Energy Technology for Carbon Neutrality

Responding to climate change is a globally shared agenda. Japan is committed to achieving carbon neutrality (net-zero greenhouse gas emission) by 2050. To accomplish this goal, agreements in society on securing an energy supply chain and cost reduction, as well as the development of next-generation energy technologies, are required. Professors and students at the Graduate School of Frontier Sciences (GSFS) held a round-table discussion, and we explored the forefront of next-generation technology research conducted by the GSFS professors, such as fusion energy, offshore wind farms, and wood biomass.

Interviewed, edited, and written by Kazutada Furui

Participants (from left)
Kazuo Hiekata: Professor and the cover story in Sosei magazine supervisor, Department of Human & Engineered Environmental Studies
Kazuho Nonomura: Second-year Master’s student, Intelligent System Design Field, Department of Human & Engineered Environmental Studies
Yasuko Kameyama: Professor, cover story supervisor, and director of the Sustainable Society Design Center
Kentaro Tanaka: First-year Master’s student, Real World Robot Informatics, Department of Human & Engineered Environmental Studies　　

Holding Balance among Stakeholder Demands

Prof. Hiekata: There are various studies and projects concerning energy technology for carbon neutrality. Professor Kameyama is an expert in climate change measures taken at international level. Could you give us an overview of the situation on carbon neutrality?

Prof. Kameyama: You may have heard that emissions of greenhouse gases, such as carbon dioxide and methane, have started growing since the Industrial Revolution, which started in the United Kingdom in the late 18th century, and that the atmospheric concentration of these gases has been rising since, attributable to global warming. As of 2020, the global temperature has risen by an average of 1.1℃ compared with the preindustrialization period of 1850–1900. You may think, what is so fussy about 1.1℃? However, while some areas have experienced higher temperature increases, others have experienced increased downpours and droughts. The abnormal weather we are observing now is far more severe than we anticipated some time ago. The temperature has already risen by over 1.0℃. We should not allow the mean temperature to increase by more than 2.0℃. If possible, it is better to keep it at less than 1.5℃. To realize a temperature increase of less than 1.5℃ by 2050, the global community agreed to achieve net-zero greenhouse gas emissions by 2050*1.

Nonomura: Attitudes toward achieving carbon neutrality seem to differ among countries.

Prof. Kameyama One way to compare countries’ efforts is to compare the years when their greenhouse gas emissions peaked in their history. For example, the United Kingdom, which experienced the Industrial Revolution before any other countries, experienced an emission peak in the 1970s. Meanwhile, Japan experienced a peak in 2013 after the nuclear power plants stopped operating in 2011 because of the Great East Japan Earthquake and fossil fuel power plants increased electricity generation.

Tanaka: I see. So, what is the difference among sectors? I heard that the electric power generation industry emits more CO2 than other sectors.

Prof. Kameyama That is right. The electricity generation sector emits CO2 the most in several countries. It accounts for 40% of Japan’s total CO2 emissions. There is a prominent difference between countries that have already started energy transformation to non-carbon energy and those that are just trying to improve the combustion efficiency of fossil fuels.

Prof. Hiekata: We are currently researching energy transformation in the shipping industry and system design in our laboratory. Precisely, we attempt to find a means to intervene through system design and change the current systems in the industry*2. First, we analyze the stakeholders’ demands. Then, we examine how systems are linked to one another, including the influence of technologies, by performing simulations based on actual data. Ideally, there should be one technology that is far superior to others to spread. However, there is no such technology. Some technologies are relatively at the same level. Technology is often chosen based on stakeholders’ interests or the political situation at hand. Efficiency also varies according to the requirements. Discussions tend to get stacked, or technology remains unused because nobody knows which is the best technology.

Nonomura: Here in the GSFS, I am researching ways to promote energy transformation in the shipping industry through social designs. Changing fuel from heavy oil to methanol or ammonia is not so difficult. Energy transformation is expected to start around 2030, and hopefully, zero emissions will be achieved in the future. However, even if a new technology is developed, achieving net-zero emissions is a pie in the sky unless we use it. I am interested in how social designs can help society to use new technologies.

Prof. Kameyama In the maritime industry, is there a division in which some countries and companies try to use new fuels even if they cost more, while others cannot accept the cost escalation at all?

Nonomura: Yes, there is. Countries in Western Europe, including EU countries, are taking measures to reduce CO2 emissions in shipping. EU countries have already conducted demonstrations to make regulations, not waiting for an international agreement. Meanwhile, arguments over national interests versus regulation-making become complicated in island and developing countries because they are afraid that companies in their countries may lose shares to companies in the advanced countries that use new technologies. There was a discussion of imposing a tax on CO2 emissions or emissions trading once. However, a new policy called the “feebate system” has been receiving considerable attention recently. It imposes fees on conventional fuel and rebates for new fuels. I study how much tax and rebate change the ratios of fuel type by the feebate system.

