Optimizing Hydrogen Storage and Transportation Systems with Simcenter Amesim

Hydrogen storage and transport are complex due to the unique properties of the gas. Its low density requires high-pressure compression or liquefaction, and its high diffusivity can lead to material degradation over time. Moreover, ensuring a safe temperature range is crucial to prevent hazardous situations.

In today’s article, we’ll be looking into the challenges behind a few Key applications:

• Compressed Hydrogen Storage Systems (CHSS): Ensuring structural integrity and performance of tanks under high pressures (350-700 bar).
• Cryogenic Hydrogen Storage: Managing thermal losses and minimizing boil-off gas (BOG) in liquid hydrogen storage (LH2).
• Pipeline Transport: Addressing pressure drops, hydrogen embrittlement, and optimizing energy efficiency over long distances.
• Intermodal Transportation: Designing safe and efficient transport solutions for hydrogen by truck, rail, or ship.

How can Simcenter Amesim Help?

Simcenter Amesim provides engineers with a powerful system simulation environment to address these challenges. By integrating physics-based models, Amesim enables virtual prototyping, performance optimization, and failure analysis before physical implementation. It also allows users to perform troubleshooting on existing and operating product models, providing in-depth system diagnostics and issue analysis in a virtual environment.

1. Designing and Validating Compressed Hydrogen Storage Systems (CHSS)

Compressed hydrogen tanks / storage systems (CHSS) typically operate at 700 bar with drastic changes in the temperature evolutions during operations. To operate properly they require precise control over pressure, temperature, and structural performance.

Let’s consider some key challenges to solve that are fully addressable with System Simulation to find out the best designs:

With Simcenter Amesim, engineers can predict and simulate:

• 📈🌡 Refueling performances: time, temperatures, pressure, based on standard or personalized refueling procedures
• 📉💧 Defueling performances: range on existing driving profiles, temperatures, valves behavior
• ⏱️ Maintenance operations: purge time estimation, leak test, etc…
• 🧪 Cycling tests: optimize cycling for normative tests or industrial processes
• 💥 Safety assessments: venting time, potential leakage impact, safety valves physical dynamic, etc…

That’s a lot to manage, and System Simulation can help there! Within few seconds of execution, System Simulation can provide metrics about any variables like pressures, temperatures, mass flow rates, power losses, efficiencies or energy saving, so it’s easy to investigate multiple scenarios.

2. Cryogenic Hydrogen Storage Systems

✈️💧 In the aviation industry, the preference goes from GH2 (gas) tank storage for small aircrafts and short range to LH2 (liquid) tank storage for larger aircrafts and medium-long range. This choice is driven by the much higher energy per unit volume of the LH2 (liquid) tank storage compared to the GH2 (gas) tank storage.

LH2 (liquid hydrogen) is much more complex to manage since it’s obtained at extremely low temperatures such as -253 °C🌡, so that thermal insulation of the tank walls becomes mandatory to prevent the boiling of the liquid hydrogen (raising its pressure drastically), also as a side-effect the freezing of the external parts of the cryogenic tank. That’s where System Simulation can help to investigate the insulation performances (number of layers, composite/metal, …) or the refueling/defueling times to get relevant results in few seconds of CPU-time.

Cryogenic hydrogen tank with LH2 (liquid), GH2 (gas) and BOG (boil-off gas)

At a certain point, discretizing the external and internal tank walls along with the insulation layers, while incorporating more complex phenomena (thermal stratification, heat convection, heat radiation, etc…), becomes necessary to accurately capture the physical behavior and enhance predictive accuracy.

In the example above, the users define the 3D shape of the tank, then thanks to the thermal management (insulated walls, concentrated and distributed heat fluxes, …), they can get the boil-off gas (BOG – evaporated vapor of hydrogen), so it’s finally easy to define the appropriate strategy to reuse the BOG for the fuel cell.

The goal here is to do the thermal management of the hydrogen tank and to take advantage of the already gasified hydrogen to supply the fuel cell with the necessary quantity of liquid at the targeted pressure. The control allows the right amount of LH2 (liquid hydrogen) for vaporization in an ideal exchanger. This exchanger therefore gives an estimate of the heat necessary to operate, while new thermal management system requirements can be derived from these results.

3. Cryo-compressed hydrogen tanks (CcH2) and cooling systems

Let’s now look at another technology for hydrogen tank storage with cryo-compressed hydrogen tanks (CcH2). They are used in some passenger cars. The concept of a cryo-compressed hydrogen (CcH2) storage is to combine the advantages of the gaseous (CGH2) and liquid (LH2) storage, namely loss-free operation and highest storage density.

A big focus is put on the heat exchanges regarding the tank geometry, including the fluid and solid walls with natural and forced convections, as well as conduction in the walls. If needed, 1D-3D coupling can be done with 3D CFD to get more refined simulation for the tank heat exchanger and its temperature distribution all around the tank walls.

