Could a space 'power bank' really beam electricity to Earth?

Imagine building a solar power station in space and transmitting the energy wirelessly to Earth, drones, satellites or even deep-space spacecraft. While still in its experimental stage, China's "Chasing the Sun" project, or "Zhuri," is bringing this ambitious vision closer to reality, achieving kilowatt-level wireless energy transfer over hundreds of meters and successfully testing power delivery to multiple moving targets.

The project is led by a team headed by Duan Baoyan, an expert at Xidian University and an academician of the Chinese Academy of Engineering. They have developed key technologies for space-based solar power and microwave wireless energy transmission. At Xidian University, a 75-meter steel support tower serves as the core test facility for the project.

Space-based solar power stations are designed to place large arrays of photovoltaic panels in orbit, where they can operate without atmospheric interference or the day-night cycle. It's like a giant "superpan" floating in space, continuously capturing solar energy.

"On Earth, energy flux density is limited by weather and geography, around 200 to 300 watts per square meter. In space, especially at geostationary orbit, it can reach roughly 1,360 watts per square meter, making it one of the most promising solutions for our energy challenges," said Fan Guanheng, an associate professor at Xidian University's School of Mechano-Electronic Engineering (SMEE).

But without wires or cables, how can a power station built in space transmit electricity across such distances?

The answer lies in microwave wireless power transmission. The process involves three main steps. First, mirrors concentrate sunlight onto photovoltaic arrays, which convert solar energy into direct current electricity. The electricity is then converted into microwaves and transmitted to receiving antennas. Finally, the antennas capture the microwave beam and use rectifiers to convert the energy back into direct current for use by devices.

"In the future, space-based solar power stations could enable energy transmission over distances of tens of thousands of kilometers," said Qian Sihao, an associate professor at Xidian University's SMEE.

From Zhuri project 1.0 to 2.0, the team upgraded the system from one-to-one fixed-point power transfer to one-to-many moving-target energy delivery. Previously, fixed-point transfer was like connecting an invisible wire to a stationary device – once the target moved, power was lost. Now, a single transmitter can supply multiple fast-moving devices simultaneously.

The researchers developed a high-precision closed-loop beam control system. "When the receiving antenna sends a guidance signal, the transmitting antenna can capture it, calculate the receiver's real-time position and orientation and accurately direct the energy beam," Qian explained.

Space-based solar power station could allow virtually uninterrupted energy collection and supply, reduce reliance on fossil fuels, cut carbon emissions and support wireless charging for spacecraft, according to Fan.

The team's next step is in-orbit testing. Their roadmap aims to build a megawatt-level station by 2030 and a gigawatt-level station by 2050.

Read more: China makes breakthrough in space solar power and wireless energy transmission