Chapter 5 - Hydrogen Storage for Mobile Application: Technologies and Their Assessment

Abstract

In post fossil energy systems, hydrogen may gain significant importance as a secondary energy carrier, especially for transportation purposes. This widely published statement is justified by the fact that hydrogen can be produced from fluctuating electricity provided, for example, by wind turbines or photovoltaic systems. The hydrogen provision depends on the availability of electrical energy and is then stored to be used depending on the given demand. However, the efficient storage of hydrogen as an energy carrier is challenging from a techno-economic point of view, for example, due to the low volumetric energy density of hydrogen under standard conditions as well as other challenging properties. Especially for mobile applications (e.g., cars, trucks, ships, trains) it is very important to have hydrogen storage options with high volumetric and gravimetric energy densities to allow highly efficient use and to be fully competitive compared to other options possible within the transportation sector. Thus, in recent years, various storage technologies and concepts have been developed to achieve this challenging goal. The three most widely developed options are high-pressure storage tanks, storage as liquid hydrogen, and storage of the hydrogen gas in metal hydride. But there are also other possibilities and ideas to allow hydrogen storage for mobile applications, such as liquid organic hydrogen carriers (LOHC), activated carbon, Metal–Organic-Frameworks (MOFs), and others. Against this background, the overall goal of this chapter is to describe the various possibilities to store hydrogen for mobile applications. This is realized based on physical and chemical principles as well as the current state of the technology. Additionally, ongoing developments and possible technological breakthroughs are outlined. Besides this, each option is characterized by comparable key figures (e.g., storage density, storage efficiency) for the current state of technology to allow an easy and transparent comparison. Additionally, the hydrogen storage systems discussed are compared to the target values of the DOE (US Department of Energy), which defines internationally accepted goals for the energy density and the costs of hydrogen storage. Finally, the various options are compared to each other. Based on this, statements are made defining which storage option under which frame condition can play which role at which point in time.