Image by Andreluiz Cunha from Pixabay
Tyre sensors, such as tyre pressure monitoring systems (TPMS) were a major step forward in vehicle safety. Since their first appearance in the 1980s (yes, really), they must have saved many lives – and countless tyre failures.
Good as they are, though, tyre sensors have one glaring weakness: they’re powered by batteries, which eventually run out. In most cases, these batteries aren’t replaceable – not because of some conspiracy by the manufacturers, but because they have to survive a hostile environment. As such, they have to be held firmly in place within the sensor and then sealed off from the outside world.
TPMS batteries last a long time – typically 5-10 years, though this will depend a lot on how much driving you do – but replacing them still carries a cost for owners and the environment. So wouldn’t it be great if someone could design a battery-less system?
That someone could just be Professor Hiroshi Tani of Kansai University.
Enter the Energy Harvester
For a number of years, Professor Tani has been working with Sumitomo Rubber Industries to develop monitoring systems that do away with batteries. You may not have heard of Sumitomo, but you’ll have heard of their subsidiary, Falken Tyres.
In 2022, Sumitomo announced that they had developed an ‘energy harvester’ for use in tyre monitoring. Energy harvesting, as the website explains, refers to:
technologies that capture, collect and harness ambient energy, which is a catchall term for light, vibration, heat and other forms of energy that are present in minute quantities all around us. This ambient energy usually goes to waste if not harvested.
In this case, the ‘waste energy’ derives from the movement of the wheel. Changes in tension within a moving tyre produce a voltage that can be exploited for power. Autocar clarifies what’s going on:
Inside the Energy Harvester are two layers of rubber covered with a film, creating a negative and positive electrode.
As the tyre deforms, the two films rub together, generating static electricity.
So, essentially it looks like the power is generated by friction. The current generated is then used to send bluetooth signals to the car. Neat!
What’s more, the information gathered by this particular system could be used to estimate tyre wear – another innovation.
Now with added high speed power generation
So far, that’s all dandy, but one shortcoming with the Energy Harvester is that it doesn’t produce much power at higher speeds. After about 40 km/hr, power output starts quickly dropping off.
To get round this, the Kansai and Sumitomo team have developed a second way of using the tyre’s motion. This time, they’re utilising centrifugal force – something we thought we understood until we read this article. Let’s just say it’s a force generated by rotating objects and move on.
Sumitomo has called this ‘Tire Internal Power Generating Technology’ – not the catchiest name, admitted, but one that does what it says on the tin.
The point is that using both sets of power generation technique together, they can get power at both lower and higher speeds, with apparently enough to start running a TPMS system.
So… coming soon?
Just because a technology looks promising doesn’t mean it will ever see the light of day. Whether it’s EV batteries or self-driving vehices, tyres or flying cars, the internet is full of breathless stories about breakthroughs that quietly disappear.
In this case, though, Kansai and Sumitomo have got something more than a concept. It’s been a tough nut to crack – we found references to battery-less TPMS from 2011 – but it looks like we could finally be getting somewhere.
And OK, maybe the battery-less TPMS isn’t going to set the world on fire, it would still be a step towards safer, more reliable tyres, and reducing e-waste.
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