Wireless Solar Power Transfer From Space

[GordMay]

Caltech's Space Solar Power Demonstrator Wirelessly Transmits Power in Space

Wireless power transfer was demonstrated on by MAPLE, one of three key technologies being tested by the Space Solar Power Demonstrator (SSPD-1), the first space-borne prototype from Caltech's Space Solar Power Project (SSPP). SSPP aims to harvest solar power in space and transmit it to the Earth's surface.

MAPLE, short for Microwave Array for Power-transfer Low-orbit Experiment and one of the three key experiments within SSPD-1, 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 ...

... Space solar power provides a way to tap into the practically unlimited supply of solar energy in outer space, where the energy is constantly available without being subjected to the cycles of day and night, seasons, and cloud cover—potentially yielding eight times more power than solar panels at any location on Earth's surface.
When fully realized, SSPP will deploy a constellation of modular spacecraft that collect sunlight, transform it into electricity, then convert it to microwaves that will be transmitted wirelessly over long distances to wherever it is needed—including locations that currently have no access to reliable power ...

More about ➥ https://www.caltech.edu/about/news/i...power-in-space

How Does Wireless Power Transfer Work?
Video ➥ https://youtu.be/w5SBF48WqV4

[stormalong]

Every radio transmitter in space aimed at the earth has "detectable power". Satellite spot beam technology is already in the microwave portion of the radio spectrum.

What is not stated in the article is any reference to efficiency. How much of the transmitted power can be received and utilized on earth. I am very skeptical about the practicality of this process. It is far more practical to convert solar power to electricity on earth and store it for night and inclement weather. That technology exists, is in common use today and will become more commonplace in the future. Obviously many (most?) cruisers and many thousands (millions?) of homeowners use this today.

There is enough solar energy arriving on earth in one day to power the planet for a year or more. I forget the statistic. It is there for us to harvest. No need to put solar collectors in space at great expense and with difficult or impossible maintainability.

The experiment that sends energy across a one foot gap to power two LEDs a joke. You can do the same thing on earth under any high tension power line or near any high power radio transmitter.

If Caltech gets $100 million for pure research that's fine but that same $100 million would be far better spent building a huge solar array in the desert and putting up a high tension power line.

[catalystcat]

This is actually kind of an open question.

Here is a paper that gives an overview of some of the power considerations, although I would take it with more than one grain of salt. (e.g., limiting the frequency to 2.45-5.8GHz; confusing things with unnecessary near field ramblings in a situation where you are pretty much never in the near field; misstating the antenna power conversion efficiency when citing phased arrays, and more.) https://eujournalfuturesresearch.spr...309-018-0139-7

As you can tell it suffers from the common problem of the writer's bias.
However, the basic format is not too terrible.

Regardless, space borne solar fields have a lot of advantages if you can solve the power beaming efficiency problems.
Note that for the orbits he discusses (GEO) it's pretty much always sunny, there can be very little "night time", there is no dust accumulation, there are fewer geographic and regulatory burdens (except for the part about not frying anything with hundred MW to GW RF beams,) etc. In some architectures, one can even skip the spaceborne battery storage and reduce the ground based storage requirements (no clouds or snow in space, and with dispersed systems, you can even have no night time).
Shorter wavelengths (if they avoid absorption bands) give effectively larger apertures and smaller diffraction. That can improve the numbers. Innovative low gravity architectures and adaptive aiming can also dramatically improve the amount of energy captured.
So, at first blush, it sounds pretty good.
But, as with most things, the numbers matter a lot and you trade one set of problems for another.

Since you are largely comparing apples to oranges when comparing ground based solar to space based solar, it requires a full economic analysis and a full design analysis. That is way, way, way beyond this thread.
For example, if you have multiple beam paths, you almost always have a space to ground path, even with large weather disturbances. So, you can save a ton of money by eliminating the old style baseload systems that you need for when your ground based solar is not producing.
Even if you could figure out the math, it all changes as the market changes. For example, the re-emergence of nuclear as the most green and effective long term base load energy source will likely disrupt the math, as will geopolitical impacts on fossil fuel usage and emerging savior technologies that could render fossil fuels CO2 competitive (see, e.g., Modern Hydrogen).

Bottom line is that we don't really have enough info to do a true analysis; any analysis we do requires predictions about the future state of technology, politics, and energy usage. As Yogi Berra said "It's tough to make predictions, especially about the future.

Since $100MM is a drop in the bucket for energy and wireless power transfer is becoming more important (ground based and elsewhere), I think it's not crazy to consider this kind of thing. There are a lot of more mundane applications anyway.

