic acid decomposition to do the first stage of compression?" So, when would that be important and how valuable is that? So, then, there are lots of questions do you ask and try and understand, "How do you do separations then of CO2 and hydrogen when you get to these high pressures?"

You need to control the selectivity so you get dehydrogenization instead of dehydration. Then, what are the best approaches to make formic acid because, as it is going backwards, and you have to go uphill, how do you form that and what's the cost of that? So, how do you trade – compare the cost of making formic acid to the cost of a physical compressor on is a really over-simplified way but these are the sorts of concepts we're trying to understand.

On to the next slide. So, this is really too wordy, I guess, but the title is really probably what I really want to get across here is that HyMARC is really trying to address gaps in knowledge. So, I touched upon some of this with the compression. What kind of reactors do you need to design for these liquid reactions? Depends on the rates at which you need hydrogen, again. If you need two grams of hydrogen per second, then it's going to be really difficult if you have to worry about a three-phase gas/solid/liquid interaction. So, if you don't need the hydrogen at those sorts of rates, would this – looking at these gas/liquid/solid reactions, when do you have to worry about that? When can you not – when do you not have to worry about that?

Then, some of them are just really more foundational in nature about designing proper catalysts that are more economical and have long stability. So, with the expertise in HyMARC and the molecular foundry and all the expertise in making MOF and materials and catalysis, hopefully we can address some foundational questions there.

Then, just kind of on almost the other end of things, for characterization, liquid phase PCT. So, pressure composition isotherms are used to get very valuable information for solid materials and metal hydrides. So, can we develop PCT approaches for looking at liquids? What would even a PCT curve for a liquid look like if you have multiple hydrogens coming off of methylcyclohexane to make toluene? What are – if you can get the thermodynamic data, that would be really valuable, but it's going to be tricky to do because it's a liquid. You have to worry about the vapor pressures of these things. Again, the expertise of the people at NREL are going to be able to answer whether or not this is feasible, what can we learn from this, and are there better ways to do this.

Then, just kind of at the end. I think I'm going to touch upon this about fuel blends. This comes to this low vapor pressure. So, are there ways you can make liquids by blending materials? So, I'll try – I think I'll have an example of that coming up. Eric, the next slide, please.

So, I'm moving, I guess, here into some research tools. So, the PCT is one of them that we're looking into and talking to NREL about but that my coworkers here have done some really fascinating work. Really nice, elegant ways to look at liquid phase transformation by NMR spectroscopy. So, PNNL really tries to bring in NMR capability into the HyMARC team to help out everybody in HyMARC as well as people that are being funded in individual projects by DOE. So, this just gives kind of this nice example of this peak NMR tube where it's been pressure tested up to 1,000-bar.

Temperature range is in kind of the area you'd want for a material. So, if you wanted to do more stuff at lower temperatures, we'd have to think about ways to do that or higher temperatures. But this gives an example of measuring in equilibrium as a function of pressure. We can do this as a function of temperature. So, again, a way to get some thermodynamic data on, in this case, these liquid carriers.

On the next slide. This is another example of what we've been trying to develop, ways to look at both thermodynamics and kinetics. It shows some calorimetry. We were looking at some liquid carriers and trying to benchmark some of the nice calculations that were done by their products and other people where we can get thermodynamic and kinetic information here. So, you can integrate the area under that curve and get your thermodynamic data. Then you look at the time dependence of that and you can get kinetic data. So, we've been looking at different catalysts. So, we have a direct way of kind of monitoring efficiencies of catalysts as far as looking at rates of reactions.

Next slide. So, here, I want to give a couple examples of what I consider rational design. So, this is where we're trying to come up with ways to keep things from doing phase separation. So, when we had opportunity to work with our coworkers at U.S. Borax, they had pointed out to us that there's these solubility tables. If you vary the ratio of the metal to the boron, you can change the solubility. So, one of the problems with the sodium-borohydride was the stability of the product. The borate is less soluble than the starting material. So, you're limited by that.

So, if you can come up with a material that had a Q, which is this ratio of metal to boron, of point-three, you get twice the solubility of the products. So, when you look at that, you say, "That could probably be sodium – like a tetraborane or a triborane. So, the triborane, there was a lot of nice work done by a number of groups. That's water stable and water soluble. So, that has an opportunity to give more hydrogen than the borate. But the challenge with this was one way. So, making these materials was the challenge. But this is kind of an example of rational design, some way to predict what you can do to help a class of materials.

