9 ms·

Heliogen targets 1500°C solar thermal

102 points by nclzz 7y ago

new299 7y ago
Bill Gross, Heliogen’s current CEO previously founded eSolar. eSolar proposed using an array of Heliostaticly controlled mirrors to direct light toward a solar cell: https://en.wikipedia.org/wiki/ESolar https://en.wikipedia.org/wiki/ESolar So... that part of the eSolar approach is carrying over into Heliogen. Last time this was posted the “AI” component of the play was less clear... But with an array of mirrors, in particular being to generate heat in some volume I guess a more complex feedback/control system may be required.
- s_Hogg 7y ago
  Are we talking about PIMCO Bill Gross here? If so, how did he wind up doing this?
  - arethuza 7y ago
    Different Bill Gross: https://en.wikipedia.org/wiki/Bill_T._Gross https://en.wikipedia.org/wiki/Bill_T._Gross
- ReptileMan 7y ago
  What exactly do you need AI for except for buzzwording? It is not as if the sun/earth trajectory or rotation speed is random. You can precalc with ease at every point which is the best position for each mirror.
  - viraptor 7y ago
    That did strike me as weird. Although they say "advanced computer vision software" so maybe they do some workaround and take the position from a camera rather than pre-calculations? Can it be the case that a few thousandths of a degree matters here and that's beyond our generalised model?
    - TeMPOraL 7y ago
      I'd imagine that the "few thousandths of a degree" is something you'd get worse with AI than with a mathematical model. AI methods introduce noise; with an explicit model you can keep adding complexity directly, until it gets more accurate than your measuring system. I suspect that the "AI" they mention is mostly photogrammetry - being able to tell the position and orientation of your mirrors from a video stream - in a feedback loop with motor controllers and temperature sensors. Use of cameras would make it close enough to "AI" that the buzzword would stick.
      - ovi256 7y ago
        >mostly photogrammetry - being able to tell the position and orientation of your mirrors from a video stream - in a feedback loop with motor controllers and temperature sensors. This. Modern photogrammetry uses computer vision techniques like deep neural nets. It's an amazing advancement. Imagine this problem: having to place a ground vehicle like a wheeled robot at an arbitrary coordinate in a room. The mirror positioning problem can be reduced to this one. Traditionally, you'd do it by building a very nice wheeled robot with non-slip wheels, wheel rotation angle sensors, fraction of a degree stepper motors, all very nice to work with, precise, and expensive. You could even solve this in an open-loop system with good enough actuators. Today, just stick a camera on the ceiling - or on the robot, if want a more challenging problem - and use CV to move a cheap RC car where you want. The Terminator will jangle and jiggle, instead of being built like a precise Swiss watch. But you'll get ten of them for the same price!
        TeMPOraL 7y ago
        > This. Modern photogrammetry uses computer vision techniques like deep neural nets. I'm surprised to hear that. What good do DNN do for photogrammetry? Aren't they too unreliable? I only have university course-level exposure to this, most of it spent learning how to compute coordinate systems and transformation matrices from points on a set of pictures taken from different position. I guess DNNs could help with object isolation and labeling (identifying same objects on a set of pictures taken from different perspective)?
  - truculent 7y ago
    Perhaps weather/clouds/objects are a thing that must be adapted to?
    - kuu 7y ago
      I guess this and also the lack of needing to make a detailed study about the sun position wherever the plant is established.
  - new299 7y ago
    I would imagine that it’s not the suns location that is the primary concern, but where you are directing the light. The light is being reflected and focused by mirrors. That light is being directly onto some volume of material. So, in this case, they want to get the material above some critical temperature (e.g. so it melts). I imagine that uniformly heating the whole volume may not be the best approach, or that you may be able to work with smaller volumes depending on your expected solar input etc. So I can see a little more justification here than the case where solar cells are just being pointed at the sun.
  - pjc50 7y ago
    The difficult problem is not knowing where the sun is but knowing where the ground is. Since all the panels are separate structures not on a single rigid slab, ground "settling" can tilt them fractionally in unpredictable ways. It sounds like what they have is machine vision as a novel input into a conventional control loop. For one panel at a time, wiggle it about and look how the light spot changes. Find the local maximum for tightest spot. That's now "locked" in the PLL sense and should stay locked for days or weeks.
    - JshWright 7y ago
