4 ms·

I'm fairly certain the air will be conditioned and inside humidity kept to an acceptable standard.

wpietri 3y ago
From the article: "The greenhouse is a volunteer affair, and it yields enough for herbs and the occasional salad! It’s also the only place on station with humidity! Since the rest of the station has near-zero humidity, it’s a treat to spend time in here."
- teh_klev 3y ago
  I'd have to question what "near-zero" actually means. I don't doubt that outside the humidity is super low, but inside I have my doubts. Super low humidity increases the risk of ESD which wouldn't be fantastic for any electronics. You'd need to walk around with a grounding strap all day otherwise you'll be zapping every bit of metal you encounter. I worked in a newly built data centre where the air conditioning (not the chillers) wasn't tuned quite right and the humidity dropped so low that we were being zapped left right and centre. So I'd love to see the actual figure they're using as "near-zero".
  - dredmorbius 3y ago
    Among other factors: humidity, even at modest levels, means frost and ice accumulation in any spaces with a thermal gradient. Given that there's a roughly 150F / 85C temperature differential from the inside (assuming ~70F / 20C interior temperature, and -70F / -55C exterior), and that it never thaws, this means frost/ice accumulation is probably a major structural hazard. Even if it was possible to humidify interior spaces, it might be avoided for that reason. (I'm of course speculating, though based on discussion of PassivHaus designs in Fairbanks Alaska and the attention paid to moisture, vapour barriers, and frost accumulation, as well as an earlier article I believe linked to HN showing the cold food storage at ASSPS which included massive amounts of accumulated frost, and that I suspect just from moisture contributed by the breathing of occupants / workers within the cold (ambient) storage structure.)
    - wpietri 3y ago
      I talked about this with an architect friend, who also mentioned that at-scale humidification is difficult, expensive, and prone to molding. In thinking about air exchange, it seems like they would have to desiccate the outgoing air and shift the moisture to incoming air, which would have to be a challenge.
      - dredmorbius 3y ago
        Interesting. I've heard of heat recovery on air exchange, but never humidity recovery. I'm not sure to what degree water is readily available at ASSPS (yes, there's snow all around, but it's cold, and actual precipitation is low), but humidifying air is ... reasonably low-cost, modulo thermal budget for melting snow/ice in the first place.
brr-fyi 3y ago
Indoor air is heated but not humidified. Relative humidity outside is high, but the temperature is very cold, so the absolute amount of water in the air is very low. Bring that same air indoors, heat it up by ~150 degrees Fahrenheit, and the resulting relative humidity is very low. Hard to measure at such low numbers. I have a handful of cheap consumer-grade sensors with me, and they all report "0%" or "lower limit" or equivalent. I can't share readings from official NSF-owned equipment. Static buildup is a real issue. It's muscle memory now for me to ground myself before touching any electronics. There's makeshift grounding points (metal tape, metal frames, etc) everywhere. I'm still not used to the little shocks every time. I humidify my bedroom at night using portable humidifiers. This takes ~1.5 gallons of water per night, which is deemed an acceptable use of water. Most people do this. I can get my room up to ~15% humidity with a reasonable amount of effort. The difference in sleep quality is noticeable. Frost buildup is a real issue in humidified spaces, given the temperature gradient to the outside, even with triple-pane windows. The greenhouse has no exterior windows, so this isn't a problem. The greenhouse is kept at ~25% relative humidity. It's the only place on station with infrastructure in place to provide humidity directly through the HVAC system.
- teh_klev 3y ago
  Much appreciated for expanding on the humidity thing. > Static buildup is a real issue. It's muscle memory now for me to ground myself before touching any electronics. There's makeshift grounding points (metal tape, metal frames, etc) everywhere. I'm still not used to the little shocks every time. I did wonder about that, and so it is a thing you need to learn to live with. As I'd mentioned in a comment below, I had the misfortune of working in a newly built data centre where the HVAC was still being commissioned/tuned that caused the humidity to drop severely in the rack zones. It was a right pain in the fingers being zapped frequently as we moved racks and other non-electronic infrastructure into place. But it was also comedic as well as you could regularly hear quiet yelps and expletives from others in the team as they too were being zapped :)
- kylehotchkiss 3y ago
  Wouldn't you need additional fire suppression at those levels of humidity? It's more dry than Southern California during the Santa Ana winds!

