Techno-Economic Challenges of Green Ammonia as an Energy Vector

By Agustin Valera-Medina and Rene Banares-Alcantara

Techno-Economic Challenges of Green Ammonia as an Energy Vector presents the fundamentals, techno-economic challenges, applications, and state-of-the-art research in using green ammonia as a route toward the hydrogen economy. This book presents practical implications and case studies of a great variety of methods to recover stored energy from ammonia and use it for power, along with transport and heating applications, including its production, storage, transportation, regulations, public perception, and safety aspects. As a unique reference in this field, this book can be used both as a handbook by researchers and a source of background knowledge by graduate students developing technologies in the fields of hydrogen economy, hydrogen energy, and energy storage.

• Includes glossaries, case studies, practical concepts, and legal, public perception, and policy viewpoints that allow for thorough, practical understanding of the use of ammonia as energy carrier
• Presents its content in a modular structure that can be used in sequence, as a handbook, in individual parts or as a field reference
• Explores the use of ammonia, both as a medium for hydrogen storage and an energy vector unto itself

• Language: English
• Publisher: Academic Press
• Release date: Sep 30, 2020
• ISBN: 9780128208861

Agustin Valera-Medina

Agustin Valera-Medina is a Reader/Associate Professor at Cardiff School of Engineering. He has a bachelor’s degree in Mechanical Engineering from UNAM, Mexico, and an MSc and a PhD in the field of Energy from Cardiff University, UK. He has participated as PI/Co-I on 23 industrial projects with multinationals including PEMEX, Rolls-Royce, Siemens, Ricardo, Airbus, and EON, attracting approximately £8.5M. He has published 145 papers (h-index 19), 26 of these specifically concerning ammonia power. He has supervised 22 PhD students, 5 on ammonia-related topics. Dr. Valera-Medina led Cardiff’s contribution to the Innovate-UK “Decoupled Green Energy” Project (2015–2018) led by Siemens and in partnership with STFC and the University of Oxford, which aimed to demonstrate the use of green ammonia produced from wind energy. He is currently PI of the project SAFE-AGT (EP/T009314/1, £1.9M) to demonstrate the use of ammonia as an efficient gas turbine fuel. He leads the combustion work package of the H2020 project FLEXnCONFU (884157), a €12.7M project conceived to demonstrate ammonia power in large turbine engines. He is also PI and co-I of projects related to ammonia for transportation, propulsion, and heat/cooling. He has been part of various scientific boards, chairing sessions in international conferences and moderating large industrial panels on the topic of “Ammonia for Direct Use.” He supported the preparation of the Royal Society Policy Briefings “Green Ammonia” on the use of ammonia as energy vector.

Book preview

Techno-Economic Challenges of Green Ammonia as an Energy Vector

Agustin Valera-Medina

College of Physical Sciences and Engineering, Cardiff University, UK

Rene Banares-Alcantara

University of Oxford, Oxford, UK

Table of Contents

Cover image

Title page

Copyright

List of Contributors

About the Editors

Acknowledgements

Chapter 1. Introduction

Climate Change

Zero Carbon Technologies

Energy Storage

Hydrogen and Ammonia

Ammonia as an Energy Vector

Summary

Chapter 2. Energy Storage Technologies: Power-to-X

Introduction

Chapter 3. Pathways for Green Ammonia

Introduction

Drivers

Challenges

Perspectives/Progress

Summary

Chapter 4. Ammonia Production Technologies

Introduction

Biological Nitrogen Fixation

History of Synthetic Ammonia Synthesis

Electrolysis-Based Hydrogen Production

Biomass-Based Hydrogen Production

Nitrogen Purification

Ammonia Synthesis Loop

Scale-Down and Intermittency

Cost of Electrolysis-Based Haber–Bosch Processes

Nonconventional Technologies

Summary

Chapter 5. Storage and Distribution of Ammonia

Introduction

Storage of Ammonia

Distribution of Ammonia

Corrosion During Storage and Transportation

Case Study: Feasibility Study for the Transport of Ammonia in Natural Gas Lines

Summary

Chapter 6. Use of Ammonia for Heat, Power and Propulsion

Introduction

Challenges

Technologies for the Production of Heat, Power or Propulsion

Summary

Chapter 7. Applications

Introduction

Marine Transportation (C-Job Naval Architects)

Power and Propulsion–Internal Combustion Engine at STFC Demonstrator (Cardiff University)

Power and Propulsion–FREA Gas Turbine (AIST)

Road Transportation (Korea Institute of Energy Research)

Summary

Chapter 8. Techno-Economic Aspects of Production, Storage and Distribution of Ammonia

Introduction

Techno-Economics of Green Ammonia Production

Techno-Economics of Ammonia Storage

Techno-Economics of Ammonia Distribution

Case Study – Distribution Requirements to Supply the Demands of a Fleet of Thirty-Six Ultralarge Container Vessels

Chapter 9. Techno-Economic Aspects of the Use of Ammonia as Energy Vector

Introduction

Chapter 10. Safety Aspects

Introduction

Anhydrous Ammonia

Corrosion

Distribution and Storage – Risks

Fertilizer, Refrigerant and Chemicals – Risks

Fuel – Risks

Nitrogen Oxides and Derivatives

Further Precautions

Case Studies

Summary

Chapter 11. Regulatory Framework

Introduction

United States of America Approach

European Union Approach

Chinese Approach

Summary

Chapter 12. Beyond the Technology: Public Perception of Ammonia Energy Technologies

Introduction

Social Acceptance of Renewable Energies

Role of Public Perception in the Advancement of Hydrogenated Vectors

Current Public Perception of Ammonia (Chemical or Fertilizer)

Recent Findings on Public Perception of Ammonia as Fuel

Public Perception of Ammonia as a Fuel: A Case Study – Mexico

Conclusions (Case Study)