      From my comfy armchair, with zero experience in this field, it seems like you could use star tracking to very accurately predict the angle of the sun (since the sun is effectively fixed in position relative to the background stars over the timescales you'd care about). Spotting the target is a little harder, but the same measurement could be made by sticking some reflectors in known positions around the target. I'm sure there are tons of considerations that aren't occurring to me (for instance, thermal expansion likely contributes substantially to making it a moving target (literally)), but I really don't see where "AI" comes into it...
      - smueller1234 7y ago
        Many years ago, I implemented star tracking for telescope alignment for auger.org. An actual basic version using libnova et al was pretty straightforward and a matter of days to prototype if I recall correctly (it was a project for a master student, so I had to do most of the work over a longer period of time). I think the accuracy was around a decimal fraction of a degree then. But the cameras of that thing have only 440 1.5° pixels (photomultipliers that sample at 5-20M samples/s). A higher resolution camera could probably do much better assuming you have a very accurate computer model of the optical properties of your telescope/lenses/camera.
      - dreamcompiler 7y ago
        Figuring out the sun's location is the easiest part of the problem. The hard part is that each mirror is a big, floppy slab that moves with wind, temperature, gear backlash, mechanical wear, rain/hail, and ground settling. The so-called "AI" here is really just a clever way to use closed-loop control so that the above factors don't matter much. (Side note: A large amount of "AI" these days just amounts to changing open-loop mechanisms to closed-loop, often by using computer vision as the state sensor. 3D printers, for example could become much more precise with no mechanical improvements if they did this. Probably some have already done so.)
  - ovi256 7y ago
    Yes, you can precalc, and then you need very precise actuators to move the mirror to that precalced position. You also need precise surveying of the ground site to know its geometry. The precise actuators and surverying are expensive. Their approach is using cheap actuators in a closed-loop system where a computer vision controller (using the four cameras on top of the tower) moves the mirrors until it gets it right. Cheap actuator slip and lag is terrible, but with the feedback of the closed-loop, it's doable. This is an approach that's now allowing hobbyists to build cheaper motorised telescopes, robot arms and so on.
Juliate 7y ago
https://en.wikipedia.org/wiki/Odeillo_solar_furnace https://en.wikipedia.org/wiki/Odeillo_solar_furnace "started operating in 1970", "Temperatures above 3,500 °C (6,330 °F) can be obtained in a few seconds". See also https://en.wikipedia.org/wiki/Solar_furnace https://en.wikipedia.org/wiki/Solar_furnace Not dismissing this press release, but at least some scale of progress should be used to compare against. Or state where the economical/industrial/regulatory innovation stands.
- scoopertrooper 7y ago
  That thing is the size of a building though.
  - Juliate 7y ago
    Granted. Size and lightweightness are definitely a point - that could be emphasized as a major argument - even the ratio with size & power capacity & heat intensity.
    - agumonkey 7y ago
      I wonder how security is handled there
      - astrodust 7y ago
        Oh man what if someone stole the sun. (In all seriousness, the security risks are pretty low here. This isn't like stealing nuclear fuel.)
        agumonkey 7y ago
        Sorry I meant safety.
- baq 7y ago
  yeah the only problem is the useful heat is contained in a very small area/volume, so this is only a research facility.
zubspace 7y ago
Another similar project in the mojave desert incinerates 6000 birds a year [1]. I wonder, how they handle that.. [1] https://www.sciencealert.com/this-solar-plant-accidentally-incinerates-up-to-6-000-birds-a-year https://www.sciencealert.com/this-solar-plant-accidentally-i...
- BurnGpuBurn 7y ago
  I was just wondering how many birds this would fry, thanks for the article.
  - VBprogrammer 7y ago
    The problem is generally trivial compared to the number killed by domestic cats and glass windows.
    - ygra 7y ago
      For wind turbines at least there's a bit of a difference, as those kill larger birds than cats, in smaller numbers, but those birds also have smaller populations. So just looking at the numbers without knowing the birds and their total populations, makes things hard to compare or judge.
      - VBprogrammer 7y ago
        Sure, thought needs to go into the location of these things; avoiding migration routes and habitats of endangered birds. Using scarecrows and possible trained predator birds (presuming these can be trained to avoid the danger zone!) etc. Of course conventional industry doesn't get a free pass here either, treatment and storage ponds, climate change, habitat destruction etc.
