Wireless Power Transfer: A prominent technology

We all want our phones, smartwatches, laptops, and even electric vehicles to charge quickly and easily through cables. However, sometimes the connector at the end of a cable may not be compatible with different models from the same brand, or we might be unable to use chargers from other manufacturers. Electric vehicles are set to become a vital part of our future mobility and are expected to be the norm in the coming years. These facts and situations made me wonder, how we can address this challenge? what solutions are currently available, and why aren’t they more widely known? Honestly, it feels like this shouldn’t be complicated at all!

For small devices, such as smartphones and smartwatches, you may be aware that they can be charged using contactless technology, eliminating the need to connect a cable. This enables the option to explore more compact wearable devices, which have gained significant attention for the valuable information that can be obtained from sensors embedded in clothing, allowing for the monitoring of various health conditions. Medical devices implanted inside the human body (pacemakers, cochlear implants, cardioverter defibrillators etc.) can also be recharged in vivo, wirelessly without the need for invasive surgery.

The above mentioned cases are in the range of low power, but what happens when we think about more power, for example electric vehicles (EV)? Today, we can charge an EV using technology that is also free of cables. This sector is one of the most ambitious ones out there. It could help solve one of the EV industry’s biggest problems: ‘range anxiety’ – the stress generated by uncertainty over whether the car will run out of energy before reaching a charging station.

🔋 How Does It Work?

This technology, known as Wireless Power Transfer (WPT), is based on the transmission of energy from a power source to a device without the use of physical wires, in other words, through the air (or skin in the case of medical devices). However, this is not just about transferring radio frequencies or microwave signals; this technology operates in a different frequency range (60-100kHz) and, of course, at wider power levels, ranging from a couple of Watts to Megawatts. This niche of frequency and power is where we can find solutions for electromobility, and where most of the post is focusing, and it is referred to as Inductive Power Transfer (IPT).

So, how can power be transferred through the air? 

The principle relies on the physical laws of electromagnetism; a magnetic field generated by a coil can induce a voltage in a nearby secondary conductor, where its magnitude is proportional to the rate of change of that magnetic field. In other words, a rapid variation (high frequency) in the magnetic field can induce a significant voltage. If the secondary is farther away, the magnetic field is less intense, and we need a faster variation to generate the induced voltage.

To explain how this actually works, imagine two coils: one called the Transmitter and the other called the Receiver. The Transmitter is a coil connected to a power source with special devices called semiconductors, allowing the creation of a changing magnetic field, kind of like an invisible bubble that grows and shrinks according to the electric current behaviour. The Receiver is a device, much like a phone or an electric car, it also contains a coil inside it. When you place said Receiver near the Transmitter, the magnetic bubble from the Transmitter causes the Receiver’s coil to generate a current, which can then charge the device.

However, one of the general issues that you will encounter with this technology is whether this power transmission is efficient or not. Having a lot of losses in the transmission could transform this technology into a hindrance to electromobility. In the interest of improvement, we can utilise another physical phenomenon called resonance, which is a desired operation in this case and non-destructive (as sometimes occurs in mechanical or electrical systems). Think of resonance as being like an opera singer who can shatter a specific crystal glass with just her voice; the singer is the transmitter, and the glass is the receiver. If the singer sings at the precise resonant frequency of the glass, it vibrates violently. Therefore, if the transmitter and receiver coils are tuned to resonate at the same frequency, the energy is transmitted with a significant reduction in losses.

For the analogies above, you could probably raise hundreds of interesting questions… how can we know the intensity of the magnetic field that we need? how can we control it? and does the coil shape have an impact on the power that can be transferred?… All these questions have answers, often several at that, and here lies the space for improvement. Of course, we can try to enhance everything, but as many may know, in a PhD, for the sake of convenience (and our mental health), it’s best to hone in on just a few of them, and in this case, I focused on controlling the magnetic field and the design of the coils.

📊 Economic Perspective

Severe economic forecasts support the enthusiasm for WPT. According to Fortune Business Insights, the global wireless power transmission (covering a wide area of applications) market was valued at $13.32 billion in 2023 and is expected to surge to $37.67 billion by 2032. The global market is forecasted to achieve a CAGR of 12.24% during the period.

Basically, this increment is explained by the growing demand for smartphones, small portable devices with awesome features capable of being online with your other devices. In this regard, by providing innovative, more dependable (such as a coffee cup in the morning or a glass of cold beer in the summer), and convenient products, businesses that utilise wireless power can gain a competitive advantage.  The EV industry sees wireless charging as an alternative to the plug-in chargers, especially if we are thinking about dynamic charging, which is basically transferring power while the vehicle is moving, for example, on a motorway, which is expected to be the jewel of this technology.

📝Final Words

To close this post, my gut says that this technology promises incredible advances in the field of EV charging, but there is ongoing research and projects. It needs more enthusiastic people, not only researching but also individuals willing to engage in engineering projects and test its capabilities, before becoming part of our lives as the Wi-Fi connection is now. While this technology has proven to be safe for humans, more focus should be placed on the high-power applications of IPT, i) such as the use of megawatt range of power for heavy-duty vehicles, and ii) the higher distance transmission, which promises to expand the horizons in terms of power delivery and its applications.

Thanks for reading,

Pablo Briceno