Summary

Appendices

Chapter 13. Future Trends

Introduction

Roadmaps, Policies and Economy

Production

Distribution and Storage

Utilization

Summary

Index

Copyright

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List of Contributors

R. Bañares-Alcántara,     Department of Engineering Science, University of Oxford, Oxford, United Kingdom

N.E. Benes,     Department of Science & Technology, University of Twente, Enschede, The Netherlands

Z. Cesaro,     Department of Engineering Science, University of Oxford, Oxford, United Kingdom

C.T. Chong,     China-UK Low Carbon College, Shanghai Jiao Tong University, Shanghai, China

S. Crolius,     Carbon-Neutral Consulting LLC, Brooklyn, NY, United States

N. De Vries,     C-Job Naval Architects, Hoofddorp, The Netherlands

C. Demski,     School of Psychology, Cardiff University, Cardiff, United Kingdom

S. Dooley,     School of Physics, Trinity College Dublin, The University of Dublin, Dublin, Ireland

O. Elishav,     The Nancy and Stephen Grand Technion Energy Program, Technion – Israel Institute of Technology, Haifa, Israel

C. Forbes,     Department of Engineering Science, University of Oxford, Oxford, United Kingdom

A. Giles,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

G.S. Grader,     The Wolfson Department of Chemical Engineering, Technion – Israel Institute of Technology, Haifa, Israel

A. Guati-Rojo,     School of Psychology, Cardiff University, Cardiff, United Kingdom

M. Gutesa-Bozo,     Termoinžinjering d.o.o, Research and Development Department, Zrenjanin, Serbia

E.L. Ifan,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

P.M. Krzywda,     Department of Science & Technology, University of Twente, Enschede, The Netherlands

L. Lefferts,     Department of Science & Technology, University of Twente, Enschede, The Netherlands

S. Morris,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

B. Mosevitzky Lis,     The Wolfson Department of Chemical Engineering, Technion – Israel Institute of Technology, Haifa, Israel

C. Mounaïm-Rousselle,     PRISME, University of Orleans, Orleans, France

G. Mul,     Department of Science & Technology, University of Twente, Enschede, The Netherlands

R.M. Nayak-Luke,     Department of Engineering Science, University of Oxford, Oxford, United Kingdom

E.C. Okafor,     National Institute of Advanced Industrial Science and Technology, Fukushima, Japan

D.G. Pugh,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

A. Roldan,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

K.H.R. Rouwenhorst,     Faculty of Science and Technology, University of Twente, Enschede, The Netherlands

J. Thatcher,     Department of Engineering Science, University of Oxford, Oxford, United Kingdom

A. Valera-Medina,     College of Physical Sciences and Engineering, Cardiff University, Cardiff, United Kingdom

Y. Woo,     Korea Institute of Energy Research, Daejeon, South Korea

H. Xiao,     College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, China

About the Editors

Agustin Valera-Medina

Agustin Valera-Medina is a Reader/Associate Professor in Cardiff School of Engineering. He has participated as PI/Co-I on 23 industrial projects with multinationals including PEMEX, Rolls-Royce, Siemens, Ricardo, Airbus and EON, attracting approximately £8.5M. He has published 133 papers (h-index 19), 24 of these specifically concerning ammonia power. He has supervised 22 PhD students, 5 on ammonia-related topics. Dr Valera-Medina led Cardiff's contribution to the Innovate-UK ‘Decoupled Green Energy’ Project (2015–2018) led by Siemens and in partnership with STFC and the University of Oxford, which aimed to demonstrate the use of green ammonia produced from wind energy. He is currently PI of the project SAFE-AGT (EP/T009314/1) to demonstrate the use of ammonia as an efficient gas turbine fuel. He leads the combustion work package of the H2020 project FLEXnCONFU (884157), a €12.7M project conceived to demonstrate ammonia power in large turbine engines. He is also PI of the project ‘Ammonia Propulsion’ (Endeavr, Welsh Government and Airbus). He has been part of various scientific boards, chairing sessions in international conferences and moderating large industrial panels on the topic of ‘Ammonia for Direct Use’. He supported the preparation of the Royal Society Policy Briefings ‘Green Ammonia’ on the use of ammonia as energy vector.

Rene Banares-Alcantara

Rene Banares-Alcantara is a Reader at the Department of Engineering Science, University of Oxford, and a Fellow and Senior Engineering Tutor in New College. He has a Bachelor's degree in Chemical Engineering from the Universidad Nacional Autónoma de México and obtained his MSc and PhD degrees in the field of Chemical Engineering at Carnegie Mellon University. He has worked at the Instituto de Investigaciones Eléctricas, Facultad de Química (UNAM) and the University of Edinburgh. He has been a principal grant holder and/or participated as co-investigator in projects funded by the European Union, EPSRC, DURSI, MCYT, SERC, Siemens and the ECOSSE industrial consortium (Air Products, Aspen Tech, BP, BNFL, DuPont, ICI, QuantiSci, KBC, Mitsubishi, Chemicals, Norsk Hydro, Simon Carves, SimSci and Zeneca). His research interests are in the area of Process Systems Engineering and the development of decision support tools. Since 2014, he has been involved in projects related to long-term (chemical) storage of renewable energy, the production of ‘green’ ammonia and its role in decarbonizing the electricity sector.

Acknowledgements

The authors would like to thank the following for their contributions. Although the current busy and difficult times have been a challenge, they found the stamina for a fruitful contribution to this work.

Chapters 2 and 3 (Energy Storage Technologies and Pathways to Green Ammonia)

Dr Nayak-Luke and Mr Cesaro who have extensive knowledge on the technical context of chemical energy storage, a keen interest in energy policy, and a strong commitment to make its implementation a reality.

