[Feature: Future Mobility Society] Osamu Shimizu: Japanese Technology Supporting the Future of EVs

Since my days as a Keio students, I have believed that the widespread adoption of electric vehicles (EVs) will solve global climate change, and I have continued my research on improving EV drive efficiency. As I continued my research, I realized that the challenges to EV adoption cannot be solved simply by improving the EVs themselves. Currently, I have expanded my research scope from EVs to the social systems that include them. Here, I would like to introduce the challenges facing EVs and the social systems designed to solve them.

To solve the problem of climate change, reductions in carbon dioxide emissions are required worldwide. Aiming for Net Zero Carbon—where net carbon dioxide emissions reach zero by 2050—countries are promoting the adoption of EVs. However, the ratio of new EV sales in Japan remains at only 1.2%.

One reason for the lack of progress in Japan is that when comparing carbon dioxide emissions from driving, there is almost no difference between hybrid vehicles and EVs in the Japanese context. In other words, at this point, the spread of EVs in Japan does not contribute to Net Zero Carbon, which is the global goal of EV adoption. Therefore, there is currently little social reason to actively promote their adoption. This occurs because thermal power generation is heavily used to generate the electricity that serves as the energy source for EVs, resulting in high carbon dioxide emissions. Additionally, EVs, which carry large batteries, use more energy to drive. Furthermore, since manufacturing batteries requires a significant amount of energy, when considering the lifetime carbon dioxide emissions of a vehicle as a product, EVs in Japan end up emitting more carbon dioxide than hybrid vehicles.

EVs also face usability issues, such as shorter driving ranges per charge compared to hybrid vehicles and the high cost of the EVs themselves. To make the driving range of an EV per charge comparable to that of a hybrid vehicle, the amount of battery currently used in EVs would need to be more than doubled. Since the factor making EVs more expensive than hybrid vehicles is the price difference between the engine and the battery, installing more batteries would lead to even higher prices for EVs. This creates a trade-off where improving usability results in a loss elsewhere. Therefore, it is not simply a matter of blindly increasing the amount of battery.

EVs also face challenges in battery charging. Rapid charging for EVs has been commercialized up to 350 kW, significantly improving output and shortening charging times compared to the past. However, refueling a hybrid vehicle is equivalent to 5,000 kW (5 MW) of electrical output, so a large gap still remains. Actually building 5 MW charging facilities would require large-scale infrastructure, making implementation difficult.

As described, there are many challenges to using EVs in the same way as conventional automobiles, and these challenges stem from the use of large quantities of batteries. I am conducting research not to simply accept current EVs and endure using them for the sake of Net Zero Carbon, but to create a mobility society that is more convenient and kinder to both the environment and people by switching to EVs.

Therefore, I believe that for the coming era of mass adoption, EVs need to use small batteries effectively, be used in ways that increase the introduction of renewable energy such as solar power, and achieve things that conventional automobiles could not do.

The future EV system I am researching as a way to achieve this is the "Dynamic Wireless Power Transfer" (DWPT) system. As the name suggests, DWPT is a technology that supplies electricity to EVs while they are driving. DWPT uses a method called magnetic resonance coupling, which is an advancement of electromagnetic induction. It is a system where power transmission coils are buried in the road, and power is transmitted wirelessly to EVs driving over them or stopped above them.

You might imagine a system like a train, but unlike trains, there is no need to bury power transmission coils in every road. By concentrating power transmission coils 30 meters before intersections in urban areas, we can realize EVs that do not need to be charged while parked. In areas without transmission coils, the EV must run on its onboard battery, but even so, the amount of battery used in the EV can be reduced to about one-eighth of current EVs. Currently, batteries costing over 2 million yen are used in EVs. Reducing this to one-eighth means the EV becomes 1.75 million yen cheaper. Therefore, usability issues such as short driving ranges per charge and high vehicle costs can be solved without trade-offs.

There may be concerns that investment in charging infrastructure will increase, but DWPT can actually reduce the amount of charging equipment. Current EVs are equipped with onboard chargers. There are 82 million cars in Japan, and if each one were to carry an onboard charger like current EVs, 82 million chargers would be needed, and rapid chargers would also need to be deployed throughout cities. On the other hand, because DWPT allows chargers to be shared, the number of chargers can be reduced to less than 20 million. Furthermore, because the location and timing of power supply are dispersed in DWPT, there is no need to use massive facilities like 5 MW chargers.

DWPT is also expected to promote the introduction of renewable energy. In recent years, with the increased adoption of solar power, daytime power generation has increasingly exceeded electricity usage in various countries. Therefore, there is a need to shift electricity demand to the daytime as much as possible. Current EVs are charged in the evening or at night after use, but DWPT provides power during the day when there is a lot of movement. By introducing DWPT, electricity demand can be shifted to the daytime, helping to promote the introduction of renewable energy.

Furthermore, DWPT will enable users to access services that conventional automobiles cannot provide. It is impossible to refuel a hybrid vehicle while it is moving, but since electricity can be sent wirelessly, the task of refueling or charging can be eliminated for the user. This enables services that could not be realized with hybrid vehicles.

In this way, by introducing DWPT, batteries can be reduced and many of the challenges facing EVs can be solved. In addition, the time and effort spent on refueling and charging, which were always necessary for conventional automobiles, will be eliminated. Therefore, I believe that EVs implemented with DWPT represent the form that EVs should take in the near future.

The main components of DWPT are coils and inverters. The frequency being standardized for DWPT is 85 kHz, which is a relatively high frequency. Coils require wire materials with low AC resistance and core materials, such as ferrite, with high magnetic permeability and low loss at high frequencies. These technologies are already used in switching power supplies and are areas of expertise for Japan. In particular, ferrite is a material invented at the Tokyo Institute of Technology (now Institute of Science Tokyo) and has a long history. Additionally, SiC (silicon carbide), a power semiconductor capable of handling high frequencies and high power, is also an area of expertise. Further advancing these technologies is required.

Japan possesses not only manufacturing capabilities but also the technologies necessary for the implementation of DWPT. First, technology for laying power transmission coils is required. Japan's civil engineering technology is among the best in the world, and high-precision, stable installation is expected. Furthermore, by adapting train operation technologies to DWPT, stable system operation can also be expected.

In this way, Japan has the foundation to be the first in the world to realize DWPT. In fact, our research group began Japan's first demonstration experiment on public roads in 2023. I believe it is important not to stop at demonstration experiments but to implement it within Japan ahead of the rest of the world. By providing the entire infrastructure system as a single package of technology, not just the automobiles, we aim to lead to the early resolution of challenges facing automobiles worldwide and will continue our research activities toward this goal.