Tanaka: As an undergraduate student, I performed simulations to analyze the effect of radiative cooling films for controlling global warming. At the GSFS, I research malfunction detection using mobile robots; however, I am also interested in climate change. According to the discussion here, various approaches, such as reconciliation among stakeholders and technology development, are required, right?

Prof. Kameyama Historical conflicts between developed and developing countries are significant issues when discussing achieving carbon neutrality. Meanwhile, renewable energy is relatively easy to accept by developing countries, which is an advantage for developed countries to support them because renewable energy requires an initial investment, but fuel costs almost nothing once installed. Furthermore, this is helpful to developing countries because they do not need mega power grid systems but just microgrids.

Hopes for New Technologies: CCS and Nuclear Fusion

Prof. Hiekata: While reducing greenhouse gas emissions, absorbing them more than now is also crucial to achieving carbon neutrality. The key technology is called “carbon capture and storage (CCS).” Have you heard of it, Mr. Nonomura and Mr. Tanaka?

Tanaka: Yes, I have, but I have not cared about it before.

Nonomura: I know about CCS in shipping, but I am not sure about situations in other sectors.

Prof. Kameyama CCS is a technology that chemically absorbs carbon dioxide and buries it in the ground when it is emitted by burning fossil fuels. Professor Toru Sato in the Department of Ocean Technology, Policy, and Environment, the GSFS, develops technology to store CO2 by hydration.

Prof. Hiekata: For international shipping, it is meaningless to use hydrogen obtained from fossil fuels without using CCS technology. Essential energy technologies to create a carbon-neutral society include renewable energy, storage batteries, CCS, “controversial” atomic power generation, and nuclear fusion.

Nonomura: I understand that nuclear fusion power generation is a technology that simulates physical reactions occurring in the sun on Earth.*3

Prof. Kameyama Nuclear fusion research and development no longer seem to be in the “sometime-in-the-future” phase. Yet, I understand that it is still unclear when they can be realized. It is a technology full of hopes and concerns. I should keep up with the latest situation.

Tanaka: I want to know if nuclear fusion can fulfill the safety conditions for actual use in a country where earthquakes often occur, such as Japan.

Prof. Hiekata: Nuclear fusion is different from nuclear fission in atomic power generation. Nuclear fusion reactors stop when safety conditions are not satisfied and abnormality occurs. Moreover, fusion reactions produce only hydrogen or helium but no high-level radioactive wastes. I am not an expert in this field, but I consider it easier to handle than atomic power.

Nonomura: What will happen to power transmission networks if nuclear fusion energy is launched? How will it affect power generation by renewable energy?

Prof. Hiekata: These are good questions. The power grid aiming for carbon neutrality must be different when gathering renewable energy interspersed throughout a country and when using large-scale power generators by nuclear fusion. This difference will influence infrastructure investment decisions on how much power transmission capacity should be allocated and to which region power is to be allocated.

Prof. Kameyama Infrastructure needs 30 to 50 years to change. We can choose what to do now only when we have visions of 30 or 50 years from now. I am concerned that Japan has no clear long-term vision. It seems like Japan can change only with a short-term vision.

Prof. Hiekata: Gathering unbiased information is desirable for drawing future visions and road maps. To accomplish this, we should increase the knowledge necessary to decide on better combinations of technologies and better ways to use them.

Prof. Kameyama Along with technology development, we, cosumers, also need to understand the importance of carbon neutrality and to choose products and services by proactive carbon-neutral companies. Technology and businesses cannot change the situation alone. Consumers’ mindset toward the goal is necessary. We always need to keep this in our minds.

Nonomura: Some companies make carbon-neutral products and negotiate with shipping companies to transport their products carbon-neutrally, and shipping companies accept their requests.

Prof. Kameyama I wish we could continue this discussion longer, but we must wrap it up now. Hope we can have this kind of opportunity again.

Prof. Hiekata: Definitely. Thank you, everyone.

Research in GSFS

1 Nuclear Fusion

Designing Antennas for Electric Drive by High-Frequency

Interview with Akira Ejiri, Professor, Department of Complexity Science and Engineering

When light atoms, such as hydrogen, are heated to higher than 100 million degrees Celsius to become plasmas, positive ions combine and generate enormous nuclear energy. This phenomenon is called nuclear fusion. The product of the three elements—temperature, density, and confinement duration—must be large to allow nuclear fusion reactions to continuously occur.

Tokamak-type devices, which confine plasmas in a donut-shaped form by a strong magnetic field, are considered the most efficient devices. Plasmas produced using a tokamak-type device have good confinement functions and stability but require a strong magnetic field. The problem is that a sizable superconducting coil is required to create a field; accordingly, the cost of power generation increases.

