Sejong University researchers have created a new system that uses infrared light to wirelessly transmit power over a distance of 30 metres.
Researchers demonstrated that the new system could transfer 400 mW of light power during laboratory tests. For the time being, this amount of power is sufficient for charging sensors; however, further advancement could result in sufficiently high levels to charge mobile phones in various public places.
According to research team leader Jinyong Ha of Sejong University in South Korea, carrying power cables for our phones or tablets could be eliminated if devices can be powered wirelessly. Various sensors, including those in Internet of Things (IoT) devices and sensors used to monitor processes in manufacturing plants, could also be powered by it.
Several methods have been studied to transfer power over long distances wirelessly; however, it was not easy to send enough power in a safe manner. As a result, the researchers developed a novel method known as distributed laser charging. This method, according to the press release, provides safe high-power illumination with less light loss.
Distributed laser charging functions similarly to traditional lasers; however, the optical components of the laser cavity are separated into a transmitter and receiver rather than being integrated into a single device.
A laser cavity is formed over the air between the transmitter and receiver when two are in line of sight. The system allows to deliver light-based power as a result. The system enters power-safe mode to maintain hazard-free power delivery in the air when a barrier blocks the transmitter-receiver line of sight.
During the development of the new system, researchers used an erbium-doped fibre amplifier optical power source with a central wavelength of 1550 nm. Because it is at a safe point on the spectrum, this wavelength is harmless to human eyes or skin at the power level used.
Distributed laser charging, according to Ha, “enables self-alignment without tracking processes as long as the transmitter and receiver are in the line of sight of each other, whereas most other approaches require the receiving device to be in a special charging cradle or to be stationary.” In the event that a thing or a person blocks the line of sight, it also automatically switches to a safe low power delivery mode.
At the laboratory
The researchers set a transmitter and a receiver 30 metres (98 feet) apart to see how the system worked. The transmitter was made of the erbium-doped fibre amplifier optical source. At the same time, the receiver included a retroreflector, a photovoltaic cell that converted the optical signal to electrical power, and an LED that could illuminate while power was being delivered. The 10-by-10-millimeter receiver can be integrated into devices is small enough.
The results showed that a single-channel wireless optical power transfer system with a channel linewidth of 1 nm could generate 400 mW of optical power over a distance of 30 metres.
According to Ha, replacing power cords in factories with the laser charging system could reduce maintenance & replacement costs. “This might be especially helpful in harsh environments where electrical connections could cause interference or be a fire hazard.”
The research has been published in Optics Express.