Battery-Free Sensors Operating on Trains For Real-Time Sensing

The Problem With Powering Sensors

Sensors are at the heart of modern electronics. Without them, circuits would be pretty clueless about the world around them. They’re how devices measure environmental factors, detect people nearby, sniff out radiation sources—you name it.

When sensors are part of a device plugged into the mains, power isn’t really an issue. But the moment you move into the world of battery-powered devices—especially ones that need to be deployed at scale—you run into a whole bunch of challenges.

First off, batteries don’t last forever. Devices running on them need to conserve energy wherever they can, which brings us to sleep modes. These modes help extend battery life by turning off unnecessary components when they're not in use. But here's the catch: if the microcontroller goes to sleep, the sensors often have to as well.

And that’s a problem. A sleeping sensor can’t read the environment. For devices that only need to wake up occasionally and take readings (like a weather station that logs temperature every hour), that’s fine. But what about devices that need to respond to sudden events—like a door sensor, a smoke detector, or a motion alarm? If the sensor is asleep, it can’t react until it's powered back up—and by then, the moment might’ve passed.

So engineers are faced with a tricky balancing act: how often should the device wake up? When should it take measurements? How can you get the most out of a battery without missing critical events?

Welcome to the fun world of low-power sensor design.

Battery-Free Sensors Operating on Trains For Real-Time Sensing

Recently, Glasgow University spinout RX Watt has developed a series of battery-free sensors designed for use in rail carriages. The sensors, which can be retrofitted to most existing carriages, utilise radio waves to power small electronics that collect data such as temperature and vibration. This data is then sent to the sensor user via a Bluetooth interface, providing real-time monitoring of the condition of the carriage.

According to RX Watt, the sensors are designed to prevent costly equipment failures by monitoring wear and tear in real-time. The use of wireless power delivery also reduces the cost and environmental impact of wiring in modern trains, as well as eliminating the need for battery replacement.

The effectiveness of the sensors has been demonstrated at the BCIMO Very Light Rail Innovation Centre, where they were used to power sensors on test vehicles, including a T69 tram and a passenger rail carriage. The sensors were shown to be safe for use in such vehicles, and were able to receive power wirelessly from a microwave source.

The development of the sensors has been supported by a number of organisations, including the Contracts for Innovation: Rail Challenges programme, which is funded by the Department for Business, Trade, and Science, and the Department for Science and Innovation. The programme is delivered by Innovate UK.

Dr Mahmoud Wagih, the founder of RX Watt and a lecturer at Glasgow’s James Watt School of Engineering, stated that the sensors are designed to monitor a number of key factors, including air quality, occupancy, wear and tear, and vibrations. The use of radio frequency power delivery allows for the sensors to be directly powered without the need for batteries or energy harvesting.

Could Batteryless Sensors Be the Future?

As electronics become more deeply woven into the fabric of modern life, powering those devices is turning into one of the biggest engineering challenges. Whether it’s smart infrastructure, environmental monitoring, or IoT systems spread across a city, keeping everything powered—especially at scale—isn’t easy.

That’s where batteryless sensors step in. These innovative devices offer a compelling solution, especially for large-scale, hard-to-reach, or remote deployments. Imagine sensors that monitor air quality in forests, track vibrations in bridges, or detect early signs of wildfires—all without ever needing a battery swap.

Right now, many of these battery-free systems are still in the demonstration or early deployment phase, but the potential is undeniable. As the technology matures and wireless power delivery becomes more efficient, we could see these devices become standard in everything from industrial monitoring to smart homes.

In a world that’s moving fast toward sustainability and automation, batteryless sensors might not just be a clever trick—they might be a key piece of the future.