On the next slide – I think here's another example that I really like from the literature where you could predict the thermodynamics of hydrogen addition to an arene ring, a cyclic compound, by knowing what its Hammett parameter is. So, here it shows different classes of materials – phenol, indols, piperidines. They all have a slightly different slope and those are the Hammett, sigma Hammett parameters down there on the X axis. So, if you know what the Hammett parameter is, you can predict what the enthalpy for hydrogen addition is. So, what I would like to know is what determines the slope of these materials and, then, can you use computational approaches to look at the two extremes of that and get the slope of the line and that tells – make some predictions about new families of compounds for the enthalpy of hydrogenation and try to understand how to lower that.

So, I think the next slide is getting close to the summary here. So, literally, we just kind of throw a bunch of things up there, kind of summarizing things. Where we really want to help the DOE and our coworkers understand these alternate concepts; you know making hydrogen carriers without making hydrogen. One approach is the electric chemical I touched on, is using water as a reactant and storing it, the compound, separately. A good way to reduce volume of these things.

How useful and valuable and when is chemical compression going to be helpful? But you have to worry about selectivity, integrating separation technologies, preserving the liquid phase when we look at the formate and bicarbonate. Bicarbonate is at least half the solubility of formate. What can you do about those sorts of things? Are there ways that you could integrate electrochemical and thermal processes to enhance some way to get hydrogen off or on or cycling?

Bio-inspired processes. Eutectic systems; this is something that we're interested in. Can you take two solids, bring them together, make a low-melting liquid and then use that and then preserve a liquid throughout. Then, there's – solids are going to be important as well in MOFs and COFs and when would those be valuable and what sorts of circumstances. Another thing that we've kind of been curious about from a foundational point of view is heterolytic absorption of hydrogen on materials versus a homolytic decision. Then dynamic materials. So, with that, I kind of – that's the summary of what we've got. So, I think now it's time to try and answer some questions.

Eric Parker

Yeah, thanks Tom and Rajesh. Reminder for everyone, if they haven't already submitted their questions via the chat box. I'll turn it over to Ned to address some of the questions we've gotten already.

Ned Stetson

All right, thank you, Eric. Yeah, so we have several questions submitted. Actually, I will assign the first question to myself. The question is, "Is DOE going to develop key technical targets for hydrogen carriers, easy energy density, conversion efficiency, et cetera for different applications?" The answer is yes.

We are in that process. One of the reasons we initially asked Argonne to start the baseline study is so we can actually start understanding how to – carriers, which people have researched at this point in time, how did they compare with the more conventional ways of moving and storing hydrogen, so we can actually start seeing where the needs for materials and where do we need to improve materials. At the same time, we're also looking at all these areas and use applications being considered under H2@Scale to identify the need for those applications, so, again, we can start identifying, "What are the key important – what key parameters are important for the move and store of hydrogen and how can carriers address that?"

So, we are in that process. We will be, at some point, issuing some technical targets. But we don't have them ready at this point in time. So, the main comparison, today, is, "What are the advantages of any carrier that's being developed with respect to either compressed or liquid hydrogen?"

So, moving to our second question. So, Rajesh, since you kind of went before Tom, I will give you the next two. So, first, it starts off with a comment. "Great study. I had not heard of anyone considering gaseous hydrogen for bulk storage, only liquid hydrogen. Will liquid hydrogen be analyzed and compared as well?" That's for you Rajesh.

Rajesh Ahluwalia

Yep, yep. So, I think we're not quite done with gaseous hydrogen because, as you know, the bulk storage of gaseous hydrogen, when we talk about ten days' worth at 500,000 kilograms is a big challenge. We don't want to rely on geologic ways because they're not always available. So, there is work to do just with the gaseous hydrogen. But liquid hydrogen is definitely another reference, in addition to the gaseous hydrogen. So, the reason we didn't look at it so much was because other institutions, including Argonne, [inaudible] and Sandia, they have looked at the liquid hydrogen. But yes, that would be a good comparison, also.

Ned Stetson

Okay, thank you. The second question for you, Rajesh, "What was the criteria that got methylcyclohexane toluene selected over the historically used decalin, tetralin, naphthalene, et cetera?"

Rajesh Ahluwalia

Yeah, I think they're all very good options and we didn't quite touch on Hydrogenious, what they are doing. We regard them as competitors. They all have advantages. We selected MCH because this was not meant to be an exhaustive study of looking at all the options, but where we could clearly see some advantages or some uniqueness. So, we looked at MCH or toluene up here. Others are competitive as well.

The reason we looked at it is because a pilot plant is being built in Japan by Chiyoda. So, it was a good reference for us to look at since we can also talk to those people. I already noted how this would couple very well. Yes, there are definitely other pairs that may be equally good, and some may be equally better, or some may be even better. I think we may look at those options as well.