From the article: "The greenhouse is a volunteer affair, and it yields enough for herbs and the occasional salad! It’s also the only place on station with humidity! Since the rest of the station has near-zero humidity, it’s a treat to spend time in here."

teh_klev 3y ago
I'd have to question what "near-zero" actually means. I don't doubt that outside the humidity is super low, but inside I have my doubts. Super low humidity increases the risk of ESD which wouldn't be fantastic for any electronics. You'd need to walk around with a grounding strap all day otherwise you'll be zapping every bit of metal you encounter. I worked in a newly built data centre where the air conditioning (not the chillers) wasn't tuned quite right and the humidity dropped so low that we were being zapped left right and centre. So I'd love to see the actual figure they're using as "near-zero".
- dredmorbius 3y ago
  Among other factors: humidity, even at modest levels, means frost and ice accumulation in any spaces with a thermal gradient. Given that there's a roughly 150F / 85C temperature differential from the inside (assuming ~70F / 20C interior temperature, and -70F / -55C exterior), and that it never thaws, this means frost/ice accumulation is probably a major structural hazard. Even if it was possible to humidify interior spaces, it might be avoided for that reason. (I'm of course speculating, though based on discussion of PassivHaus designs in Fairbanks Alaska and the attention paid to moisture, vapour barriers, and frost accumulation, as well as an earlier article I believe linked to HN showing the cold food storage at ASSPS which included massive amounts of accumulated frost, and that I suspect just from moisture contributed by the breathing of occupants / workers within the cold (ambient) storage structure.)
  - wpietri 3y ago
    I talked about this with an architect friend, who also mentioned that at-scale humidification is difficult, expensive, and prone to molding. In thinking about air exchange, it seems like they would have to desiccate the outgoing air and shift the moisture to incoming air, which would have to be a challenge.
    - dredmorbius 3y ago
      Interesting. I've heard of heat recovery on air exchange, but never humidity recovery. I'm not sure to what degree water is readily available at ASSPS (yes, there's snow all around, but it's cold, and actual precipitation is low), but humidifying air is ... reasonably low-cost, modulo thermal budget for melting snow/ice in the first place.

brr-fyi 3y ago

Indoor air is heated but not humidified. Relative humidity outside is high, but the temperature is very cold, so the absolute amount of water in the air is very low. Bring that same air indoors, heat it up by ~150 degrees Fahrenheit, and the resulting relative humidity is very low. Hard to measure at such low numbers. I have a handful of cheap consumer-grade sensors with me, and they all report "0%" or "lower limit" or equivalent. I can't share readings from official NSF-owned equipment. Static buildup is a real issue. It's muscle memory now for me to ground myself before touching any electronics. There's makeshift grounding points (metal tape, metal frames, etc) everywhere. I'm still not used to the little shocks every time. I humidify my bedroom at night using portable humidifiers. This takes ~1.5 gallons of water per night, which is deemed an acceptable use of water. Most people do this. I can get my room up to ~15% humidity with a reasonable amount of effort. The difference in sleep quality is noticeable. Frost buildup is a real issue in humidified spaces, given the temperature gradient to the outside, even with triple-pane windows. The greenhouse has no exterior windows, so this isn't a problem. The greenhouse is kept at ~25% relative humidity. It's the only place on station with infrastructure in place to provide humidity directly through the HVAC system.

teh_klev 3y ago
Much appreciated for expanding on the humidity thing. > Static buildup is a real issue. It's muscle memory now for me to ground myself before touching any electronics. There's makeshift grounding points (metal tape, metal frames, etc) everywhere. I'm still not used to the little shocks every time. I did wonder about that, and so it is a thing you need to learn to live with. As I'd mentioned in a comment below, I had the misfortune of working in a newly built data centre where the HVAC was still being commissioned/tuned that caused the humidity to drop severely in the rack zones. It was a right pain in the fingers being zapped frequently as we moved racks and other non-electronic infrastructure into place. But it was also comedic as well as you could regularly hear quiet yelps and expletives from others in the team as they too were being zapped :)
kylehotchkiss 3y ago
Wouldn't you need additional fire suppression at those levels of humidity? It's more dry than Southern California during the Santa Ana winds!