      - usrusr 7y ago
        But aren't most larger birds predators that are highly habitat/food supply constrained? That kind of population could be quite resilient to moderate increases in mortality. (I might be assigning far more importance to predator-Peru cycles than is warranted though, I was reading about what I now found is called https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equatio... at a very young age and the concept stuck for life)
honopu 7y ago
I think the point of calculating using imaging vs a model that requires layout and flat land etc is this would be cheaper to build. You have to build one collection tower/ target, and the mirrors can aim themselves. This greatly reduces the grading, measurement etc and makes installing on existing land without needing to flatten at all, or to some crazy tolerance, much easier. I can see this used in rolling hills, with less impact etc possible.
tempodox 7y ago
Inertia must be incredibly strong. Otherwise, why did it take so long to come up with something that strikingly simple? The last time someone allegedly had an idea like that was around 212 B.C., in the defense of Syracuse.
- trickstra 7y ago
  Because of oil lobby mostly. The idea is nothing new, it was just easier to burn oil instead of building new industry from ground up and going against all existing oil companies.
  - nradov 7y ago
    That "oil lobby" conspiracy theory is such nonsense. There are several developed countries with minimal oil reserves and no domestic oil companies. If alternative energy industries were really practical before then those countries would have built it.
- gnode 7y ago
  The technology is fundamentally simple, but not practical on a small scale. There are plenty of large, yet simple projects which nobody cares to invest in because there are better (including more expedient, or proven) alternatives. CSP requires a large investment compared to PV solar, as it needs to be done at scale to make coolant systems, towers, turbines and generators cost effective. It needs its own large allocation of land, rather than be distributed. It also, like PV solar, has poor temporal availability, so compares badly to fossil fuels, nuclear and hydro. It has potential to be cheaper than PV, and integrate well with thermal energy storage. It could also be more efficient, if the temperature can be increased (due to Carnot efficiency). However, the convenience and falling prices of PV panels may prevent CSP becoming popular.
- masklinn 7y ago
  > Inertia must be incredibly strong. Otherwise, why did it take so long to come up with something that strikingly simple? It didn't? There are both solar ovens and solar power plants in active use. The issue's mostly that it's historically been fairly inefficient and expensive (compared to other electricity production sources). Prices have been coming down through improved efficiency and economies of scale, the plants being built these days are bid under $75/MWh and construction has been ramping up a lot especially in high-irradiation locations e.g. Morocco onlined their first station in 2017 (510MW CSP, 72MW PV) and is already building a second one, and Dubai is apparently aiming for 5GW installed by 2030.
Tangokat 7y ago
I wonder who Heliogen hired to do their PR. Must be a really good (or expensive) campaign. There is nothing new in high temperatures and the AI part is pure buzzwords.
- epistasis 7y ago
  I imagine that being able to throw around the name Bill Gates is as big an advantage as a good PR firm.
aj7 7y ago
Very skeptical that this is a practical means to supply 1500C to an industrial process. Do they plan on piping heat via liquid metal, or what? Do you shutdown on cloudy days and sen everyone home?
- arcticbull 7y ago
  Just store some molten salt in a really big thermos
  - astrodust 7y ago
    Since thermal energy is only lost at boundaries, the larger the amount you have, the smaller the net surface area per unit of volume. This is how you can store huge blocks of ice well into the summer (e.g. https://en.wikipedia.org/wiki/Ice_house_(building) https://en.wikipedia.org/wiki/Ice_house_(building)), but also how a giant underground mass of molten salt that's not in physical contact with the surrounding ground could store a lot of heat for a long time.
    - masklinn 7y ago
      > Since thermal energy is only lost at boundaries, the larger the amount you have, the smaller the net surface area per unit of volume. You do need to do the initial melting work though. It took two months for Crescent Dunes to melt its 32 tons of salt.
nanomonkey 7y ago
I'd love to see something like this put into use for smelting titanium. We really need to start embracing it as a building material as it doesn't corrode or break down like wood, steel, aluminum does...plus it's light and strong which would allow moving houses and vehicles made from it much less energy intensive. It would be great to invest the energy into building materials that can last instead of continuously having to fight corrosion.