Chapter 4 (Ammonia Production)

Mr Rouwenhorst, Mr Krzywda, Prof. Benes and Prof. Lefferts whose encyclopaedic approach to ammonia production techniques (past, present and future) provide a useful background to the book subject.

Chapter 5 (Storage and Distribution of Ammonia)

Dr Elishav, Dr Mosevitzky-Lis and Prof. Grader whose expertise in the field was critical to improve the quality of the chapter. Their prompt support genuinely was paramount in achieving our publishing targets.

Chapters 6 and 7 (Use and Applications of Ammonia)

Mr De Vries, Dr Okafor, Dr Xiao, Dr Gutesa-Bozo, Dr Woo, Dr Dooley and Dr Giles whose contributions have enabled a unique set of chapters that include the novel literature based on personal knowledge, bespoke program development and constant research efforts.

Chapters 8 and 9 (Techno-economics of Production, Storage, Distribution and Use of Ammonia)

Dr Nayak-Luke, Mr Cesaro, Mr Thatcher and Mr Forbes whose combined contributions have been key in showing the techno-economic feasibility of green ammonia from production to use.

Chapter 10 (Safety Aspects)

Mr Crolius, Dr Pugh and Mr Morris whose knowledge and understanding of health and safety aspects and extensive recognition of global trends can be hardly encountered elsewhere.

Chapter 11 (Regulatory Framework)

Mr Ifan and Dr Chong whose constant work and continuous contributions provided the background for a chapter that can be used as a reference at a global scale.

Chapter 12 (Public Perception)

Miss Guati-Rojo whose untiring dedication provided research that has never been documented, while Dr Demski offered ample support and expertise to materialise such a research.

Chapter 13 (Future Trends)

Dr Rouwenhors, Dr Elishav, Dr Mosevitzky-Lis, Dr Roldan, Prof. Grader and Prof. Mounaïm-Rousselle whose understanding of the requirements for an ammonia-based economy was crucial for the improvement of the chapter. Their continuous revision and prompt recommendations were highly appreciated.

Chapter 1: Introduction

A. Valera-Medina, and R. Bañares-Alcántara

Abstract

Climate change and its associated impacts to humanity and the planet have led researchers, industries and governments to seek for alternatives to reduce greenhouse gas emissions. Most accepted and commercially deployable technologies rely on the capture of energy from renewable sources such as wind, solar and marine energy. However, these technologies present a distinctive challenge because of their intermittency. Complete emissions mitigation using these technologies will require backup storage capable of supporting the grid when these renewable sources are not able to deliver the required power. Amongst the storage options under scrutiny, chemical storage possesses unique characteristics in terms of scale and storage duration. Chemicals such as hydrogen have set the pace on this field, although hydrogen is difficult to handle and expensive to store over long periods. Ammonia appears to be an ideal hydrogen vector that can potentially alleviate some of the incurred costs and high energy requirements of hydrogen, whilst using the expertise that the fertilizer sector has gained on the use of this chemical over more than 100 years. Ammonia is presented as a novel option to support energy decarbonization.

Keywords

Ammonia; Climate change; Energy storage; Hydrogen; Renewable energy

Climate Change

Climate change has been one of the major challenges of the past decades, engaging the attention of scientists, industries and governmental bodies all around the globe. Climate change, mainly caused by the increase in carbon dioxide concentration in the atmosphere, is certainly a major shaper of our current understanding of the world, thus establishing itself as a crucial force for change and development.

Climate change, as explained by the Intergovernmental Panel on Climate Change (IPCC), has been mainly triggered by the emission of anthropogenic gases, including carbon dioxide and nitrogen oxides, which are estimated to have caused a global average temperature increase of approximately 1.0°C, with a range between 0.8 and 1.2°C. The panel has estimated that between 2030 and 2050 the temperature increase will reach 1.5°C if emissions continue to raise, a situation that is highly possible [1] (Fig. 1.1). More importantly, these emissions will continue to impact the climate, persisting for centuries or millennia, with a direct impact on human activities and living standards [2].

Recent studies conclude that anthropogenic emissions (greenhouse gases, aerosols and their precursors) up to the present are unlikely to cause further warming of more than 0.5°C over the next decades. However, further increase in emissions will lead to a temperature increase higher than 2.0°C, a condition that will set more risky scenarios based on geographic location, economic development, vulnerability and mitigation options [1].

Some of the impacts of climate change can already been seen with a variant weather. The heat-trapping process of greenhouse gases will continue to increase, thus leading to longer frost-free periods [3,4]. The process will be accompanied by an increase in precipitations in some regions, with resulting flooding [3,5]. Simultaneously, droughts and heat waves lasting days and weeks will be more intense, with summer temperatures expected to rise [3,6]. This increment of temperature will also trigger large-scale events such as hurricanes with stronger, more frequent occurrences. Over the past decade, hurricanes have increased their intensity due to favourable weather conditions, with hurricanes such as Patricia (2015) that reached category 5 in just 24   hours with wind velocities of up to 342.6   km/h [7]. Artic and permafrost regions are also expected to be affected with the increase in temperatures. Current trends show a continuous decline of ice in these areas, ice that melts into the seas, thus increasing the sea level. It is estimated that Artic sea ice is now declining at a rate of 12.8% per decade since records began (in 1981) [3] (Fig. 1.2.).

Sea level rise, another important parameter to consider when discussing climate change, is also crucial to the impacts that this phenomenon is causing to the planet [8]. Owing to the decrease of ice caps and expansion of water due to higher temperatures, it is estimated that since 1880, there has been a rise of approximately 0.20   m in sea levels. This trend is expected to continue with a projected rise between 0.30 and 1.2   m, at a current rate of 3.3   mm per year, over the 21st century [1,3] (Fig. 1.3). To put this number in perspective, an increase in sea level of 0.1   m implies that up to 10 million more people would be exposed to risks of climate change, assuming no adaptation [1].

