Solar Power from Space? Caltech’s $100 Million Gambit

Billionaire makes secret donation for electricity from orbit

NED POTTER


A NASA artist's rendering from 1999 of a solar power station in orbit. Like many other space-based solar designs, it required many connected parts, which translates to considerable launch costs.
NASA


In 1941 Isaac Asimov, the science fiction writer, published a short story called "Reason." It was a cautionary tale about robotics and artificial intelligence, but it's also remembered now for its fanciful setting: A space station that gathered solar energy to send to the planets via microwave. Ever since, space-based solar power has been an out-there idea—something with potential to change the world, if we can ever master the technology, and muster the funds, to do it.

Donald Bren has done his share of reading about solar power, and since he is one of America's wealthiest real estate developers, he's in a position to help muster the funds. The California Institute of Technology has just announced that, since 2013, Bren and his wife Brigitte have given the school more than US $100 million to help make photovoltaic power from orbit a reality.

That's a lot of money, and, importantly, the work has been spread out over a decade. A team at Caltech is aiming for the first launch of a test array in late 2022 or 2023.

"This is something that's pretty daring," says Ali Hajimiri, a professor of electrical engineering and a co-director of Caltech's Space Solar Power Project. The long timeline, he says, "allows you take chances, and take risks. Sometimes they pay off and sometimes they don't, but when you do that, in an educated, controlled fashion, you end up with things that you never expected."

Bren, 89, made most of his fortune—estimated between $15.3 billion and $16.1 billion—building offices and homes in Orange County, California. He is majority owner of New York City's iconic MetLife Building. He's also donated land and money for environmental conservation. He gives few interviews (he declined to speak for this story), and while Caltech's Space Solar Power Project has been public, Bren's support of it was a secret until now.

High Earth orbit is a great place for a solar farm—the sun never sets and clouds never form. But to generate a meaningful amount of electricity, most past designs were unrealistically, and unaffordably, massive. Engineers depicted giant truss structures, usually measured in kilometers or miles, to which photovoltaic panels or mirrors were attached, absorbing or concentrating sunlight to convert to direct current, then transmit it to the ground via laser or microwave beams. Hundreds of rocket launches might be needed to build a single installation. It was technology too big to succeed.

"What was really required to make this compelling was to have a paradigm shift in the technology," says Harry Atwater, the Howard Hughes Professor of Applied Physics and Materials Science at Caltech and a leader of the project. "Instead of weighing a kilogram per square meter, we're talking about systems we can make today in the range of 100 to 200 grams per square meter, and we have a roadmap for getting down to the range of 10 to 20 grams per square meter."

How? Through no single step, but perhaps the biggest change in thinking has been to make solar arrays that are modular. Lightweight gallium-arsenide photovoltaic cells would be attached to "tiles"—the fundamental unit of the Caltech design, each of which might be as small as 100 square centimeters, the size of a dessert plate.

Each tile—and this is key—would be its own miniature solar station, complete with photovoltaics, tiny electronic components, and a microwave transmitter. Tiles would be linked together to form larger "modules" of, say, 60 square meters, and thousands of modules would form a hexagonal power station, perhaps 3 km long on a side. But the modules would not even be physically connected. No heavy support beams, no bundled cables, much less mass.

"You can think of this as like a school of fish," says Atwater. "It's a bunch of identical independent elements flying in formation."

Transmission to receivers on the ground would be by phased array—microwave signals from the tiles synchronized so that they can be aimed with no moving parts. Atwater says it would be inherently safe: microwave energy is not ionizing radiation, and the energy density would be "equal to the power density in sunlight."

Space solar power is probably still years away. Analysts at the Aerospace Corporation's Center for Space Policy and Strategy caution that it "will not be a quick, easy, or comprehensive solution." But there is ferment around the world. JAXA, Japan's space agency, is hard at work, as is China's. Launch costs are coming down and new spacecraft are going up, from internet satellites to NASA's moon-to-Mars effort. The Aerospace Corp. analysts say terrestrial power grids may not be the first users of solar power satellites. Instead, they say, think of…other space vehicles, for which a microwave beam from an orbiting solar farm may be more practical than having their own solar panels.

