Compressed Hydrogen in Fuel Cell Vehicles

On-board Storage and Refueling Analysis

Shitanshu Sapre, Kapil Pareek, Rupesh Rohan

• Publisher: CRC Press
• Year: 2022
• Print ISBN:
  9781032154893
• eBook ISBN:
  9781000584905
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book highlights the challenges of using hydrogen as a fuel for sustainable transportation including introduction of various hydrogen storage technologies, storage requirement for fuel cell vehicles, compressed hydrogen storage system, and refueling analysis with thermal management. Furthermore, thermodynamics and kinetics involved during refuelling, heat transfer issues in storage tank and effect of severe operating conditions on structure of storage tank under SAEJ2601 refueling conditions are discussed in detail.

Features:

• Covers design and analysis of on-board storage/tank for compressed hydrogen in fuel-cell vehicle applications.
• Discuss heat transfer issues and effect of severe operating conditions on structure of storage the tank.
• Includes the structural analysis of composite storage tank.
• Provides assessment on refueling process of compressed hydrogen storage system and novel refueling process.
• Deals with thermodynamic and kinetic involved during refueling as per SAEJ2601.

This book aims at researchers, professionals, and graduate students in automotive engineering, energy and power, materials, and chemical engineering.

1 Introduction Hydrogen Storage Techniques

DOI: 10.1201/9781003244318-1

1.1 Hydrogen Storage Methods

For the development of the future hydrogen economy, a safe and efficient means of storing hydrogen is required in onboard, portable and stationary applications. Storage is a challenging issue that cuts across production, delivery and end-use applications of hydrogen as an energy carrier. Indeed, for a successful application of hydrogen as an energy carrier, hydrogen should be stored safely and efficiently as conventional fuels [1]. One of the most challenging applications in this field is hydrogen storage for mobile or onboard applications. Hydrogen storage is a key enabling technology for the successful penetration of hydrogen fuel cell vehicles in the gasoline vehicle market [2].

The size, weight, and density are deciding factors for any storage system for particular applications. However, sometimes characteristics of fuel also play a significant role in defining the suitability of the storage system. Hydrogen possesses unusual physical and thermodynamic properties that make it difficult to call any storage system as efficient for particular applications. Under normal temperature and pressure, the density of the gas is very low near about 0.08238 kg/m³, e.g. for storing 5 kg of hydrogen, which implies a volume of around 60 m³ and energy content of 600 MJ (166.65 kWh). For the same weight and energy content, the gasoline volume is 0.019 m³.

Given these numbers, it is clear that for efficient storage, hydrogen density should be increased by reducing the volume taken by the gas under normal temperature and pressure conditions. As a consequence, the “normal state” of hydrogen has to be changed in order to store it efficiently. This can be accomplished by increasing the pressure, decreasing the temperature below the critical temperature or reducing the repulsion interaction between hydrogen molecules by binding them with another material.

Thus, for storing hydrogen, various methods have emerged as a perfect solution for hydrogen storage. They have been classified as (1) physical storage (2) materials-based storage (as shown in Figure 1.1). However, all methods have their advantages and disadvantages based on their storage capacity and operating conditions.

Figure 1.1 Various hydrogen storage methods [3].

1.2 Physical Hydrogen Storage

In this class, hydrogen at normal state is converted into high pressure or low temperature gas. Based on the storage pressure and temperature, the storage system is subclassified as liquid, cryo-compressed and compressed. All these approaches are used to increase the storage density of hydrogen (Table 1.1).

Table 1.1 Physical Hydrogen Storage Methods [5,6]

Hydrogen storage methods	Storage Density (g/L)	Operating Pressure and Temperature
Compressed	40	70 MPa, 15°C
Liquid	71	0.1 MPa, −253°C
Cryo-compressed	90	35 MPa, −233°C

For hydrogen fuel cell passenger cars, around 5–6 kg of hydrogen storage with high gravimetric and volumetric storage density is required to achieve the drive range of more than 500 km. For this, pure hydrogen can be stored as liquid at −253°C or high-pressure gas up to 700 bar in a suitable container.

1.2.1 Liquid Hydrogen Storage

Hydrogen density can be increased by liquefying the hydrogen to attain a storage density of 70 g/L at 1 bar and −253°C. Liquid hydrogen is mainly considered as a distribution method to take advantage of high hydrogen density at low temperature. During the liquefaction of hydrogen, the ortho hydrogen is converted into the para form with heat release that evaporates the liquefied hydrogen into the gaseous one backward. The ortho-para conversion catalysts are usually used during liquefaction to avoid such boil-off.

Liquid hydrogen occupies less volume than pressurized storage and is particularly attractive for attaining higher storage densities. However, some unusual properties of liquid hydrogen such as low boiling point, negative Joule–Thomson Coefficient and low vaporization enthalpy impose technical barriers to its acceptability. The low boiling point of hydrogen necessitates a high level of purification of less than 1 ppm to avoid clogging. Similarly, low vaporization enthalpy generates the need of well-insulated storage vessels.

The cryogenic liquid starts to evaporate after a certain period of time called the boil-off phenomenon. This leads to the 2–3% loss of hydrogen per day and extra energy input is required for storage vessels. This cannot be prevented, even with a very effective vacuum insulation and heat-radiation shield in place. Hydrogen boil-off is considered an issue in terms of refueling frequency, cost, energy efficiency and safety, particularly for vehicles parked in confined spaces, such as parking garages [7]. Therefore, each technology requires well-insulated and expensive cryogenic storage vessels to prevent boil-off and maximize dormancy. Figure 1.2 shows generation 2 cryogenic pressure vessel with aluminum-lined, carbon fiber wrapped surrounded by a vacuum space for storing cryogenic hydrogen [8].

Figure 1.2 Generation 2 cryogenic capable pressure vessel design [7].

Moreover, the liquefaction process is energy-intensive and consumes approximately 35% of the energy content of the stored hydrogen. Therefore, liquid hydrogen is limited to flight and space applications where high volumetric and gravimetric energy storage densities are required regardless of its high-power consumption. The net energy consumed is approximately 10 kWh/kg and it contributes 40–50% of capital expenditure (CapEex) of the liquid hydrogen storage system [9]. Hence, energy expenditure and boil-off due to leakage is a major challenge to the liquid hydrogen storage for long-term storage and of hydrogen storage for automotive applications.

1.2.2 Cryo-compressed Hydrogen Storage

Cryo-compressed, currently the latest approach for storing the hydrogen at a pressure above normal state and temperature similar to or less than liquid hydrogen. It is a combination of two approaches where hydrogen is compressed to higher pressure up to 35 MPa and temperature −233°C. The high pressure and cryogenic storage increase the gravimetric and volumetric density while overcoming the boil-off loss (dormancy) from liquefied hydrogen storage. As a result of increasing the pressure of liquefied hydrogen the storage density increases to 90 g/L [10].

The density of cryo-compressed is much higher than compressed and relatively increased compared to the liquid hydrogen as in Figure 1.3 due to the increase in pressure of storage. Hydrogen can be stored in an insulated tank at a temperature of...

Table of contents

• Cover Page
• Half Title page
• Title Page
• Copyright Page
• Contents
• Preface
• Author Biographies
• Abbreviations
• 1 Introduction Hydrogen Storage Techniques
• 2 Compressed Hydrogen Storage
• 3 Compressed Hydrogen Refueling Stations
• 4 Refueling of Compressed Hydrogen
• 5 Heat Transfer Analysis
• 6 Structural Analysis of Type IV Tanks
• 7 Conclusion and Future Directions
• Index