Health, livelihoods, food security, economic growth, water supply and human security will also be impacted because of climate change. Vulnerable communities, in particular, will be those suffering the most from these effects, with expected scenarios where poverty and economic disadvantage will augment across the globe [2]. Ozone-related mortality will raise with amplification of heat waves in urban areas [9,10]. Risks from malaria, dengue fever, cholera and other related diseases will increase, with millions of diagnosed cases and deaths related to these illnesses [1,11–13].

The scenario is as detrimental on ecosystems as it is on the human impacts. Biological impacts are foreseen on biodiversity and ecosystems, with loss of species and extinction. Of the 105,000 species studied, 18% of insects, 16% of plants and 8% of vertebrates are potentially in danger to lose over half of their geographic range [1,14]. High-altitude tundra and boreal forest are particularly in danger [15]. Fisheries, sea colonies and reefs have already started to show their limited resistance to temperature rise [1,16,17].

Fig. 1.1 Observed global temperature change and modelled responses to stylized anthropogenic emission and forcing pathways. 

Courtesy of IPCC (Figure SPM1 IPCC. Summary for Policymakers. Glob warm 15°C an IPCC spec rep impacts glob warm 15°C above pre-industrial levels relat glob greenh gas emiss pathways, context strength glob response to threat clim chang; 2018. Available from: https://www.ipcc.ch/sr15/chapter/summary-for-policy-makers/.

Fig. 1.2 Change in Artic ice caps from 1979 to 2018. 

Courtesy of NASA. The effects of climate change. Glob Clim Change. 2019. Available from: https://climate.nasa.gov/effects/.

Fig. 1.3 Satellite sea level observations at the NASA Goddard Space Flight Center. 

Courtesy of NASA. The effects of climate change. Glob Clim Change. 2019. Available from: https://climate.nasa.gov/effects/.

However, reaching a stage of net-zero emissions can halt global warming and climate change on multi-decadal timescales. Thus zero carbon technologies are on trend, setting up the pace to tackle the increase in emissions and their related impacts on life on Earth.

Zero Carbon Technologies

Carbon emissions mitigation has gained considerable adepts across the world (Fig. 1.4). Support has been given specially to clean technologies capable of harvesting energy from sustainable, low-polluting sources. Of special interest are wind, solar and marine energy, together with the use of biomass as a precursor to the production of zero carbon molecules (i.e., hydrogen) [19,20]. Nuclear energy has also been considered for the production of zero carbon energy vectors [21]. Although these two technologies are important in the present context, they are going to be left aside in order to avoid conflicts about their nature (sustainable or not). Nevertheless, the process for the production of zero carbon vectors via these technologies is the same.

Wind energy, in particular, is one of the most commercialized renewable energy technologies across the world. The use of wind energy goes back to the Pharaonic era as boat propeller to pump water in the Mediterranean and to power windmills for wheat grinders almost 3000 years ago. The production of power from wind has gained acceptance worldwide because of its clean nature and high potential. Similar to any other rotating dispositive, wind turbines can be connected to electric generators to produce energy. Although wind power varies across the year, this type of energy is very consistent over short timescales. For this reason, an increasing number of wind turbines are deployed globally, supporting the creation of wind farm facilities that are interconnected to the grid to supply large power outputs [22]. However, one of the main issues with technologies at such a large scale is the management of excess capacity. Some options include energy export to neighboring areas, disconnection or a concept that has been gaining more support, energy storage [23]. According to the International Energy Agency (IEA) [18], the total installed capacity of wind energy was 467.4   GW in 2016, a trend that has been dominated by onshore facilities. Onshore technologies have evolved over the past 5   years to maximize the electricity produced per megawatt of installed capacity, unlocking sites with lower wind speeds. Wind turbines have become bigger, with taller hub heights and larger rotor diameters. Simultaneously, the dimensions and the number of units in offshore facilities keep increasing, with farms such as Walney Extension (in the United Kingdom) reaching capacities of 659   MW [24]. The reduction in production costs, a consequence of a more mature market, support from subsidies and a well-known technology have all contributed to an exponential raise of energy produced by wind [22,25,26]. Forecasts predict up to an eightfold increase in wind power generation over the next 20 years, thus emphasizing the high impact that the technology will have by then [18,27]. However, as mentioned previously, management of these large resources is critical to improve profitability whilst supporting the grid with zero carbon energy in the long term.

Fig. 1.4 Electricity generation by source, excluding pumped storage. (A) Includes geothermal, solar, wind, tide/wave/ocean, biofuels, waste, heat and other forms of energy. (B) In these graphs, peat and oil shale are aggregated with coal. 

International Energy Agency. Key world energy statistics. IEA Publ; 2019. Available from: https://webstore.iea.org/world-energy-outlook-2019. All Rights Reserved.

Similar to wind energy, solar energy has also gained extensive attention worldwide. Solar energy has become a paramount energy source for the development of renewable energy systems. Solar energy is the conversion of sunlight into useable energy forms, and it has been employed before historical records were produced. Some interesting stories recount the development of solar concentration panels by Archimedes to burn warship sails of Roman warships. These stories continue in time until the development of today's devices. Solar photovoltaics, solar thermal electricity and solar heating-cooling are now well-established solar technologies [28–30]. Particular applications such as heating and cooling have generated a vast amount of research over the recent decades, as solar energy sources are reliable, predictable and free [31]. In particular, solar energy can be employed for heating/cooling applications such as hot water delivery, space heating and industrial processes, with systems that range from small devices to industrial complex processes [29,31]. The cumulative installed capacity of solar thermal installations reached an estimated 456   GWh by the end of 2016 [29]. Solar photovoltaic systems have also received a large boost across economies such as the People's Republic of China, Japan, the United States and Europe, with installed capacities that reached almost 300   GW in 2016 [29,32,33] (Fig. 1.5). However, as in the case of wind energy, solar energy varies based on weather conditions and seasonal periods. Moreover, vast amounts of solar energy cannot be harvested economically in difficult-to-access areas that are far from electric grids, making them expensive in terms of installation and maintenance in the consolidation of electric grids that connect generation sites to user points. These facts, combined with the extreme variability in some regions, can be overcome with the use of proper energy management techniques such as energy storage, thus enabling the distribution of excess energy when and where it is needed.

