Community > Forum > Technology & Science > Solar thermal mirrors repurposed at night for astronomy?

Solar thermal mirrors repurposed at night for astronomy?

Posted by: Optimistic Brian - Tue Jun 10, 2014 10:56 am
Post new topic Reply to topic
 [ 10 posts ] 
Solar thermal mirrors repurposed at night for astronomy? 
Author Message
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Thu Apr 17, 2014 6:40 pm
Posts: 30
Post Solar thermal mirrors repurposed at night for astronomy?   Posted on: Tue Jun 10, 2014 10:56 am
I'm sure there are all sorts of reasons why this is impractical, but the thought struck me as significant enough to mention:

Out in the desert where the night sky is clear as glass, the world is building massive solar thermal plants with truly gargantuan arrays of mirrors. Since these plants are for solar energy, the mirrors just sit idle at night.

Could there be ways to utilize these mirror arrays for astronomy? I know they lack the purity and precision of mirrors used in professional telescopes, but there are so many of them and the fields are so unbelievably huge, so perhaps that compensates for their crudeness? Could useful astronomy science be done with them?

Ivanpah solar plant in the California desert:

Image


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
avatar
Joined: Mon Jun 24, 2013 7:39 pm
Posts: 68
Location: San Antonio, Texas
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Tue Jun 10, 2014 3:00 pm
If the secondary components of an astronomical telescope were placed in a suitable geostationary orbit to receive the light focused by the surface mirrors (primary array) and;

the reflective surfaces of the primary mirrors had been made to the finest astronomical standards and;

the mechanical mounts had been made with greater precision than those of any ground-based astronomical telescope, allowing the primaries to focus the incoming light into the orbiting secondary unit more than 22,000 miles (>35,700 km) away and;

the software controlling the primaries were upgraded to allow the mirrors to adapt to atmospheric aberrations and;

the necessary sensory equipment were added to inform the adaptive software and;

suitable image-processing software were included with the system to correct for distortions the adaptive optics technology is unable to eliminate and;

there were no wind in the desert...

The short answer is no.

Existing ground-based telescopes can already produce better images than a repurposed solar plant ever could. The array would have to be designed and built from the beginning as an astronomical observatory to make the effort worthwhile.

In Jon Hogan’s thread, “Planets at near stars?” I have conjectured an optical telescope analogous to your solar power plant idea being established on the "desert" of the far side of the moon, sheltered from the optical and meteorological interference an Earth-based “super telescope” would encounter.


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Thu Apr 17, 2014 6:40 pm
Posts: 30
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Tue Jun 10, 2014 4:46 pm
USJay wrote:
The short answer is no.


I don't think it's a necessary assumption in this scenario to require that the mirrors do all the same work as the mirrors in a traditional telescope. We don't have to insist that they both gather light and resolve the images all the way. Why could they not simply be used as a massive augmentation to a traditional telescope?

And even if the results were not as good as, say, Mauna Kea, so what? You would have utilized infrastructure that already exists toward a new purpose without sacrificing anything because it just sits idle at night anyway.


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
avatar
Joined: Mon Jun 24, 2013 7:39 pm
Posts: 68
Location: San Antonio, Texas
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Tue Jun 10, 2014 7:00 pm
Believe me, I wish the idea would work just as much as you do. Your concept of using the mirrors of a solar power concentrating array as a “massive augmentation to a traditional telescope” effectively converts the array into the primary mirror of the augmented telescope. Every reflection or refraction inside any telescope loses a bit of the original information carried by the light, so every mirror or lens must be as accurate as possible to make the final image worthwhile. To borrow your words, for any telescope to work, every single optical element must indeed “both gather light and resolve the images all the way.”

Also, where would you put the traditional telescope that is being augmented? I have already suggested a geostationary orbit. One other possibility would be a permanent high-altitude helium-filled aerostation well above the jet stream, but such an unprecedented engineering challenge would probably cost more than the satellite. Nothing is cost-free. We would not be able to coax a solar power station into double-duty as an astronomical observatory “without sacrificing anything” and even after all that expense, with all the optical imperfections inherent in a non-astronomical solar power array, the results unfortunately could not compete with telescopes already in use.

That does not mean the fundamental configuration is not sound. A huge array of mirrors laid out in the desert somewhere (Atacama perhaps?) and specifically engineered for astronomical observations could conceivably work as the primary for a telescope with amazing light-gathering ability. There would still be the problem of atmospheric distortion. Keeping all those mirrors clean and steady in the wind might be tricky too.


