Let's hydrogenify for transportation – but where to start?

Introduction

Finally, as so often in politics, what logical reasoning and millions of hours of R&D work couldn’t achieve was brought to us by “accident”. Due to the corona crisis, the EU decided to do a big economic stimulus package and I am very happy that (at least on this side of the ocean), several governments decided to direct money towards where it is most urgently needed: A sustainable energy ecosystem, where hydrogen plays in important role as a key technology.

There are numerous discussions going in which areas of industry and transportation hydrogen will have more advantages than disadvantages on the short- and long run. In this article, I would like to share my personal view on this topic.

#1 Marine

Which transport sector has to be a number one priority in transitioning to hydrogen? I my eyes, clearly shipping of high-volume freight and large cruise ships. It is both a must-must-do and low hanging fruit at the same time. I will explain both.

Why is it a must do? At a first glance container vessels or oil tankers (which will become hydrogen tankers eventually) emit about 55 to 140 times less CO2 per freight-ton-kilometer (FTK) than aircraft and 10 to 25 times less CO2 than heavy-duty vehicles due to their low speed and high utilization [1]. However, the pure volume that is transported by ships annually is gigantic: 60.000 billion FTK were performed by ships – more than by any other kind of transportation [2,3,4]. Therefore, the total CO2 emissions amount to 2.5 % of total worldwide GHG emissions, which is about 940 million tons CO2 per year; with a potential increase by up to 250 % until 2050 if we continue business as usual [5].

However, what makes the emissions of ships special is the fuel that is usually used for ships named HFO (heavy fuel oil). It is created as a “low quality” by-product when crude oil is processed during the production of gasoline. This type of fuel creates significantly more other greenhouse gases besides CO2 during combustion, so that 15 % of all NOx emissions and 13 % of all SO2 can be attributed to ships [6]. Furthermore, and what is maybe the most important point is that the fine dust emissions are not regulated by the international standard MARPOL Annex VI that sets threshold for all the other emissions. Therefore, as for instance reported by the German NGO “NABU”, the fine dust emissions in harbors are regularly at very high levels [7].

Now to the second point: Why is it a low hanging fruit? Normally, three things are brought up as impediments for a transition to hydrogen: (1) Infrastructure, (2) Weight, volume and efficiency of fuel cells and hydrogen storage, and (3) Costs. In the marine sector, solutions to all three issues are straight forward.

Let’s start with the infrastructure: A total volume of 792 million TEU (twenty-foot equivalent unit) was shipped in 2018 worldwide. More than half of it, 409 million TEU, were served by only 30 harbors of which a big majority is based in China, Germany and the Netherlands – countries that are pioneering the hydrogen transition already. This means that the required infrastructure is very localized, and a focused effort would have tremendous impact. Also, harbors are situated right at the seafront (surprise, surprise J); hence, close to offshore wind parks that can be used to produce the required electricity for hydrogen production as close as it can get. Personally, I cannot imagine a better synergetic scenario to build up a hydrogen supply chain.

Secondly, ships have probably the most relaxed requirements on weight, volume and efficiency of fuel cells in comparison to all other means of transport. Already today fuel cells from Siemens are used as part of the drive train in German military submarines. This means, that these fuel cells already fulfill requirements that are way over the top compared to what would be demanded for civil use of shipping. If this is still “too progressive”, an intermediate step could be combustion engines based on hydrogen as explored by BMW in the 90s. Also, concerning the hydrogen storage, ships offer way more flexibility than any other means of transport.

At last, the question of cost: As said above, the technological requirements are quite relaxed, therefore the costs of production, too. Also, the shipbuilding industry is not a high-volume industry like automotive, therefore not dependent on the economy of scale to kick in. Furthermore, the money saved on emission certificates could compensate for the higher initial cost of hydrogen.

#2 Railway

Right after the marine sector, I would prioritize the transition in railway. When I talk about railway here, I don’t mean high speed rail which usually uses bow collectors to get electric energy directly from the grid but regional rail that mostly utilizes diesel locomotives. Although their contribution to total GHG is comparably low, I see three major reasons why replacing diesel locomotives can be quick win but a quite important one.

First of all, we don’t have to develop one. Already back in 2018, a fuel cell powered version of the Alstom Coradia Lint, names “iLint” (s. Fig. 2), started its regular operation in Germany. I bow my head humbly to the engineers and far-sighted managers who could convince their management to invest into this technology and then execute successfully, so that Alstom became truly a pioneer in the field. The development appears to have happened quite fast. In 2014 a Letter of Intent was signed by several governmental stakeholders and after less than 3 years the first real-world test runs were taking place [8,9]. As with ships, an important prerequisite, that allowed this development to happen quickly, are the mild requirements concerning the weight and volume of the fuel cell system (balance of plant) compared to e.g. planes or cars. The locomotive of a train actually requires some minimum weight to have enough friction between wheels and rails in order to operate properly. Therefore, “super-light” (and therefore also expensive) fuel cells do not bare any advantage in rail applications. This is why this type of transportation is a “quick win”. Technology is here, you just have to buy it.

