The Godzilla of Solar Ovens | Hacker News Reader

The Godzilla of Solar Ovens

spectrum.ieee.org

82 pointsmcspecter42 comments

As the article suggests, the Mt Louis Solar oven was a prototype that lead to the real godzilla, the Odeillo Solar Furnace:

https://en.wikipedia.org/wiki/Odeillo_solar_furnace

This thing is massive and a beauty to look at. I remember going through the tour in the 90s, there were very thick steel plates on display that where melted like butter in the center it was really impressive. https://books.google.fr/books?id=VQEAAAAAMBAJ&pg=PA88&lpg=PA...

The Mt Louis Solar oven has been used for quite a few interesting projects, one of the most interesting that I recall was the disposal of certain extremely toxic chemicals at very high temperatures.

I built a 10' parabolic concentrator out of an old K-band satellite dish by laminating it with mylar and that - even though quite small - was the scariest thing I ever built.

It's only a few square meters but in full sun and with the focal point about 2-2.5 square centimeters you had to be extremely careful.

I'd be interested in the health and safety of working around these systems.

It feels like the sort of thing it would be very easy to forget the danger of as there's minimal moving parts and no scary sounds.

Surprised a henchman hasn't been thrown into the danger area in a James Bond film yet.

Well there have been issues with flash fried birds at a recently built solar plant. And i think they also have a incident where the mirrors got misaligned and set the collection tower on fire.

That said i think you would feel the heat radiating from the thing, as no mirror is perfectly reflective.

On sunny days, London's 'walkie talkie' building makes the sidewalk nice and toasty (and melts plastic bits on your car) with its south-facing concave glass wall: http://www.bbc.com/news/magazine-23944679

Not quite a solar furnace, though.

There's a hotel in Vegas with a slight.... design flaw, causing similar problems:

http://www.nbcnews.com/id/39403349/ns/travel-news/t/death-ra...

Actually hang on, is it the same architect??

https://en.m.wikipedia.org/wiki/Rafael_Viñoly

Maybe he's actually out to burn things on purpose... /s

Some people just want to watch the world burn

This and the Odeillo plants are pretty amazing. It is remarkably easy these days to build something which can create some really amazing temperatures. I used a Fresnel lens from a 50" rear projection TV to build a concentrator for the kids as part of a science project. We have also used more commercial solar ovens[1] to cook bread and other parts of dinner in the backyard or at camp.

That said, I've always wondered if you could build an industrial processor based on this technology. Can you bake iron out of hematite? Aluminum out of bauxite? The interest stems from research on how one might actually go about mining asteroids effectively. Using an inflatable mylar coated mirror could you effectively distill metallic elements out of a rocky asteroid?

[1] https://www.sunoven.com/

Using this on earth is hard because any clouds prevents this from get into extreme temperate ranges. So, you have low utilization in the 10-30% range.

This also gets vastly harder the further you get from the Sun and the asteroid belt is not all that close. A solar concentrator + solar panel + more traditional methods may work better especially out in the ort cloud.

Possibly, but you can make a kilometer diameter mylar mirror which folds up into a pretty small pouch. A small puff of gas to inflate the 'struts' and poof you've got more sun to work with. The asteroid belt is nominally 2.5AU from the Sun and using the inverse square law would suggest 1/6th the amount of solar insolation. So the Odeillo oven has 2600 sq meters of mirror and generates temperatures of 3000 degrees. Our 1km dish would have 785,400 sq meters so about 302 times the surface area, with 1/6th the insolation we should get about 50x the energy out of it if my math is correct.

Aiming a 1km dish is not going to be easy not to mention station keeping. Also, while it's clearly producing a lot of heat and may even vaporize iron that's not the goal. Further without Gravity many approaches for refining materials don't work as heating a chunk may just eject it into space.

Alternatively if you look at it as a large and relatively cheap tool it may be useful as a relatively small part of the process.

I like this. Imagine if you took something like this to the desert, you could have the means to convert sand into silicon without needing to use a locally-sourced fuel to generate the required heat (For what it's worth, I realise the sand that goes into silicon wafer production usually has to be purer than commonly-found sand, but I still think this production method may prove useful, perhaps for the silicon that goes into solar panels).

you would still need carbon for reducing the silicon dioxide into silicon

Burn magnesium in carbon dioxyde captured from the air then electrolyse the magnesium oxyde to get useable magnesium back?

