Inductive Power Projection Ltd offers the first commercial high-performance wireless battery charging system for drones and other electric vehicles, capable of transferring kilowatts of power over metre-scale distances. The problem we are solving is Autonomous Power, the last primary technological barrier to growth, and the key enabler for delivering environmental sustainability, net zero, and so much more for uncrewed autonomous systems.
The Science…
The critical relationship that needs to be understood with inductive power transfer is that coil coupling efficiency between the wireless transmitter and receiver is proportional to the product of the squares of frequency and magnetic flux density (i.e. power transfer efficiency ∝ B2 f2). For decades, wireless power developers have been slogging it out trying to get the technology developed with frequencies of a few tens of kilohertz, that the mathematics show is just too low a frequency for efficient power projection. The reason for this is historical – when wireless power systems were first developed, the engineers looked about and found pre-existing kHz-frequency inductive heating technology on the shelf and just used that with little thought to the physics. We took an alternative approach and came to this from the physics, which clearly shows that the optimal frequency is a few tens of megahertz. This means that our system is super light-weight, with measured 99% transfer efficiency between the transmitter and receiver across useful z-gaps and lateral displacements. We do not need to use expensive and heavy ferrite cores vulnerable to overheating and fires (leave those for the kHz folk), nor costly, Litz multi-wound coils (leave those for the kHz folk too). Our system is air-cored and uses single turn thin-walled copper tubes (i.e. plumbing).
There are alternatives to inductive wireless charging. Plug-in is the obvious, and great if you have personnel to plug it in or work in a very clean environment. Robotic plug-in, and its close relative battery changers, have been developed, and some look cheap, but these have a long and expensive service tail and it might be a long way to go to clean that terminal. Lasers and microwaves have also been shown to work, but these are inefficient although the only options for far-field (e.g. powering kilometres away). But for near-field (within about a metre) then inductive is clearly the way to go, and cheaper and more developed than you might think!
Finally, people ask me several questions about inductive wireless charging. The most common is, How long will it take to charge my battery? Well, I think this question comes from the experience of people with mobile phone chargers where, after charging all night, the phone is still only 50% full. Our system is as quick as using a plug-in.
The second question is, Why not use this for charging cars, even while driving on a road and get rid of the batteries? Well, most electric vehicle owners are happy to plug in because it is very cheap, whereas even cheap wireless comes with a bigger price tag. As for dynamic charging for moving cars, where do I start…? That every vehicle would need a compatible wireless receiver, and how good is that working out for plug-in! Also, think of the infrastructure development costs, and consider that only 39% of the UK national rail network has been electrified after over 140 years of rail electrification (see Volk’s Electric Railway). Hmm. Inductive wireless power: The Future that is affordable, efficient and ready to go!