This brings me to the second point: Who are the buyers? The railroad service is run by a small number of companies which act as - I would title it - “rational market participants” (maximizing their profit or/and fulfilling their purpose to provide an excellent transport service) which is in big contrast to a huge number of “private clients”, e.g. the automotive sector, who can be lead strongly by rather irrational motives. In many countries the bespoke companies also enjoy a large governmental participation. Therefore, the legislator can anticipate quite well their rationale and think about a legislation that would help to twist the market equilibrium towards hydrogen. To some extent this is already happening i.e. by legislation that puts an upper threshold on the CO2 emissions permitted on particular railway routes, but an investment into hydrogen infrastructure along such railroad routes would help further. Again, compared to automotive, in the case of train, the infrastructure problem is much easier to solve: The infrastructure can be designed exceptionally well since the rails are fixed and the demand can be predicted according to the existing schedule.

The quick win and an important pay-off that we get with an investment into hydrogen for regional rail service is that it would certainly help to create a large-scale public acceptance for the technology. If you ask a person on the street about hydrogen, you will get a history lesson about what happened to the “Hindenburg” in 1937. Fact is, that most of use a vehicle which is loaded with a highly explosive liquid on daily basis and feel very safe about it. Why? Because we got used to it by doing it all the time. At least in many European countries regional rail is a very common way of going from A to B. When people go with a hydrogen train day-by-day and it works out well – this is what their perception of hydrogen is going to be: “A safe ride with a sustainable technology – I’m proud to use it.” As a nice goody on the tech side, we get thousands of millions of roadmiles of experience in running fuel cell technology which will surely benefit for the development of better fuel cells also for other industries.

#3 Aviation

When ships and regional rail is on its transition towards hydrogen, a strong focus has to be on the aviation sector. Although the total GHG emissions from aviation that amount to roughly 905 million tons CO2 per year or about 2 % of total GHG emissions worldwide [10] are significantly lower than of trucks or cars, most of these emissions are released at high attitude. At high attitudes (~ 10 km) the impact of emissions is considered to be 2 to 5 higher (depending on the reference) than at sea-level [11, 13]. Including this factor, the impact of GHG emissions from aviation have to be taken much more seriously than it appears at a first glance.

Obviously, flying airplanes with hydrogen is a serious technological challenge. For all aircraft sizing, the integration of liquid hydrogen tanks is a tricky issue. Also, flying imposes the highest requirements in terms of low weight, volume and high efficiency for the fuel cell system. As explained in a previous article, a meaningful utilization of fuel cells is limited to aircraft with cruise speeds below 250 knots, such as eVTOLs, small business jets or commuter aircraft (with less than 20 passengers). Nevertheless, especially for narrow-body (A320/B737) and wide-body (A350/B787) type of aircraft that is responsible for more than 80 % of emissions [12], hydrogen powered turbines are a viable option that is probably even closer to commercial use than fuel cells, although companies like ZeroAvia made great progress in this demonstration the usage of fuel cells in general aviation.

In contrast to these challenges, aviation also poses two big chances. On the one hand, as in the case of rail or ships, in the first place the required infrastructure can be limited to a very finite number of airports. Not in all cases but in many, such airports are close to the sea so that there is also the possibility to produce hydrogen by off-shore wind (e.g. Tokyo Airport, LAX, Schipol in Amsterdam, Shanghai Airport and several others). Solar could be an option for big hubs like Dubai. Furthermore, while for instance road transport is extremely cost sensitive, in the case of aviation the price per installed kW that an airline is willing to pay is much higher. Therefore, high-cost + high-tech concepts that would not be economically viable in most other sectors, can be become a widely used product in the aviation sector before being adopted by other industries. This would an interesting case in which not the aviation industry rides the train paid by the automotive industry but the other way around.

#4 Cargo Vehicles

Why have a I put aviation in front of cargo? Isn’t road cargo (including buses) the largest polluter right now and projected to be in 2050 as well by a large margin if we continue business as usual [14]? This is absolutely true and a reduction of emissions in this sector is absolutely necessary. However, in contrast to ships or aviation, due to the specifics of this type of transport and the typical mission profile, I think that hydrogen is not the only way to go but alternative solutions to hydrogen might even be better for the decarbonization of trucks.

I will present just one idea here that was put into prototyping and realization by Roland Edel, CTO of Siemens Mobility, several years ago. It is actually quite simple: The largest distance on a road mission from A to B trucks spent usually on the motorway. Why not adapt a concept from railway to trucks – namely bow collectors. After all, in Germany the highway system has roughly the same length as the electrified railway system (roughly 5000 km). Although the concept might look somewhat stupid and ugly at a first glance (s. Fig. below left), we should not be deceived by its appearance. There is very good proverb among software engineers for this situation: “If it’s stupid and it works, it ain’t stupid”.

