5G as a wireless power source?

5G could provide more than just fast connection speeds – it might soon deliver power to your devices too. But is the promise of wireless power transfer too good to be true?

Researchers at the Georgia Tech Institute for Electronics and Nanotechnology have developed an antenna system for 5G energy harvesting that could eliminate the need for batteries in IoT devices.

In their paper, “5G as a wireless power grid”, published in the January 2021 edition of Scientific Reports, researchers Aline Eid, Jimmy Hester and Manos Tentzeris outline their revolutionary new design for a playing card-sized antenna that can harvest spare electromagnetic energy from 5G signals and convert it to power – in effect, turning 5G networks into wireless power grids.

Wireless power transfer has been the goal of many scientists and researchers for decades, most notably by Nikola Tesla back at the turn of the last century, whose infamous Wardenclyffe Tower failed to transfer an electrical charge from Long Island, NY to Niagara Falls, despite the considerable funding of his benefactor, J. P. Morgan.

Hester, who is also co-founder of Atheraxon, a developer of 5G RFID tech spun out of Georgia Tech, said: “With the advent of 5G networks, this could actually work and we’ve demonstrated it. That’s extremely exciting — we could get rid of batteries.”

Recently, the RCA Airnergy has claimed to be able to charge devices using ambient wi-fi, while GuRU Wireless hopes to power robot vacuum cleaners with millimetre wave (mmWave) energy.

mmWave energy harvesting in the 28GHz band has been possible for some time, albeit impractical over long-ranges, as power-harvesting tends to require large rectifying antennas (or rectennas) that must be pointed directly at the transmission source – perfect for a housebound Roomba, but impractical for use in mobile devices.

The Georgia Tech team solved this by 3D-printing a 2”x4” Rotman lens, a beam-forming network commonly used in radar, to see targets in multiple directions without having to physically move the antenna. Like a prism in reverse, the Rotman lens diffracts six antenna beams into one, permitting much wider coverage.

According to the Friis Transmission Equation, the loss between the transmitter and receiver is greater at high frequencies, such as those that 5G signals transmit at; although more spectrum is available at this frequency, the power loss is too great at long ranges, so only point-to-point communication is possible.

Even with the Rotman lens, the device only managed to harvest around 6 microwatts (μW) of energy at a range of 180m from the 5G base station; this falls far short of the 5W (5,000,000μW) it takes on average to charge a smartphone, but is enough to power small IoT sensors.

In short, this new “development” is still somewhat inefficient, since the power drops off with distance quickly. But with some refinement, the device could power sensors such as this ultra-low power sensor proposed in 2018, which requires 26-63μW of power.

They could charge up a small battery, capacitors, or temperature sensors in hard to reach locations, for which replacing batteries would be a tricky task. And what these new devices lack in power, they make up for in versatility, in both size and applications in flexible structures, such as wearables. The paper itself concludes by saying the availability of wireless power may charge “5G-powered nodes for the IoT and… long-range passive mm-wave RFIDs.”

Though this case hardly represents the next ambitious stage of powering consumer devices, it does demonstrate the possibilities for new, emerging tech, greatly enhanced by 5G. Wireless power transfer could be just one of many sources of income for CSPs, much in the same way as data revenues augmented that of voice.

Wireless power has far to go before providing a reliable alternative to the grid, however this emerging technology has countless applications in sensor tech for smart agriculture and smart cities, providing the foundations for a growing IoT sensor network.

Just don’t go throwing your phone batteries out yet!