[Reading Science] First Successful Wireless Power Transmission and Reception in Space

California Institute of Technology Research Team
Secures Core Technology for Space Solar Power Plant

For the first time in history, an experiment successfully transmitted and received energy wirelessly in space. A core technology has been secured that can send power generated by space solar power, which is more than eight times more efficient than on the Earth's surface, to any location on Earth.

Inside the space solar power plant technology demonstration satellite SSPD-1, developed by the California Institute of Technology. The electricity generated through solar power was converted into microwaves and transmitted wirelessly from the transmitter to the receiver (right), successfully lighting up an LED. Photo by California Institute of Technology website.

On the 12th (local time), space-specialized media Space.com reported that the California Institute of Technology (CIT) successfully conducted such an experiment recently with the experimental satellite (Space Solar Power Demonstrator, SSPD-1) launched in January via SpaceX's Falcon 9 rocket as part of the Space Solar Power Project (SSPP).

This satellite consists of the power generator body called 'DOLCE', the photovoltaic cell 'ALBA', and the ultra-light microwave wireless power transmission device 'MAPLE'. The satellite produced power through solar energy, converted it into microwaves, and transmitted it to Earth. Subsequently, the CIT research team succeeded in receiving it on the ground using equipment installed on the roof of the Gordon & Betty Moore Engineering Research Laboratory at the Pasadena campus in California. Additionally, inside SSPD-1, they successfully conducted an experiment where microwave-converted power was exchanged between transmission and reception devices about 1 foot apart, lighting up two LEDs.

Ali Hajimir, deputy director of SSPP, explained, "The experiments conducted so far have confirmed that power can be successfully transmitted and received in space," adding, "We were able to detect energy transmission to Earth, and the equipment that succeeded in ground tests also worked in space."

The research team is particularly pleased that the MAPLE device operated normally despite being exposed to the harsh space environment?space radiation, solar heat radiation, and extreme temperature changes?without any special protective measures, enabling easier scaling up in the future. Deputy director Hajimir said, "As far as we know, no one has succeeded in wireless power transmission experiments in space before. We achieved this for the first time through flexible yet lightweight structures and independently developed integrated circuits."

The MAPLE device developed by the research team wirelessly transmits energy in space by utilizing the interference effect of light. Light has wave properties, and when two lights combine with the same wavelength and phase, constructive interference occurs, strengthening the combined wave. If the wavelengths are the same but the phases differ, destructive interference occurs, canceling each other out. The research team used this principle to precisely control the wavelength and phase of light, rapidly changing the direction of energy in nanosecond (one-billionth of a second) units to remotely transmit it to the desired receiver, successfully demonstrating this technology in the experiment.

The research team is currently evaluating the performance of individual components that make up the MAPLE device. This is a challenging process that requires about six months of effort. The results will be used to develop large-scale space solar power generation and transmission equipment that can be commercialized and practically applied in the future. Deputy director Hajimir stated, "Just as the internet expanded access to information, we expect space solar power technology to 'democratize' access to energy," adding, "The fact that infrastructure is not required for energy transmission means that energy can be remotely supplied even to places destroyed by war or natural disasters."

Space solar power generation can operate 24 hours a day, unlike terrestrial solar power, which fluctuates due to terrain, weather, and day-night cycles. It can produce at least eight times more power from solar cells of the same performance compared to ground-based solar equipment. A significant advantage is that power can be sent and used anywhere on Earth without building large-scale infrastructure for generation, transmission, and storage. It can also be utilized in space environments such as the Moon and Mars. However, safety, economic feasibility, and actual carbon emission reduction effects need to be verified.

In response to the recent need for carbon reduction to tackle climate change, major countries worldwide are rushing to start projects. The European Space Agency (ESA) has been intensively conducting related research and development since 2019 and plans to commercialize a 2GW-class space solar power plant in the 2040s. China and Japan are also researching with commercialization goals set for the 2030s to 2040s. South Korea is developing core technologies at the Korea Aerospace Research Institute and the Korea Electrotechnology Research Institute and is preparing for a low Earth orbit demonstration by the late 2020s.