Finally, another technology that can also be considered is marine energy. Marine energy, as solar and wind energy, is also a renewable resource that can be accessed at large scales across the world. This energy can be obtained from ocean waves, tides, salinity differentials or temperature gradients that generate currents with enough kinetic energy that these can be harvested for power production [34]. This type of energy has accompanied humans since pre-historic times. However, it would be until the 19th century that patents would appear for the recovery of energy from ocean waves. Decades after these discoveries, the development of new devices would see the onset of turbines similar to those used in wind energy systems, such as buoyant bodies that would harvest the oscillatory movement of waves, osmotic mechanisms that employ salinity differentials and devices that exchange heat caused by temperature gradients to produce power [8,35–38]. However, due to its immature technical development compared to the previous two technologies, only a mere 0.5-GW capacity had been installed by 2018, with 1.7   GW under construction [34]. High costs, challenging market environments and the need for constant energy production at reliable power outputs are still the main barriers for full deployment of these technologies. Public and private funds have been withdrawn because of the economics of these systems, which could well benefit from proper energy management techniques coupled with advanced technologies. Therefore better economics and energy management could free the potential of 748   GW power by 2050, creating in the way 160,000 direct jobs [34].

Fig. 1.5 Solar photovoltaic (PV) generation and cumulative capacity by region, 2017–23. 

IEA. Market Report Series: Renewables. 2019; International Energy Agency. Solar energy. Renewables. 2019. Available from: https://www.iea.org/topics/renewables/solar/. All Rights Reserved.

It is not surprising that new markets are opening to the use of all these technologies. Countries such as Australia, Chile, Argentina, Morocco and Mexico are all investing in the development of large-scale farms (solar, wind, marine) for energy recovery [39]. As it would be expected, opening of these sites is related not only to local or national energy independency agendas but also to get access to trillionaire shares that these new markets represent. Developed economies, which are known to be depleting their fossil streams, are more inclined to increase commercialization of these renewable sources. For example, Australia has embarked on the development of vast solar sites that will produce energy that will be shipped to Japan, thus enabling the latter to meet its carbon reduction obligations whilst ensuring the availability of energy supply for its growing industry [40]. Mexico exhibits similar scenarios across the US-Mexico border [41], Chile and Argentina have announced their new contracts with China [42], and the Sahara region is seen as the future for European clean energy at a large scale [43].

Therefore it can be concluded that most of these technologies (and those that have not been addressed but that will also represent an important share in the total mix of future energies) require an energy management technique to improve their resilience, reduce costs and support the transition toward a zero carbon network whilst enabling their deployment to diverse regions across the world. The feasibility of having all these renewable resources grid-interconnected is very low because of costs and transmission inefficiencies. In contrast, energy storage is a technique that can ensure energy management coupled with distribution flexibility and presents a feasible solution that can be implemented in a short term whilst complying with the cost and technical requirements.

Energy Storage

A competitive cost of renewable energy, in combination with the effects of climate change and the drive for global decarbonization, will ensure that this commodity is traded internationally. In order to enable this scenario, several strategies can be implemented:

• Direct use of grid-supplied electricity from renewable energy: Interconnection between regions allows the transmission of resources and their utilization based on demand and production. The implementation of this method is restricted to short distances or relatively limited flows. Moreover, it is evident that in the case of full renewable energy penetration, this concept is constrained by production times, local demand, costs and policies. Also, the cost of implementation is still high, especially in the case of offshore production locations, where costs can go up to €8 billion/1000km, with large variations in transmission efficiencies depending on the interconnection type [44] and factors that contribute to energy losses and cost increase for long distances. Although it is expected that smart grids will alleviate some of these problems and enable a smooth integration of various renewable energies [45], the lack of flexibility might be a barrier that other energy management options can tackle.

• Energy curtailment: Over the past years, several wind operators have received millions of euros to turn off their equipment, mainly wind turbines, as national grids deemed their energy production to be sourced at the wrong time [46]. This has led to changes in legislation around the globe that have mitigated the problem. However, there are still regions that include this option in their energy management programs.

• Energy storage via chemical or mechanical devices: Energy storage enables the recovery and storage of different types of energy in order to be used at another time and/or another location. There are many methods to store energy and each depends on the location, time of use and technology maturity. Fig. 1.6 shows some energy storage technologies, out of which batteries, pumped hydro, compressed air, supercapacitors and flywheel storage have the highest maturity. However, other potential storage vectors such as chemical storage via synthetic methane, hydrogen and ammonia are currently in the demonstration stage as energy storage options for longer periods [47].

Fig. 1.6 Power versus time of storage. Comparison between different energy storage technologies.

As depicted in Fig. 1.6, chemical energy storage is capable of supporting energy power in gigawatt scales. In contrast with its closest contender, i.e., pumped hydro, chemical storage allows flexible deployment of the resource, without the geographic constraints required to build a hydroelectric plant [48]. Moreover, chemicals such as methane, hydrogen and ammonia can be stored either in artificial containers at high pressures and/or low temperatures or in geologic deposits such as salt caves, further decreasing costs and implementation times [49]. Another great advantage with this form of energy storage is that chemicals can be stored for days, weeks, years and even decades without major losses or quality decay (as long as the conditions and storage medium are not reactive with the chemicals). Compared to other alternatives whose storage time is only of hours, the advantage of chemical storage lies in its long time energy deployment.