Plant some trees, make charcoal?

A bit difficult to do if we're in a desert, I think...

You mean like this?

https://vimeo.com/25401444

It's an artist's project but he IS melting sand.

Solar panel silicon purity is above 99.98%, and often significantly closer to 100%.

Here's a study on "how impure silicon can we use for solar panels", and they only go up to 100 ppm feedstock impurity:

https://www.ecn.nl/news/item/how-silicon-purity-affects-the-...

Edit: should be "above 99.998%".

Would bricks or roads created from melted sand be stable enough? This is something I've thought about as well. There are parts of the world that have lots of sunlight and lots of sand. Imagine being able to 3D print roads and buildings out of melted sand. I think the idea has some merit that needs further exploration.

I used to live in a place with a strong ecological ethos for recycling, but no economic use of recycled glass. I always wondered if one could pulverize glass and extrude extremely durable housing structures using a solar-fired glass melting 3d printer.

Throw bottles in; slowly extrude house on sunny days...

That's a really interesting idea. 3d printing glass is a thing (and it looks awesome), but I'm not sure how to get the solar heat to the moving printhead without overheating the rest of the printer.

http://www.thisiscolossal.com/2015/08/3d-printed-glass/

See also this godzilla of solar plants :) http://www.fastcoexist.com/3057288/this-huge-new-solar-farm-...

>By 2020, China plans to build 10 more—the equivalent of 100 solar farms the size of Crescent Dunes.

The ability of china to scale never ceases to amaze me.

One of the upsides of not being a democracy is that NIMBY, environmentalism and health&safety can be pushed much further down on your list of concerns/priorities.

All true, but in this case there's millions of acres of cheap desert in the US. I think there's other forces than those retarding solar progress.

On a grander scale one could put solar plants in the sahara and use their power to split water into hydrogen and oxygen. To transport energy, that is.

It's an interesting idea for a place like Australia - use solar power to desalinate water, and pump it inland. You could create an oasis in the middle of nowhere, sort of like Las Vegas.

You still have to deal with the bi-product of salt and other various minerals that come out of the desalinated water.

Genuine Aussie sea salt...

Most of them are of value? I mean, we buy salt, and esp. sea salt, and most of the other minerals are going to either salable, or at least disposable in some way. You'll even be getting very small amounts of stuff like gold too. (really not much at all, but hey, there's 20 million tons of gold in there)

That doesn't mean that nobody cares. Republicans in the West hate solar because of their historical ties to coal and petroleum.

Environmentalists dislike these things because they are essentially a death ray for birds.

Ya. Armchair treehuggers, like their brethren on the right, can be exhausting. Every year, feral cats kill billions, wind turbines 500k, office buildings another 100k...

Focusing on least harm is far more constructive then selective outrage.

(I volunteered at Audubon for a decade, trying to conserve habitat for fish, birds, trees, etc.)

My favorite example of this is line 2 of the Beijing subway system. It's a circular route approximately following the old city wall. During planning, there was a great debate over how to build it. Boring tunnels would have been too expensive, but the cheaper cut and cover would have destroyed many homes. Instead, they just demolished the centuries-old city wall and built it there.

I don't mean to praise that decision, but I think it's a great example of both the advantages and disadvantages of that sort of dictatorial decision making.

One wonder if wind power could be used to melt salt in a similar fashion, to stabilize the output.

You could, but it would be extremely inefficient to convert motion to electricity to heat and back to electricity again.

If you want to do this on the cheap, see if you can find an old C-band mesh satellite dish. They can be found for free in rural areas of the US and Canada where people have them rotting in their yard. Like so:

http://www.vk3nro.com/122East2014/CBandDish.png

Cover in aluminum foil or mylar or whatever is cheap and highly reflective. Cook food at the location of the feed focus.

I have a 2.5m solar oven and it's brilliant. It can boil a litre of water in a minute or so on a sunny day.

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23 September 2013??

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