Photovoltaic converters for power transmission systems

Scientists from the University of Hahn in Spain and the University of Santiago de Compostela conducted research to determine the most suitable semiconductor materials for high-power light transmission in terrestrial and underwater environments.

HPOT, also known as laser power transfer, is a method of transmitting continuous power to a remote system using a monochromatic light source through an optical photovoltaic converter.
"In the coming year, our goal is to begin manufacturing OPCs based on indium gallium nitride and aluminum indium nitride as proof of concept, laying the foundation for exceeding the maximum efficiency reported so far," researcher Pablo Sanmart í n told PV Magazine.

The research team has identified potential targets for high-power optical wireless transmission, including remote mobile electronic devices such as small aircraft, drones, robots, satellites, as well as applications in underwater wireless power transmission, to improve the operational capabilities of autonomous underwater vehicles. However, they pointed out that the current system efficiency is limited to around 20%.

So far, gallium arsenide based OPCs have been used the most in HPOT research because they are considered mature and mature. However, the series resistance loss of this material is relatively high. Therefore, researchers have provided III-V InGaN and InAlN wide bandgap semiconductors as potential OPC materials, as they can match the optimal wavelength range of water.

Their modeling considered three types of composite mechanisms and validated them by comparing the results of GaAs with empirical results from scientific literature.

The researchers said, "The consistency between the obtained results is noteworthy, with a relative error maintained below 1.6% for all parameters and input power density.".

The team conducted a series of tests and found that the maximum efficiency of GaAs was 67.3% at 70 Wcm-2, InGaN was 70.6% at 75 Wcm-2, and InAlN was 70.3% at 150 Wcm-2. In the atmosphere, InGaN has the highest efficiency within 10 km, ranging from 70.5% to 65.3%, while InAlN has an efficiency of 70.3% to 65.1%. Under compression conditions, the GaAs results are relatively low, ranging from 67.3% to 62.4%.

When the medium is water, nitrides also exhibit better results. InGaN achieved an overall efficiency of 9.8% at 100 meters, while InAlN achieved a global efficiency of 8.6%. In contrast, the results of gallium arsenide are much worse, with an efficiency decrease to 2.4% at only 1 meter.

"This type of semiconductor cannot actually be used for underwater applications," scholars say. It is worth noting that the global efficiency of nitride based OPC still exceeds 46% at a distance of 20 meters.

The research team suggests that nitrides may generate approximately ten times more energy in the same amount of time. They exhibit over 63% high efficiency under auroral intensity of 1000 Wcm-2. In contrast, the highest achievable efficiency of GaAs at 100 Wcm-2 is approximately 67.3%.

They explained, "This enhancement is mainly attributed to the reduction of series resistance loss under strong illumination, from 28% to around 14%, which is due to the use of higher energy gap materials leading to a decrease in current density.".

They described their findings in their recent publication "Broadband Gap III-V Group Materials for Efficient Air and Underwater Optical Photovoltaic Power Transmission" in Solar Materials and Solar Cells.

"It is worth noting that the potential manufacturing of these devices is limited by potential technological manufacturing limitations that may arise during this process, as semiconductors are grown with sufficient quality to achieve the required doping levels or avoid lattice mismatch between layers," the researchers said. The feasibility of this process also depends on whether a preferred wavelength or similar wavelength is provided. In addition, monochromatic light sources should be able to provide such a strong power density and ensure that the beam has operable angular dispersion within the considered distance.

Source: Laser Net