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Cal-Tech Scientists Transmit Space-Based Solar Power to Earth For First Time

Cal-Tech Scientists Transmit Space-Based Solar Power to Earth For First Time

Meanwhile, the Japanese are working on similar technology that will make an attempt to beam solar energy from space in 2025.

In an amazing breakthrough for energy development, scientists from the California Institute of Technology have successfully demonstrated that solar energy can be collected in space and beamed down to Earth in a seemingly endless supply.

The institution announced Thursday a power signal transmitted by a small demonstration unit orbiting 550 kilometers above the planet was recently detected by a receiver on the rooftop of a laboratory on Caltech’s Pasadena campus.

Ali Hajimiri, Bren professor of electrical engineering and one of two co-directors on the project, confirmed transmission occurred May 22.

“It took a few moments for it to sink in, then everybody got really excited,” he said in an interview Thursday. “This technology for wireless energy transfer can have a tremendous impact on lives, both on Earth and in space.”

The 50-kilogram Space Solar Power Demonstrator (SSPD-1) is testing three key technologies that would make it possible to convert sunlight into electrical energy and then send it in the form of microwaves to receivers anywhere on the planet.

The wireless power transfer was demonstrated by MAPLE (Microwave Array for Power-transfer Low-orbit Experiment). The array was one of three key technologies that were being tested being tested. The unit consists of an array of flexible, lightweight microwave power transmitters driven by custom electronic chips that were built using low-cost silicon technologies.

It uses the array of transmitters to beam the energy to desired locations. For SSPP to be feasible, energy transmission arrays will need to be lightweight to minimize the amount of fuel needed to send them to space, flexible so they can fold up into a package that can be transported in a rocket, and a low-cost technology overall.

MAPLE was developed by a Caltech team led by Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering and co-director of SSPP.

“Through the experiments we have run so far, we received confirmation that MAPLE can transmit power successfully to receivers in space,” Hajimiri says. “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.”

Meanwhile, the Japanese are working on similar technology that will attempt to beam solar energy from space in 2025.

Nikkei reports a Japanese public-private partnership will attempt to beam solar energy from space as early as 2025. The project, led by Naoki Shinohara, a Kyoto University professor who has been working on space-based solar energy since 2009, will attempt to deploy a series of small satellites in orbit. Those will then try to beam the solar energy the arrays collect to ground-based receiving stations hundreds of miles away.

Using orbital solar panels and microwaves to send energy to Earth was first proposed in 1968. Since then, a few countries, including China and the US, have spent time and money pursuing the idea. The technology is appealing because orbital solar arrays represent a potentially unlimited renewable energy supply. In space, solar panels can collect energy no matter the time of day, and by using microwaves to beam the power they produce, clouds aren’t a concern either.

However, even if Japan successfully deploys a set of orbital solar arrays, the tech would still be closer to science fiction than fact. That’s because producing an array that can generate 1 gigawatt of power – or about the output of one nuclear reactor – would cost about $7 billion with currently available technologies.

It costs about $5 billion to build one nuclear power plant. So, a solar array would be marginally more expensive.

I am for developing both technologies, as we will see which one can deliver the energy goods.


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smalltownoklahoman | June 5, 2023 at 7:20 pm

Not the first time I’ve heard of this tech but I’m glad to see it’s being tested. Would like to see this country reembrace nuclear too for long term energy needs.

Leslie, my apologies. This is the first I have heard of this news. We all need to know about this.

RFK Jr. on the murder of his father — a family friend had him read the reports.

Tesla was experimenting on electrically creating a link to the ionosphere to tap into the power. But they may be beyond the brain power of even Cal-Tech.

henrybowman | June 5, 2023 at 8:23 pm

Microwaves sent from beyond /
Cook duck soup in Walden Pond /
And wait until you see the havoc /
Dodging beams cause our air traffic.

    gibbie in reply to henrybowman. | June 5, 2023 at 8:47 pm


    I didn’t think of air traffic. I was thinking of faulty aim.

    In order to produce enough energy to be useful, the microwaves would have to be extremely dangerous.

    Sigh. No, microwave power transmission will be with *un* pulsed waves, so you could stand in the full-power beam and get nothing more than slightly warmer, and passing aircraft would not even have their radios disrupted. A full-size receiving antenna would be a one-mile circle made up of thousands of hand-sized diodes producing a gigawatt or more power 24/7/365 regardless of cloud cover or sunlight.

      smalltownoklahoman in reply to georgfelis. | June 5, 2023 at 9:24 pm

      Yes, IIRC death beams from space is one of the misconceptions that had to be dealt with. People just hear microwave and immediately thing it’s going to cook whatever it’s aimed at.

        henrybowman in reply to smalltownoklahoman. | June 5, 2023 at 9:47 pm

        Not exactly a layman. Spend a decade prior to retirement erecting large wireless point-to-points in the 2.4-5GHz range, complete with the requisite FCC/OSHA warning labels. And they only had the power to send signal under two miles, never mind power.

