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Using the power of the sun to roast green chile (sandia.gov)
210 points by bookofjoe on Aug 22, 2022 | hide | past | favorite | 115 comments



This was a great reminder that it's Hatch Chile season! If you're not in NM, you can check out a site like https://ihatchchile.com for a local Chile roast - some time in the next 2-3 weeks, you can probably find one in the parking lot of one of your local-ish grocery stores.

Get more than you think you'll eat.


Thank you for sharing this. You've opened me up to a whole new world of experiences! Do you typically buy the hatch chile in the grocery store, then have them roasted outside? Or will it be available for sale in the parking lot already roasted? Thank you again!


In New Mexico at least, you buy them inside the store in large quantity, take your shopping cart full of them out to the propane fired roaster set up in the parking lot, help the attendant dump your chiles in the barrel, watch them tumble and crackle in the flames, then finally tell the attendant when they are roasted/charred to the degree you want them to be. Every grocery store does this, and during the roasting season, the entire town will smell like roasted chiles. It's possible that other places with less of a chile culture might use a modified routine.


In season, I usually go to one of the roasters set up in a parking lot. They’re all over Albuquerque and most of NM but also Denver and Pueblo and probably other cities in the southwest. There are several stands on Federal in Denver, for instance.

You choose your variety of chile (and the heat) and buy it in 25 lb increments. They fresh roast it for you at that time. 25 lbs is a lot of chile and it’s perishable, so you have to take it home and process it. Ideally will last most of the year. I peel and eat as much as I can while it’s fresh, and for the rest, it’s best to freeze it with the skins still on, as they’re easily removed when it’s thawed.


It can go either way - just ask the people manning the roaster what to do, they’re happy to help.


We picked up our years supply on Saturday.

Sadly, last year had no flavor, but this year tastes good, but the heat scale seems to be offset down one level

In the Seattle area, Haggen does this - but not King County this year! Whole Foods used to do roasting but seem to not do that anymore

Since an internet page is forever, finding THIS YEARS roasting schedule is not a trivial problem


Seattle locations? I'd love to find somewhere that does this in Seattle. I've searched a bit with no luck, anyone know where does the on-location roasting?


Carpinito Brothers out in Kent is doing one this Friday, Saturday, and Sunday from 10 until 4 PM. They are a great spot if you haven't been there before.


Hatch chilies really are the best. I’m sure part of it is the limited seasonal availability though.


This reminds me, it's Chile season in New Mexico right now!

Every year we get 2 boxes and have them roasted, then clean and freeze them. Towards the end of the year the stash gets a little low and have to start rationing.

The boxes are big, but much smaller after roasting. They then put the roasted chiles in plastic bags so you can carry them home. You then have to wait a few hours to peel and de-seed the chiles because they are so hot from roasting.

It's a tradition here and many people from all walks of life are out buying roasted chiles from now until the frost.


how do you freeze them? I tried once and the plastic bag had a lot of ice after a couple of weeks


There's no particular trick to freezing them. Maybe you used the wrong sort of bag? Most people use Ziploc style freezer bags or their generic equivalent. You do need to carefully squeeze all the air out before sealing. A vacuum sealer works great too if you happen to have one.


make sure there’s no air in the bag. I have added a tiny bit of water/saline solution.

I tend to leave them whole after cleaning the seeds.

If you have a vacuum sealer that’s the way to go


I saw a story about this last week and I'm hoping someone can explain why this is novel - were sun ovens not a popular thing there? Feels like I saw people using drum cookers to roast things as far back as the 90's... it did seem like this is a more advanced cooker, and perhaps it being at scale is the story?


Might be the level of heat required?

> Using 38 to 42 of the 212 heliostats — mirror-like devices used to focus sunlight — at the thermal test facility, Ken was able to achieve a temperature above 900 degrees Fahrenheit uniformly across the roasting drum, he said. This is comparable to the temperature of a traditional propane chile roaster.

