Indoor solar cells power IoT devices using electric light

Finding power sources for IoT devices is one of the many challenges to their widespread adoption, as many will need to run without wires or batteries.

It is estimated that by 2025, many facets of our lives will be mediated through 75 billion IoT devices, a majority of which will be located indoors. Many will need to become autonomous, meaning that they should no longer need batteries or a grid connection to operate.

A new type of dye-sensitised solar cells that harvest light from indoor lamps could be the answer.

The cells are capable of converting up to 34 per cent of visible light into electricity to power a wide range of IoT sensors.

The team from Uppsala University, Sweden, used a copper-complex electrolyte, which makes them ideal for harvesting indoor light from fluorescent lamps and LEDs.

Their latest results establish dye-sensitised solar cells as leaders in power conversion efficiency for ambient lighting conditions, outperforming conventional silicon and solar cells made from exotic materials.

The research could revolutionise indoor digital sensing for smart greenhouses, offices, shelves, packages and many other smart everyday objects.

“Knowing the spectra of these light sources makes it possible to tune special dyes to absorb indoor light. While generating large amounts of energy, these indoor photovoltaics also maintain a high voltage under low light, which is important to power IoT devices,” said assistant professor Marina Freitag.

The researchers also designed an adaptive power management system for solar-powered IoT sensors.

In contrast to their battery-limited counterparts, the light-driven devices intelligently feed from the amount of light available.

Computational workloads are executed according to the level of illumination, minimising energy losses during storage and thus using all light energy to the maximum of its availability.

Combining AI and automated learning, the solar cell system could help to reduce energy consumption and battery waste.

In the future, it is thought that billions of IoT devices self-powered by indoor solar cells will provide everything from environmental information to human-machine and machine-machine communications. Such advanced sensors can further enhance the next wave of robotics and autonomous systems currently in development.

“Ambient light harvesters provide a new generation of self-powered and smart IoT devices powered by an energy source that is largely untapped. The combination of high efficiency and low cost with non-toxic materials for indoor photovoltaics is of paramount importance to IoT sustainability,” Freitag said.

Last month, researchers from the University of California demonstrated prototype “anti-solar panels” which can generate power in the dark from wasted thermal energy.