To address this problem, a spherical tokamak-type device was devised for confining plasmas in a relatively weak magnetic field. Researchers conduct experiments with this device across the globe. A spherical tokamak-type device requires careful control of current flow to achieve high efficiency. Ejiri is developing a method for heating and driving current using high-frequency waves and researching the physics of waves to support this method.

“We realized the potential of spherical tokamak-type devices very early and designed experimental devices, Tokyo Spherical Tokamak (TST) and TST-2, in the early 1990s. We built them mostly on our own with students and have conducted experiments with these devices since,” says Ejiri.

Currently, Ejiri is devising various types of antennas to inject high-power high-frequency waves into TST-2, trying various structures, and conducting experiments with the prototypes.

Three types of antennas installed in TST-2

“In recent years, experimental work in the nuclear fusion field has been completely divided, and scientists tend to stay in their bubbles of expertise. However, scientists with a full picture of the project are essential, particularly in big science. We educate young researchers to become such scientists through experiences of operating and managing a relatively compact experimental device in our laboratory,” says Ejiri.

Ejiri participates in joint research projects with research centers within Japan and overseas, striving to expand the field of nuclear fusion research.

Magnetic Reconnection for a Cost-Effective Fusion Reactor

Interview with Michiaki Inomoto, Professor, Department of Advanced Energy

“Nuclear fusion needs at least 100 million degrees Celsius. Even the deuterium–tritium reaction, which is the easiest reaction to achieve, does. The temperature of the initial plasma generated in a confining device using an electric field is approximately 100,000℃. Then, plasmas are heated up to around 10 million degrees Celsius by their electric resistance and electric current flowing in them. However, another technique is required to heat them above 10 million degrees Celsius,” explains Professor Inomoto.

Currently, the major heating techniques use high-frequency waves or a neutral beam. However, the Ono-Inomoto-Tanabe Laboratory focuses on the third method: plasma-merging/magnetic reconnection.

“Magnetic reconnection is a phenomenon commonly occurring in the natural world, such as solar flares. We estimate that this phenomenon can help heat plasmas and yield energy to ions efficiently once the reconnection conditions are satisfied in the confined plasmas. And that can lead to the practical application of fusion electric generation sooner,” says Inomoto.

Inomoto and his team have already succeeded in generating high-temperature plasmas by promptly heating a spherical tokamak-type device using a plasma-merging/magnetic reconnection method without a costly external heating device. They are currently conducting joint research projects with nuclear fusion startups overseas and their outcome is highly expected.

A soft X-ray ring was observed in the University of Tokyo Spherical Tokamak (UTST) device during an experiment using the plasma merging technique.

The top part of the UTST, a spherical tokamak-type device for plasma merging

2 Woody Biomass

Controlling the Time for Lignification of Plant Cells

Interview with Misato Ohtani, Associate Professor, Department of Integrated Biosciences

Woody biomass is derived from wood, including living trees in the woods, remainders from lumber mills, and scrap wood from wooden house demolition. When woody biomass is burned, it emits CO2. However, plants absorb and fix CO2 in the atmosphere via photosynthesis, which means that CO2 will be absorbed again when the woods change generation.

Ohtani is currently researching the biosynthesis of woody biomass at the molecular level and its biomass applications.

“I especially focus on plant cell lignification. Lignin is a polymer that interacts with cellulose or other materials to form a rigid structure. Lignin deposits on cell walls and lignifies them, strengthening the plant body. Lignin accounts for 20%–30% of the dry mass of wood materials and is essential for producing woody biomass,” says Ohtani.

Her previous research was related to identifying the master switch of genes that control lignification in plant cells. She is currently verifying whether woody biomass could be more efficiently used as an energy resource by controlling the time of lignification in various plant cells.

Moreover, various fossil fuel-originated materials may be replaced by woody biomass. Gene manipulation can change woody biomass for efficient degradation, decrease its complexity, and simplify its form for manipulation. She is currently working on synthesizing animal proteins from spider webs within a plant body.

Fossil fuels, such as oils, produce various materials essential for society, such as plastics. Ohtani sees a future where these fossil fuel-origin materials will be replaced with biomass.

Ohtani succeeded in increasing woody biomass and alternating lignin levels.

3 Energy Supply System

Resilience of Electric Power Systems
Essential for the Increased Use of Renewable Energy

Interview with Jumpei Baba, Professor, Division of Advanced Energy

The diffusion of renewable energy is essential for realizing a carbon-neutral society. However, we cannot simply increase renewable energy; we need an appropriate power system to transmit power to consumers.

“Most renewable energies produce electricity in direct current. Therefore, the power is converted to alternating current in the inverters and transmitted to electric power systems. If electricity produced from renewable energies increases, it will be difficult to stably manage power supply systems,” says Baba.

