Demonstration of Wireless Power Transfer for Solar Power Satellite

Wireless Power Transmission from space to ground
It represents basic configuration for wireless power transfer from space to ground. Sunlight is converted to direct current (dc) power by solar array and then changed to microwave power by phase detection and conjugation circuit. Pilot signal is used to know location of receiving antenna. Power Signal is transferred from space by retrodirective antenna array and received on ground by receiving antenna.

Demand for renewable energy sources is increasing due to depletion of fossil fuel resources and global warming. Solar power is a big renewable source but it is not always available such as the night time as well as on rainy and cloudy days. Solar power is available 24 hours in space, so space solar power system was proposed. Electric power will be transferred wirelessly from space to ground in form of microwave. Human safety standards for exposure to microwave power are considered for designing the space solar power system. Large array antennas with size of 2.375km x 2.5 km will be used to transmit the power. Power will be received on ground by antenna with diameter of 3.5 km. Previous methods require synchronization among elements of large antennas. There is also a concern of antenna deformation. Solutions for rectification of deformation have been proposed but require long processing time.

We proposed digital retrodirective method to resolve issues of synchronization and antenna deformation. Pilot signal is sent from the receiving antenna towards retrodirective antenna array. Phase detection and Phase conjugation of pilot signal is performed by digital processing. With the proposed method, each antenna will work independently without need of synchronization. For case of antenna deformation, compensation will be performed in less time with digital signal processing. We performed experiment in anechoic chamber to demonstrate the digital retrodirective method. Four antennas were used to receive pilot signal and to transmit power signal. Deformation for antennas was corrected with required limits of accuracy and antennas worked properly being independent.

Our method gave solution for some issues related to wireless power transfer from space. It will be help to realize space solar power system for getting uninterrupted renewable energy.

Bibliographic information of awarded paper
  • Title: Demonstration of Digital Retrodirective Method for Solar Power Satellite
  • Author name: Mudassir Raza and Koji Tanaka
  • Journal title: Electronics
  • Publication year:2021
  • URL:

Department of Space and Astronautical Science, Raza Mudassir