Wireless Power Transfer: The Global State of the Technology

What wireless power transfer means

Wireless power transfer is the delivery of electrical energy across a gap without a conductor. The transmitter converts mains or DC power into a field — magnetic, electromagnetic, or optical — and a receiver converts that field back into usable DC. Everything else is a question of frequency, distance, and efficiency.

Four families dominate practice today, and they are not competitors so much as answers to different distances.

The four approaches

1. Inductive coupling (millimetres)

Two tightly coupled coils, operating around 100–200 kHz. This is the Qi standard in every phone charging pad, and the same physics powers electric toothbrushes, cochlear implants, and industrial connectors in wet or explosive environments. Efficiency is high — 70–90% — but alignment is unforgiving and range is essentially zero.

2. Magnetic resonance (centimetres to a metre)

Loosely coupled resonant coils tuned to the same frequency, usually 6.78 MHz. Resonance tolerates misalignment and multiple receivers on one transmitter, which is why it underpins wireless charging for electric vehicles, warehouse robots, and medical carts. Efficiency falls with distance but stays practical at tens of centimetres.

3. Radio-frequency far-field (metres)

A transmitter broadcasts low-power RF in the sub-1 GHz or 2.4/5.8 GHz ISM bands; receivers use a rectenna — antenna plus rectifier — to harvest microwatts to milliwatts. Efficiency is low in absolute terms, but for duty-cycled sensors that average microwatts it is more than sufficient, and it is the only approach that delivers power at room scale with no alignment at all.

4. Optical and microwave beaming (kilometres)

Collimated laser or phased microwave beams carrying watts to kilowatts over long distances. This is the domain of high-altitude platform resupply, remote installations, and space-based solar power research, with demonstrations run in the United States, Japan, China and the United Kingdom. It is real, but it remains capital-intensive and tightly regulated.

Where the technology stands worldwide

• Consumer. The Wireless Power Consortium's Qi2 specification, with magnetic alignment borrowed from Apple's MagSafe, has effectively settled the phone-charging question. Over a billion Qi-certified devices are in circulation.
• Automotive. SAE J2954 defines inductive charging for light-duty electric vehicles at 3.7–11 kW. Pilot dynamic charging roads have been run in Sweden, France, Israel, Italy, South Korea and the United States, with Detroit and Balocco among the most-cited installations.
• Industrial and logistics. Automated guided vehicles and warehouse robots increasingly charge opportunistically at pick stations rather than docking, removing the largest single cause of fleet downtime.
• Medical. Transcutaneous energy transfer for ventricular assist devices, implants and neurostimulators eliminates percutaneous driveline infections — the single largest failure mode of implanted hardware.
• IoT and sensing. RF power harvesting is the fastest-moving segment, driven not by novelty but by the maintenance economics of dense sensor networks.
• Space and defence. Power beaming trials, notably orbital demonstrations by Caltech and long-range terrestrial microwave tests by JAXA and DARPA-adjacent programmes, have proven the principle at meaningful power levels.

Standards and regulation

The regulatory landscape is mature rather than experimental. Qi and Qi2 come from the Wireless Power Consortium; AirFuel Alliance governs resonant and RF classes; SAE J2954 and IEC 61980 cover electric vehicles; ISO 15118 handles the communication layer. Exposure is bounded by ICNIRP guidelines, enforced through the FCC in the United States, ETSI and the RED in Europe, and equivalent bodies elsewhere.

For room-scale RF systems the practical constraint is not safety but spectrum: transmit power must fit inside ISM band allowances, which in turn sets the energy budget available to each receiver. Good WPT engineering is therefore mostly receiver engineering.

Wireless power transfer in Switzerland

Switzerland's contribution to wireless power is characteristically precise rather than loud. Swiss research groups and institutes work on resonant coupling, rectifier efficiency, and medical implant power, while the country's strength in instrumentation, MedTech and building automation gives WPT unusually direct routes to application. Swiss engineering norms — long service life, low maintenance, strict conformity — align neatly with a technology whose entire value proposition is the removal of maintenance.

E & B works on the RF far-field branch: room-scale wireless power for battery-free smart sensors. The argument is economic before it is technical. A building with a thousand wireless sensors is a building with a thousand coin cells on a rolling replacement schedule; the sensor is cheap, the truck roll is not. Harvesting power from the room removes the battery, the maintenance window, the disposal stream, and the installation map that nobody keeps up to date.

What comes next

Three developments matter over the next few years. First, GaN and advanced CMOS rectifiers are lifting far-field conversion efficiency at low input power, which directly widens the deployable radius. Second, beam-steering transmitters are turning broadcast power into targeted power, spending energy only where a receiver actually sits. Third, standards convergence around AirFuel RF and Qi2 is removing the integration risk that kept large buyers on the sidelines.

None of this makes wireless power a replacement for the grid. It makes it a replacement for the battery in the specific and very large class of devices that measure, report, and otherwise sip power. That class is growing faster than any other part of the electronics market.

Frequently asked questions

Further reading

• RF Wireless Power, Smart Sensors & IoT: A Technical Guide
• Object 27 — Athena EOS energy-harvesting smart sensor
• Object 23 — POWRTILES-powered warehouse robotics