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.