Energy

China tests world-first full-function space solar verification tower

China tests world-first full-f...
Xidian University has built a 75 meter-tall ground verification system to perform and test all phases of space-based solar power generation and transmission
Xidian University has built a 75 meter-tall ground verification system to perform and test all phases of space-based solar power generation and transmission
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Xidian University has built a 75 meter-tall ground verification system to perform and test all phases of space-based solar power generation and transmission
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Xidian University has built a 75 meter-tall ground verification system to perform and test all phases of space-based solar power generation and transmission
Members of the research team with the ground verification system
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Members of the research team with the ground verification system
The 75 meter-tall tower holds up a mock satellite capable of tracking the Sun, concentrating solar energy, converting it into electricity, then converting it again into microwaves and beaming it to a rectenna on the ground some 55 meters below
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The 75 meter-tall tower holds up a mock satellite capable of tracking the Sun, concentrating solar energy, converting it into electricity, then converting it again into microwaves and beaming it to a rectenna on the ground some 55 meters below
The facility began construction in 2018
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The facility began construction in 2018
China's Xidian University has built the world's first space solar ground verification system capable of performing and testing all phases of space-based solar power collection and transmission
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China's Xidian University has built the world's first space solar ground verification system capable of performing and testing all phases of space-based solar power collection and transmission
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In many ways, space is the perfect place for a solar energy array. There are no clouds in the way, no seasonal variability, no atmospheric filtering, and your solar panels can operate at peak efficiency around the clock, since the planet doesn't block the Sun. Put a solar panel in space, according to some estimates, and it'll generate 6-8 times more energy than it can down here on Earth.

Getting the power back down to the surface? Now there's the problem. Geosynchronous orbit, in which a satellite stays more or less right above a single point on the Earth, is about 36,000 km (22,500 miles) up in the air. That's nearly three times the width of the Earth, and a bit further than most extension leads can reach. Transmission, plus the hideous expense of space launches, has been the problem.

But space launch costs are coming down with the advent of reusable rockets and alternative launch technologies, and the world is in desperate need of reliable clean energy, so research on space solar continues, particularly focused on improving the efficiency of wireless power transmission, in the hope that we're just a couple of breakthroughs away from commercially competitive extra-terrestrial power generation.

China's Xidian University has built the world's first space solar ground verification system capable of performing and testing all phases of space-based solar power collection and transmission
China's Xidian University has built the world's first space solar ground verification system capable of performing and testing all phases of space-based solar power collection and transmission

One such research project concerns this "full-link, full-system space solar power ground verification system," built at Xidian University in Xi'an, North-Central China – a former capital of China under many dynasties and a city best known to the Western world as the place where 8,000-odd terra cotta warriors were found in a subterranean chamber back in the 70s.

Under the direction of Duan Baoyan, this 75-m (246-ft)-tall ground verification system, which began construction in 2018, has been designed to enable research into "high-efficiency light concentrating and photoelectric conversion, microwave conversion, microwave emission and waveform optimization, microwave beam pointing measurement and control, microwave reception and rectification, and smart mechanical structure design."

According to a Xidian University press release, the facility has recently been approved by a group of visiting experts after demonstrating wireless microwave transmission of power across a 55-m (180-ft) distance. It's the first system in the world to cover the full range of space solar functions, including tracking the Sun, concentrating light, converting it to electricity, transmitting it in microwave form, and receiving it at a separate rectenna – and the university says it's running successful tests some three years ahead of schedule.

Members of the research team with the ground verification system
Members of the research team with the ground verification system

The upper part of the structure suspends an array of dishes that acts as a surrogate satellite, focusing sunlight, converting it to energy and sending it down to the ground, where a rectenna dish collects it.

The research team is under no illusions: getting from 55 m to 36,000 km with high enough efficiency to make space solar worthwhile will "require successive struggles of several generations," according to the press release. It'll be a long time before money spent on this tech bears more fruit than simply building more solar arrays here on the Earth. Indeed, should a space-based energy transmission antenna be deployed, the ground-based rectenna array will most likely need to be several kilometers across in order to receive a useful amount of energy.

In the meanwhile, companies like New Zealand's Emrod are pushing forth on wireless microwave power transmission for applications closer to the Earth, like replacing high-voltage power lines across difficult terrain.

Source: Xidian University

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8 comments
8 comments
FB36
Trying to get solar power from space to ground is an extremely bad/impractical/expensive/risky idea!
Even the smallest solar array that can provide any significant amount of power to ground would probably mean billions of dollars of cost!
When same amount of solar power on the ground would cost an extremely tiny fraction/percentage of that!
TedTheJackal
So I clicked on the source link and it went to a page written in what I assume is Chinese and I'm like oh Loz, you forget that not everybody reads Chinese. I've been to Xian, BTW. Couldn't read Chinese there either. Took a forbidden picture of the Terracotta Army. But it's an interesting notion that the project will "require successive struggles of several generations". If they can predict technological evolution on a scale of generations their imagination is bigger than mine, but it's good to see someone thinking long term. Launch costs are going to come down, we'll definitely still need power, and the sun will definitely still be out there. Potential weaponization is a concern, but if we haven't killed ourselves off in "several generations" then maybe we'll have progressed past all that.
Trylon
I'd really like to see this come to fruition. I've been reading stories about space-based power systems for almost five decades now (as well as about O'Neill space colonies) and the giddy optimism of those early times have long since given way to the cruel realism that I probably won't see these things in my lifetime.
christopher
So, only 35,999,945 meters left to go... bad luck to birds, planes, etc that fly under the beam, and lets hope that whatever the beam does to the atmosphere it's slicing through isn't making more toxic byproducts (ozone?) than it's avoiding...
unclejoe
You got it FB36.
A billion dollars could purchase enough solar power units to produce a half gigawatt.
Also, space to ground is still subject to atmospheric conditions.
This process would work very well in a space to space mode.
Power source for orbital / lunar installations & projects.
And then there's Mars.
Douglas Rogers
On the ground, photovoltaics can't produce enough energy to reproduce themselves but, in space, they can! This is huge!
Carl23
@Douglas Rogers - "On the ground, photovoltaics can't produce enough energy to reproduce themselves"; I've been in the power business for over 20 years, and have no idea what this means. Can you please clarify?
Carl23
@FB36 - I wouldn't be so sure without actually running the calcs. 6-8 times the output is huge, and in space you don't need foundations, racking or many of the other design elements required on Earth. The PV material itself also doesn't need to be as robust as there is no wind or hail, and you don't need someone to periodically clean the panels either. Sure launch costs are high, but those continue to come down dramatically. There's also the aesthetic/benefit of not tying up land with solar panels.

I'm more concerned about issues raised by others, like atmospheric impacts, and some not raised here like instantaneous cutoffs in case the beam goes off target (including the means to keep such events from causing grid upsets). You clearly wouldn't locate receivers in an urban setting as depicted in the article, but likely in a desert. That would resolve most of the safety concerns, as well as minimizing weather impacts and bird risks. You'd have some additional transmission losses due to the distance from load centers, but those would be small compared to the generation increase.