Ned Stetson

Okay, thank you. Tom, I'll give you a couple now. So, one question we have is, "Can the bicarbonate react with calcium hydroxide to release additional hydrogen? Calcium carbonate could be a marketable chemical – or could calcium carbonate be a marketable chemical?"

Tom Autrey

Good question. I think – I mean we've been talking about this. So, when you're looking at these scales of 50,000 kilograms per day for storage, it is – if you make 50,000 kilograms of something else, is there a market for that? So, there might be some smaller amounts that you could use, but I don't have an answer for that. I think those – all things should be considered. Could you do something with these byproducts? Good question.

Ned Stetson

Okay, thank you. Tom, I'll let you take the first stab at this and then I may chip in as well. So, the question is, "Some of the paths shown emit CO2 at the point of use. Is that a consideration?"

Tom Autrey

That one I don't know if I should – I can touch. I'm going to punt on that one because I – yeah, I'm just not going to say anything that's going to get me in trouble, I guess. You – I'll let you handle that one.

Ned Stetson

Yeah, I thought that was going to be the case, Tom. So, yes. CO2 emission is a concern. However, if it's a technology that consumes CO2 on the formation of the carrier and then – but CO2 is released again so the net emission of CO2 is near zero, then it's definitely something of consideration. One of the issues with carriers that we – even though we may have a perfectly reversible reaction, we are temporarily and spatially separating the generation of further – the uptake of hydrogen generation in that carrier versus where hydrogen gets released. So, in that case, where CO2 would be released again. So, we – our preference would be carriers and pathways that have at least near zero emissions of CO2.

Okay, so I'll actually take the next question again. "How does DOE design its targets? How are the targets used?"

So, thank you for this question. We take a number of different factors in consideration when we establish targets. So, as I mentioned, we have Argonne came with this baseline study now. HyMARC is starting some foundation research which will also provide us some input. But we will be carrying out this message such as workshops on carriers where we get stakeholders and, hopefully, a broad range of stakeholders from people who would be producing hydrogen and generating carriers, the people who would be transporting and using carriers and the people in use, get feedback from these stakeholders. We could also do surveys and request information to get information. Then we pull that information together. Then we go back and, again, take in all this information. We then try to determine target space on the input from the end use and the stakeholders. So, let's see.

Tom Autrey

Ned, can I just add to that? That you mentioned the workshop and then I did – I forgot to mention that we will be doing a workshop on hydrogen carriers the week of February 11th. That will probably one and a half days. It might be the 12th and 13th. I'm working with Tom Gennett at NREL to organize that. We have the rooms for, I think, the 11th, 12th, and 13th or at least the 12th and 13th so people could travel in on a Monday. So, we'll address some of those, getting stakeholders in and trying to get feedback from a larger group on answering those questions.

Ned Stetson

Okay. I think we have time for one more question. We do have one here. Tom, this is for you. "Have you considered the auto thermal cycle described by Air Products where the reversal partial oxidation of the carrier delivers the heat of reaction for the dehydrogenation?"

Tom Autrey

We haven't – we looked at that a few years ago. I mean that's an example of a creative approach, an alternative approach to doing these things. At the time, we were interested in coupling exothermic and endothermic reactions together and using an exothermic reaction for releasing from the BCN compounds, the cyclic BCN compounds, because one of those steps is exothermic and the others are endothermic. So, Kristen Brooks helped with some of that analysis. That's a great example of alternative concepts that need to be looked at to try a couple of these things. So, we have – I've looked at that. I know about that. That is a good example of an alternate approach to things. There's no right answers or wrong answers right now.

Ned Stetson

All right, thank you, Tom. Thank you, Rajesh. I think we're getting close to the end of the hour here. So, I do want to thank all of you for listening to the webinar. I will turn it over to Eric in just a minute. But I do want to repeat or emphasize what Tom mentioned is that there is a workshop being planned by the HyMARC team. This will actually be very valuable input into the DOE consideration for targets. We are working on H2@Scale. So, you will be hearing and seeing a lot more about H2@Scale going forward in the future.

Again, all of this is being integrated into the H2@Scale framework. So, with that, I would like to thank all of you from the DOE side for attending and listening to the webinar. If you have any questions, please feel free to submit them to the website or you can send them directly to myself. So, with that, Eric, I'll turn it back to you.

Eric Parker

Yeah, thank you, Ned, and thank you, Rajesh and Tom, for a thoughtful and informative presentation. That does conclude our webinar for today. If we didn't get to your question or you think of one later, please feel free to email Ned or the presenters, like he mentioned. Also, be on the lookout for a recording and the presentation file to be posted online in the near future. I encourage everyone to sign up for the monthly newsletter which includes information on future webinars and workshops like those mentioned. With that, I'd like to wish everyone a great rest of their week and goodbye.

[End of Audio]