Safety Analysis of Long-Range and High-Power Wireless Power Transfer Using Resonant Beam

Resonant Beam Charging (RBC) is a promising Wireless Power Transfer (WPT) technology to realize long-range and high-power charging for electronic devices. However, the safety mechanism of the RBC system has not been investigated so far. In this paper, we propose an analytical model based on electromagnetic field analysis for evaluating the performance of the RBC system with external object invasion, such as the benchmark for the WPT safety, irradiance on the invading object. For the RBC system with $\text{5}\;$ m transmission distance and $\text{1}\;$ W output electric power, the safety numerical analysis of radiation illustrates that the maximum irradiance on the invading object is $\text{0.81}\;\text{W/cm}^2$ , which is approximately $1/10$ compared with $ \text{8.22}\;\text{W/cm}^2$ for the comparable laser charging system. Particularly, the peak irradiance on the invading object of the RBC system satisfies the Maximum Permissible Exposure (MPE) requirement for human skin, which is $\text{1}\;\text{W/cm}^2$ in the standard “Safety of Laser Products IEC $60825-1$ ”. Hence, the RBC system can realize skin-safe WPT with Watt-level power over meter-level distance.