It is important to fully understand the concept that we are trying to emphasize. If a car is to be modified to use a particular clean energy storage technology instead of gasoline and if the car is to be employed for short distances, then a supercapacitor or an ammonia tank might not be the best energy storage option. However, in the case of a large transatlantic tanker, whose trip usually takes weeks in open seas, having a chemical as fuel would make sense. Thus it is clear that each energy storage strategy has its own application niche, and finding the most cost-effective, efficient and reliable option for each case is essential.

Chemical storage in the form of hydrogenated fuels is essential for the transition to a more flexible, coupled energy market. Current contenders in this field are methanol, methane, hydrogen and ammonia. The first two options contain carbon and, although it can be captured from the atmosphere [50], do not contribute to decarbonization and CO2 global reduction. Therefore only hydrogen and ammonia can be more certainly assumed as the main options to decarbonize the energy market whilst providing security of supply. Other chemicals that have been previously assessed, such as hydrazine [51] and ammonium nitrate [52], are unstable and difficult to handle by the general public and thus are out of the scope of commercial developers.

Hydrogen and Ammonia

For more than 200 years, hydrogen has been an option for the production of energy, with only water and heat as main byproducts. Jules Verne prophesied in his novel The Mysterious Island (1874),

And what will they burn instead of coal? asked Pencroft. Water, replied Harding. Water as fuel for steamers and engines! Water to heat water! But water decomposed into its primitive elements. Replied Cyrus Harding, … I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it will furnish an inexhaustible source of heat and light … Water will be the coal of the future [53].

Modern research has continuously tried to untangle the complexity of using hydrogen for the production of energy at various scales and locations, going from local production to large national grids, from diminutive devices to large-scale systems. Current efforts have fully positioned hydrogen as one of the most promising contenders in the future of energy production, with vast research, development and investment in the area [54].

One of the most recent works that compiles these global efforts is the report produced by the IEA that was presented at the G20 Forum in Japan in the summer of 2019 [55]. The report emphasizes the need to search for alternative technologies capable of using hydrogen as an energy vector. As depicted in Fig. 1.6, it is clear that the use of this chemical presents several advantages in terms of scalability and storage duration.

Japan particularly emphasized its commitment to the decarbonization of its economy via hydrogen [55]. Owing to the large momentum that hydrogen has reached among businesses and governments, it is presented as the chemical storage of the future with fast implementation in current technologic and economic scenarios. The versatility of hydrogen is due to its relatively easy production, storage, distribution and final use. Hydrogen can be obtained from almost all renewable biomass sources and has been obtained over decades from fossil sources (i.e., via steam reforming), thus giving this molecule a unique advantage. Moreover, hydrogen can be transported as a liquid or gas for its use in fuel cells, combustion engines or process industries [55], thus increasing its use over the years (Fig. 1.7).

However, the creation of a hydrogen economy faces several constraints that still require further development from all the stakeholders involved in its deployment. These constraints are related to the production, distribution and use of the molecule in a safe, economic and easy-to-handle manner. For example, in terms of costs, the production of hydrogen via renewable energies (to mitigate the use of fossil fuels and their inherent carbon footprint) requires the reduction in price of electrolysis systems. Although it is expected that by 2030–50 the costs of electrolysers will be lower than the use of carbon sequestration technologies due to mass production and component improvement, current costs of producing hydrogen via electrolysis are still high when compared with the use of cheap and abundant fossil fuels (Fig. 1.8) [55].

Although this could also be detrimental for ammonia, the distribution of hydrogen presents a difficult task because of its high diffusivity and low density. Being the smallest molecule in the universe, hydrogen tends to permeate many materials and therefore requires special considerations to transport it [56]. Although some economies (e.g., Germany, the Netherlands, Denmark) already inject hydrogen in their natural gas grids [57], the concentration is still low enough to avoid the diffusion of the molecule through seals or gaskets, thus posing a challenge to increase the load of hydrogen in these systems.

Another important parameter to consider is the use of hydrogen for the production of energy at many scales. For example, at small scales, such as for individual transportation, it would require the implementation of distributed fuelling stations [55]. Although various nations are nowadays attempting to deploy the former, regulations are still a barrier because of the explosive nature of hydrogen, an issue that is magnified by fuelling operations that would require more strict controls to avoid leaks generated by regular users who are untrained to handle the chemical. At medium scale, the distribution of heat via hydrogen also needs new devices that can handle higher hydrogen contents, which tend to be highly reactive and more dangerous [55]. Finally, large power systems also require novel approaches to reduce instabilities generated by the use of hydrogen. For example, large gas turbines powered via this chemical are prone to either highly unstable regimes (i.e., flashback) or large NOx emissions as a consequence of the high reactivity or high temperatures of hydrogen flames, respectively. Although industries are currently working to mitigate these effects and make use of large equipment for the reconversion of hydrogen to energy at large scales more accessible [58], it is clear that there are various barriers that need global efforts and bespoke solutions before hydrogen can be fully implemented as the dominant energy storage vector.

Fig. 1.7 Global demand of hydrogen, 1975–2018. DRI, Direct Reduction of Iron in steelmaking. 

International Energy Agency. The future of hydrogen – executive report; 2019. Available from: https://www.iea.org/hydrogen2019/. (Accessed 19 June 2019). All Rights Reserved.

Fig. 1.8 Production costs of hydrogen through different technologies. CAPEX, capital expenditure; CCUS, carbon capture, utilization, and storage; OPEX, operational expenditure; WACC, weighted average cost of capital. 

International Energy Agency. The future of hydrogen – executive report; 2019. Available from: https://www.iea.org/hydrogen2019/. (Accessed 19 June 2019). All Rights Reserved.