Your standard oven certainly isn't going to get to 900 degrees Fahrenheit. So maybe 90's drum cookers could roast things like chicken wings, but probably not chiles.


Yeah, this appears to be more for fun than anything. Sandia has done concentrated solar research for decades. Roasting chiles is a New Mexico tradition. Hey, lets throw a chile roaster on the top of the solar collector tower! I'm only surprised it wasn't done earlier.

Not really a practical or serious technology at this time.


“Ken acknowledged that it’s not feasible to build a tower and field of heliostats just for roasting foods like green chile, coffee or grains. However, he and his colleagues are exploring a much smaller and more modular solar-roasting system that conceivably could be transported to farmers’ markets, grocery stores and chile festivals for roasting small batches of green chile, like the propane-burning steel-drum chile roasters currently use.”


The temperatures to cook green chili are really high - you want to get some good caramelization/burnt spots on the outside, at scale, very quickly. That's why they usually use big propane burners on the outside of the steel cage drum and rotate the peppers.

Most solar ovens can get high temps, but they require tradeoffs on scale or speed.


Thanks for this comment. I didn't realize that cooking green chiles was different!

My grandfather was a farm worker. He would bring home red chiles from the fields and roast them in the sun on his roof. So my first reaction to this story was "what's the big deal?"


In New Mexico, roasting chiles is a thing. My wife, raised there half a century ago, roasts her own to this day. Because, they're better that way of course!


Definitely. During Chile season you can smell the roasters set up all over town. One of the best smells, in my opinion.


Our supermarket usually has pre-roasted inside. On Saturday we were disappointed to not find any. As we left the store, the aroma of roasting peppers came our way and we found the loot we were in search of.

The smell sucks people in. Can’t do that on a web site - yet


I love that smell so much!


Sun ovens are for lower temperatures. Propane roasters are used because you want to singe the outside of the pepper fast enough to not overcook the inside. This solar roaster hits 900F and it's still quite a bit slower than the propane. But it's good enough for good flavor apparently.


So this is interesting - I think both you and Qworg above are sharing something that is news to me... so when y'all roast peppers, you are just trying to put a char on the outside, but you are leaving the inside not fully cooked and/or still "al dente"?


Ideally, yes, but the pepper still winds up fully cooked, it's just that it's not mush.

You want to blister the skin so it peels off easily. That's the main goal, but a lot of flavor comes out of caramelizing / charring things during the process, as well.

If you cook things too much, the entire pepper just turns to mush.

Heating things up enough to blister the skin means that the inside is steamed in the process. You want to get it so that it's cooked, but will still hold up enough to be peeled and sliced.


In the recipes I've seen, if you're charring the skins under an oven broiler or on a grill, you can then put them in a bowl and cover them, to let them finish steaming and make the skin easier to peel off.


Freezing them after sitting in the bag long enough to cool really separates the skin from the edible bits well, too. Wear gloves, of course.


I broil Anaheims (a milder cultivar of the same species) about once a week to make green chile Beyond burgers. I poke a few slits in each pepper, broil them 5 minutes to a side about three inches from the flame, and seal them in a takeout container for a few minutes before skinning. To skin them, I cut around the stem and remove the seedy core, then split the pepper in half with a lengthwise cut. After laying flat the skins should peel off very easily.

Cooking them perfectly is a balancing act of distance to the flame and the cooking time. I always use the broiler on the highest setting. It takes a few iterations with every new oven for me to dial in the exact timing and distance. Ideally you want to char the outside, while retaining the "structure" of the pepper flesh - not too mushy, but still a little toughness.

It doesn't nearly compare to the complexity of a real hatch pepper, but being 3000 miles from Hatch NM, I'll take it!


You might think about like the difference between broiling and baking. There are roasted pepper dishes where the peppers are cooked through during the roasting, but that's not what this is.