Cryo-compressed hydrogen tanks (CcH2) with coolant heat exchanger

The model allows to implement complicated simulation sequences with repeated driving/refueling cycles until the fluid steady state conditions are reached after refueling. While the density is adjusted to the consumption, to get higher consumption rates with higher densities. Simulations of parahydrogen/orthohydrogen can be implemented for a complementary analysis of H2 isomers to assess the impact of fluid composition.

4. Optimizing Hydrogen Pipeline Transport

Hydrogen pipelines must balance efficiency, safety, and cost-effectiveness over long distances. Simcenter Amesim supports:

• Dynamic simulations of pressure losses and flow behavior in extensive pipeline networks.
• Evaluation of compressor stations’ sizing and energy consumption.
• Multi-phase flow simulations for pipelines carrying hydrogen blends.

5. Improving Hydrogen Intermodal Transport

Transporting hydrogen via tankers, ships, or railcars requires robust design strategies to ensure safety and efficiency. With Simcenter Amesim, engineers can:

• Simulate pressure and temperature variations during transit, ensuring optimal storage conditions.
• Model loading/unloading procedures to minimize energy losses and maintain structural integrity.
• Assess safety measures, including leak detection and emergency venting.
• Optimize tank configurations and refueling strategies for high-pressure hydrogen storage systems.

Let’s look into a 5 tank 700-bar hydrogen storage system model in Amesim, for a valuable insight on what can be simulated.

The system considered consists of 5 high-pressure type IV hydrogen tanks, 3 being positioned behind the truck tractor cabin, and 2 at both sides between the front and rear axles, as illustrated on figure 1 below.

Figure 1: Hydrogen tanks configuration

We can make some assumptions and considerations:

• Gas Equation of State (EOS): At 700 barA and standard temperature, hydrogen exists in a supercritical state, with a compressibility factor exceeding 1.4. This necessitates the use of a Real Gas Equation of State (EOS) to accurately describe its behavior. Simcenter Amesim offers several EOS models for this purpose, including Van der Waals, Redlich-Kwong, Redlich-Kwong-Soave, Peng-Robinson, MBWR, and Helmholtz. In this example, the Redlich-Kwong-Soave (RKS) equation is applied.

• Thermal Considerations: Beyond selecting an appropriate EOS, accurately modeling the thermal behavior of the system is crucial.
• • • Inside the Tank: Free and forced convective heat exchanges between hydrogen and the inner liner are accounted for. Nusselt correlations determine the heat transfer coefficient, with the free convection correlation based on the Grashof and Prandtl numbers, while the forced convection correlation depends on the Reynolds number.
    • Tank Wall Layers: The three material layers of the tank are modeled with radial heat conduction, considering their respective thicknesses and thermal conductivities.
    •  External Heat Exchange: Heat transfer from the outer tank surface to the surrounding environment follows a standard Nusselt correlation for forced convection around a cylinder, assuming an ambient air velocity of 5 m/s.

Below the corresponding model in Amesim:

Type IV hydrogen tanks have a non-metallic (polymer) inner liner and an outer full reinforced composite wrapping. Both characteristics enable to ensure the hydrogen tightness and to sustain high pressures.

Figure 2: Hydrogen tanks configuration – Simcenter Amesim sketch

Note that for these scenarios, the simulation time stops when the SOC reaches 5% or a maximum time of 10 hours.

The results of the 3 simulated scenarios are gathered on the figure below (see associated scenario color) – the gas temperature is the one at the mixing chamber linking all tanks:

Figure 4: results of defueling scenarios – Gas temperature [degC]

Figure 5: results of defueling scenarios – Gas Pressure [barA]

Figure 6: results of defueling scenarios – State Of Charge [%]

Figure 7: temperature evolution of the tank materials and H2 temperatures for scenario #1

Figure 8: temperature evolution of the tank materials and H2 temperatures for scenario #2

Figure 9: temperature evolution of the tank materials and H2 temperatures for scenario #3

Check out the full application case here: Simulating a 700 bar Compressed Hydrogen Storage System for trucks with Simcenter system simulation (link)

Conclusions: Accelerating Hydrogen Infrastructure Development

Simcenter Amesim enables engineers to virtually validate hydrogen storage and transportation systems, reducing development costs and minimizing risks. By leveraging digital twins and system simulations, companies can accelerate time-to-market and ensure compliance with industry regulations.

As hydrogen adoption grows, the ability to optimize storage and transport technologies will be a key differentiator. With Simcenter Amesim, engineers can develop more efficient, safer, and cost-effective hydrogen solutions.

Are you working on hydrogen storage or transport systems? Contact us to learn how Simcenter Amesim can enhance your engineering workflow.