Hydrogen Storage

Based on Hydrogenation and Dehydrogenation Reactions of Small Molecules

Thomas Zell, Robert Langer, Thomas Zell, Robert Langer

• Publisher: De Gruyter
• Year: 2019
• eBook ISBN: 9783110534658
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Energy

Thomas Zell and Robert Langer

1Introduction: hydrogen storage as solution for a changing energy landscape

Abstract: The expansion of sustainable technologies and infrastructures for the production and delivery of energy to the final consumer and the development of new technologies for energy production, storage and distribution, are challenging and inevitable tasks. Power plants based on the combustion of fossil fuel resources or nuclear power plants are not suitable to provide energy in the future due to significant disadvantages and dangers associated with these outdated technologies. The development of new sustainable technologies for the production of energy is desirable. Besides focusing on the production step, the change in global energy landscape requires also new and improved energy storage systems. Requirements for these storage solutions will strongly depend on the application. Storing energy by producing and consuming hydrogen is in this context a very attractive approach. It may be suitable for storage of energy for transportation and also for the bulk energy storage. Due to physical restrictions of high pressure hydrogen storage, alternative techniques are developed. This is, in turn, an ongoing task with multidisciplinary aspects, which combines chemistry, physics, material science and engineering. Herein, we review the production and consumption of energy, different energy storage applications, and we introduce the concept of hydrogen storage based on hydrogenation and dehydrogenation reactions of small molecules.

Keywords: Energy Storage, Energy Transportation, Greenhouse Gases, Hydrogen Generation, Hydrogen Storage

1.1Introduction

The continuously growing world population and dwindling resources of fossil fuels, raise the demand for alternative sources of energy. In addition, the combustion of those fossil fuels is the main source for the greenhouse gas carbon dioxide (CO2) [1, 2]. Besides CO2, depending on the combustion conditions, also other greenhouse gases such as methane (CH4) and nitrous oxide (N2O) may be formed in substantial amounts [3].

In this context it seems unfortunate that the world’s energy demand is accommodated to a large extend by the combustion of fossil fuels such as coal, oil, and natural gas [3]. In the following paragraph, the distribution of the different energy sources is discussed on the example of the United States of America (US), one of the leading economies. It should be noted that the statistics on the energy may vary strongly in other countries.

1.2Current energy landscape – US statistics

In 2016, for example, the overall energy production of the US was based to 33% on natural gas, to 28% on petroleum (which includes crude oil and natural gas liquids), to 17% on coal, to 12% on renewable energy, and to 10% on nuclear energy, Figure 1.1 [4]. Similar numbers are found for the US energy consumption of 2016, Figure 1.2. Taking a closer look at the electric energy generation shows that the relative percentage of renewable energy here slightly higher, but still underrepresented, Figure 1.3. The total electric energy produced in the US in 2016 was based to 30% on coal, to 34% natural gas, to 20% nuclear power, and to 15% on renewable energy, whereas oil/ petroleum contributed less than 1% [4].

Figure 1.1: US overall energy production in 2016.

Interestingly, the CO2 emissions of the residential sector are significantly smaller as one may expect. The statistics for the US of 2016 show that only 20% of the CO2 emissions are attributed to the residential sector, whereas the vast majority stems from other sectors such as the transportation (36%), industrial (27%), and commercial sector (17%), Figure 1.4 [4].

For transforming to a more sustainable energy landscape, the reduction of CO2 emissions is essential. This so called “Decarbonization” can be achieved by using CO2-neutral technologies [5]. Attempts of CO2 capture and subsequent transformation to useful chemical raw materials were discussed as possible solution for decreasing atmospheric CO2 [6–17]. Especially over the last decades a wide array of synthetic methods for transforming CO2 into various value-added products have been developed [16]. Besides using CO2 as C1-building block this concept could in principle also reduces atmospheric CO2, simply by the fact that no fossils feedstocks need to be consumed.

Figure 1.2: US energy consumption in 2016.

Figure 1.3: US overall electricity production in 2016.

The use of nuclear energy as transition technology is often discussed in the context of reducing CO2 emissions. The generation of electric energy by nuclear power plants is not sustainable and associated with risks for humanity and environment [18]. Although supporters of this technology may claim that it can reduce global warming [19] by reduced green-house gas emissions and that the technology is getting safer year by year [20], the tremendous effects of accidents are disastrous, Fukushima being a recent example [21–25].

Figure 1.4: CO2 emissions of the US in 2016 according to sectors.

Along these lines, the US federal government defines as major energy accidents, incidents which either result in the loss of human lives or in the damage of property of over 50,000 US$ [26]. In the years 1952–2009, worldwide 99 of those incidents have been reported, which fulfill the aforementioned criterion. The overall damage is summing up to an estimated 20.5 billion US$. In terms of fatal incidents in that period (1952–2009), the nuclear energy sector lies on second place of all energy sources, number one being hydroelectric dams.

Besides the running facility, also the storage of nuclear waste is dangerous. Although deep geological disposal is thought to be the best solution for the final disposal of radioactive waste, it by far cannot be considered green or sustainable. Notably, there is and will not be a 100% safe solution for the storage of radioactive waste. It remains questionable, if this technology may currently be used during a transition period until the infrastructure for the use of renewable resources is fully developed.

However, given the clear disadvantages of nuclear energy, it is imperative that the infrastructure green, safe and sustainable alternative energies are developed.

Different technolog...

Table of contents

• Cover
• Title Page
• Copyright
• Preface
• Contents
• List of contributing authors
• 1 Introduction: hydrogen storage as solution for a changing energy landscape
• 2 CO2-based hydrogen storage: CO2 hydrogenation to formic acid, formaldehyde and methanol
• 3 CO2-based hydrogen storage – formic acid dehydrogenation
• 4 CO2-based hydrogen storage – Hydrogen generation from formaldehyde/water
• 5 CO2-based hydrogen storage – hydrogen liberation from methanol/ water mixtures and from anhydrous methanol
• 6 Hydrogenation of carbonyl compounds of relevance to hydrogen storage in alcohols
• 7 Dehydrogenation of alcohols and polyols from a hydrogen production perspective
• 8 Hydrogenation of nitriles and imines for hydrogen storage
• 9 Transition metal-catalyzed dehydrogenation of amines
• 10 Homogeneously catalyzed hydrogenation and dehydrogenation reactions – From a mechanistic point of view
• Index