Indeed, even an Italian red pepper salad is best done directly on a grill or the flames of the burner, and not in an oven or anything.


the skin on chiles is pretty thick and unpleasant (waxy, hard, flavorless). ideally you want to blacken the hell out of the chile exterior. depending on recipe you either peel the chiles at that point or just use them as-is.


There are lots of solar driers, but this is a roaster with temps high enough to char the chilies.

They may have eliminated a lot of CO2, but the smoke could still use some attention! (You definitely don't want to get your head near there to see how the roasting is coming!)


Yes if you're willing to build a huge heliostat you can heat things to arbitrary temperatures. I first saw this dish-shaped heliostat in the mid-90's in Texas, and its biggest problem was controlling it so it didn't melt the hot side of its generator.

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

The only thing that's really new in solar in the last thirty years is the steady progress of semiconductor physics and technology. All the rest of it just follows from "sun is large and hot" which has been known for a long long time.


Mirrors work in both directions. No matter how big you build the heliostat, the best you can do is bring the thing it's heating into thermal equilibrium with the sun. Its temperature will never exceed the temperature of the sun. To make an electrical analogy, increasing the size of the heliostat is like reducing the output impedance of a power supply while leaving the voltage unchanged.


> No matter how big you build the heliostat, the best you can do is bring the thing it's heating into thermal equilibrium with the sun. Its temperature will never exceed the temperature of the sun.

If you build it large enough, though, it'll raise the temperature of the sun!


Only if you add a heat source on the earth side that's hotter than the sun.

All a solar concentrater does is increase the rate of energy transfer between the object being heated and the sun. The hot side gets colder and the cold side gets hotter. The only thing driving this energy transfer is the temperature difference, so once the temperatures are equal there is no more energy transfer. If you make it really huge, the temperatures equalize faster. This can increase the equilibrium temperature of the object because it's also losing heat to its environment. Bigger mirrors push the equilibrium temperature closer to the temperature of the sun, but never exceed it. It doesn't matter that the mirrors focus the radiation, because mirrors are not directional. They work equally well to transfer energy from the object to the sun if the object happens to be hotter. Whoever downvoted me doesn't understand thermodynamics.


The sun's temperature is not fixed, it's the equilibrium temperature between the energy generated by internal fusion and the energy that escapes via radiation. If you build mirrors that reflect an appreciable amount of the sun's radiation back to the sun, its temperature will rise.


Wonder if this technique, which allows the drum to get to 900F, could be used instead of gas for wok cooking?


There is a restaurant in Armenia that uses mirrors to bake dishes for customers. At least when the sun is out. https://www.atlasobscura.com/articles/solar-energy-cooking-a...

"Armenian scientists Gregor Mnatsakanyan and Vahan Hamazaspyan originally created the satellite dishes with dreams of distributing them around the country. Hamazaspyan, a pioneer in the study of solar energy use, began developing the first prototypes in the 1980s, after the devastating Spitak earthquake. Satellite solar ovens, he hoped, would feed his countrymen affordably during hard times."


Totally, assuming you're able to situate the wok in the middle of the New Mexico desert, and are satisfied with the safety profile of not putting your hand near it lest it become part of the dish.


I remember as a kid, in India, solar, gobar/bio gas and alternative ways of cooking and heating were all the rage. Then liquified petroleum gas became cheaper and everything just died. Here’s[1] an example of what I’m talking about. It was mostly for rural areas without reliable ways of delivering cooking fuels.

[1] https://www.rudrasolarenergy.com/solar-cookers.html (parabolic mirror based “cooker”)

https://www.indiamart.com/proddetail/gobar-gas-plant-3976916... (basically methane collected from composting)


Oh wow I vividly remember in the second grade there's a story of grandma cooking noodles using a solar cooker (it was in the Chinese textbook for Mainland China circa 1998).

