Wireless Solar Power, Data Transmission Designed for IoT

Doctoral student Xiaozhe Fan measures the light emitted by a gallium arsenide solar cell. (W. Daniel Leon-Salas, Purdue University)

28 September 2018. A process for capturing light to power Internet of Things, or IoT devices, is shown to use the same solar cells to transmit data over an IoT system. Researchers at Purdue University in West Lafayette, Indiana describe their techniques in the 19 September issue of the journal IEEE Transactions on Circuits and Systems I: Regular Papers. The team also received a 3-year $450,000 grant from National Science Foundation to advance their work into hardware platform prototypes.

Purdue’s Technology Integration Lab or tinyLab led by engineering professor Daniel Leon-Salas is harnessing light for both solar power and data signals to spur adoption of IoT systems that promise to extend Internet connectivity to everyday objects. But many of these devices in homes or businesses are not stationary — tracking shared tools in a workshop, for example — so the devices need both power and communications capability in highly compact components.

The solutions proposed by Leon-Salas and colleagues use the ability of solar cells to both absorb and emit energy when stimulated by light or electricity in the form of photons, a phenomenon known as luminescence. For most solar cells, however, luminescence is not symmetrical; they absorb many more photons than they give out. The Purdue team’s solution uses solar cells made from gallium arsenide, a semiconductor material with greater electronic properties than silicon, but also efficient at both absorbing and emitting photons.

The researchers are building solar cells with gallium arsenide that absorb solar energy for power, but also use optical communications with ambient light to transmit data. The NSF grant supports work in their lab to answer basic questions about the technology, such as how far and fast data can travel and basic architectures for these systems, particularly when using the least amount of power. The team aims to build and validate working prototypes of a self-powered gallium arsenide solar cell platform. This approach, says the team, will avoid interference with radio-frequency or RF communications devices in an already crowded RF spectrum.

The IEEE journal paper gives a preview of this work. In the paper, Leon-Salas and doctoral candidate Xiaozhe Fan demonstrate a lab circuit powered by a gallium arsenide solar cell that uses the same cell to transmit and receive data. Tests show the circuits can send and receive data over a distance of 50 centimeters. “We created a revolutionary way to use light to power these devices,” says Leon-Salas in a university statement. “Light energy is the most available form of ambient energy, with much higher energy density levels than radio-frequency or mechanical ambient energy sources.”

The researchers believe the technology can be deployed in so-called smart homes and factories, as well as for agricultural and environmental monitoring. Purdue says its technology transfer office is securing a patent on the technology, and is available for licensing.

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