Power supply and demand must always be evenly balanced in the supply system. In the case of imbalance, the frequency fluctuates, making the power supply unstable. Conventionally, the balance was secured by connecting systems to multiple thermal and nuclear power plants that use synchronous generators because synchronous generators have an inertial force that can flatten the frequency fluctuation to some extent in the case of a collapse of the supply–demand balance. In contrast, electricity generated by renewable energy does not have an inertial force. In power supply systems with poor inertial force, even minor problems can cause outages in sequence or blackouts in an entire distribution area.

“Scientists now see potential in the grid-forming converter. This converter may be able to make an electric power system gain inertial force using power electronics devices with control ability similar to that of a synchronous generator,” explains Baba.

With real-time measurement of the remaining generation capacity in solar panels, a grid-forming converter can be installed in a solar power generation system and increase the inertial force when a curtail output order is issued. The remaining generation capacity can be estimated by detecting the voltage and current output of solar panels at the moment. Baba is working on developing a method to use the remaining generation capacity as an inertial force.

“Nevertheless, it will take a decade to implement a change in electric power systems. Although I estimate that we do not have much time to reach 2050, it is not a good idea to rush to use renewable energies without careful consideration,” says Baba.

Baba’s stance is to spread necessary things for the future and use them when needed while supervising a system as a whole.

Measurement of parameter temperature dependence

Solar panel for examining methods of measuring maximum power generatio

4 Offshore Wind Power

Importance of Establishing an Industrial Infrastructure

Interview with Ken Takagi, Professor, Department of Ocean Technology, Policy, and Environment

Offshore wind power is expected to be a game changer among other renewable energies because it does not significantly impact the environment. Japan has begun bidding to install them in the “general sea area.” However, Professor Takagi, an expert on the cost reduction of power generation by offshore wind farms, reveals his concerns for its future.

“Technology development for wind power generation is done. What we need to do next is to put it into practice. In Europe, offshore wind platforms are widely used because they can divert human resources and supply chains from the Northern Sea oilfield, but Japan has no such industrial infrastructure. There are two types of turbine foundations: one is bottom-fixed, and the other is floating. The shoaling beaches of European oceans are good for the bottom-fixed foundation type, but the Japanese oceans are totally different. We cannot be optimistic about the spread of offshore wind farms in Japan,” says Takagi.

If you look at the global situation, wind turbines are becoming increasingly large. The largest turbine in the world now has a rotor with a diameter of more than 230 m and a tower of more than 140 m.

“We need to establish an industrial infrastructure to catch up with the world, and academia must provide useful information and data to stakeholders. In addition, it is important for society to appreciate the actual cost of renewable energy, aside from developing technology to reduce costs.” highlights Takagi.

A tower loaded onto a self-elevating platform vessel

5 Energy Policy

Scenario Analysis to Prepare for Uncertain Futures

Interview with Masahiro Sugiyama, Professor, Institute for Future Initiatives, the University of Tokyo

Sugiyama is an expert in long-term climate policy, analyzing scenarios of energy systems for achieving net-zero emissions by 2050. Scenario analysis is not to foresee some certain future but suggests futures with wide variations to help the government’s policy-making and decision-making in businesses.

“Scenarios and visions are different things,” emphasizes Sugiyama. “Visions are one or two wishful goals. Surely, governments should present visions because people want them. However, the future is uncertain. If you stick only to your vision and follow it, you tend to fail. When we conduct scenario analysis, we prepare for various consequences that can happen, including good and bad options.”

In his recent investigation, he interviewed over 100 experts on whether decarbonization is desirable and feasible, using questions with five categories of percentages for possibility rather than a binary choice of “feasible versus infeasible.”

“Most people chose ‘100% reduction’ as desirable. On the other hand, they assigned a 33%–66% probability for the feasibility of the 100% emissions reduction goal. Most professionals consider it desirable, but they are not sure if it can actually be realized,” explains Sugiyama.

He also surveyed the preventing factors for decarbonization. He and his colleagues prepared 22 options and asked the interviewees to rank them. The top two answers were “difficulty of clean energy supply” and “Japan’s national strategies.” These results clearly show our challenges in achieving net-zero emissions by 2050.

Scientific technology, political events, economic development, and changes in social values can dynamically change the future. Various other factors, not only energy technology, also affect the transition to net-zero emissions; particularly, the concept of sociotechnical system (complex of society and technology) is important. Scenario analyses are essential for energy transformation in sociotechnical systems.

All: All interviewees
IAM/AIM: Experts in the Intergovernmental Panel on Climate Change or Integrated Assessment Modeling

Ju, Y., Sugiyama, M. & Shiraki (2023)
https://www.nature.com/articles/s43247-023-01079-8