Therefore other molecules have been considered to support the transition of hydrogen into the global economy. One of them, ammonia, presents a unique opportunity to employ the vast knowledge that industries have gained over 120 years since the chemical was synthesized at industrial scale. Ammonia, a highly hydrogenated molecule, enables the deployment of hydrogen produced close to renewable energy sites. It is interesting to note that ammonia contains 17.2   wt % of hydrogen, thus making it one of the molecules with more percentage hydrogen [48]. Ammonia can easily be condensed into liquid at relatively low pressures and high temperatures (−33°C at 0.1   MPa or 15°C at 0.8   MPa), thus making its distribution easier and cheaper than that of hydrogen. Moreover, liquid ammonia has a greater volumetric hydrogen density than liquid hydrogen itself (i.e., the volumetric hydrogen density of liquid hydrogen at −253°C is approximately 70 kg   H2/m³, whereas at 27°C and 1.0   MPa it is 106 kg   H2/m³ [59]).

In contrast to hydrogen, which is a small, highly diffusive molecule, ammonia has a viscosity and density similar to those of methane, making it easier to handle. Correspondingly, the use of ammonia over the decades, i.e., since the use of synthesis gas from Mond's processes [60] to the implementation and global commercialization of the Haber-Bosh process [61], has created a vast reservoir of international experience that has led to the creation of large-scale storage sites (e.g., those located at the QAFCO ammonia production facility at Mesaieed, Qatar, with an overall footprint of around 1   hectare) fed by complex global distribution lines [62]. This vast infrastructure is supported by pipeline grids that run for thousands of miles across the United States and Russia, with some smaller infrastructure in Europe that is combined with trains, trucks and tankers that supply the chemical for fertilizer applications [48].

Ammonia has a slow reaction rate [63]. Although this might seem unfavourable for the production of energy, ammonia can be doped with hydrogen or methane to speed up its speed of reaction, thus enabling a proper control of these blends [64,65]. Large-scale systems that operate with ammonia blends will have the advantage of greater combustion control (i.e., less prone to flashback or blowoff) whilst ensuring continuous operation with lower temperatures, minimizing thermal emissions and thermoacoustic patterns [66–68]. Besides, the use of ammonia in combustion systems also enables de-NOxing chemical recombinations thus mitigating unwanted NOx emissions, which are one of the barriers for the use of this fuel in large power systems [69]. The interest that ammonia has raised across the community has also led to the study and development of fuel cells that can directly use ammonia for transportation purposes [70], internal combustion engines for maritime and automotive use [71] and many other technologies that will be addressed in the following chapters.

Therefore ammonia presents a unique alternative that gains more adepts every day. Diverse organizations and government agencies have recognized the potential of ammonia, and the IEA has added ammonia to its energy plans and future trends since 2018 (Fig. 1.9) [72]. Organizations across the globe (e.g., Japan, Strategic Innovation Promotion [SIP]; the United States, REFUEL; the United Kingdom, BEIS; Australia, NH3 chapter) have also recognized the potential of this chemical to support decarbonization and mitigate climate change [48].

It must be emphasized that ammonia, as any other energy vector, has its own application niche, and it would be naïve to consider that it can solve all power requirements worldwide. Similarly, ammonia needs to be considered for its unique characteristics as an enabler of hydrogen for long-distance distribution and/or long periods of storage, thus ensuring that its use can reduce energy distribution and storage hassles across the globe.

Ammonia as an Energy Vector

Ammonia is an example of zero carbon chemical storage and has been identified as a sustainable fuel for remote applications because of its high hydrogen content. Ammonia can be obtained either from fossil fuels or via renewable energy sources (wind, biomass, photovoltaics, marine) where stranded energy supply may be converted to hydrogen [73]. Some of the advantages of ammonia over hydrogen are its lower cost per unit of stored energy, i.e., storing ammonia over 182 days would cost US $0.54 per kg-H2 compared with US $14.95 per kg-H2 for pure hydrogen storage [48], and higher volumetric energy density (7.1 vs. 2.9 MJ/L). Ammonia has a gravimetric energy density of 22.5   MJ/kg, comparable to other fuels (e.g., low ranked coal, 20   MJ/kg; methanol, 22.7   MJ/kg); it can be easily liquefied at 8   bar; and it has an existing proven and reliable infrastructure that transports ∼180 Mtons of ammonia annually [74]. Moreover, ammonia contains more hydrogen per unit volume than liquid hydrogen itself [59]. For these reasons, the IEA has recognized the role of ammonia as the prime energy vector that can contribute to the decarbonization of the planet in the short to medium term [39]. It is important to note that the ammonia to power concept is equivalent to the delivery of a hydrogen economy via hydrogenated nitrogen; hence, the ammonia community sees itself as part of the hydrogen community However, ammonia-based systems face four main challenges:

Fig. 1.9 Applications of hydrogen. 

Birol F. Hydrogen: accelerating & expanding deployment. Hydrogen energy ministerial, Tokyo. IEA; October 23, 2018. Available from: https://www.nedo.go.jp/content/100885441.pdf. (Accessed 15 November 2019). All Rights Reserved.

1. high-efficiency, carbon-free ammonia synthesis;

2. clean, high-efficiency conversion to power at medium to utility scale;

3. public acceptance through safety regulations and appropriate community engagement;

4. economic viability for full global deployment.

Development of new devices and techniques that can use green ammonia can accelerate the adoption of the hydrogen economy through the following:

1. Reducing emissions: Ammonia offers the possibility of fuelling devices without direct CO2 emissions. NOx is the main pollutant and this remains a challenge.

2. Improving security of supply: Ammonia facilitates the exploitation of renewable electricity by enabling large-scale energy storage and on-demand conversion. Notably, it has the potential to solve the flexibility problems posed by variable, intermittent renewable power generation.