[GordMay]

Originally Posted by stormalong

... There is enough solar energy arriving on earth in one day HOUR to power the planet for a year or more. I forget the statistic. It is there for us to harvest. No need to put solar collectors in space at great expense and with difficult or impossible maintainability...

Less than half [maybe much less] of the solar energy, that reaches Earth [the top of the atmosphere, directly facing the Sun] is available to terrestrial photo-voltaic collectors.

About 30 percent of incoming solar radiation is reflected out into space, and plays no role . Of the remaining 70 percent, 23 percent of incoming solar radiation is absorbed in the atmosphere, either by water vapor, atmospheric particles, dust and ozone.
The remaining 47 percent passes through the atmosphere, and strikes the Earth’s surface, where it’s available to conventional solar panels.

That’s, still, way more power than we use.

[stormalong]

Originally Posted by GordMay

Less than half [maybe much less] of the solar energy, that reaches Earth [the top of the atmosphere, directly facing the Sun] is available to terrestrial photo-voltaic collectors.

About 30 percent of incoming solar radiation is reflected out into space, and plays no role . Of the remaining 70 percent, 23 percent of incoming solar radiation is absorbed in the atmosphere, either by water vapor, atmospheric particles, dust and ozone.
The remaining 47 percent passes through the atmosphere, and strikes the Earth’s surface, where it’s available to conventional solar panels.

That’s, still, way more power than we use.

Good, hour rather than day - way more energy available. Keep in mind that the energy absorbed by the atmosphere is not wasted. It is vital for warming the planet.

The only problem with huge solar farms on earth is the land required. Most of the currently unused flat land is concentrated in deserts far away from the energy demand. In the future it may be practical to power Europe from North African deserts. That is a topic also discussed by the science and engineering community. Still, power transmission through power lines, maybe superconductors seem to be more manageable than transmitting it from geostationary orbit, 23,300 miles above the surface of the planet. Another future possibility is that manufacturing and with it population would migrate towards the energy sources.

Still, although a very interesting topic, what does it have to do with cruising on boats?

[donradcliffe]

There's going to be some big safety issues with the energy beam. The ground around the concentrated solar thermal plant at Ivanpah is littered with roasted bird carcasses.

[GordMay]

Originally Posted by donradcliffe

There's going to be some big safety issues with the energy beam. The ground around the concentrated solar thermal plant at Ivanpah is littered with roasted bird carcasses.

The Ivanpah Solar Electric Generating System is a concentrated solar thermal plant, in the Mojave Desert.

It’s important to put that bird death toll in context.
Every year as many as 988 million birds, or nearly 10% of the US’ avian population, die from colliding with windows, according to a study*, published in 2014.

* “Windows may kill up to 988 million birds a year in the United States”
➥ https://www.sciencenews.org/article/...-united-states

The oil industry contributes far more, to bird deaths, each year, than the worls’s largest [392 megawatt] solar-thermal power plant, at Ivanpah.

More than one million birds died, due to the Deepwater Horizon oil spill.
Every year an estimated 500,000 to 1 million birds are killed in oilfield production skim pits, reserve pits, and in oilfield wastewater disposal facilities.
Up to 402,000 birds have died. due to oil development ,in Canada’s tar sands.

The Center for Biological Diversity, estimates that 28,000 birds are cooked annually at Ivanpah; the owner, BrightSource Energy, puts the number at 1,000.
The birds are called “streamers”, for the trail of smoke, that follows behind them, as they plunge to Earth.

This Mojave Desert solar plant kills 6,000 birds a year ~ LA Times
“... Federal biologists say about 6,000 birds die from collisions or immolation annually while chasing flying insects around the facility’s three 40-story towers, which catch sunlight from five square miles of garage-door-size mirrors to drive the plant’s power-producing turbines...”
➥ https://www.latimes.com/local/califo...nap-story.html

The environmental, and safety impacts, of microwave wireless power transmission systems, must also be considered.
Potential effects on people, wildlife, plants, and ecosystems need to be thoroughly assessed, to ensure that the deployment of such systems, does not pose unacceptable risks.

It will be crucial, to mitigate potential risks, associated with prolonged exposure to high-power [non-ionizing] microwave beams.
Proper beam alignment will be crucial, to maximize the efficiency of power transfer, and minimize unintended exposure to microwave radiation.
Precise beamforming techniques, and tracking mechanisms, should ensure that the microwave beam is accurately directed, towards the intended receiver, reducing the risk of exposure to unauthorized, or unintended targets.

[GordMay]

‘Greening’ the electricity grid faces many obstacles: local opposition to energy projects, affordability concerns, a lack of grid connections between utilities, etc.


