Scientists developing solar panel that doubles as a Li-Fi receiver

Existing on-roof solar panels can receive data, acting as a broadband receiver for hilltop laser transmissions, says a scientist.

SolarCity solar panels

SolarCity's system tends to be lower profile than others and it include a drip edge that helps keep ice dams from building up underneath the photovoltaic panels.

Credit: Lucas Mearian

Light-based data communications, or Li-Fi, which uses LEDs to create networked communications, can be integrated into a solar panel to create a self-powered Li-Fi receiver.

The solar panel receives light from the LED to create power, and also receives light from the network to act as the broadband receiver, thereby powering itself, the technology's inventor says.

Solar cells

The currently prototyped solution allows "a solar cell to be tightly integrated into communication nodes, to then receive relatively high bandwidth data while also providing electrical power for the nodes' operation," the University of Edinburgh's Edinburgh Research and Innovation subsidiary says on its website.

Edinburgh Research and Innovation promotes the university's research for commercialization.

Uses

Self-powered Li-Fi communications terminals could be used for low-cost beacons, backhaul, rural broadband, sensors, and the Internet of Things, among other uses, the organization says.

Speeds obtained in laboratory tests have been 1 megabit per second (MB/s).

Those speeds can be increased to 7 MB/s with a technique called Orthogonal Frequency Division Multiplexing (OFDM) that encodes digital data on a number of carrier frequencies.

Switching lights on and off

Li-Fi is a form of Visible Light Communications (VLC). It works by turning off-the-shelf LED lights off and on within nanoseconds—too rapidly for the human eye to see. In fact, the lights don't need to be visible at all; they just need to be on.

"Subtle changes of the brightness," create the communications, lead scientist Harald Haas said in a September TED Talk.

VLC has some security advantages over common radio, such as Wi-Fi, in that the transmitter and receiver need to be able to see each other. In other words, the transmission can't penetrate walls or other dense materials, although it can be reflected by walls.

That restriction of the carrier can mean that, within a building, the send and receive elements of the network need to be in the same room. There's no signal spill-over to an adjacent area.

That makes it more secure than Wi-Fi, which propagates freely.

Interference

Another potential advantage to Li-Fi over traditional radio is that visible light can reduce interference.

I've written about using light-based communications in interference-sensitive environments before, in "Light-based networks could replace wires for hospital patients."

In the case of hospitals, where radio signals can be a problem due to interference, there's a reliance on wired networks. With light-based patient networks, care-providers could allow non-critical patients to be monitored and also move around, conceivably freeing up beds.

Ambient-powering rural broadband

But it's also in the mission to bring Internet to remote areas that this combination of solar panel and optical Li-Fi data node could be promising, the researchers think.

Communications terminals could be self-powered, as could rural broadband, for example, the developers said.

And existing photo-voltaic solar panels could be adapted to accept the data signals, the LiFi Centre says on its website.

Lasers on a hillside or a lamppost could provide the signal, Haas said in the TED Talk.

The Li-Fi Research and Development Centre is a University of Edinburgh lab geared towards experimenting with the technology.

IoT's carbon footprint

Carbon-reduction is another selling point of the solar panel-based Li-Fi, the scientists say.

"Machine to machine data links are multiplying," and "explosive growth" in M2M data links "puts extreme burdens on carbon reduction targets," they say in a document (PDF) on their website.

"Self‐powered communication nodes will remove a major barrier to data communication growth" overall, the report says.

In this case, "a solar cell has become a receiver for high speed wireless signals encoded in light," Haas says. And it could do this constantly, "while it has retained its principal function as an energy harvesting device."

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