Unlike Tesla’s plans, electricity isn’t delivered by air per se.
Unlike Tesla’s plans, however, electricity isn’t delivered by air per se. Here the term “wireless” refers to the fact that you don’t have to plug the device into a wall outlet or other power source. Instead, the charging surface and the device being charged must be in contact.
As it stands now, there are two major wireless power standards. One, called Qi, is the product of a group of companies known as the Wireless Power Consortium. The other is the AirFuel Alliance, which makes an array of devices that generally carry the brand name PowerMat. While the two groups are competitors, the underlying technology is essentially the same.
Both rely on something called “resonant inductive coupling.” While it sounds complicated, the actual process of transferring power is not as complex as you think. It involves two coils — one a transmitter and the other a receiver — to create an electrical connection. Let’s look at the process in a little more detail.
Resonant inductive coupling (which is also referred to as inductive or resonant power transfer) works like this. Direct current (DC) is supplied to the charging system by a power source. In the transmitting coil, this is energy is converted into alternating current (AC) within the transmitter itself.
This AC energizes the transmitter coil, causing the coil to generate a magnetic field. Placing a receiving coil nearby triggers or induces AC within that receiving coil, and the process happens in reverse to charge the power source of the receiving device.
If you have an induction cooktop in your kitchen, the process here works much like that. In your kitchen, that magnetic field is heating a piece of metal in the special type of cookware necessary to cook on these ranges. Wireless power works in almost exactly the same way — but instead of using that energy to heat a piece of metal, it’s used to fill up a battery.
There are a few tangible benefits to wireless charging technologies. The most obvious is the lack of wires. No doubt you have spent quite a bit of time at some point fishing around in a mountain of cables to find where you put your charger. Another nice feature is that the technologies can be built into a wide array of everyday objects — say, a kitchen countertop or a desk.
The lack of a power plug also allows manufacturers to eradicate a potential entry point for water, dust, and other corrosive materials that might make their way into your device. It also includes built-in functionality to shut down the process when charging is complete.
Regardless of the technology, wireless charging is still a rather inefficient process. As much as half of the energy is lost, either in the process of creating the magnetic field or the process of sending the energy from the transmitting to receiving coil. This is part of the reason why wireless charging is not as quick as wired.
As we mentioned earlier, the charging surface and the device itself must be in contact. This means that once you remove the device from that charging surface, it halts the process. These technologies are also quite expensive to produce at the moment, so if your device doesn’t have it built in, you’ll likely have to pay a pretty penny to add it retroactively.
Since both technologies generally work in the same fashion, it’s difficult to give one method the advantage over the other. However, Qi has thus far attracted the most attention. The group counts more than 200 companies as members, and is the technology of choice for most smartphone manufacturers who’ve opted for wireless charging. Qi is also working on wireless charging for not only mobile devices, which require 5 watts, but a 120-watt standard for monitors and laptops, and a high-end spec that can deliver up to 1 kilowatt of power.
Don’t count out the AirFuel Alliance, however. While it does focus on inductive charging, it signed a deal in 2014 to merge with another wireless consortium called Alliance for Wireless Power (A4WP). A4WP’s technologies work through magnets, and the two groups are currently pooling their resources and patents. This could result in some interesting technologies down the road.
Built-in support for wireless charging isn’t widely available, but by and large those who do support the Qi standard. In September, Apple announced the latest iPhone iterations would support Qi charging. That said, modern popular phones that support it include:
- iPhone 8, iPhone 8 Plus
- iPhone X
- Samsung Note 8
- Samsung S8, S8 Active
- Samsung S7, S7 Active, S7 Edge*
- Samsung S6, S6 Active, S6 Edge, Galaxy S6 Edge Plus
- Samsung Galaxy Note 5
- BlackBerry Priv
- Moto Z (with mod)
- *also supports AirFuel
Most other devices — including older iPhone models — will support the technology with the addition of a special case or an attachment of some kind. Keep in mind, however, that adding wireless charging technologies after the fact is quite expensive: We would recommend buying a device with the technology built in, instead.