Heliogen, backed by Gates, says it has achieved a solar breakthrough
edition.cnn.com
edition.cnn.com
I don't doubt you could have done this open loop with a very rigid (expensive) platform before (including solving problems of ground subsidence). But now you can do it with a reasonably priced platform closed loop, which is what makes it actually possible.
Open/closed loop basically means whether you check the result of an actuation. What we're really talking about is the point at which the loop is closed.
A completely open loop would run the motor for the predicted time.
A simple closed loop would run the motor until the mirror is pointing at the predicted angle, using an encoder to know where the mirror is pointing. The control loop encompasses a mechanical part of the system, but not the end-thing we want controlled. Or put another way, the loop is closed for actuator angle but is not closed for where reflected light goes.
A better closed loop would run the motor until the mirror is reflecting sunlight exactly where we want it-- using magic to know where the light from this mirror is going.
In practice, you often end up with multiple nested control loops on this kind of system, each of which is closed.
You might have a voltage controller deciding how much to turn on the motor transistors based on voltage feedback...
You might have a motor speed controller which decides what voltage to give the motor based on speed feedback...
With another position controller deciding what speed the motor should try to go based on position feedback...
And then the magical-mirror-aiming thing deciding where the position controller should try to point it based on other feedback.
And then the industrial process controller deciding how many mirrors should be pointing at the thing based on temperature feedback...
And some other controller deciding what the temperature should be based on process feedback...
And then humans turning the knobs on that controller based on QA feedback.
(And each of these control loops usually gets at least 2x slower as the one it encloses).
Heliogen, a clean energy company that emerged from stealth mode on Tuesday, said it has discovered a way to use artificial intelligence and a field of mirrors to reflect so much sunlight that it generates extreme heat above 1,000 degrees Celsius.
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The article describes a bit about the role the AI is playing, and Heliogen didn't seem to me to have used "AI" as a buzzword
In principle I think you are right, but that would mean for each plant you build you need the exact position of each mirror, the oven chamber and the motion of the sun through the day and year. I think the "AI" approach scales better, as it is rather simple "AI" application.
If every mirror has drifted a small angle, and you're trying to point them all at a very small target-- it's hard.
[1] https://learn.sparkfun.com/tutorials/what-is-gps-rtk/all
That is, with two GPSes, you can measure their vector distance very precisely by correlating their measurements.
But it doesn't help you precisely measure angles, which is a big part of this problem.
That's just my reading of it, not asserting anything myself.
Yeah, depending on the level of precision required, there are _tons_ of variables that could have an impact here. Year to year the angle of the sun changes slightly on any given solar date, as various components of the Earth's orbit "wobble" (axial tilt, eccentricity, precession, etc). Even on an hour by hour basis, thermal expansion could have a significant impact. Any significant structure is going to settle to some extent over time, etc...
I think it's a scale issue, each mirror needs the same apparatus and AI, but doing it traditionally with reactive optics would need a multitude of different pieces?
But also the position of the sun in the sky is not predictable enough to do this completely open loop because of variances in atmospheric refraction... but it's pretty easily measured at the site.
I'm just going by the HelioMax blurb, where it talks about the calibration time. It makes sense that a system that automatically achieved accurate mirror aiming would also be able to maintain higher temperatures across varying conditions (and recover from disturbances and so on).
To solve the geometry problem, you need to know the inputs, i.e. position of the sun, mirror, and the target. Obvious way is calibrating in advance but that’s not reliable enough, due to wind and thermal expansion acting on the target (it’s elevated) and seismic activity acting on the ground. Another thing, need accurate orientation sensors in the mirror and/or motors capable of precise absolute positioning. All these technical challenges are solvable, but they reduce reliability, reduce focus precision especially over time, add non-trivial costs to the installation.
Instead, apparently they have 4 fixed mounted cameras around the target, looking downwards at the center of the mirror array. The sky doesn’t have distinct features unless clouds, but the sky has these color gradients, vertical one from horizon to zenith, also radial one around the sun. Just seeing these 4 colors might be sufficient to correctly orient the mirror.
Animats gave a nice summary [1] of the Vox article [2] that went into some detail. [1] https://news.ycombinator.com/item?id=21580596 [2] https://www.vox.com/science-and-health/2019/11/19/20970252/c...
Could probably find enough information here [0] what is needed.
[0] Practical Astronomy with your Calculator https://www.amazon.com/dp/0521356997/ref=cm_sw_r_cp_api_i_-v...
Also, once the AI is written, you can save time on each install by not having to precisely locate each mirror. Get it close enough, and let the magic box fix up the small errors in real time.