102 points by nclzz 7y ago

Bill Gross, Heliogen’s current CEO previously founded eSolar. eSolar proposed using an array of Heliostaticly controlled mirrors to direct light toward a solar cell: https://en.wikipedia.org/wiki/ESolar https://en.wikipedia.org/wiki/ESolar So... that part of the eSolar approach is carrying over into Heliogen. Last time this was posted the “AI” component of the play was less clear... But with an array of mirrors, in particular being to generate heat in some volume I guess a more complex feedback/control system may be required.

s_Hogg 7y ago
Are we talking about PIMCO Bill Gross here? If so, how did he wind up doing this?
- arethuza 7y ago
  Different Bill Gross: https://en.wikipedia.org/wiki/Bill_T._Gross https://en.wikipedia.org/wiki/Bill_T._Gross
ReptileMan 7y ago
What exactly do you need AI for except for buzzwording? It is not as if the sun/earth trajectory or rotation speed is random. You can precalc with ease at every point which is the best position for each mirror.
- viraptor 7y ago
  That did strike me as weird. Although they say "advanced computer vision software" so maybe they do some workaround and take the position from a camera rather than pre-calculations? Can it be the case that a few thousandths of a degree matters here and that's beyond our generalised model?
  - TeMPOraL 7y ago
    I'd imagine that the "few thousandths of a degree" is something you'd get worse with AI than with a mathematical model. AI methods introduce noise; with an explicit model you can keep adding complexity directly, until it gets more accurate than your measuring system. I suspect that the "AI" they mention is mostly photogrammetry - being able to tell the position and orientation of your mirrors from a video stream - in a feedback loop with motor controllers and temperature sensors. Use of cameras would make it close enough to "AI" that the buzzword would stick.
    - ovi256 7y ago
      >mostly photogrammetry - being able to tell the position and orientation of your mirrors from a video stream - in a feedback loop with motor controllers and temperature sensors. This. Modern photogrammetry uses computer vision techniques like deep neural nets. It's an amazing advancement. Imagine this problem: having to place a ground vehicle like a wheeled robot at an arbitrary coordinate in a room. The mirror positioning problem can be reduced to this one. Traditionally, you'd do it by building a very nice wheeled robot with non-slip wheels, wheel rotation angle sensors, fraction of a degree stepper motors, all very nice to work with, precise, and expensive. You could even solve this in an open-loop system with good enough actuators. Today, just stick a camera on the ceiling - or on the robot, if want a more challenging problem - and use CV to move a cheap RC car where you want. The Terminator will jangle and jiggle, instead of being built like a precise Swiss watch. But you'll get ten of them for the same price!
      - TeMPOraL 7y ago
        > This. Modern photogrammetry uses computer vision techniques like deep neural nets. I'm surprised to hear that. What good do DNN do for photogrammetry? Aren't they too unreliable? I only have university course-level exposure to this, most of it spent learning how to compute coordinate systems and transformation matrices from points on a set of pictures taken from different position. I guess DNNs could help with object isolation and labeling (identifying same objects on a set of pictures taken from different perspective)?
- truculent 7y ago
  Perhaps weather/clouds/objects are a thing that must be adapted to?
  - kuu 7y ago
    I guess this and also the lack of needing to make a detailed study about the sun position wherever the plant is established.
- new299 7y ago
  I would imagine that it’s not the suns location that is the primary concern, but where you are directing the light. The light is being reflected and focused by mirrors. That light is being directly onto some volume of material. So, in this case, they want to get the material above some critical temperature (e.g. so it melts). I imagine that uniformly heating the whole volume may not be the best approach, or that you may be able to work with smaller volumes depending on your expected solar input etc. So I can see a little more justification here than the case where solar cells are just being pointed at the sun.
- pjc50 7y ago
  The difficult problem is not knowing where the sun is but knowing where the ground is. Since all the panels are separate structures not on a single rigid slab, ground "settling" can tilt them fractionally in unpredictable ways. It sounds like what they have is machine vision as a novel input into a conventional control loop. For one panel at a time, wiggle it about and look how the light spot changes. Find the local maximum for tightest spot. That's now "locked" in the PLL sense and should stay locked for days or weeks.
  - JshWright 7y ago
    From my comfy armchair, with zero experience in this field, it seems like you could use star tracking to very accurately predict the angle of the sun (since the sun is effectively fixed in position relative to the background stars over the timescales you'd care about). Spotting the target is a little harder, but the same measurement could be made by sticking some reflectors in known positions around the target. I'm sure there are tons of considerations that aren't occurring to me (for instance, thermal expansion likely contributes substantially to making it a moving target (literally)), but I really don't see where "AI" comes into it...
    - smueller1234 7y ago
      Many years ago, I implemented star tracking for telescope alignment for auger.org. An actual basic version using libnova et al was pretty straightforward and a matter of days to prototype if I recall correctly (it was a project for a master student, so I had to do most of the work over a longer period of time). I think the accuracy was around a decimal fraction of a degree then. But the cameras of that thing have only 440 1.5° pixels (photomultipliers that sample at 5-20M samples/s). A higher resolution camera could probably do much better assuming you have a very accurate computer model of the optical properties of your telescope/lenses/camera.
    - dreamcompiler 7y ago
      Figuring out the sun's location is the easiest part of the problem. The hard part is that each mirror is a big, floppy slab that moves with wind, temperature, gear backlash, mechanical wear, rain/hail, and ground settling. The so-called "AI" here is really just a clever way to use closed-loop control so that the above factors don't matter much. (Side note: A large amount of "AI" these days just amounts to changing open-loop mechanisms to closed-loop, often by using computer vision as the state sensor. 3D printers, for example could become much more precise with no mechanical improvements if they did this. Probably some have already done so.)
- ovi256 7y ago
  Yes, you can precalc, and then you need very precise actuators to move the mirror to that precalced position. You also need precise surveying of the ground site to know its geometry. The precise actuators and surverying are expensive. Their approach is using cheap actuators in a closed-loop system where a computer vision controller (using the four cameras on top of the tower) moves the mirrors until it gets it right. Cheap actuator slip and lag is terrible, but with the feedback of the closed-loop, it's doable. This is an approach that's now allowing hobbyists to build cheaper motorised telescopes, robot arms and so on.

