It gets worse. Every generation of wireless communications needs more electricity. If successful, 6G Communications will need sharply increased electrical power just like the overlapping topics of data centers, artificial intelligence and electric vehicles. Making all that electricity brings a leap in cooling challenges.

6G challenges

A closer look at 6G reveals added problems. It must offer stellar data handling and ubiquity to justify its investment. That means the feebler higher-frequency emissions at 0.1-0.3THz, later adding near-infrared communication and maybe far infrared 0.3-1THz. To boost these, reconfigurable intelligent surfaces RIS, almost never seen with 5G, become essential in the propagation path and lots of them. It was hoped that almost all of these will use only a whisper of electricity and need no cooling because they will be semi-passive. But that is limited to only collimating the beam when redirecting it around obstacles. To work well and provide security, such panels must be very large and placed near to source or user, so siting becomes very problematic. Further, semi-passive RIS performance is reduced by the multiplicative fading effect. Anyway, you need one fully active tile so, “the system knows the RIS”.

Electrical autonomy examples arriving that last for the life of their host equipment Source: Zhar Research report, “6G Communications: Self-powered Infrastructure and Zero Energy Client Devices ZED: Markets 2025-2045”

Here come active RIS

There is now recognition that the much smaller, more easily sited, active RIS with strong power supply must be widely deployed. They amplify and focus the beam getting it much further, so far fewer are required. Many 6G paybacks are impossible without active RIS, such as adding sensing and SWIPT. This Simultaneous Wireless Information and Power Transfer would, in a later stage of 6G, enable service to such things as unpowered internet of things nodes, even without batteries. It would use backscatter already seen with unpowered radio frequency identification RFID and anti-theft tags. See Zhar Research report, "6G Communications: Reconfigurable Intelligent Surface RIS and Reflect-array Materials and Hardware Markets, Technology 2025-2045".

Base stations reinvented

6G will need more base stations than 5G. They will need far more power – at least 50kW. To limit numbers, one proposal is “the tower in the sky” meaning high altitude pseudo satellites HAPS loitering in the stratosphere at 20km. These are solar-powered fixed-wing drones and inflatables already aloft for weeks and potentially aloft for years, providing better latency than satellites and no doppler issues from speed. Repairable, they should be cheaper. Their optical transmission to personal devices has already been demonstrated. See Zhar Research report, “"6G Communications: Optical, Optronics and Aerospace Materials and Devices Markets 2025-2045". On Earth, 6G base stations may merge into high-rise buildings to contain cost and avoid ugliness. For the big picture, see the 6G report, “6G Communications Grand Overview: Materials, Hardware Markets 2025-2045”.

Challenges with other 6G hardware

Other 6G hardware from customer premises equipment CPE to client devices such as 6G smartphones will use more power to provide better services, a challenge compounded by more miniaturisation demanding new thermal and other solutions. See Zhar Research report, “6G Communications Thermal Materials for Infrastructure and Client Devices: Opportunities, Markets, Technology 2025-2045”.

6G will be self-powering

Dr Peter Harrop CEO of Zhar Research advises,

“Overarching all of this is the need for 6G infrastructure and client devices to be self-powering with technology that lasts the life of the host equipment. To become “Zero Energy Devices ZED” 6G client devices will integrate multi-mode energy harvesting, now improving rapidly because SWIPT is a long way away.”

See Zhar Research report, “6G Communications: Self-powered Infrastructure and Zero Energy Client Devices ZED: Markets 2025-2045” which also covers those massive terrestrial 6G base stations will being widely deployed often away from grid power. Digging up roads to power all those active RIS is ridiculous.

Harrop adds,

“Consequently, all will employ sources such as on-board photovoltaics with emerging long duration energy storage in compact form such as redox flow batteries and their even smaller hybrid versions both soon capable of delaying electricity by up to one month to cover intermittency of wind and solar.”

See Zhar Research report, “Long Duration Energy Storage LDES beyond grids: markets, technologies for microgrids, minigrids, buildings, industrial processes 0.1-500MWh 2024-2044.” One of the smallest, long-life storage options emerging is described in Zhar Research report, “Lithium-ion capacitors and other battery supercapacitor hybrid storage: market forecasts, roadmaps, deep technology analysis, manufacturer appraisal, next successes 2024-2044”.