Searching for a couple keywords on Taobao and apparently you can still buy those things. E.g. https://www.taobao.com/list/item/wap/595475929092.htm


ah it's gobar gas, I kept searching for bogar gas in futility just like 2 days ago from an idea an Indian colleague of mine shared with me some 10 years ago. Seems like bio-gas has become the preferred term for this technique.


If there's enough sunlight to grow chiles locally in the region, there'll be enough sunlight to use this approach. Chiles won't really grow that well without good daily sunlight and relatively warm temperatures.


> and are satisfied with the safety profile of not putting your hand near it lest it become part of the dish

that's not different from regular cooking, your home oven might not get that hot but lots of cooking implements do


Your range is cooking primarily through conduction though, it only heats what it touches. This is heating through direct electromagnetic radiation, if anything gets in the sun beam it will fry at 900 degrees. Move your hand in the wrong place and you will have massive burns in an instant without touching anything.


At the Sandia central collector the main beam is much hotter than 900 degrees and it's not uncommon for birds to be cooked instantly and drop from the sky if they happen to fly too close to the beam's focal point. This is one reason why the heliostats are always kept defocused unless an experiment is taking place.


that's no joke, you can check out this guy's channel and see all sorts of stuff instantly combust or begin to melt https://www.youtube.com/watch?v=drE54ctrHBY. 1000W/m^2 can concentrate into some serious power. Scary and dangerous stuff.


The sun is the same temperature no matter where you are on earth, so you could reach 900 degrees regardless of where you are, as long as you can see the sun. You would just need to make the reflectors larger as you got farther north.


[flagged]


I'm a native (American) English speaker and with a quick search of my 15 year old reddit account comments, I can guarantee you that native speakers would use "situate" just like that.


You... don't think I'm a native English speaker? My guy, I was born in Canada, of British descent and live in San Francisco. I was just being highfalutin. And to head that one off, it was a self-referential joke. Technically English is my second language, but I don't think that plays into it these days.


What's this "inedible" skin? What kind of chillies are these?

My sense is that these are being roasted to make chillis rellenos. But I thought chillis rellenos were usually made with pasilla chillies? I didn't think those were noted for having tough skin.

Also, IME roasting is one thing, skinning another. My process is: roast chillies; put in plastic bag in fridge; wait 10 mins; scrape off skin. Where's the solar fridge, and the team of chilli scrapers? Scraping one chilli is a job that takes about a minute. A 20lb drum of raosted chillies I'd guess is a day's work.


> What's this "inedible" skin? What kind of chillies are these?

If I had to guess, I'd say they're Hatch aka New Mexico chilies.[0] Once roasted, the now blistered skins are easily separated, discarded, and the remaining fruit can be consumed and enjoyed.

[0] https://en.wikipedia.org/wiki/New_Mexico_chile


Thanks.

I'm a brit, and can't get fresh chillies from the USA or Mexico. I have a stash of dried Mexican chillies, and I can buy fresh chillies from the Netherlands, but they don't say what the variety is.

There are quite a few UK growers that produce fresh chillies, but they're usually Habanero, Ghost or Reaper; they mainly sell them bulk to makers of hot sauce, not retail. And some middle-eastern shops sell ultra-mild large green fresh chillies, that I think are used in shawarma wraps and greek salads. They have no heat at all.


Honestly, if you enjoy fresh chilies and you're in Europe I'd recommend growing them. The seeds are small, light, and inexpensive to ship. As I understand it, chilies quite forgiving and easy to grow. You could order the seeds from the regular suspects or try something like r/SeedSwap.[0]

[0] https://www.reddit.com/r/seedswap/


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

For better or worse it's more common than salt here; they are being roasted to make everything.


Even McDonald's serves a green chile cheese burger. It's probably an unwritten law for burger shops there.


Hmm. s/pasilla/pueblo/ - a pasilla is a dried pueblo I believe, but I'm far from expert in these matters. TIL that you can make a chilli relleno with a pasilla. I think I'll try it.