        The risk isn’t so much ending up like David Koresh as it is ending up like Dianne Feinstein.

      randian in reply to georgfelis. | June 6, 2023 at 5:52 am

      I’m not impressed. A nuclear station produces a hell of a lot more than a gigawatt while not requiring the destruction of more than 3 square miles of land to do it.

        “Destruction” is a bit dramatic for draping a collection of hand-sized Schottky diodes on pole across a mile-wide circle, far less dense than solar cells, more like netting that should let enough sunlight through to use the ground below for cattle grazing.

      oneoclock in reply to georgfelis. | June 9, 2023 at 9:51 am

      Uh, RF energy at microwave frequencies does not need to be pulsed to be dangerous.

    scooterjay in reply to henrybowman. | June 5, 2023 at 8:58 pm

    Sweeping Beam Of Death, be gracious and incinerate us in 33 milliseconds. I don’t want to suffer.
    In the sweet, Holy name of AI we gaslight,

E Howard Hunt | June 5, 2023 at 8:39 pm

Let me know when they can clean my dishes in under 2 hours from outer space.

The giant windmills, that destroy ocean ecology, will be obsolete a symbol of greed and stupidity.

Wait til they focus 369 gigawatts of microwave energy on reservoirs for large cities and boil off the water?
Don’t underestimate rf energy.

Could we put a receiver on President Biden, to power him up?


thad_the_man | June 5, 2023 at 10:14 pm

As a physicist ( HEP/GR) I have to ask, how lossy is this? I’ve heard of this before ( at least 30 years before) , and worried about losses and how that affects weather.

    henrybowman in reply to thad_the_man. | June 6, 2023 at 2:11 am

    I’m familiar with the communications microwave frequencies, from 900MHz to 60GHz.

    A standard joke in the industry is, “If your signal path is clear, use 5GHz. If it intersects a tree, use 2.4GHz. If it intersects two trees, go down to 900MHz. For three or more trees, use a chainsaw.” By the time you get up to 60MHz, high humidity or fog will smother your signal, much less rain.

    I notice a distinct lack of any references to frequency or wavelength in any of the cited resources. Deliberate, or dumbing-down?

healthguyfsu | June 5, 2023 at 10:28 pm

How about we just harvest bolts of lightning for 1.21 g(j)igawatts.

    henrybowman in reply to healthguyfsu. | June 6, 2023 at 2:12 am

    Possible, of course, but suffers from the same problem as wind power: is it going to be there when you need it?

      You just have to plan your time travel events to decent thunderstorms.
      On the plains of Kansas or in Texas, you can probably do so readily.

      healthguyfsu in reply to henrybowman. | June 6, 2023 at 11:57 am

      If we go back in time, we will know exactly when and where lightning will strike the clock tower. Old newspaper clipping are very reliable for this down to the second.

Wonder how they are going to mitigate the know side effects of MWW in humans such as depression not to mention the disruption of magnetic fields used by animals such as birds to migrate?

inspectorudy | June 6, 2023 at 4:42 am

As we see from science, many things are possible but not practical. How many years have we heard about nuclear energy from fusion? They recently showed it possible but the equipment is so huge and expensive for the little power generated that it is decades away if ever. The same thing happens in the medical field. Time and money usually win out if the invention offers a major change in results. One thing to be considered is the maintenance of any space-borne device. An earth-bound nuclear reactor can be repaired expensively but quickly. A space-borne power plant is another whole story. Also, it would be completely vulnerable to enemy destruction. A 7 billion dollar plant that could be damaged or destroyed with very little effort by a villain like the Chinese blaming it on a faulty guidance computer on a cheap satellite. I’m no humbug but this is nothing to get excited about. A breakthrough in battery technology would be something that would really cause a stir.

Never underestimate these schemes “unintended consequences”, which they always seem to be either uninterested in or to minimize, (see solar, wind, cloud seeding, and every other hair-brained scheme).
How about we just stop spending trillions upon trillions of dollars on all this stuff since the whole climate change stuff is nothing but a huge fallacy to begin with, and pay off the debt or something that might actually accomplish something beneficial in the here and now.
Scientific progress toward good, sound and useful ends is always welcome. But this constant messing around with Mother Nature for the sake of a false premise to begin with is insanity.
We have all the energy we need to power the world right now but it doesn’t comport with the Lefts fake fear campaign of “We’re all gonna die!”

    henrybowman in reply to DelightLaw1. | June 6, 2023 at 3:11 pm

    “How about we just stop spending trillions upon trillions of dollars on all this stuff since the whole climate change stuff is nothing but a huge fallacy to begin with”

    To be fair, this field of investigation has little to do with “globular warmening” and more to do with “wicked cheap source of energy.”

