Energy

World-first space solar demonstration beams power from orbit to Earth

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How the DOLCE array will look once unfurled
Caltech
How the DOLCE array will look once unfurled
Caltech
The 50-kg SSPD, now in orbit, carries three major systems for testing
Caltech
Prototype of the flexible antenna sheet used in the system, which will enable the entire solar array to be rolled up for launch and unfurled in space
Caltech
Engineers loading the DULCE portion of the SSPD onto the Momentus Vigoride spacecraft prior to launch
Caltech
The SSPD team with the receiver array on the roof of a Caltech engineering lab
Caltech
Photo from orbit, showing the interior of the MAPLE module. Transmitter array to the right, receivers on the left
Caltech
LEDs in the MAPLE module light up to confirm wireless power transmission across a short distance
Caltech
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A Caltech team is celebrating the world's first space-based wireless power transmission, and the first time detectable levels of power have been beamed down to Earth. The Space Solar Power Project (SSPP) aims to unlock huge orbital clean energy resources.

Space-based solar could solve a lot of Earth's clean energy problems; an orbital solar setup can harvest sunlight 24/7 – and the good stuff, too, unmolested by atmosphere or weather conditions. Theoretically, the solar potential in space is eight times better per square meter than a solar panel on Earth.

Thus, several groups are attempting to get things started, despite some incredibly daunting challenges. One of which is the size of a useable array – as we pointed out just before this orbital prototype was launched, back in October last year. The eventual size of a commercially relevant space solar array might be around 3.5 square miles (9 sq km), with similarly massive receiver arrays down on Earth to capture the energy transmitted to the surface.

This could require as many as 39 space launches, even with the clever, ultra-lightweight, self-deploying modular array the Caltech team is working on. This would feature a series of modules, each around a cubic meter (~35 cu ft) at launch, but capable of unfurling into huge flat squares, around 50 meters (164 ft) per side, with solar cells on one side and wireless power transmitters on the other.

Of course, as we discussed when we wrote about this project last year, space launches are not cheap, and thus the economics look difficult as well, with a Levelized Cost of Energy (LCoE) predicted to be between US$1-2 per kWh –nearly six times the retail price of electricity in the USA.

Nonetheless, the project is charging full steam ahead, buoyed by more than US$100 million's worth of donations from Irvine Company chairman Donald Bren. And it's now announced the results of its first phase orbital prototype testing.

Engineers loading the DULCE portion of the SSPD onto the Momentus Vigoride spacecraft prior to launch
Caltech

The 50-kg (110-lb) Space Solar Power Demonstrator (SSPD-1) was loaded into a Momentus Vigoride spacecraft and sent into a low orbit by a SpaceX rocket on January 3 this year. It was designed to test three systems: the DOLCE module was designed to test design and deployment mechanisms for the lightweight, foldable structures the SSPP team hopes to use in a larger array. It's yet to begin unfolding. The ALBA module was there to test a number of different solar cell designs to see which would be most effective in space, and these tests are ongoing.

And the MAPLE (Microwave Array for Power-transfer Low-orbit Experiment) module was designed purely for early-stage verification of the wireless power beaming technology that would take solar energy and send it back to Earth, aimed precisely at receiver stations on the surface without any moving parts at the transmitter.

Part of this MAPLE test sequence involved a short-range power-beaming demonstration in which a transmitter array sent power to two different receiver arrays, only about a foot (~30cm) away from the transmitters. This was a chance to validate the team's beam-steering technology – which uses nothing but phase manipulation and constructive/destructive interference between waves to precisely direct the beams – in the harsh temperatures and radiation environment of space. And sure enough, the team was able to light up little LEDs on each receiver at will.

LEDs in the MAPLE module light up to confirm wireless power transmission across a short distance
Caltech

"To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures," said Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering and co-director of the SSPP team. "We are doing it with flexible lightweight structures and with our own integrated circuits. This is a first."

The MAPLE unit also has a small window through which the transmitter array was able to beam energy directly down to Earth, aimed at a receiver unit on the roof of an engineering lab at Caltech Pasadena. And again, this experiment was successful; the power beam was detected at the ground station, at the expected time and frequency, and with the correct frequency shift predicted based on the distance traveled.

This wasn't a useful amount of power, but it validates the team's ability to precisely target a power beam over great distances, and confirms that the gear involved can survive the trip to orbit.

"The flexible power transmission arrays are essential to the current design of Caltech's vision for a constellation of sail-like solar panels that unfurl once they reach orbit," said Sergio Pellegrino, Joyce and Kent Kresa Professor of Aerospace and Civil Engineering and co-director of SSPP.

"In the same way that the internet democratized access to information, we hope that wireless energy transfer democratizes access to energy," Hajimiri continued. "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."

So the technology for a space-based solar array is absolutely coming along nicely. As stated earlier, the economics of such a project in a commercial setting don't exactly look rosy, but who knows what kind of tricks a good business head might be able to use to turn those tables. Certainly a fascinating project to keep tabs on.

Source: Caltech

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8 comments
Chase
I was really hoping New Atlas' article on this was going to include some details about transmission efficiency and where they plan to park a full-size power plant in orbit. My best guess is that if they want to keep the keep the transmitters on the back side of the panels they will need to park the thing in L1, about a million miles from Earth. I know you can do some fancy things with microwave transmissions, but at some point massive signal power losses are inevitable. Even then, the ground stations are moving targets that can only get power during the day when terrestrial solar panels are at maximum chooch as well. The only way for 24/7 power is to park the plant in geosynchronous orbit, but then the solar panels and transmitters have to move a lot relative to each other in order to keep sight of both targets, and I'm assuming Isaac Newton might have some concerns about that. You'd have to burn fuel to counter the constant motion. Just my armchair analysis.
WONKY KLERKY
As writ previously:
Just wot will be the effects on atmosphere + anything, live or mechanical, flying through it directly through/in vicinity of beam ? ? ? ? ? ?
+
In the case of the inevitable misdirection of focus onto receiver:
Ground level adjacent buildings etc / land / vehicles AND . . . .................. BODS ? ? ? ? ? ?
vince
To male it cost effective they need to get working first a space elevator using 62000 mile long carbon nanotube elevatirs capable of raising materials at a cost of $100 to $400 a pound which is 2 orders of magnitude cheaper than spaceX launched materials (about $20,000 per pound). If we had a space elevator functioning then space based solar transmitted by lasers would be 10 times cheaper than current estimates and cheaper than ground based solar due to 24/7 solar power without neesd for storage.
Malatrope
I just want to point out that these things are already solved. Any data transmission going through a Starlink receiver could be rectified to produce "a tiny amount of power". Yes, in this case the beam forming array (electronic beam steering has been around for 50 years) is on the ground rather than in orbit, but the problem is the same no matter which direction it goes. This project seems mainly to resemble a student technology demonstration of things we already know how to do.
CraigAllenCorson
"the first time detectable levels of power have been beamed down to Earth"
Not quite. Radio communication waves are "detectable levels of power", and we have been beaming those down to Earth ever since Sputnik.
TpPa
They should be able to fill in the gaps between all the internet satellites going up
ljaques
@Wonky, I'd guess that they would need to determine NO FLY zones above the receivers, and they'd have to ensure that no planes or satellites flew through the beamed energy. Everything would be hunky dory as long as everyone stayed in their NO FRY zones and the transmitter stayed focused on the receiver.
MCG
I would think the geothermal cutting-edge tech just written about today by New Atlast will give this team a run for its money, however, it appears to be an excellent system for emergencies, developing communities, and indigenous communities needing to get "on the map".