Juliate 7y ago

https://en.wikipedia.org/wiki/Odeillo_solar_furnace https://en.wikipedia.org/wiki/Odeillo_solar_furnace "started operating in 1970", "Temperatures above 3,500 °C (6,330 °F) can be obtained in a few seconds". See also https://en.wikipedia.org/wiki/Solar_furnace https://en.wikipedia.org/wiki/Solar_furnace Not dismissing this press release, but at least some scale of progress should be used to compare against. Or state where the economical/industrial/regulatory innovation stands.

scoopertrooper 7y ago
That thing is the size of a building though.
- Juliate 7y ago
  Granted. Size and lightweightness are definitely a point - that could be emphasized as a major argument - even the ratio with size & power capacity & heat intensity.
  - agumonkey 7y ago
    I wonder how security is handled there
    - astrodust 7y ago
      Oh man what if someone stole the sun. (In all seriousness, the security risks are pretty low here. This isn't like stealing nuclear fuel.)
      - agumonkey 7y ago
        Sorry I meant safety.
baq 7y ago
yeah the only problem is the useful heat is contained in a very small area/volume, so this is only a research facility.

zubspace 7y ago

Another similar project in the mojave desert incinerates 6000 birds a year [1]. I wonder, how they handle that.. [1] https://www.sciencealert.com/this-solar-plant-accidentally-incinerates-up-to-6-000-birds-a-year https://www.sciencealert.com/this-solar-plant-accidentally-i...

BurnGpuBurn 7y ago
I was just wondering how many birds this would fry, thanks for the article.
- VBprogrammer 7y ago
  The problem is generally trivial compared to the number killed by domestic cats and glass windows.
  - ygra 7y ago
    For wind turbines at least there's a bit of a difference, as those kill larger birds than cats, in smaller numbers, but those birds also have smaller populations. So just looking at the numbers without knowing the birds and their total populations, makes things hard to compare or judge.
    - VBprogrammer 7y ago
      Sure, thought needs to go into the location of these things; avoiding migration routes and habitats of endangered birds. Using scarecrows and possible trained predator birds (presuming these can be trained to avoid the danger zone!) etc. Of course conventional industry doesn't get a free pass here either, treatment and storage ponds, climate change, habitat destruction etc.
    - usrusr 7y ago
      But aren't most larger birds predators that are highly habitat/food supply constrained? That kind of population could be quite resilient to moderate increases in mortality. (I might be assigning far more importance to predator-Peru cycles than is warranted though, I was reading about what I now found is called https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equatio... at a very young age and the concept stuck for life)

