Japan, which is moving to practical use of "wireless power supply", has begun a battle for the 1.5 trillion yen market with the world

Japan is moving to commercialize "wireless power supply" technology that supplies electricity without using wired cables. The Ministry of Internal Affairs and Communications plans to allocate dedicated radio waves in three bands by the end of fiscal 2021. Japan, the United States, and China are competing to develop wireless power supply technology that overturns the conventional wisdom that electricity is transmitted through cables. A battle for the global market, which is said to exceed 1.5 trillion yen in 10 years, has begun. (Kunikazu Yamada)

[No cables needed] Power Electronics "The Last Frontier"

The wireless power supply system, which charges digital devices by placing them in close contact with a dedicated stand, has been put into practical use for some smartphones, etc., but currently there are few Technological development is progressing that can transmit electricity even if it is far away. If it becomes possible to supply electricity to a remote location by carrying electricity on a radio that flies through the space, there will be no need for wired charging. You can use your smartphone or computer without worrying about running out of battery, and you can drive an electric vehicle (EV) anywhere. Wireless power supply, which has such potential, is called the “last frontier” in the field of power electronics.

According to Yano Research Institute, the global wireless power supply market (based on business sales) is expanding at a pace of more than 10% every year. It is expected to be about 1.55 trillion yen, a sixfold increase. More than 80% are for small digital devices such as smartphones, smart watches, and wireless earphones. Demand is also expected to increase in fields such as industrial machinery such as automatic guided vehicles (AGV) in factories, electric bicycles, and monitoring sensors for nursing care.

Relieving the stress of running out of batteries

There are methods to send electricity wirelessly to a place a short distance away, such as using microwaves, which are one type of electromagnetic wave, or via a magnetic field. Until now, power supply using microwaves could not be performed in Japan except for experiments. This is because the hurdles for practical application were high due to the regulations of the Radio Law.

However, the environment for the realization of the system is now in place. The Ministry of Internal Affairs and Communications plans to revise the radio law within fiscal 2021 and allocate three frequency bands for wireless power supply: 920 megahertz (one million mega), 2.4 gigahertz (one billion giga), and 5.7 gigahertz. The effects on the human body and radio wave interference with other communication devices will be verified, and if there are no problems, the range of use will be expanded to outdoors and spaces where there are people.

Revision of the Radio Law expands the scope of use... Accelerating development by companies

Development by companies is also accelerating. MinebeaMitsumi is collaborating with Kyoto University to utilize wireless power supply for tunnel maintenance and inspection. A sensor is installed in the tunnel, microwaves are applied to the sensor from a moving vehicle, and information is acquired from the sensor while supplying power. In 2008, he succeeded in conducting an experiment to check the looseness of bolts based on the information obtained. In the future, it will be possible to automatically collect information such as water leaks and cracks just by driving through a tunnel, which will lead to labor saving and efficiency in infrastructure inspections.

Panasonic will embark on a demonstration experiment of wireless power supply for IoT (Internet of Things) sensors from fiscal 2021. It can simultaneously deliver 1 watt of power to multiple sensors within a range of 5-10 meters. Another feature is that the receiving component integrated with the sensor is as small as a business card. It is expected to be used for monitoring nursing care, factories, offices, etc. By devising the design of the antenna and the internal circuitry, the receiving side was able to utilize weak radio waves efficiently.

In addition to this, we are also promoting the development of technology that prepares multiple power transmitters and synthesizes their power at a specific point to supply it. Since the output of each power transmitter is weak, it is expected that it will reduce the impact on the human body and lead to cost reduction.

The wireless power supply of the US venture company Osia, which is looking to enter the Japanese market with the semiconductor trading company Marubun as a window, is devising a way to send radio waves with a target. The power transmission side uses the beacon signal to detect the power supply route and adopts a method of focusing on the receiving side. It can be charged even if the receiving side moves.

[Methods other than radio waves]

There are various types of wireless power supply other than radio waves. The mainstream uses the magnetic field generated when current is passed through a coil, and although the transmission distance is shorter than that of microwaves, the power transmission efficiency is high. Omron is working on the development of a product that uses the "electromagnetic induction method," in which two coils face each other and the magnetic field generated by passing an electric current through one coil sends power to the other coil. Adopts a technology that selects the optimum power supply frequency at the coil stop position, enabling highly efficient power supply even if the coil is misaligned.

Electric power to the coil→Magnetic field use　On-site robot power supply, safe

TDK-Lambda adopts a "magnetic field resonance method" that transmits power by causing magnetic field resonance between coils. We have developed a power supply system for industrial equipment such as AGV. It is also possible to supply power to robots that cannot use cables due to the fear of disconnection, which is expected to save labor and improve safety at work sites.

Rohm Group's Lapis Technology is working on a chipset (integrated circuit) for wireless power supply. The mounting area of ​​the receiving board is 230 square millimeters, which is the smallest mounting area in the industry in the 1-watt power supply class. It is now possible to install the sensor in wristband blood pressure monitors, smartwatches, and hearing aids, which was difficult with the company's conventional products. We are also developing modules using chipsets.

In order to compete with overseas countries such as the United States, which is leading the way in the practical application of wireless power supply, and China, which is said to hold a quarter of the number of related patents, "Japan must move with the trinity of technology, business, and system." If we can't win," asserts Kyoto University Professor Masaki Shinohara, who is a leading researcher in wireless power supply research.

Of these three elements, the legal system is the most difficult. After the revision of the Radio Law, the use of wireless power supply is limited to indoor environments where there are no people, and it cannot be used in the city. In order to avoid radio wave interference, operators must submit a notification to the local communication office each time they install a wireless station, and it has been pointed out that depending on the region, it takes time and effort to apply.

The person in charge of the Ministry of Internal Affairs and Communications said, "It is true that it is taking time to institutionalize wireless power supply, but it is a necessary measure to introduce it in a way that does not affect the world. If it is proven in the future, concerns will be dispelled," he said, but the weak support of the system could lead to Japan falling behind.

Both technological innovation and safety

If many people recognize the merits of wireless power supply and show a willingness to accept it in society, it is possible that the range of use will expand more quickly. However, it is difficult to do so if it is limited to unmanned indoor use like this time, and "is in a dilemma" (industry insider). How do we adopt and utilize wireless power supply, which has the potential to greatly change people's lives? There is also the question of social attitudes.

Nikkan Kogyo Shimbun November 4, 2021