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Wireless charging: No strings attached?

Just what is so compelling about an extended screen with the front camera protruding in the middle?

On 12 September 2017, Apple announced the new iPhone 8 and iPhone X. For a small fortune, you are essentially buying a repackaged iPhone 7 with an array of trivial features such as Animoji, the “revolutionary” software that creates custom 3D emojis based on your own facial expressions. Oh, and the iPhone X also has the exclusive feature of a slightly stretched-out screen. Great. But wait, there’s more… Both phones support wireless charging under the Qi standard: just place the phone on a special charging mat and voilà – the battery starts charging up without the use of any wires.

This may seem just as pointless as the Animoji to some – a novelty feature of minor convenience, if any at all – but the very fact that Apple has chosen to adopt this technology is an indicator of the importance that wireless charging holds. There is still much room for improvement, which means that wireless charging has much more potential yet to be unearthed.

Wireless charging has actually been around for quite some time, but until recently it was only used to power electric toothbrushes and a handful of Windows phones, neither of which can be considered mainstream. The very basis of wireless charging was first posited by Nikola Tesla over a century ago when he created the Tesla coil and a basic wireless lighting system. He also had plans to build a wireless electricity transmitter that could, in theory, transmit electrical energy across the Atlantic from Colorado to Paris. Unfortunately, though, that one did not work.

Electromagnetic induction is also the basis of transformers, which are used to convert between higher and lower voltages

What Tesla did provide us with was the basis of resonant inductive coupling, which is the main technology employed today in wireless charging for mobile devices. Essentially, there is a transmitter coil in the charging mat that generates a magnetic field when electricity flows through it. This then induces an electric current in a receiver coil, which is embedded in the device you want to charge. In this way, electricity is transferred from the charging mat to your device via the process described above: electromagnetic induction.

Of course, however, the charging mat has to be connected to the mains, which does negate the purpose of wireless charging to some extent. However, if the efficiency and range of resonant inductive coupling can be increased, then larger charging surfaces for multiple devices or even “power hotspots” that provide wireless electricity within a certain range could become reality. Perhaps you will never have to worry about your phone running low on charge again.

Various other types of wireless power transmission also exist, and have varying degrees of success. Capacitive coupling and magnetodynamic coupling are both short-range technologies; whilst unsuitable for charging mobile devices, they could potentially be used to charge electric cars. On the other hand, microwaves and lasers have a much longer range, and it has been proposed that they could be used to beam power to satellites and even spacecraft! Think about it: one of the biggest problems currently with space exploration is that probes have a limited energy capacity, and thus a limited distance they can actually travel under our control. Without an external power supply they will eventually run out of juice, which is exactly where wireless power transmission comes into play. If we could continuously direct microwaves or lasers towards them, then space exploration would reach incredible new heights.

Wireless power transmission is likely to be fundamental in our journey to the stars. Thank you, Nikola Tesla.

At this moment, you may be wondering why wireless charging is currently restricted to powering toothbrushes and iPhone Animojis rather than space probes in the outer reaches of the Solar System. The key problem is that the relevant technologies simply are not developed enough yet. It is like seeing a huge treasure chest before you, yet being unable to unlock it. Close-range power transmissions using technologies such as resonant inductive coupling are still feasible at an acceptable efficiency, but we still have a long way to go before the long-range transmissions that Nikola Tesla dreamed of are achievable.

For now, all wireless charging can do is bring some minor convenience into our everyday lives, but it is important that we persist in its development. The road ahead may be difficult and unreasonably long (it has been over 100 years already!), but one day we may find that it leads us into the greater universe and beyond.