“using microwaves to beam the power they produce, clouds aren’t a concern either.”

If that’s true, why do satellite TV and radio go wonky in bad weather?

“That’s because producing an array that can generate 1 gigawatt of power”

But a nuclear reactor or “fossil fuel” powered plant delivers the majority of the power it generates in the form of useable electricity. If the array in space generates 1 gigawatt of power, how much of that is actually delivered to the ground and converted into electricity?

There will be transmission losses and those will be increased in cloudy, rainy, humid, etc weather. Not to mention that as RF energy passes through rain, humidity, clouds, etc, it will transfer energy to them (see “microwave oven”). What effect will that energy added to the environment have on weather? The climate?

I’m no scientist but what I remember from my introductory physics class is “energy cannot be created, nor destroyed, only changed in form”. So, we’re going to capture energy from the sun that would have normally bypassed earth and beam it onto the planet. Some of that energy will be converted to heat through losses during transmission, more of it will be converted to heat after being received on earth and converted into electricity. Where does that heat go from there? Won’t we just be adding to the total amount of heat energy in the Earth’s ecosystem? Isn’t that pretty much the definition of “Global warming?” I thought that was bad.

Wouldn’t it be better to continue to convert energy that is already present on earth into forms usable by humans? Seems to me that’s much less damaging than adding energy to the system that otherwise would have been traveling through space unimpeded.

Maybe I’m completely out to lunch, but this does not seem to me like a good idea.

    henrybowman in reply to Sailorcurt. | June 6, 2023 at 3:19 pm

    Clearly the transmission problem is lossy compared to earthbound generation. And unless the density of the energy being received by the ground station (in joules per square meter) exceeds the values for terrestrial insolation, it’s a less efficient form of energy than just plain solar (not that solar is at all efficient next to alternative sources, especially nuclear).

    Now, reflect that in many places, the good old sun itself is enough to damage or kill you in a reasonably short time. What’s the comparative energy density of these microwaves? What’s the microwave equivalent of heatstroke?

    How many times more powerful than the sun is a pocket laser? Yet, you can bring down an aircraft (pilot) with one. Again, what’s the comparative energy density?

a power signal transmitted … was recently detected by a receiver
Just a note here – the beam was detected. There was nothing about it being useful, nor what level of power was actually received (compared to what was sent).

    docduracoat in reply to GWB. | June 6, 2023 at 10:17 am

    You have a valid point.
    However this shows that the technology is possible.
    It’s only a matter of ramping it up.
    And dealing the side effects that will inevitably occur.

    CaptTee in reply to GWB. | June 6, 2023 at 12:47 pm

    Of course, they aren’t talking about how much power will be lost by heat dissipation and how that will affect “man-made global warming”.

      henrybowman in reply to CaptTee. | June 6, 2023 at 3:20 pm

      Right. When somebody asks “what about clouds and fog” and the answer comes back “no problem, this beam will boil them away,” somebody else might get a clue.

There is this great scene in the movie “The Core” that shows what could happen if beaming power back to Earth were to go wrong

This sounds technically fascinating and laudable, but also impractical for any power solution at scale. We should be focusing on building more nuclear power plants, not on chimeric energy conceits.

    henrybowman in reply to guyjones. | June 6, 2023 at 3:25 pm

    Agreed. This is another case of “follow the political science.” This year, Germany is congratulating themselves on shutting down all their nukes. They lucked out with a mild winder this year. We haven’t heard the last consequence of this idiocy.

Huh. That entire thread that I commented on this morning was pulled down. MWW has been linked to much mental illness. Here is the link and this is hard science not “I read on Reddit” stuff

In this experiment, the power transmitted was 0.2 watts.
The power received was just enough to be detectable.

That suggests a very lossy transmission. In order to get 1 Mw of power on the ground, you would have to transmit much more.

Also, having Gw microwave beams pointed at the Earth’s surface is, in fact, very hazardous in spite of what some may say. My cousin worked on microwave antennas on Adak, and they used to stand in the beams to warm up a little. They all developed cataracts, and found that the microwaves had caused the cataracts. They all received medical disability. I can imagine what would happen to an airliner’s electronics if it flew through a Gw-level microwave beam.

    oneoclock in reply to OldProf2. | June 9, 2023 at 10:00 am

    Exactly. We have to measure RF levels in front of rooftop mounted cell site antennas to protect contractors who might inadvertently get in front of them. They are transmitting at about 10- 20 watts.

    So many people are screaming about exposure to 5G cellular signals. And now they want to beam 1,000 MW signals to earth at microwave frequencies? smh