Eliminating the remaining emissions from our electricity supply is, also, only half of the job. Total electricity generation will have to be, something like, twice greater, by 2050, as our populations grow, and as electricity becomes the dominant energy source, for powering cars and home heating.

As the search for clean energy sources continues, and the costs of climate change continue to rise, the costs, and challenges, of building space-based solar power generating stations may become more reasonable, especially as we start looking off the planet, to satisfy our growing energy needs.

At the end of the day, nobody has an interest in a grid, that's not reliable, or, that's not affordable.
And, we all have an interest, in a grid that's ‘clean’.

Since, I doubt, that there will be any single transformative [magical?] technological solution to green power; I believe it behooves us, to explore all possible solutions.

[catalystcat]

Some random notes on the comments above, because it helps me avoid getting back in the water to finish cleaning my hull:


1. Regarding energy usage - remember, discussing this from a US/Euro/Asia centric viewpoint overlooks that African population is projected to exceed US plus Europe population by 2050. https://www.statista.com/statistics/...ent-1950-2020/ And, India is now (or soon will be) the world's most populous country. https://www.un.org/development/desa/...ulous-country/
While current energy usage stats per person are lower for India and way lower for Africa, that gap will shrink. So, in considering energy consumption and generation, and environmental affects, you need to take India, Africa and other regions into account.

2. Ultrahigh voltage is the way to go for much of ground based power transmission. The higher voltage means lower currents, thus lower resistive loss. (I will avoid discussion of "imaginary/reactive component" of power sloshing around the grid and producing its own energy waste - https://clouglobal.com/the-hidden-fo...%20supply%20it. )

The US and much of Europe has invested a lot in the grid components with an assumed maximum voltage. It also assumes AC voltages and currents. That means retrofitting will be expensive. Since China started with a more clean slate, it has begun implementing ultrahigh voltage as it expands - https://www.reuters.com/business/ene...rt-2022-08-03/ . It has also implemented some of this as DC power.
Much of Africa is also a clean slate (leaving aside megacity local infrastructures, like Lagos)
So, the analysis of best is likely regionally different.

3. The impact on animals of large green projects is pretty complex and is impaired by almost religious beliefs on both sides. So, both sides tend to talk past each other. That makes it difficult to discuss things like carbon footprint of wind farms (concrete, carbon materials, etc.) and other impacts.

To give one example, I will refer to the problem of birds. Array-type thermal solar fields have a similar problem to beamed power. They grab a lot of energy and concentrate and direct it somewhere. In a large array, the concentrated temperature can destroy usual materials, even things as tough as SiC. So, anything flying through the concentrated area pretty much gets fried.

Wind farms have an analogous problem in that birds get hit by blades and killed.

Here's a weird thing - in speaking with a large energy infrastructure company a few years ago, they noted that they get little blowback when the windfarm killed a bunch of "regular" birds or bats. But, let one or two raptors get killed, and the blowback gets intense. What makes this even trickier, is that some raptors like to float in the updraft of windy areas. That led to a whole lot of raptor deterrent inventions.

I don't know if anyone has done anything close to a comparative analysis of bird deaths from wind farms vs. thermal solar vs. beamed power (there are ground based beamed power demonstrators) vs anything else.

4. There are a ton of factors that go into analyzing any proposed system. As a simple example, adding a bunch of conventional solar panels to cover a large section of desert could change a large area from white (energy reflective) to dark (energy absorptive). At some scale this could impact the earth's albedo. But, if you make the solar panels absorb at conversion wavelengths but reflect at mid to far infrared, you could theoretically get your solar power, but increase the thermal reflectivity of that desert. So, something as simple as a wavelength selective filter/reflector changes the analysis of this factor by a LOT.


5. A bit of a rant to end - It's complex, people are raising good points, and we should figure out how to evaluate and compare the different approaches in a somewhat quantitative fashion without all the chest beating and attacking of the messengers. There are tons of really good ideas out there.


At the end of the day, the issue becomes one of a failure to really, accurately and honestly look at all of the impacts of any of the systems people propose versus existing systems. Any honest discussion gets sidetracked by people on either side imposing biases, citing limited anecdotal evidence, and otherwise sabotaging the discussion.



In this forum, people have been remarkably open to issues on both sides and I haven't seen anyone yet called a blasphemer for identifying issues. That's great.

Now, if that behavior could only be translated to other discussions, like flashing anchor lights or LI battery safety or navigation issues.

[catalystcat]

Interesting article from last month. https://www.geekwire.com/2024/powerl...-beaming-moon/

These guys are real and have been developing this since 2007.

Disclaimer: The founders used to work for me and I had a small part in getting their startup going.