"Is there a need for a lot of additional work? Yes," says Hajimiri. But "some of the ingredients that were major showstoppers before, we are moving in the direction of addressing them."

All of this has the Caltech engineers excited. "It's important for us to be willing to take chances," Hajimiri continues, "and move forward with challenging problems that, if successful, would work toward the betterment of our lives."


Ned Potter  a writer from New York, spent more than 25 years as an ABC News and CBS News correspondent covering science, technology, space, and the environment.

Space Solar Power Project Set To Go Ahead Thanks To $100 Million Donation


TO MAKE THE OLD CENTURY-OLD DREAM OF SOLAR POWER BEAMED FROM SPACE A REALITY, ONE OF THE REQUIREMENTS IS ULTRATHIN, ULTRALIGHT SOLAR CELLS INTEGRATED WITH ANTENNA THAT CAN BEAM THE ENERGY PRODUCED TO RECEPTORS ON EARTH. IMAGE CREDIT: CALTECH


By Stephen Luntz

10 AUG 2021

Solar panels will soon be launched into space, not to power satellites or missions to other planets, but to test the practicality of beaming energy down to Earth. A prototype launch of this old dream is planned for 2023.

No matter how cloudy the weather where you live, there is somewhere 100 kilometers (62 miles) away that gets more sunlight than any desert; low Earth orbit. For decades this observation has inspired the idea to place solar cells in space, turn sunlight into electricity, and beam it down to Earth for use. The idea was proposed in the 1920s, and the first technical paper was published in 1968. At a minimum, there are no clouds to interfere, and if the panels are moved sufficiently far they can avoid the Earth's shadow, allowing them to collect sunlight 24/7, eliminating solar's intermittency problem.

Caltech trustees Donald and Brigitte Bren believe in the idea so strongly they donated more than $100 million dollars for Caltech to explore it, originally anonymously, in what is now called the Space-based Solar Power Project (SSPP). The Brens aren't investing in the idea and have no commercial interest in any development that may come out of it. “It shows the magnitude of the generosity," said Caltech Professor Ali Hajimiri, co-director of the SSPP, in a statement. "They really want to change the world and truly see this as an opportunity to make a lasting difference for the planet, while generating a broad range of novel technologies with impact in many areas such as wireless power, communications, and sensing."

Bren's contribution will literally get the project off the ground, but there remain very big questions about whether the idea will ever be viable compared to using batteries or other storage for electricity produced from ground-based solar. Once the electricity has been produced it needs to be beamed back to Earth, which the SSPP plans to do with radio frequency electrical power. This then needs to be captured and turned back into electricity, inevitably with some losses, before it is ready to use.

The initial prototypes will measure 1.8 meters by 1.8 meters (6 feet by 6 feet) and weigh about 4 kilograms (9 pounds), a tenth of the lightest solar cells previously manufactured. Conversion to radio frequency waves for transfer is integrated into the cells, avoiding the need to concentrate power at a central point.

Many satellites have larger solar arrays, so we know this is possible. However, it's still very expensive. After all, it costs an estimated $250,000 to take a person on a suborbital joyride.

In addition to the technical problems the project must face, it will also attract some other objections. Even people unsympathetic to 5G conspiracy theories or tales of wildfire-causing space lasers, may be worried about the targeting of beams carrying the energy to power a city.

Moreover, ground-based solar power promises to democratize electricity production. Some of the population can afford to put solar panels on their roofs, backed up with a battery system, giving themselves independence from power companies. Space solar power goes the opposite way, almost certainly operating on scales beyond anyone but governments and the world's largest companies.

On the other hand, even if the idea never works as planned, the advances in ultralight solar collection and transmission may have other uses that justify the investment.