11 ms·

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 usin

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?

Qworg 4y ago
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.
- jf 4y ago
  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?"
AdmiralAsshat 4y ago
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.
- pavon 4y ago
  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.
  - ianai 4y ago
    “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.”
- deleted 4y ago
  [deleted]
sp332 4y ago
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.
- poulsbohemian 4y ago
  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"?
  - jofer 4y ago
    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.
    - mbg721 4y ago
      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.
      - ianai 4y ago
        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.
  - SamBam 4y ago
JoeAltmaier 4y ago
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!
- gaetgu 4y ago
  Definitely. During Chile season you can smell the roasters set up all over town. One of the best smells, in my opinion.
  - artursapek 4y ago
    I love that smell so much!
  - craz8 4y ago
    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
wrycoder 4y ago
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!)
jeffbee 4y ago
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 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.
- mrob 4y ago
  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.
  - murderfs 4y ago
    > 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!
    - mrob 4y ago
      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.

Qworg 4y ago

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.

jf 4y ago
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?"

AdmiralAsshat 4y ago

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.

pavon 4y ago
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.
- ianai 4y ago
  “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.”
deleted 4y ago
[deleted]

sp332 4y ago

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.

poulsbohemian 4y ago
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"?
- jofer 4y ago
  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.
  - mbg721 4y ago
    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.
    - ianai 4y ago
      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.
- SamBam 4y ago

JoeAltmaier 4y ago

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!

gaetgu 4y ago
Definitely. During Chile season you can smell the roasters set up all over town. One of the best smells, in my opinion.
- artursapek 4y ago
  I love that smell so much!
- craz8 4y ago
  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

wrycoder 4y ago

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!)

jeffbee 4y ago

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 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.

mrob 4y ago
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.
- murderfs 4y ago
  > 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!
  - mrob 4y ago
    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.