TU Delft: Now everyone can build battery-free electronic devices

Called BFree, the system includes energy-harvesting hardware (the BFree Shield) and a power-failure-resistant version of Python, one of the most accessible and most used programming languages. All the user needs is a basic understanding of Python in order to quickly and easily turn any do-it-yourself (DIY) smart device into a battery-free version. With this technology, novice programmers can now turn their DIY battery-powered motion sensor, for example, into a solar-powered sensor with an infinite lifetime.

The research will be presented virtually on Wednesday, Sept. 22, at UbiComp 2021, the premier conference for ubiquitous computing. Users can find instructions for how to use the new technology here.

Asking the wrong question
‘Right now, it’s virtually impossible for hobbyists to develop devices with battery-free hardware, so we wanted to democratize our battery-free platform,’ says Northwestern’s Josiah Hester, who co-led the work. ‘Makers all over the internet are asking how to extend their devices’ battery life. They are asking the wrong question. We want them to forget about the battery and instead think about more sustainable ways to generate energy.’

‘The maker community is typically more interested in rapidly deploying their devices, and that quickness doesn’t always go well with sustainability,’ adds TU Delft’s Przemyslaw Pawelczak, who co-led the work with Hester. ‘We wanted to design a viable product that can connect these two worlds.’

The Maker Movement’s battery problem
A technology-focused extension of DIY culture, the Maker Movement comprises a diverse group of inventors, designers and computer programmers who build their own hardware and software for electronic devices, including motion sensors, displays, actuators and more. Combined with cloud computing, the ability to develop fast, cheap and connected devices enables the Internet of Things (IoT).

While the growing number of people who can build and program devices presents an exciting future for technology, Hester, Pawelczak and their team are daunted by the number of batteries that will be used and eventually end up in landfills. ‘Many people predict that we’re going to have a trillion devices in this IoT,’ Hester said. ‘That could really cause a terrible ecological disaster. What we’re doing, instead, is truly giving power to the people. We want everyone to be able to effortlessly program devices in a more sustainable way.

Invisible for the user
But simply forgoing a battery is not as simple as it may sound. When devices bypass the battery and instead rely on energy harvesting, the power supply is no longer constant. If the sun goes behind a cloud, for example, then solar power might be temporarily disrupted.

With BFree, the researchers have solved this issue. The technology enables devices to run perpetually with intermittent energy. When power is interrupted, BFree pauses calculations. When power returns, it automatically resumes where it left off without losing memory or needing to run through a long list of operations before restarting. Not only does this save energy, the technology also is more intuitive for the user than traditional programs, which lose all memory of what happened immediately before a power failure and need to restart from the very beginning.

To make the process user friendly, the researchers coded BFree with software to interpret Python programs for battery-free devices. A user only needs to attach the BFree Shield onto the Adafruit Metro M0 maker platform (or slightly modify it to work with other CircuitPython-based platforms) and then program the device as they typically would. The BFree software takes care of the rest, allowing the program to run without batteries — purely from harvested energy — and operate perpetually through power failures.

‘We wanted to make it totally invisible for the final user,’ says Vito Kortbeek, who is a Ph.D. candidate in Pawelczak’s group. ‘So we tried to keep the original experience of the device the same without the user seeing how we changed the software to interpret the Python files for battery-free technology.’ And that is good news, according to Hester. ‘Now everyone can build and program smart, sustainable devices. This makes the future vision of ubiquitous computing more sustainable, useful and environmentally responsible.’