I went deep into research on solar cookers and solar ovens (for recreational / personal use) a few months ago and found this video to be the most informative comparison of many of the most popular products / categories, if anyone is inspired by this article: https://www.youtube.com/watch?v=UsFrXjMA01M


I wonder if they would get better results with a retro-mirror on the other side of the roaster to reflect IR and catch any rays that didn't get into the roaster

---

The other question is: is it cheaper to do this, or just to set up solar panels and a resistive heating element based roaster.

I don't know of any super high temperature heat pumps, but that's the next thing I think of in making the process more efficient.


I can't imagine resistive heating winning against this, since current photovoltaic panels are relatively inefficient compared to just shoving the radiation directly into your target.


Not in energy efficiency, in cost efficiency.


At those temperatures you'd need something multi-stage with liquid metals, which is going to be a nightmare to engineer - you'd need some way of preheating it to melt it so you could turn it on in the first place, for example. And heat pumps are much less efficient at high temperature differentials, as would be the case here.


Heating the peppers/anything in an open drum is probably far from optimal. To reach high temperature one may concentrate the beam on a way smaller black metal pipe isolated from the air by using i.e quartz tube. Then pump the hot air through an thermo isolated rotating container.


Neat. Maybe community roasters could be setup and a whole town's worth of peppers could be roasted by the sun.


Maybe they can combine this with the molten salt reactor story and get something really flavorful going.


Green chile is an American treasure. Thank you Sandia national labs. Very tasty science.


Red chile is better.

- A contemptuous New Mexican.


They're each great on different foods IMO. Nothing better than a green chile cheeseburger, or a red chile enchilada plate at The Shed.


Yeah, I was just trying to start a NM flamewar.

What's more confusing to me is that different places cook them differently. Some places I love green and hate red, and some vice versa.

Though in places that do both equally well, I gotta say I'm team red :).


one day I’ll be able to tolerate the red at posas

not yet, though!


You both can be right with Christmas! (Red & Green)


Few things better in life than a Chimichanga covered in Christmas.


This is so cool! As a teenager I helped a buddy build an incredibly dangerous contraption that boiled water using a parabolic reflector and it was a lot of fun!

This actually makes me want to buy one to play with…


I saw one built from an old giant satellite dish that could light a hot dog on fire in seconds even when it was deep cold winter full of snow outside. 10/10 would eat hot dogs that way again.


There's an opportunity here to have a solar-powered Rube Goldberg contraption for transforming water and green coffee beans into something truly delightful.


Opportunity for organic, free trade, solar-roasted coffee


We have that in Pueblo, Colorado (also home of the best green chile) https://solarroast.com/


Oh man, I wish I had enough karma to downvote this comment! (I’m in NM ;))


I'm only a former resident, but I've downvoted him on your behalf. :)


> also home of the best green chile

Them's fight'n words.

> https://solarroast.com/

I do like that coffee. Nice strong robust roast without tasting burnt.


The Pueblo Chile Growers Association is more than ready for the fight!

The next Chile & Frijoles Festival is Sept 23-25th https://pueblochilefestival.com


Did you mean fair trade?


lol yes, but 'free trade' sounds good too


This uses the sun in a very specific way to roast peppers but technically the sun is the only source of energy in our solar system, therefore everything is using the power of the sun by definition! (including photosythesis, hence fossil fuels)


Hmmm I think radiation and gravity (thereby including geothermal heat) might be energy sources that are independent of the sun?


Gravity is not a source of energy, it's an energy store. You need to put in energy to get back energy (at least the way i think you are proposing it here)

Radioactive materials are also due to the sun, ours or others elsewhere in the universe. Earth does not produce them.

Whatever heat our planet had in the beginning and continues to have, originated from the sun. No sun, no heat


But is gravity really providing energy? It's only because of the sun that certain things are able to rise to a higher level of gravitational potential energy, and then drop back "down", thereby releasing the potential energy they had gained.


