VHF Wireless Power Transfer

There are wide sociopolitical issues concerning road transportation's greenhouse gas emissions, and the UK's strategy is to encourage wide adoption of electric vehicles (EVs). Cable-free wireless power transfer (WPT) (also known as inductive power transfer) can potentially overcome the drawbacks of wired EV chargers, and represents a potentially transformational method for improving the EV operation and user experience, especially with opportunity charging, for example for a van in a loading bay. Aside from its convenience, WPT can enable significant downsizing of the onboard EV battery, and has the potential for dynamically charging EVs on the move.

Significant snags for WPT exist. The power transfer efficiency is highly reliant on precise alignment of the transmitter coils (usually buried in the ground) and the receiver coils on the vehicle. Heavy-duty EVs also require much higher charge rates than WPT can currently offer.

Increasing the operating frequency of WPT systems increases the power density, solving both these issues and making WPT far more attractive all-round. State-of-the-art systems work at 85 kHz for a host of reasons including the use of ferrite cores, the skin effect, and available power electronics.

Inductive Power Projection Ltd have recently invented and protected a new way to create VHF magnetic fields for different applications. We're not frequency-limited and so operate in the VHF band (loosely defined as 30MHz-300MHz). After consulting with the Advanced Propulsion Centre, we realised the potential value for VHF-WPT for charging EVs, and following a technical peer review with Warwick Materials Group, it became clear that by using VHF we avoid a "difficult frequency region" above 85kHz.

With our present understanding, our VHF-WPT charging method can project in excess of 400 kW per module, easily to 800 mm at very high efficiencies (\> 99% for the wireless part); this compares with current state-of-the-art WPT systems where 50 kW/module is considered excellent, and an ambitious target for reach is 300 mm. A tough target of 500 mm lateral misalignment has been identified, which we can exceed even without a large vehicle-side receiver coil. However, the feasibility of VHF-WPT needs to be studied and tested in order to better understand the limitations, and this project does that, using the equipment we already own, and techniques developed during our previous work.

There's a significant market opportunity for our solution, but two identified technology gaps will be worked on by our two research organisation partners.