Ammonia Fuel Cells

Ibrahim Dincer, Osamah Siddiqui

• Publisher: Elsevier
• Year: 2020
• ISBN:
  9780128228265
• Topic: Physical Sciences
• Subtopic: Energy

Ammonia Fuel Cells covers all aspects of ammonia fuel cell technologies and their applications, including their theoretical analysis, modeling studies and experimental investigations. The book analyzes the role of integrated ammonia fuel cell systems within various renewable energy resources and existing energy systems.

• Covers the types of ammonia fuel cells that have been developed over history
• Features explanations of the underlying fundamentals and principles of ammonia fuel cells, along with methods to assess the performance of different types of cell
• Includes case studies considering different applications of ammonia fuel cells and their significance in the future of clean energy

Chapter 1

Introduction

Abstract

This chapter deals with the importance of reducing the dependence on fossil fuel-based energy. Historical energy demand statistics in the recent decades are used to depict the rise in energy demands across the globe as well as the corresponding increase in carbon dioxide emissions. In addition, a comparison of carbon emissions arising from different fossil fuel energy resources is presented for the present scenario as well as recent decades. The alarming statistics are highlighted to show the necessity of reducing the usage of fossil fuel and increasing the implementation of renewable energy resources. Further, the shifting trend toward the usage of energy resources entailing low carbon contents with a historical perspective is presented. These include the shift from wood as the initial source of energy to the introduction of coal and oil that were used in various industries across the globe. Next, the advent of natural gas leads to natural gas-based power generation in various parts of the world. Moreover, the increased attention toward low carbon fuels lead to the usage of carbon-free hydrogen fuel that is expected to become a major fuel in the upcoming years. In addition, the historical background of fuel cell technologies is also described, presenting the major technological developments that lead to final commercialization of fuel cells.

Keywords

Energy; CO₂ emissions; Fossil fuels; Fuel cells; Historical background

Since the industrial revolution, power generation has been playing a vital role in the advancement of any nation, which has, therefore, become a central element of any economy that drives the increase or decrease in the national production levels. A continuous and reliable generation of power is essential to attain a sustainable and stable economy as well as industrial sector. However, the increased dependence on fossil fuels for power generation in the recent decades has deteriorated the environment considerably. The change in the global primary energy demands since 2010 are depicted in Fig. 1.1. The energy demands increased by nearly 1.5% in the beginning of the previous decade. This rise in demands has decreased marginally in the beginning of this decade. Also, toward the middle of this decade, the primary energy demands had increased by a comparatively lower amount. Nevertheless, since 2016 the energy demands have risen sharply where the rise increased from 0.6% in 2016 to 2% in 2017. This has increased further to 2.9% in 2018. Hence, every year due to several factors, such as industrialization, urbanization and modern development, the specific energy demands tend to increase continuously. The change in the amount of increase has varied in the recent past, however, there has been a steady increase in the demands. Moreover, as the world swiftly moves toward a technology-enriched livelihood, the demands for energy are expected to rise rigorously. The energy demands are of particular interest due to their direct relation with environmental impacts. Currently, the global energy production heavily relies on fossil fuels and the increase in energy demands will directly affect the usage of fossils across the globe. This is attributable to various factors. First, the power generation sector that provides electricity to run any industry, corporate office, or transportation sector is dependent on fossil fuels across the globe. This implies that as technical and infrastructural development continues to proceed, the usage of carbon-rich and environmentally detrimental fuels continues to rise. In addition, in various sectors such as transportation, the current technology includes the usage of hydrocarbon fuels, which has led to significant environmental detriments across the globe.

Fig. 1.1 Percentage change in global energy demand based on 2009. Data from Ref. [1].

Such alarming facts have led to serious concerns across the globe and in various countries attention is being paid toward reducing the dependence on as well as usage of fossil fuels. However, in several parts of the world, fossil fuel-based resources comprise the major energy sources and their dependence could not be reduced significantly until recently. Fig. 1.2 depicts the total usage of coal, oil, and natural gas across the globe since the year 2000. As can be observed from the figure, the usage of each of these carbon-rich energy resources has increased continuously. Although various global efforts and agreements were made to reduce fossil usage as well as associated environmental impacts, the usage of such resources has increased steadily as shown in the figure. This is attributable to various factors such as increased energy demands. To meet the energy demands, these readily available resources are utilized extensively across the globe leading to considerable environmental damage. The usage of coal increased from nearly 2300 Mtoe in 2000 to nearly 3800 Mtoe in 2018. This denotes a significant increase of 65%, which shows the heavy dependence of various countries on fossil fuels across the globe. Similarly, the global usage of natural gas increased from approximately 2000 Mtoe in 2000 to nearly 3340 Mtoe in 2018. This also signifies an increase of 67% in the usage of the carbon-rich fossil fuel. In addition, oil is also used extensively in various sectors ranging from the industrial sector to the transportation sector. The usage of oil has also seen a steady increase in the recent years where an increase of nearly 25% is observed from 2000 to 2018. These are global estimates that constitute the usage by all countries. Some countries where fossil fuel-based energy resources are a source of income and aid in the development of the economy, entail a steady increase in the production as well as usage of carbon-rich fuels. However, these nations could essentially direct efforts toward the utilization of clean and renewable energy resources where applicable. For instance, some geographical locations receive high-intensity solar radiation across the year. Such locations should employ different types of solar-based power generation techniques. Similarly, some locations have high wind energy potential across the year that should be harvested. Also, other renewable energy resources including biomass, geothermal, and hydropower should also be considered where they are suitably applicable.

Fig. 1.2 Global consumption of coal, natural gas, and oil. Data from Ref. [2].

