Recently, SoftBank announced its plans to integrate wireless charging into its next generation of 5G cellular towers. What features will the new technology provide, what challenges does wireless power transmission face, and it will ever become mainstream?

What features will SoftBank be introducing into their wireless charging concept?

Recently, Japanese tech giant SoftBank announced that it will be integrating wireless charging technologies into its 5G base stations. The idea behind the wireless charging system is to provide wireless devices such as headphones and remote sensors the ability to charge and/or be powered while in use. Technologies such as beam forming can allow for efficient energy transmission between the charging point and the device in use.

There is some concern from the Japanese regulators that such wireless charging systems may cause interference. To ensure safety, SoftBank will keep the transmitted energy to 1mW at a distance of 10 meters, but if trials show success, the range will be increased to 100 meters. Thus SoftBank will be using a frequency of 28GHz to minimise interference.

Furthermore, the Japanese government will start by enabling indoor wireless charging before allowing outdoor charging (which is expected to be done in 2024). Considering that many devices are becoming wireless, and the energy consumed by devices is shrinking, many believe that wireless charging is the future of power distribution.

What challenges does wireless power face?

Anyone who has studied electronics and physics to a basic level will understand that wireless energy transmission is no small feat. The biggest hurdle facing engineers trying to develop wireless energy transmission is making the mode of transmission efficient.

Most wireless energy transfer systems to date use either radio waves or electromagnetics. Both of these suffer from the inverse square law, which means that doubling the distance between a transmitter and receiver decreases the received power by 4 times. Thus, wireless power transmission is only ever suitable for close distances (tens of cm) and is currently only found in smartphone stands whereby the distance between a smartphone and charging base is no greater than 1cm.

The other major challenge wireless energy transmission faces is the number of conversion steps needed to transmit energy. The first stage is converting the electricity into something that can be transferred, such as radio. The second stage would be sending the radio waves towards the receiver, and at this point, the radio is converted back into electricity. The third stage is converting that electricity into something useable by the end device (such as a higher voltage). Each stage has an associated conversion efficiency, and the many stages introduced make wireless charging far less efficient than wired charging.

Will wireless charging become mainstream?

Despite the positive intentions of SoftBank, it is unlikely that power will be distributed via cellular stations. The first is that the world is looking towards greater energy efficiency in an attempt to reduce CO2 emissions, and transmitting energy wireless (which has efficiencies less than 10%), would be seen as highly wasteful.

The second challenge is that wirelessly transmitting power could have a potentially harmful effect on the human body. The myth that cellular signals cause cancer has mostly been disproved, with many studies showing no changes in cancer development of those living near cellular towers and power lines. Still, the effects of high-powered radio waves are not well known. While cellular energy is not ionising, it can cause tissue to heat up (just like a microwave does with water in food).

Overall, it is hard to say if wireless energy transmission will ever become mainstream, but considering the increasing need for efficient systems, wireless charging may only be a gimmick for convenient device charging (i.e. integrated charging plate in a table or desk).