CHAPTER 1: INTRODUCTION
1.2 Hydrogen Energy
Since the industrial revolution from the middle of 18th century to the 19th century, science, technology, and the quality of our life have been in huge progress. In this development process, we have made a lot of energy sources consumption associated with economic growth. The world energy consumption amount has been increasing with an average rate of 2.5%/year from 3.7 billion toe in 1965, and reached to 13.5 billion toe in 2017 (toe: tonne of oil equivalent), as shown in Fig. 1-1. From now on, it will keep increasing due to future economic growth in developing countries. For example, there are the sustained economic growth and rising demand in China, the world’s largest energy consumer since 2009. Chinese energy consumption presented its highest growth since 2012, mainly driven by power generation, strong industrial demand and increasing transport fuel consumption encouraged by a growing vehicle fleet [1].
On the other hand, these days, people in the world have started facing several problems. The excessive consumption of fossil fuels by the industrial revolution is thought to be causing the form of oil prices soaring upward, and the increase of carbon dioxide ratio in air, leading to acid deposition including sulfur oxide and nitrogen oxygen.
Frequent occurrence of abnormal climates has made us feel all more realities for environmental problems, such as global warming.
Figure 1-1: Change in energy consumption in the world. Reprinted from the webpage [1].
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To solve these problems, the Kyoto protocol was adopted in December 1997 at the Conference of the Parties III (COP 3), where developed countries agreed to the goal for decreasing their emissions of greenhouse gases including carbon dioxide. The 21st United Nations Climate Change Conference (COP 21) was held in Paris in December 2015, where both developed and developing countries agreed to work together to realize “Low-carbon-dependent future society” [2]. Today, the introduction of new energy has been a certain focus of interest for people all over the world. On the other hand, the activities for new energy in Japan are still not comparable with the ones in Europe and United States, in terms of utilization of renewable energy technology.
Japanese society is dependent on carbon-based energy, such as fossil fuels.
Previously we were increasing the number of nuclear power plants to decrease the emission of greenhouse gases, such as carbon dioxide. Since the accident at the Fukushima No. 1 nuclear power plant in 2011, however, all of the nuclear power plants were stopped once and go back into the previous “Carbon-dependent society”. Moreover, it is a risk to keep a society dependent on fossil fuels since much of the fossil fuels are imported to Japan from politically unstable regions. Even though we have developed next-generation energy technologies for decades, it is still difficult to utilize the renewable energies such as solar-, geothermal-, wind-, and hydroelectric-power, because of their lower energy densities per area, limitation depending on climates.
Moreover, hydrogen is gaining increasing attention in recent years as a clean energy to utilize fossil fuels more efficiently, and as an energy carrier in the future energy system.
In Japan, a future society with hydrogen energy has been described in the “Basic Energy Plan”, and the government has regarded the year 2015 as a “First Year of Hydrogen”. In fact, in the upcoming Tokyo Olympic held in 2020, the energy supply for the stadium and the player’s dormitories will be partially provided by hydrogen energy to appeal the potential value of “Hydrogen Society” to all over the world, which has been one of the hottest projects in Japan. To achieve this goal, development of fuel cells efficiently generating energy with hydrogen is brisk and lively.
Hydrogen is a secondary energy source, and thus must be produced from other resources. These days, steam reforming of fossil fuels, such as CH4, is generally adopted, and also active development for other clean energy technologies such as electrolysis of water by renewable energy resources is now ongoing. Even though hydrogen does not exist as pure gas but in the forms of chemical compounds like H2O and CH4, it is the most abundant element on the earth and also constitutes more than half of the entire universe (it exists in the forms of H2O even on the moon, as shown in Fig. 1-2). Energy-carrying hydrogen can be used in a number of applications, including chemical industry, metal
Alternative Solid Oxide Fuel Cell Electrode Materials for Highly-Efficient Electrochemical Energy Systems
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Electricity, the most common secondary energy source, is now obviously essential in our life, and there is a complementary correlation between electricity and hydrogen.
Hydrogen can be stored in large quantity, but it is not the case for electricity since storage of electricity is restricted by battery capacity.
Electricity is transferable just with electrical conductor, but it is not the case for hydrogen since gas cylinders or pipelines are needed.
In the future, hydrogen is expected to make its application more diverse, utilizing the complementary correlation with electricity, leading to replace conventional carbon-based fuels and solve environmental problems. Some advantages of hydrogen energy are summarized as follows:
Energy-saving effect by highly-efficient energy utilization.
Checking global warming and air pollution by low emission of environmental load substance.
Energy diversification by the potential of hydrogen to produce from various materials.
There still remain societal, technical, and economic hardships to realize such hydrogen-electricity energy system. However, hydrogen and fuel cells can be keystones in the future energy system, to enable us to live in a sustainable and hopeful society.
Figure 1-2: Water content map on the Moon. Reprinted from the reference [3].
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