Hydrogen distribution

Having defined a HDV-HRS portfolio as well as a suitable hydrogen production technology, the final category required is the hydrogen supply from the production site to the station. Hence, this section focuses on the hydrogen distribution considered in this thesis.

At the HDV-HRS, hydrogen can be provided on-site at the station (using a local electrolyzer) or delivered from a central electrolyzer at a place with low electricity costs. On-site hydrogen production needs almost no additional distribution effort.⁵⁰ On the other hand, hydrogen delivery to the station involves additional expenditures to cover the costs of either using trucks or a dedicated pipeline network (Emonts et al., 2019).

There are three options for truck delivery of hydrogen: gaseous hydrogen (GH), liquefied hydrogen (LH) or liquid hydrogen using liquid organic hydrogen carriers (LOHC). Truck trailers transporting gaseous hydrogen have payload capacities of up to 640 kg hydrogen (cf. Elgowainy et al. (2014)), which equals about 13 FC-HDV refueling processes. Based on the HDV-HRS portfolio in section 4.2.2, the smallest station (“XS”) would require 1.5 truck deliveries per day on average and the largest

“XXL” station would need almost 50 daily deliveries. These routines seem unpractical for real-world infrastructures and are accordingly ruled out by leading hydrogen

50 104 of today’s 343 active HRS have on-site hydrogen production. At 239 HRS, the source of hydrogen is “unknown” (cf. DoE H2 Tools (2019)).

delivery companies (Edwards, 2018) and in this thesis as well. Liquid hydrogen delivery has the advantage of being able to store more than five times as much hydrogen per trailer (up to 3.5 tons per trailer, cf. Air Liquide Hydrogen Energy (2019)) and would avoid the challenge of multiple deliveries per day even for small stations. Unfortunately, “liquefying hydrogen requires far more energy than compressing into a tube trailer” (Bauer et al., 2019)⁵¹ and additionally suffers from boil-off effects of about 1.5 % per day (Töpler and Lehmann, 2017). These factors have a substantial negative effect on energy efficiency so that liquid hydrogen trailer deliveries are also excluded in this thesis. The third hydrogen delivery option is to use LOHC. LOHC carries hydrogen within a liquid molecule structure (i.e. hydrogen is bound to the LOHC) during transport and is unloaded after distribution. Hydrogen carried with LOHC acts like conventional fuels under standard conditions, e.g. no additional pressure tanks or cooling are necessary in contrast to gaseous or liquid hydrogen, respectively. However, similar to liquefying hydrogen, loading LOHC with hydrogen requires large amounts of energy, i.e. of 100 % input energy, about 70 % remains within the stored hydrogen and 30 % is used to load the LOHC with hydrogen (Jörissen, 2019).⁵² In addition, the LOHC represents about 90 % of the total weight (and hydrogen only 10 %), which makes it “especially advantageous for long-term storage [or] long distance transport applications” (Niermann et al., 2019b), such as maritime, neither of which is the case for HDV-HRS. To sum up, none of the truck delivery options seems suitable for a HDV-HRS network in Germany and all are excluded from further analysis.

Hydrogen pipelines are well established throughout the world with about 4,500 km of installed assets, of which 390 km are in Germany. Hydrogen pipelines are currently most commonly used in the chemical industry (DoE H2 Tools, 2019). Accordingly, pipelines seem a good option for transporting large amounts of hydrogen overland without large energy losses, especially to supply a larger HRS network, e.g. on a national scale (Seydel, 2008; Robinius, 2015). Moreover, German highways are inalienable federal property, therefore, theoretically, there is the chance of a shorter installation time for pipelines here (Wulfhorst, 2017).⁵³ In contrast, a pipeline network alongside existing natural gas pipelines may imply property right challenges and usually does not run near German highways (cf. Seydel (2008) and Krieg (2014)).

Thus, besides on-site hydrogen production, a hydrogen pipeline network seems another feasible option to distribute hydrogen from a central electrolyzer to a national HDV-HRS network. The advantages and disadvantages of each delivery technology are summarized in Table 15.

51 Converting hydrogen into a liquid accounts for an energy loss of about 30% to 40% (based on the lower heating value of hydrogen) (cf. Chisholm and Cronin (2016); Niermann et al. (2019a)).

52 Furthermore, once hydrogen is unloaded from the LOHC (e.g. at the HRS), the LOHC needs to be transported back to the loading location (e.g. the electrolyzer).

53 Compared with most other German street types that are state or private property, which would have to be bought or expropriated in order to install pipelines.

Table 15: Advantages and disadvantages of hydrogen delivery technologies and their suitability for HDV applications

Delivery option Advantage Disadvantage HDV suitability

On-site

GH trailer  established technology  only small volume of

hydrogen per trailer Low⁵⁴

To determine whether a pipeline network is competitive with on-site production, techno-economic parameters are defined for the hydrogen pipeline. First, the pipeline diameter depends on the specific hydrogen mass flow rate and vice versa:

𝐷 = √

with

D diameter [m]

𝑚̇ (hydrogen) flow rate [kg_h2/s]

𝑣 speed [m/s]

𝜌 density (at standard conditions) [kg/m³)

Equation (13) determines the required pipeline diameter based on the given mass flow between a specific HDV-HRS location (i.e. its daily hydrogen consumption) and the central electrolyzer. In the case of parallel pipelines, e.g. due to two HRS relatively close to each other, the diameters of each station are added to result in a single pipeline. Krieg (2014) defines 100 mm as the minimum and 600 mm as the maximum diameter for hydrogen pipelines. In this thesis – similar to the discrete HRS sizes – discrete pipelines diameters are applied in steps of 100 mm (i.e. 100 mm, 200 mm, 300 mm, 400 mm, 500 mm and 600 mm). Based on the required hydrogen diameter, the specific pipeline investment per diameter dependent on hydrogen mass flow rates

54 GH trailer delivery may be interesting for the initial market diffusion of FC-HDV and infrastructure.

is determined as shown in Table 16, ranging from 360 to 1,570 €/m (Krieg, 2014). The lifetime of a hydrogen pipeline network is assumed at 40 years (Krieg, 2014).

Table 16: Pipeline diameter and resulting hydrogen flow rate (in tons per day) as well as investment (in € per meter) based on (Krieg, 2014)

Diameter Hydrogen flow Investment

[mm] [t/d] [€/m] asset investment, no additional distribution investments are taken into account.