A were buzzing this week after an out-of-this-world milestone. In a kind of galactic Thomas Edison-esque moment, the Caltech team demonstrated, for the first time, their ability to wirelessly transmit power in space and beam a detectable amount back to Earth. The experiment of space solar power is still very much in its prototype stages, but the implications are potentially game-changing, said Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering at Caltech and co-director of the Space Solar Power Project team. “In the same way that the internet democratized access to information, we hope that wireless energy transfer democratizes access to energy,” Hajimiri, the experiment’s primary investigator, said in a statement announcing the milestone. “No energy transmission infrastructure will be needed on the ground to receive this power. That means we can send energy to remote regions and areas devastated by war or natural disaster.” He added: “To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures.” In effect, successfully demonstrating that power can be wireless transmitted in space opens the door to harnessing power from the Sun and sending it to Earth. Along with the for the project was policy fuel: To combat climate change, the U.S. government pledged to make its energy sector pollution-free by 2035. As it stands, current renewable energy sources lack fossil fuels’ consistency. Solar cells, in particular, suffer atmosphere, weather and nighttime. But for years, researchers have dealt with what has been an elusive solution: Under development for decades, space solar power, the process of harnessing solar power in space and beaming energy back to earth using solar power satellites, was not just the stuff of sci-fi. Ten years ago, Caltech formed the Space Solar Power Project, which culminated in a Jan. 3 launch milestone. The launch affirmed hopes about the future of a technology once deemed technically possible but economically infeasible. Officials tout Caltech’s SSPP project as an example of modern, private-sector aerospace research at work. The project has been fully funded from private sources, developed at a private institution, and the experiments were launched by Momentus, a private aerospace company, mounted aboard a Momentus platform. But the project really got off the ground in 2011 when billionaire real estate developer Donald Bren approached Caltech with a proposal to fund research into space solar power. Bren pledged a donation of more than $100 million to be paid throughout the lifespan of the project. Additionally, Northrup Grumman Corporation, a
MILITARY and aerospace company, pitched in $12.5 million. Bren, in the announcement last week, said the milestone was a major step forward. “The hard work and dedication of the brilliant scientists at Caltech have advanced our dream of providing the world with abundant, reliable and affordable power for the benefit of all humankind,” Bren said in the announcement. But how does it all work? The successful experiment — known as MAPLE, short for Microwave Array for Power-transfer Low-orbit Experiment — demonstrated two key functions: the ability to send a concentrated beam of energy to receivers at will and the possibility of beaming power to a specific location on Earth. Space Solar Power involves collecting solar energy in space, converting that energy into electromagnetic waves and beaming those waves to receivers on Earth. The benefit is that solar cells in space are able to collect eight to nine times more power than solar cells on Earth by eliminating the inefficiencies of atmosphere, seasons and the day-night-cycle. The first of the MAPLE experiments tested the technology’s ability to successfully direct a beam of energy at a precise location in the harsh environment of space. To do it, Hajimiri’s team directed a microwave beam from the transmitter arrays in space to one of two LEDs also onboard the satellite. Each LED individually lit up when the microwaves were directed at its receiver, proving that the beam could be precisely directed at targets. A second experiment consisted of directing the energy beam from MAPLE to a receiver on the roof of the Moore Laboratory on Caltech’s campus. By ensuring that the receiver on earth picked up the signal at a predetermined time and frequency the researchers at Caltech were able to conclude that they had successfully received energy on Earth from the orbiting experiment. The SSPP team envisions a future where fleets of thousands of lightweight solar satellites orbit the globe, collecting solar energy and beaming it down to receivers on the ground. Alongside the MAPLE experiment, the Momentus satellite also holds experiments testing ultralight photovoltaic technologies and flexible, lightweight
spacecraft structures, both of which will be integral for the realization of this vision. Additional results from MAPLE, along with data from the other experiments onboard, are being collected by the SSPP team. Caltech President Thomas F. Rosenbaum said the milestone foreshadows “a remarkable payoff for humanity: a world powered by uninterruptible renewable energy.”