3. Reducing costs of hydrogen transition: The capital costs of ammonia energy storage are comparable to or lower than those of compressed air and pumped hydro but without the associated geographic constraints and the ability to enable much longer storage periods than batteries [47]. Moreover, considerable infrastructure already exists along with well-established safe handling procedures, reducing investment in infrastructure and training [73]. Also, ammonia can transport more hydrogen than most alternative methods (i.e., liquid hydrogen or hydrogen injection into the national gas grid), thus reducing distribution costs while easing deployment. However, conversion of this trapped hydrogen needs to be improved to increase efficiency and benefits.

Developments in the production of ammonia not only are related to the improvement in cost, distribution and final use but also include the search of new alternatives to produce ammonia without generating hydrogen. Current Haber-Bosch processes employ hydrogen and nitrogen at efficiencies of ∼50%, thus requiring large quantities of energy with massive waste. Therefore research is focusing on alternative synthesis methods such as electrochemistry, electrocatalysis, photocatalysis and photoelectrocatalysis [75]. Research groups are also taking inspiration from biochemical processes. The use of bespoke catalysts can eventually lead to the electrochemical recombination of nitrogen and water to form ammonia by using the water hydrogen atoms directly without having to produce molecular hydrogen [75]. Bacteria are also being investigated in the efforts to produce cheaper ammonia. Some bacteria use large protein complexes called nitrogenases to grab nitrogen out of the air and make ammonia [76]. Although most of these technologies are still very young, their potential to tackle the cost and production problems facing the industry is evident.

In terms of small-scale use, ammonia can be employed in fuel cells at various power loads. Automotive fuel cells are known to be under development for the use of pre-cracked ammonia (i.e., hydrogen) or direct ammonia use, delivering power that can compete with commercial devices [48,70,73]. Initiatives in the United Kingdom and Kenya have also demonstrated the use of ammonia-fuelled cells that power small communication devices located in isolated regions, thus ensuring autonomous operation whilst disconnected from the grid [62,77].

Similarly, although important technical and economic challenges still exist after 50 years of development, ammonia as a fuel has been gaining importance across the world. Important milestones on the use of ammonia as a fuelling source for gas turbines have been accomplished by Japan through its SIP Program [78]. A consortium formed by 22 members (industries, research institutions and governmental bodies) has worked toward demonstrating the use of ammonia to satisfy Japan's energy needs. Hydrogen, produced in Australia and transported to Japan as ammonia, may feed future systems that are under scrutiny. Notably, Tokyo Gas, the SIP consortium leader, unveiled its road map to produce the first 100-MW ammonia gas turbine by 2030 [79]. Result from the consortium have progressed from the use of kerosene/ammonia blends to pure ammonia, demonstrating that the latter can be efficiently burned with NOx emissions below 50   ppm [63,80,81]. However, a challenge is the low power output consequence of relatively lower Reynolds (Re) numbers at which the flames stabilize. Moreover, the low efficiencies of current ammonia devices based on regular Brayton cycles call for the use of other advanced thermodynamic concepts.

Current developments have demonstrated that gas turbines, internal combustion engines and fuel cells can have a stable operation under various conditions and blends [80,82]. However, NOx emissions are still a major concern. Currently, for units fuelled with gaseous fuels other than natural gas, the European legislation has set a concentration limit of 200 mg/Nm³ [83], which has been reduced to 75 mg/Nm³ for new units. Interestingly, theoretic and experimental works in the United Kingdom predict NOx emissions below the European threshold by increasing pressure in the combustion chambers (as in large-scale systems) [84], while current results from industrial trials (2   MW) by SIP have started producing good combustion performances with NOx below the Japanese threshold (150 mg/Nm³) [85], opening new opportunity windows for many devices fuelled by ammonia.

Fig. 1.10 Power to ammonia/hydrogen to power.

For all these reasons, ammonia has the potential to be produced and used as an important energy vector. Ammonia also offers the advantage of greater flexibility than other chemicals, as it can be used not only for fuelling or fertilizing applications (its main use nowadays) but also for chemical processes, dying, cleaning products and in refrigerants, etc., thus giving producers and users versatility in its commercialization (Fig. 1.10).

This book brings together the expertise of many groups that through the years have dedicated their efforts to enable the efficient, cost-effective and safe production, distribution, storage and use of ammonia for the decarbonization of energy and the progression towards a hydrogen economy.

Summary

Climate change, a phenomenon caused by anthropogenic activities, is one of the greatest challenges of our century. In order to mitigate unwanted emissions causing climate change, renewable energy sources have been implemented and deployed all across the globe. However, further global energy distribution will require the inclusion of energy management techniques that will incorporate energy storage for flexibility and reliability. One of the most prominent methods for energy management is through chemical storage via chemicals such as methane, hydrogen and ammonia. From the vast amount of available chemicals, hydrogen and ammonia are well-known, zero carbon molecules that have been handled over decades through well-developed industries. Being carbon free, these two chemicals present a viable decarbonizing solution for global energy storage. In particular, ammonia presents a unique opportunity for long-distance/long-term storage, as it contains large quantities of hydrogen and can be easily condensed into liquid at near-ambient pressures and temperatures, employing a vast infrastructure and know-how for its distribution and storage. Moreover, ammonia enables a versatile commercialization, as it can be used for fertilizing, chemical or fuelling purposes. Therefore this book is focused on ammonia as an energy vector, compiling some of the work that groups around the world have pursued over the years to make ammonia a reliable, flexible and affordable energy vector.

Acknowledgements

The Cardiff University gratefully acknowledges the support from the Welsh European Funding Office (WEFO) through its program Flexible Integrated Energy Systems (FLEXIS), project no. 80835.

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