Current state of development and prospects

Electric transportation

Germany’s Climate Change Act of 2021 tasked the country’s transport sector with reducing carbon dioxide equivalent emissions by 85 million metric tons by 2030. The target means approximately halving emissions in 10 years. Around 35 percent of transport emissions originate from commercial vehicles, more than half of which is caused by long-distance transportation. Hydrogen is considered a promising fuel for bringing down carbon dioxide emissions from commercial vehicles used on long journeys. The following article summarizes selected content from a recent study on the state of development and the prospects for hydrogen refueling infrastructure for long-distance commercial vehicles.

Current prototypes and small fleets of hydrogen trucks generally use 350-bar compressed storage technology. This was originally developed for bus applications for local public transportation and therefore is tried and tested and readily available. This storage technology, fitted in existing installation space, enables a range of about 400 kilometers (250 miles) which is sufficient for many applications (e.g., back-to-base modes of operation).

For long-haul trucking, longer ranges of around 1,000 kilometers (620 miles) are desirable. To make this possible within the existing installation space, hydrogen storage technologies with a higher energy density are required. Three alternative hydrogen fuel options form the subject of current discussion: 700-bar compressed hydrogen, subcooled liquid hydrogen (sLH₂) and cryogenic compressed hydrogen (CcH₂).

Various manufacturers such as Nikola Motor and Toyota have already been trialing the 700-bar technology in pre-series vehicles. It can therefore be assumed that this technology will come into use for long-distance transportation. Due to the early stage of technical development, for example, it is still impossible to estimate at the moment whether one of the other two storage technologies will also penetrate the market.

In terms of realizable refueling quantities and speed, there is little to distinguish the three hydrogen fuel options. In each case, refueling 80 kilograms of hydrogen for a range of 1,000 kilometers (620 miles) can be completed within 10 to 15 minutes (see fig. 1). Nevertheless, these achievable refueling speeds and times are industry estimates which first need to be confirmed in real operation.

Prior to being launched onto the market, all three hydrogen fuel options will need to go through the international standardization process, both for the refueling process and for the refueling couplings. This will ensure the interoperability between vehicles and filling stations of different manufacturers and in different countries. Initial ISO standardization procedures have already begun.

Road tanker, pipeline or on-site electrolysis

There are marked differences in how hydrogen is supplied to a refueling station and to a refueling system itself depending on which particular hydrogen fuel type is used (see fig. 2). In the case of 700-bar compressed hydrogen, the fuel can be delivered to the filling station either in gaseous or liquefied form. If it is provided as a gas, the fuel is supplied to vehicles by means of high-pressure compressors and high-pressure buffers that are operated at pressures of up to 1,000 bar. Hydrogen is dispensed either via overflow filling or via direct compression into the vehicle tanks through booster compressors.

If liquefied hydrogen is delivered, the pressure is raised while in its liquid state by a cryopump. Next, the pre-compressed hydrogen is evaporated and dispensed to the vehicle. The electrical energy requirement for the filling station is much lower for the liquid hydrogen pathway than for the compression of gaseous hydrogen. Even so, the upstream liquefaction of hydrogen is associated with a high level of energy input.

If sLH₂ or CcH₂ fuel is offered, then liquid hydrogen is the first choice for supplying the filling station. This can be fueled directly into the vehicle from the filling station’s storage tank via a transfer pump or cryopump.

The availability of liquid hydrogen in Europe is currently extremely limited. Across the whole continent, there are three locations with liquefaction capacities which are, however, already used for other purposes. Furthermore, their capacity is insufficient to supply future truck fleets with fuel. This becomes clear if you compare the capacities of today’s liquefiers with the expected capacities of future hydrogen refueling stations.

Today’s hydrogen liquefiers usually have a daily capacity of 5 to 30 metric tons. At Germany’s only liquefaction site, in Leuna, the capacity is, for example, 2 x 5 metric tons a day. In the medium term, the capacities for hydrogen filling stations are anticipated to be between 1 and 8 metric tons a day per station. Different studies assume a hydrogen fuel demand for Germany of 1.2 million to 1.8 million metric tons per annum for the year 2045 which will largely be driven by the demand from long-distance trucking.

It is clearly evident that for this to be achieved the capacity for liquid hydrogen has to be greatly expanded and, if necessary, supplemented by importing liquid hydrogen. This is also the case if the demand for hydrogen fuel is partially covered by the provision of gaseous hydrogen (e.g., for supplying vehicles with 350-bar or 700-bar storage technology).

Figure 3 shows two different layouts of hydrogen refueling stations with a dispensing capacity of more than 2 metric tons a day. The particular components needed vary depending on whether the hydrogen is delivered as a gas or liquid. Both setups require gas supply components, valves, sensors and a process control system.

Falling hydrogen costs

If you look at fuel costs in relation to distance traveled, a diesel price of EUR 1.4 per liter (including taxes) roughly corresponds to a hydrogen fuel price of EUR 5 per kilogram. The meta-evaluation of present studies reveals a decrease in hydrogen fuel costs of more than EUR 10 per kilogram today to around EUR 4 to EUR 6 per kilogram (excluding taxes). Depending on the study, this cost level is expected to be reached by 2030 or in the years thereafter. The available cost data in these studies relates almost exclusively to 700-bar fuel. Cost data on sLH₂ and CcH₂ is only available to a very limited degree but indicates a comparable cost level.

Achieving these decreases in cost requires savings to be gained through mass production and scaling along the entire hydrogen delivery chain, from hydrogen production to the refueling system. Also the entire delivery infrastructure needs to be well utilized. In addition, optimized supply and logistics concepts must be put in place. In order for cost parity to be reached between diesel and hydrogen fuel for the end user in terms of distance traveled, differentiated charges and/or taxes must be levied on both fuels.

The energy tax for diesel in Germany is currently EUR 0.47 per liter. By 2025 a carbon dioxide levy of around EUR 0.15 per liter will be added on top of this. These charges indicate that mile-for-mile cost parity could be achievable provided that hydrogen for fuel cell vehicles remains exempt from taxes. If a tax is levied on hydrogen fuel in the future, the charges on diesel would also have to be increased in parallel so that cost parity between the fuels is maintained.

For fuel cell vehicles to become a means of long-distance transportation in the years ahead beyond subsidized projects, the total transport costs must not exceed the level of conventional trucks with diesel engines. The fuel costs considered in the study are only a single element in this. Lowering the costs for vehicles or applying appropriate carbon dioxide charges/emissions-related road charges or energy taxes could together ensure overall cost parity.

About the study

The study was commissioned by e-mobil BW and was published by the H2BW platform which amalgamates activities relating to hydrogen and fuel cell technology in the German state of Baden-Württemberg. The authors are the company Ludwig-Bölkow-Systemtechnik and the Institute of Vehicle Concepts at the German Aerospace Center. The study investigated the current state of development and the prospects for hydrogen refueling infrastructure for commercial vehicles used in long-distance transportation.

Authors: Jan Zerhusen, Ludwig-Bölkow-Systemtechnik GmbH, Ottobrunn, Munich, Germany, Jan.Zerhusen@LBST.de
Mathias Böhm, Institute of Vehicle Concepts at the German Aerospace Center, Berlin, Germany, Mathias.Boehm@dlr.de