The recent breakdown of energy resource utilization across the globe is depicted in Fig. 1.3 where the global percentage of energy resources used for primary energy supply is presented. As depicted in the figure, majority of the energy supply was attained from carbon-rich resources. These included 27% coal, 22% natural gas, and 32% oil resources [3]. These three carbon-rich fossil fuels comprise nearly 80% of the total fossil fuel usage. The deployment of clean energy resources such as biofuels, nuclear, solar, etc., entails a minor portion of the overall usage. Although, after collective and collaborative efforts, the percentage usage of clean fuels has risen in the recent years, the present scenario still entails a heavy dependence on carbon-rich fossil fuels. The usage of biofuel and waste for power generation has gained pace and has been implemented in various countries across the globe. This entails the production of biofuels from waste that comprises useful fuels such as ethanol and biodiesel. Ethanol can be made from several plant-based raw materials that are generally referred to as plant biomass. Moreover, biogas is another type of biofuel that is produced from the anaerobic digestion of organic matter. Raw materials including manure, sewage, as well as agricultural waste can be deployed to produce biogas. This comprises mainly methane and carbon dioxide. Since methane has a sufficient value of combustion heat that is emitted when burnt with oxygen, it is used as a fuel for power generation. Although biogas also entails CO₂ emissions with its usage as a fuel, it is generally considered as a renewable energy resource owing to the carbon cycle. In this process, the CO₂ emissions resulting from the combustion of biofuel is recycled through its usage by plants during photosynthesis. Plants use CO₂ to synthesize glucose through the photosynthesis reaction that includes the production of glucose from water and carbon dioxide in the presence of sunlight. Moreover, nuclear power is also considered to be environmentally benign by various well-known organizations as it does not result in carbon emissions. However, there are other environmental as well as safety hazards associated with the usage of nuclear power that have raised concerns in various parts of the world. In addition, the nuclear power plant accidents and tragedies resulted in decreased attention toward nuclear-based power generation. These resources entail high carbon content and thus results in considerable amount of greenhouse gas (GHG) emissions.

Fig. 1.3 Percentage of resources utilized for primary energy supply globally. Data from Ref. [3].

The CO₂ emissions that resulted globally from energy-related fossil fuel usage in the past 20 years from 1998 to 2018 are depicted in Fig. 1.4. As depicted in the figure, there has been a significant increase in the CO₂ emissions in the past decade. In 1998, the global CO₂ emission from energy-related fossil fuel utilization was recorded to be 23.4 Gtonne. This increased significantly to 33.2 Gtonne in 2018 [4]. There exists a direct relation between the usage of fossil fuels for energy-associated activities and the increase in the CO₂ emissions, which have been identified to increase the global warming phenomenon. As can be observed from the figure, there is a trend of exponential rise in CO₂ emissions where the rate of increase in emissions with time is rising continuously. Every year the rate of change rises by a specific amount and the importance of reducing these emissions is evident from such observations. The exponential rise in CO₂ emissions can be linked to the increased usage of fossil fuels as presented earlier. The rise in CO₂ emissions is particularly alarming owing to the greenhouse effect that it entails. Solar radiation entering the Earth’s atmosphere is reflected by various objects and is trapped within the atmosphere due to the presence of GHGs such as CO₂. The trapped solar radiation leads to the trapping of thermal energy within the atmosphere of the Earth. This has been found to disturb the global temperatures where an increase in the average temperatures has been evidently proven in the recent years. This can have various detrimental effects on the ecosystem where the ice glaciers can start melting at alarming rates leading to a rise in sea levels. When sea levels rise, various dangers are posed toward countries situated near the oceans and other major water bodies. In addition to this, the weather cycles and associated cold as well as hot climate temperatures can also be affected by global warming phenomenon. The global warming phenomenon has raised major concerns about the sustainability and stability of the ecosystem as well as the future generations to come. Hence, there have been global concerns, efforts, and initiatives directed toward obtaining a solution to this increased fossil fuel dependence and the associated environmentally harmful emissions. Apart from carbon-based emissions, combustion of fossil fuels also results in the emission of nitrogen oxides (NO_x) and sulfur oxides (SO_x). These emissions have been proven to be detrimental to both human health and the environment.

Fig. 1.4 Global carbon dioxide emissions arising from fossil fuel usage for energy-related activities which is also correlated in an exponential form. Data from Ref. [4].

Owing to these major concerns associated with fossil fuel usage, more environmentally benign energy production technologies, systems, and devices are being looked into with the objective of reducing the current environmental burden. Primary efforts in the recent past were directed toward solar, wind, and other environmentally benign power generation methods. However, the intermittency of these energy resources has hindered their widespread usage. Both solar- and wind-based power plants entail the disadvantage of not having a reliable and continuously stable input source of energy. Solar power plants require sufficient solar radiation input to operate and this depends heavily on the weather conditions in the specific area where the power plant is situated. Specifically, for solar thermal power plants (solar heliostat, parabolic trough, etc.), the availability of sufficient incoming solar radiation is necessary to heat the working fluid to the temperatures required for operating the plant. In addition to this, after sunset the solar-based power plants can only rely on the excess energy stored during the day. The conventional energy storage methods including thermal energy storage and batteries are capable of provid...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Nomenclature
• Chapter 1: Introduction
• Chapter 2: Fundamentals
• Chapter 3: Types of fuels
• Chapter 4: Ammonia fuel cells
• Chapter 5: Analysis and modeling
• Chapter 6: Integrated ammonia fuel cell systems
• Chapter 7: Case studies
• Chapter 8: Conclusions and future directions
• References
• Index