And indeed, analyzing the concept in more detail, one can find that the well-to-wheel efficiency of it is above 80%. This is significantly higher than for a hydrogen solution, where we the efficiency is around 25 %. This reduces the required installed power more than a factor of 3. And we talk about tens of GWs of required energy generation. Furthermore, a huge number of loading cycles for batteries (as would be the case for a EV solution) as well as a large number of high-capacity batteries can be avoided – which is an additional plus for sustainability.

Thinking the concept a step further, maybe it has an ideal synergy with a concept that was proposed and analyzed recently: A solar panel roof for Germany highways (s. Fig. below right). Again, what sounds rather ridiculous and stupid at first, might not be so stupid after all. If all the highways would have a solar panel roof, in total about 60 GW electric capacity could be generated. Today, the cost of solar is about 1 €/W peak, so that the total project would cost about max. €60B. Sounds like a lot? Well, annually about €20B is spent by logistic companies on diesel fuel for trucks. Maybe this money is better invested in green energy harvesting over highways with electric bow collector lines for e-trucks. Also in case of trucks, there is this wonderful correlation that trucks normally drive during daytime when electric energy from solar is available.

#5 Passenger Cars

At least for me, the last transportation sector that urgently needs hydrogen are electric cars. I mean the Hyperion xp-1 (s. Fig. below left) looks really fancy but so does the Rimac C_Two (s. Fig below right). But this should not be our basis to think about the right choice of technology.

I think that with the latest advancement in battery technology, hydrogen-fueled cars largely lost their unique selling point “the range of a hydrogen-based car is comparable to a gasoline car but a battery will not bring you further than from your home to the local grocery store”. Looking at the latest news, the newest Lucid Air achieved a range of over 800 km on a single charge [15]. With an Audi A5 or BMW 430 I can’t go much further without refueling. And we know that this is not the end of what is possible by far. LiS and LiPo technology are on their way and also new cathode materials are on brisk of allowing faster charging times and more recharging cycles without compromising energy density. 

Another argument that is usually brought up is that we do not have sufficient grid capacity for recharging. Maybe, this is true if we swap all cars to electric at once but this is a rather unrealistic scenario. However, even in this extreme case, probably most of us still could charge our electric cars without bringing the grid to its knees [15]. Therefore, even if the sales of electric cars go through the roof, we have can expand our generation capacity and grid at a reasonable pace.

On the other hand having hydrogen driven cars leaves us mostly with a big disadvantage: The necessity of building up a much larger primary energy generation (can conversion to hydrogen) than in the case of electric cars. Consequently, this point with the arguments above combined, brings me to the conclusion that we should focus our “hydrogenification efforts” rather in other areas of transportation than cars.

Conclusions

Without any doubt, we need a decarbonization in the transportation sector as soon as possible. While for some areas of transportation, a transition to a hydrogen economy is rather complex and other alternatives appear easier, in two areas, the transition to hydrogen is a “low hanging fruit”. For aviation a transition to hydrogen is inevitable.

I see shipping and railways a must-dos for hydrogen that requires only the necessary financial resources to complete the transition. In contrast for aviation, still significant R&D efforts are necessary for a successful transition. For trucks and personal cars, alternative solutions such as EV would probably be preferable to hydrogen.

References

[1] IMO GHG Study 2019

[2] UNCTAD secretariat calculations based on data from Clarkson Research 2017

[3] ICAO: Air Cargo 2017 Facts & Figures

[4] OECD Data: Freight Transport

[5] European Commission of Energy, Climate Change and Environment: “Climate Action – Reducing emissions from the shipping sector”

[6] R. Winkel: “Shore Side Electricity in Europe: Potential and environmental benefits” in Energy Policy 88 (2016), pp. 584-593

[7] NABU: “Messungen des NABU zeigen hohe Luftschadstoffbelastung durch Schiffe“

[8] Ministerium für Verkehr Badem-Würtemberg: „Minister Hermann unterzeichnet Absichtserklärung mit Alstom über Einsatz von Brennstoffzellen-Schienenfahrzeugen“ (2014)

[9] Alstom: „Erfolgreiche erste Testfahrt von Alstoms Wasserstoffzug Coradia iLint bei 80 km/h“ (March 2017)

[10] Environmental and Energy Study Institute: “Fact Sheet: The Growth in Greenhouse Gas Emissions from Commercial Aviation” (2019)

[11] F. Fichert et al.: “Aviation and Climate Change” (July 2020), ISBN 9781472479174

[12] B. Graver et al.: “CO2 emissions from commercial aviation, 2018” for the international council on clean transportation (2019)

[13] Gov.uk: “Greenhouse gas reporting: conversion factors 2020”

[14] Statista.com: “Global transportation CO2 emission share by subsector 2050”

[15] forbes.com: “EVs Are Not A Problem For The Electric Grid, They Are The Solution”

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