Solar panels on Earth already provide us with a clean energy source, but they can be a blot on the landscape and practically useless after dark.
Scientists in California have now found a solution: sending solar panels into space so that they can use the power of the sun 24/7.
In a world first, the researchers beamed solar energy to Earth from a spacecraft called MAPLE, which launched into orbit in January.
MAPLE is equipped with solar panels that can withstand ‘the harsh conditions of space’, including wild temperature fluctuations and solar radiation.
“Space solar power” – a concept coined by science fiction writer Isaac Asimov in 1941 – could potentially produce eight times more energy than solar panels at any location on the Earth’s surface.
Above the Earth, there are no clouds and no day or night to obstruct the sun’s beam – making a solar station in space a constant green power source
The project is led by Caltech’s Space Solar Power Project (SSPP), which aims to harvest solar energy in space and send it to the Earth’s surface as a permanent energy source.
What is solar energy in space?
Solar energy in space is a concept of generating electricity from solar energy in space and then sending it to Earth.
A spacecraft uses solar panels to capture solar energy. A “power transfer system” then converts the solar energy into a form that can be transmitted to Earth, such as microwaves or lasers.
Receivers on Earth then convert the emitted energy back into electricity that can be supplied to a national grid.
SBSP has the potential to provide the world with a large, reliable and clean source of energy.
The experts hope it can provide a better green alternative to fossil fuels and even renewable energy sources such as geothermal, wind and nuclear power.
“Through the experiments we’ve done so far, we’ve got confirmation that MAPLE can successfully transfer power to receivers in space,” said Ali Hajimiri, a professor of electrical engineering at Caltech.
“We’ve also been able to program the array to direct its energy toward Earth, which we’ve detected here at Caltech.
“We had tested it on Earth, of course, but now we know it can survive the journey to space and operate there.”
Solar panels on Earth consist of several ‘solar cells’ – small devices that convert radiation from the sun into electricity.
Solar cells have existed on Earth since the late 1800s and currently generate about 4 percent of the world’s electricity, in addition to powering the International Space Station.
But critics of the technology point out that they often don’t work in countries that are plagued by cloudy weather for most of the year, such as the UK.
Other problems with the technology in general are that these panels take up a lot of ground and can be an eyesore, often on green land that could be cleared for other uses.
The Caltech team therefore developed MAPLE, short for Microwave Array for Power-transfer Low-orbit Experiment, which was launched on Jan. 3 aboard the Transporter-6 mission from Cape Canaveral.
Artist’s rendering of what the Caltech team’s in-space solar energy demonstrator looks like when unfolded
MAPLE consists of a series of flexible lightweight microwave power transmitters powered by electronic chips built with low-cost silicon, the team said.
They need to be flexible so they can fold into a package that can be carried in a rocket and then unfold once in orbit, much like NASA’s James Webb Space Telescope.
MAPLE’s transmitters convert the solar energy into a form that can be sent back to Earth, such as lasers or, in this case, microwaves.
The array of transmitters can direct the energy to desired locations, such as a receiving station on Earth that feeds power into the national grid.
As the first in the world, MAPLE’s emitted energy was detected by a receiver on the roof of a building on Caltech’s campus in Pasadena, California.
The received signal appeared at the “expected time and frequency,” according to the experts, and had the correct change in frequency as predicted from its journey from space.
“As far as we know, no one has ever demonstrated wireless energy transfer in space, even with expensive, rigid structures,” said Professor Hajimiri.
‘We do it with flexible lightweight constructions and with our own integrated circuits – this is a first.’
Ultimately, the academics envision a “constellation” of spacecraft that will collect sunlight, convert it into electricity, and then wirelessly transmit that electricity over long distances where it is needed.
This may be especially important for the places that do not currently have access to reliable power, such as developing countries.
It’s unclear what will now happen to the orbiting MAPLE spacecraft, or if it will form the basis of this constellation.
Photo from space of the interior of MAPLE, with the transmission array on the right and the receivers on the left
Sensing current from MAPLE on the roof of the Gordon and Betty Moore Laboratory of Engineering on Caltech’s campus in Pasadena, California
However, according to the Caltech team, the technology is not quite ready for large-scale application, as solar power generation and transmission needs to be rethought for large-scale use in space.
Solar panels are bulky and heavy, making them expensive to launch, and they require extensive wiring to transfer power.
Professor Hajimiri’s team is now assessing the performance of individual elements within the system – a ‘precise process’ that can take up to six months.
Once complete, the team can track anomalies and trace them back to individual units, providing insight for the next generation of the system.
Caltech is not alone in its solar energy efforts in space; the UK government is also exploring the feasibility of building solar power stations in space.
In 2020, it commissioned new research into the concept of such solar plants as a way to meet the Earth’s growing energy needs.
A brief history of solar energy in space
The idea of Space-Based Solar Power stations has been around since 1941.
Science fiction writer Isaac Asimov first wrote about it in the short story Reason.
In the story, he wrote about a space station that transmits energy collected from the sun to different planets using microwave beams.
There were a number of concept designs from the 1970s, but they were not considered economically viable.
The basic concept includes a space station with a solar panel to convert solar energy into electrical energy.
Then it would use a microwave transmitter or laser transmitter to send the energy to a collector on Earth.
The UK has joined Japan, China, Russia and the US in pursuing the idea of power generation in space.
As of 2008, Japan made the idea of solar energy in space a national goal.
Advantages of the technology include the fact that it is always solar noon in space with a full sun.
Collecting surfaces can also receive more intense sunlight than on Earth.
However, they would be large satellites that cost a lot of money to launch – although launches have become cheaper thanks to commercial firms.