Understanding Hydrogen Tanks: Applications, Types, and Materials

Introduction

Hydrogen tanks play a significant role in various applications, from industrial settings to fuel cell electric vehicles (FCEVs). Although they share similarities with other gas storage tanks, such as propane tanks, hydrogen tanks have unique characteristics due to the nature of hydrogen as a gas or super cold cryogenic liquid.

Hydrogen Tanks: A Brief Overview

Hydrogen tanks are containers designed to store hydrogen, either as a gas under high pressure or as a super cold cryogenic liquid, also under pressure. They serve a similar purpose to propane tanks, which store propane under pressure as a liquid, to maximize the amount of fuel they can contain.

For hydrogen storage, the process involves raising the temperature at which any gas will liquify, or its boiling point by increasing the pressure of the gas. However, there is a limit to this effect, and these limits vary with each gas. Unlike propane, hydrogen's critical temperature is still well below -200 degrees Fahrenheit, making it impractical to store as a liquid for most applications, including FCEVs.

In such applications, hydrogen is stored as a gas under high pressure at approximately 4000 psi.

Material and Design Considerations

Steel Tanks: In industrial settings such as refineries, filling stations, and other static applications, hydrogen tanks are typically made of steel. These materials are chosen because they can withstand high pressures without becoming brittle or losing structural integrity.

Lightweight Tanks for FCEVs: Carbon fiber, along with various liners, is used to create lightweight hydrogen tanks suitable for fuel cell electric vehicles (FCEVs). The liners can be made of aluminum or high density polymers, and there are currently four distinct types of hydrogen tanks defined based on their composition, ranging from Type one to Type four.

Evolution of Hydrogen Tank Designs

Originally, hydrogen tanks were made of steel, a material strong enough to handle high pressures. Later, aluminum alloys were used due to their lightweight properties, maintaining the same strength as steel but adding a reduction in weight, which is crucial for vehicular applications.

Most current hydrogen pressure tanks feature a composite outer layer with a liner made of steel or aluminum. Adding to the complexity, metal hydride storage systems are of particular interest, as they can achieve much higher hydrogen densities than compressed gas, doing so at ambient temperatures. This technology offers a significant advancement, particularly in the context of FCEVs.

Conclusion

The development of hydrogen tanks has been driven by the need to store hydrogen safely and efficiently. From the use of steel in industrial settings to the advent of lightweight carbon fiber materials for FCEVs, the evolution of these tanks continues to innovate. Understanding the types and materials used in hydrogen tanks is essential for ensuring safe and effective hydrogen storage across various applications.