Hydrogen Storage System for Fuel Cells Energy Supply
Basic considerations for storing hydrogen
Hydrogen storage is a necessary key element enabling the use of hydrogen as a fuel or energy source in any application. Arguably, the success of any kind of fuel is based largely on mankind’s ability to store and transport it.
Hydrogen can either be stored in its pure form, or it can be absorbed by another material (like a sponge would take up water) necessitating its extraction when needed. This yields the following general types of hydrogen storage methods.
What are the main types of hydrogen fuel storage?
1. Hydrogen storage in physically pure form
a) Gaseous storage
- Storage at ambient pressure. In this form hydrogen takes up a lot of volume in comparison to the energy it can provide. Also depending on the amount of hydrogen being stored, the low weight of the spatial volume occupied (low specific weight) in comparison to air leads to a buoyancy in air – meaning that the container, if made of a very light weight material, at some point may lift off the ground if not otherwise restrained.
- Storage at higher than ambient pressure. In this form, considerably more hydrogen can be stored in a given space. As hydrogen molecules are among the earth’s smallest, special care needs to be taken to ensure that the containers are leak- and diffusion-proof, even at higher pressures. Thanks to advances in materials science this does not present a problem any longer and hydrogen can be stored readily in hydrogen tanks at pressures up to 1200 bar. Typical storage pressures are 200 bar in steel tanks or bottles, 350 bar tanks in truck and industrial applications and 700 bar or 800 bar in vehicle applications.
b) Storage in liquid form.
- LH2 – Liquefied Hydrogen. After it has been cooled below its boiling point at -252.8°C, hydrogen becomes liquid and, like any liquefied gas, it takes up much less space per kg than in its gaseous state. It can then be handled as a liquid, however extremely good insulation is required in order to manage and reduce ensuing evaporation (boil-off) of the stored hydrogen.
- Cryo-Compressed Hydrogen. This is liquefied hydrogen which has been further compressed to reduce the volume required to store it. Besides providing sufficient insulation for the extremely low temperature required the containing vessel must provide sufficient stability for the desired pressurization.
2. Material-based storage of hydrogen
- This method of hydrogen energy storage entails using another material in such a manner, that the molecules of that medium somehow capture the hydrogen molecules until they are again induced by some external means to release it.
- Due to the potentially simplified logistics of the carrier material in comparison to pure hydrogen, this form of storage offers huge advantages for the storage of hydrogen. The carrier material can be a larger solid, a powder, a liquid with low or even very high viscosity.
- Drawbacks may arise from the logistics requirement of the “used”, i.e. consumed carrier medium, the need to recycle the carrier medium after its use, and the complexity added in the hydrogen energy storage system.
- Recent years have seen multiple innovations in the area of materials-based storage of hydrogen and this area promises to be a continuous source of new impetus in the quest for hydrogen to become a primary provider of energy on our planet.
What are the main performance criteria of a hydrogen storage system?
The following parameters are key decision-making factors in the design and selection of a hydrogen storage system for a given application:
- Volume taken up by the storage system
- Storage quantity of hydrogen
- Weight of the storage system
- Transportability of the hydrogen storage system
- Output pressure and temperature of stored hydrogen
- Impurities introduced into the stored hydrogen
- Required energy taken up by the storage system
- Energy required to introduce and extract hydrogen from the storage system
List of some hydrogen storage system suppliers
While the list shown below is not exhaustive, the following suppliers currently offer complete hydrogen fuel storage systems:
- Air Products
- Air Liquide
A system for hydrogen fuel storage always consists of tanks, valves and sensors which perform basic functions relating to storing hydrogen. In addition, the type of system requires several other components such as compressors and filters which are specific to the storage type.
Last update: 4.11.2021
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