Specifically regarding geothermal energy, this is available due to the gravity that formed the Earth.


Nuclear energy? Geothermal heat? Tidal energy? ...


Not uranium.


Do they mean chillies?


No, they mean chile. That is the way it's spelled in Spanish and parts of Southern US.

It also doesn't really matter, does it?


It's pretty regional. Southerners tend to use "chili" for both the pepper and the dish in my experience, while southwesterners almost exclusively use "chile" for the pepper and "chili" for the dish. I've only seen Brits/indians use "chilly/chilli" (two ll's).


And then there is the country to differentiate from too -capitalization can help, but not always.

So there is vegetable, dish, temperature, country and informal variant word for child (though this last one is only an issue in orthography)


I was an embarrassing number of years old when I realized Jimi Hendrix wasn't just really into Voodoo Chili.

I mean. Still a minor. But it stings to this day.


You're still excused while you kiss this guy.



Well it kinda matters since Chile is a country. Why use Spanish spelling in English.


"Turkey" is also a country, and yet through a combination of context and capitalization, we don't seem to have any trouble telling whether that or the bird was intended. This seems like a non-problem.


Half the uses of "chile" around here capitalize the vegetable. From the title it could have been about solar power in South America or something.


You’re really reaching here. How could “roasted green chile” possibly be referring to the country?

You’d be surprised how quickly and frequently you are interpreting the correct definition of words in english just based on context.

Learning another language helped me realize this. I would, frustrated, complain about how two words sound the same or are spelled the same and my older wiser friend would simply point out examples in english that I have no problem with.

Anyways, unless you were confused yourself and you’re being modest about it, I wouldn’t be so quick to assume anybody else is having trouble grappling with the word here.


No?


Sandia National Labs working on the big questions of our time, I see ;-)

Disclaimer: I love New Mexico -- I'm just taking the piss. It's probably one of the most underrated states in the union.


I'm surprised it wasn't at LANL, considering one of the shops in Los Alamos near the lab has this amazing hatch chile burrito that's under $8 and is 10/10 in terms of flavor.


There are such places near SNL too. More, because Albuquerque is much larger than Los Alamos.

e.g. Vick's Vittles, Tia Betty Blues, Golden Pride, and of course the old standby Grandma's K & I Diner which has been feeding nuclear engineers for 62 years.


Do you have a name?


Possibly the Chile Works or El Parasol?

El Parasol: https://elparasol.com/

Google Street View of the sign to the Chile Works, off Trinity Drive: - https://www.google.com/maps/@35.8796938,-106.3006991,3a,75y,...


Personally I'd go to Viola's. But in general, you're not going to have to look far for a good burrito with green chile in NM.


I, too, as a former Los Alamos resident, immediately thought of Viola’s. I don’t have any idea how many hundreds of Christmas breakfast burritos I’ve enjoyed there. Haven’t been in years since my Dad retired from LANL and moved to ABQ.


True. I like Josie's in Santa Fe, also especially for the huevos rancheros at breakfast, with a side of posole.


I know you're acknowledging you're joking.

For those who do find themselves bothered by this kind of thing, these projects are almost always a few layers deep on what they're actually researching. I would assume this is more fun demo with a potential economic application in large scale roasting but that the research value (and intern training value) are in the general research area of broad solar concentrator R&D. If you look at the publication history for the folks involved you'll see a lot of papers on molten salt solar concentrators (materials, plant design, physics of etc).

Sandia does a lot of really interesting and valuable research (across all the sites but NM and CA in particular).


I was actually wondering if they meant fusion.


A key innovation of electricity is that it is a fungible form of power transmission. In particular, this allows the decoupling of concerns between the generation of energy and the application of energy.

I hope green energy enthusiasm doesn't take us back to the days of waterwheels being directly connected to grist-mills.




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