Caltech Team Demonstrates Wireless Power Transfer in Space, Beams Power Down to Earth
Space advocates have long dreamed of large solar power satellites capable of beaming clean energy down to Earth. That dream took a step toward reality recently when Caltech’s Space Solar Power Demonstrator (SSPD-1) wirelessly transmitted power in space and beamed detectable power to Earth for the first time.
SSPD-1 is the first space-based prototype of Caltech’s Space Solar Power Project (SSPP). The payload was launched as a hosted payload on Momentus’ Vigoride 5 orbital transfer vehicle (OTV) aboard SpaceX’s Transporter-6 mission on January 6.
The power was transmitted by the Microwave Array for Power-transfer Low-orbit Experiment (MAPLE), which is one of three technologies being tested on SSPD-1. MAPLE consists of an array of flexible lightweight microwave transmitters controlled by custom electronic chips built using low-cost silicon technologies.
“Through the experiments we have run so far, we received confirmation that MAPLE can transmit power successfully to receivers in space,” Caltech electrical and medical engineer Ali Hajimirisaid, co-director of the project, said in a news release. “We have also been able to program the array to direct its energy toward Earth, which we detected here at Caltech. We had, of course, tested it on Earth, but now we know that it can survive the trip to space and operate there.”
MAPLE has two separate receiver arrays located about 1 foot (30 cm) away from the transmitter that converted the energy to direct current (DC) electricity and used it to light up a pair of LEDs. MAPLE lit up each LED individually and shifted back and forth between them.
“To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures. We are doing it with flexible lightweight structures and with our own integrated circuits. This is a first,” Hajimiri said in the release.
MAPLE also has a small window through which the array can beam energy. Researchers were able to detect transmitted energy using a receiver on the roof of Caltech’s Gordon and Betty Moore Laboratory of Engineering on May 22, marking the first time in history that energy was successfully sent to Earth from orbit.
In addition to MAPLE, SSPD-1 has two other experiments on board. ALBA consists of 32 different kinds of photovoltaic cells to evaluate which ones perform best in the harsh environment of space.
Then there’s the Deployable on-Orbit ultraLight Composite Experiment (DOLCE), which is a structure measuring 6 by 6 feet (1.8 x 1.8 meters) that is designed to demonstrate how to build, pack, and deploy a modular spacecraft.
Plans call for SSPP units to be folded into 1 cubic meter (35 cubic feet) packages and unfurled into flat squares measuring about 50 meters (164 feet) per side. Solar cells would be installed on one side to absorb energy from the Sun, while the other side would carry wireless power transmitters that would face Earth.
“In the same way that the internet democratized access to information, we hope that wireless energy transfer democratizes access to energy,” Hajimiri said in the news release. “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.”
Hajimiri and his 35-member team have philanthropist Donald Bren to thank for their program. Long intrigued by the possibility of space-based solar power satellites, Bren, the chairman of the Irvine Company and member of the Caltech Board of Trustees approach then-president Jean-Lou Chameau in 2011 to discuss the creation of a research program.
Bren and his wife, fellow Caltech trustee Brigitte Bren, agreed to provide more than $100 million to support the program and endowed professorships through the Donald Bren Foundation.
“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 press release.
Northrop Grumman Corporation also provided $12.5 million between 2014 and 2017 through a sponsored research agreement to help fund the development of the technology.
“The transition to renewable energy, critical for the world’s future, is limited today by energy storage and transmission challenges. Beaming solar power from space is an elegant solution that has moved one step closer to realization due to the generosity and foresight of the Brens,” Caltech President Thomas F. Rosenbaum said in the release. “Donald Bren has presented a formidable technical challenge that promises a remarkable payoff for humanity: a world powered by uninterruptible renewable energy.”
