Nuclear quadrupole resonance sensor for safer wireless power

Wireless power transfer (WPT) is likely to be widely adopted throughout the automotive industry as it represents the most simple and effective charging solution for electric vehicles. A strong magnetic field, generated by a car and the ground can present certain safety risks, should a person or animal enter the field.

Oxford researchers have developed an elegant safety solution that uses nuclear quadrupole resonance to detect biological material within the WPT magnetic field. The device can differentiate between human and animal tissue and may provide feedback to a kill-switch for the WPT system. This approach is affordable and more reliable than existing radar-based solutions.

Charging ahead without wires

The global sales of electric vehicles are expected to top 1 million for the first time in 2017 (Frost & Sullivan, 2017) and with this increased demand comes a need for a more convenient and efficient method of recharging on-board batteries. Wireless charging is an attractive solution, as it reduces the amount of input required from the vehicle owner and eliminate cumbersome leads and charging stations.

Current wireless charging systems are typically based on inductive charging, where a magnetic field is generated between a coil located on the ground and one in the vehicle. Fields generated in this way generally exceed 85 kHz.

Wireless power transfer safety

There is a widely perceived danger with wireless power transfer (WPT), that humans or animals could step into the generated magnetic field while the device is in use. It is a requirement that such systems do not expose users or animals to harmful levels of electromagnetic radiation and that it adheres to guidelines set out by the International Commission on Non-ionising Radiation Protection (ICNIRP). In order to prevent this, effective “trip switches” are needed, where the power can be cut in the presence of biological material.

Nuclear quadrupole resonance

Researchers at the University of Oxford have developed a sensor, based on nuclear quadrupole resonance (NQR), capable of detecting biological material in proximity to the WPT field. The NQR system differentiates between humans or animals and can provide feedback to the WPT device to trigger a shut-down when necessary. The power can then be restored once the biological material is clear of the field.

We believe the main benefits of the Oxford solution are as follows:

  • Lower cost and more reliable than current radar solutions
  • Differentiation between different biological material
  • Fewer false positives than other safety devices
  • Easily integrated into existing WPT systems
  • Allows WPT manufacturers to adhere to ICNIRP guidelines

Patent protection

A patent has been filed that covers this technology. Oxford University Innovation Ltd. is keen to talk to anyone who could aid in the commercialisation of this device.

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