Back to top
Profile
Space Station Commander
Space Station Commander
User avatar
Joined: Mon Dec 18, 2006 11:15 pm
Posts: 930
Location: Columbus, GA USA
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Wed Jun 11, 2014 1:13 am
Optimistic Brian wrote:
You would have utilized infrastructure that already exists toward a new purpose without sacrificing anything because it just sits idle at night anyway.


Keep in mind that Jay has a specific unwavering opinion on the right way to implement his vision for multi-element telescope array.


Yeah collimating hundreds of mirrors would be a pain. But the same adaptive optics techniques use to process atmospheric distortion would be useful in clearing up the "noise" produced by a non-precision array, you would just have to throw more computing horsepower at it or maybe break it down into sections each with their own objective collector. It would never be able to compete with the clarity of a purpose built astronomical telescope, but it might be useful for wide-field use such as asteroid hunting and the like.

I think it would be worthwhile to at least investigate the potential. It would be a great graduate level project.


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
avatar
Joined: Mon Jun 24, 2013 7:39 pm
Posts: 68
Location: San Antonio, Texas
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Wed Jun 11, 2014 3:37 am
James, your exhaustively educated estimations are ever entertaining! My specific unwavering opinion is that the science of telescope design is mature and rigorous. Brian suggested the array might be used for “a new purpose without sacrificing anything.” How would you apply your hypothetical adaptive optics techniques to Brian’s “infrastructure that already exists” in the form of thousands of very large and comparatively floppy mirrors mounted on equally sloppy drive mechanisms without exceeding the cost of the original installation? And toward what would you aim the reflection, the boiler of the solar power plant?

I suppose if the solar array just happened to have been built in a deep valley (for reasons unknown) the secondary elements might be suspended high above the boiler tower Arecibo-style. Otherwise your options are an improbably handy very near very tall mountain, an aerostation or a satellite.


Back to top
Profile
Space Station Commander
Space Station Commander
User avatar
Joined: Mon Dec 18, 2006 11:15 pm
Posts: 930
Location: Columbus, GA USA
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Wed Jun 11, 2014 4:21 am
I don't know and don't have the time to devote to even considering solutions. However I don't discount the idea out of hand either.


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
avatar
Joined: Mon Jun 24, 2013 7:39 pm
Posts: 68
Location: San Antonio, Texas
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Wed Jun 11, 2014 6:09 am
Brian, I greatly admire your desire to make the most of an investment that is inherently idle half the time, but the exceedingly poor quality of the images could not hope to justify the enormous cost of converting a solar power plant by day into an astronomical observatory by night. I look forward to reading about whatever you turn your imagination to next.


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Thu Apr 17, 2014 6:40 pm
Posts: 30
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Sat Jul 26, 2014 9:51 pm
USJay wrote:
Brian, I greatly admire your desire to make the most of an investment that is inherently idle half the time, but the exceedingly poor quality of the images could not hope to justify the enormous cost of converting a solar power plant by day into an astronomical observatory by night. I look forward to reading about whatever you turn your imagination to next.


Then consider the reverse proposition: Could a giant mirror array be constructed for astronomy purposes that could, during the day, operate as a solar thermal facility that generates revenue for the operation of the telescope? Doesn't have to be net-profitable, just end up costing less on balance than the same telescope without power-generating capabilities.


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
avatar
Joined: Mon Jun 24, 2013 7:39 pm
Posts: 68
Location: San Antonio, Texas
Post Re: Solar thermal mirrors repurposed at night for astronomy?   Posted on: Sun Jul 27, 2014 12:28 am
I had the same thought. That might be workable – definitely difficult, but certainly more practical than the reverse. The big question is still where to focus the gigantic array in the first place. A typical array laid out on a wide open plane would probably require either an aerostation (buoyant atmospheric platform) or a satellite to carry the secondary elements.

An other possibility that springs to mind is to build a telescope similar in configuration to the experimental solar furnace operated by CNRS (National Scientific Research Center) in the French Pyrenees. The primary array could be set up on one mountainside with the secondary set up miles away on a facing mountainside.

This would allow the entire system to be ground-based. The trade-off is that the field of view would be cut in half by the horizon. Of course, all the other concerns regarding atmospheric distortion and environmental conditions still apply, but designing the whole thing as a telescope first and solar power plant second does make more sense.


Back to top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 
 

Who is online 

Users browsing this forum: No registered users and 10 guests


© 2014 The International Space Fellowship, developed by Gabitasoft Interactive. All Rights Reserved.  Privacy Policy | Terms of Use