> The problem is that in the past concentrated solar couldn't get temperatures hot enough to make cement and steel.
> While other concentrated solar companies attacked this temperature problem by adding steel to make the technology stiffer and sturdier, Heliogen and its team of scientists and engineers turned to artificial intelligence.
> Heliogen said it is generating so much heat that its technology could eventually be used to create clean hydrogen at scale.
Sitting in 2020 the technology is near trivial. The problem is that some knucklehead would point a bunch of them at the same window and set curtains and pigeons on fire. (You’d do this because you had a large room with few windows, so dispersed mirrors would give you multiple dispersed lighting spots in the room… and incinerated pigeons.)
I was unable to make the leap to what happens if you are a deliberate and well reasoned knucklehead! In a controlled situation a megawatt of light might be just the thing.
Addendum: The mass field of mirrors introduces a lot more work. Some of the immediately interesting problems:
• you need a “everyone stop shining at the target” mode for emergency stop, but the mirrors need to move away from the target in such a way that they don’t create convergences elsewhere. Obviously sweeping your portal to hell down the tower would be a bad idea. So you have a collection of autonomous, free thinking mirrors, but when commanded to stop hitting the target they need to not make the same decisions.
• your camera probably needs to be able to stare into the heart of a thousand suns (literally). But it also needs to see in ordinary daylight. Maybe a pinhole filter that moves over the lens would be appropriate.
• with 999 mirrors shining on the target, you will not be able to see your own contribution to aim. There probably needs to be a “hey! Everyone else look away for a second” command for unit to aim and calibrate itself. See complexities from the first bullet and not incinerating things you like.
So yeah, they could have started with my garden heliostats, but then it would be a crack the knuckles, bring in the eggheads, and get to work operation to solve all the hard problems.
I don't really know if this would be possible, but sailing ships can rig their sails to propel them against the wind.
Yes, domestic cats kill orders of magnitudes more birds, but that argument a. depends on relative scale that people don't grok, and b. coming from an energy company reinforces the preconception that they're callous.
Add radar and a sufficiently smart AI, and they could turn a PR problem into a marketing pitch by showing birds flying through unscathed while the mirrors shift to avoid them.
See: https://newatlas.com/optical-illusion-raptors-airplanes/5675...
Around 60% of CO2 (see 1) emissions during cement manufacturing are just a byproduct of the chemical process converting calcium carbonate to lime (see 2) - nothing that solar power can help with.
1) https://precast.org/2013/05/concrete-and-co2/ 2) https://www.ipcc-nggip.iges.or.jp/public/gp/bgp/3_1_Cement_P...
[1] https://en.wikipedia.org/wiki/Environmental_impact_of_aviati...
And even if we overcome this, we will need so much solar panel and batteries that we simply don't have enough raw materials to do so (to replace a 1GW nuclear core you need to cover half of Paris with solar panels, source http://www.assemblee-nationale.fr/15/rap-enq/r2195-t1.asp).
In France, 95% of the stored electricity is done using reversible-damns (you pump water up to store, you empty the water and generate electricity when you need it), only 2% using batteries. We basically put damns everywhere we could on the territory. We have 2 days max of storage. How can we now store weeks/months of solar-panel/wind electricity we don't need to use it when we need it?
Batteries are inefficient for grid storage, oversized, heavy and too short term. That's it. We now know for decades that damns are the easiest way to do it and we can't do more than a few days of storage.
At one moment we simply have to face the maths and physics. Trusting the "next big thing" in battery storage/solar production, even if we do 5x more energy, even if we develop long lasting ones, will not work in the end. Our needs are too big and the amount of minerals and other raw materials we need is way too big. That's it.
For electricity production, photovoltaics is superior to concentrated solar power.
Of course it worked the first time they turned it on - they were using 4 photodiodes. The "AI" and "computer vision" is just to get funding and hype.
I'm going to start taking solved problems and applying BS "AI" to them to get funding, sheesh.
Using $50 of computer and camera to steer instead of photodiodes and analog controller (presumably in a splayed viewport configuration) lets you lose the $1000 foundation and simplify the calibration. It’s no longer a precision operation, just a pointing out the target.
"Bill Gates is smart, therefore he can't be fooled or wrong" is not a strong argument.
But yes, fiducial marks probably don't work well here due to too many variables.
You have four photodiodes surrounding the target, and 1000 mirrors aligned to reflect the sun toward that target. One of the 1000 mirrors goes out of alignment, and your photodiodes tell you so. How do you know which mirror needs to be adjusted?