honopu 7y ago

I think the point of calculating using imaging vs a model that requires layout and flat land etc is this would be cheaper to build. You have to build one collection tower/ target, and the mirrors can aim themselves. This greatly reduces the grading, measurement etc and makes installing on existing land without needing to flatten at all, or to some crazy tolerance, much easier. I can see this used in rolling hills, with less impact etc possible.

tempodox 7y ago

Inertia must be incredibly strong. Otherwise, why did it take so long to come up with something that strikingly simple? The last time someone allegedly had an idea like that was around 212 B.C., in the defense of Syracuse.

trickstra 7y ago
Because of oil lobby mostly. The idea is nothing new, it was just easier to burn oil instead of building new industry from ground up and going against all existing oil companies.
- nradov 7y ago
  That "oil lobby" conspiracy theory is such nonsense. There are several developed countries with minimal oil reserves and no domestic oil companies. If alternative energy industries were really practical before then those countries would have built it.
gnode 7y ago
The technology is fundamentally simple, but not practical on a small scale. There are plenty of large, yet simple projects which nobody cares to invest in because there are better (including more expedient, or proven) alternatives. CSP requires a large investment compared to PV solar, as it needs to be done at scale to make coolant systems, towers, turbines and generators cost effective. It needs its own large allocation of land, rather than be distributed. It also, like PV solar, has poor temporal availability, so compares badly to fossil fuels, nuclear and hydro. It has potential to be cheaper than PV, and integrate well with thermal energy storage. It could also be more efficient, if the temperature can be increased (due to Carnot efficiency). However, the convenience and falling prices of PV panels may prevent CSP becoming popular.
masklinn 7y ago
> Inertia must be incredibly strong. Otherwise, why did it take so long to come up with something that strikingly simple? It didn't? There are both solar ovens and solar power plants in active use. The issue's mostly that it's historically been fairly inefficient and expensive (compared to other electricity production sources). Prices have been coming down through improved efficiency and economies of scale, the plants being built these days are bid under $75/MWh and construction has been ramping up a lot especially in high-irradiation locations e.g. Morocco onlined their first station in 2017 (510MW CSP, 72MW PV) and is already building a second one, and Dubai is apparently aiming for 5GW installed by 2030.

Tangokat 7y ago

I wonder who Heliogen hired to do their PR. Must be a really good (or expensive) campaign. There is nothing new in high temperatures and the AI part is pure buzzwords.

epistasis 7y ago
I imagine that being able to throw around the name Bill Gates is as big an advantage as a good PR firm.

aj7 7y ago

Very skeptical that this is a practical means to supply 1500C to an industrial process. Do they plan on piping heat via liquid metal, or what? Do you shutdown on cloudy days and sen everyone home?

arcticbull 7y ago
Just store some molten salt in a really big thermos
- astrodust 7y ago
  Since thermal energy is only lost at boundaries, the larger the amount you have, the smaller the net surface area per unit of volume. This is how you can store huge blocks of ice well into the summer (e.g. https://en.wikipedia.org/wiki/Ice_house_(building) https://en.wikipedia.org/wiki/Ice_house_(building)), but also how a giant underground mass of molten salt that's not in physical contact with the surrounding ground could store a lot of heat for a long time.
  - masklinn 7y ago
    > Since thermal energy is only lost at boundaries, the larger the amount you have, the smaller the net surface area per unit of volume. You do need to do the initial melting work though. It took two months for Crescent Dunes to melt its 32 tons of salt.

nanomonkey 7y ago

I'd love to see something like this put into use for smelting titanium. We really need to start embracing it as a building material as it doesn't corrode or break down like wood, steel, aluminum does...plus it's light and strong which would allow moving houses and vehicles made from it much less energy intensive. It would be great to invest the energy into building materials that can last instead of continuously having to fight corrosion.