| You're misunderstanding the point. The world is ambient. Your device is not. You are trying to extract water from the world so your device needs to be lower than ambient. > So when I take a shower and then and then see water condensing on the inside of my single pane bathroom window on a cold night, it means there's got to be a hidden Peltier cooler in there somewhere? Or in a more exact comparison, if I have an outdoor greenhouse on a cold but sunny day, and I see water condensing on the inside of the glazing, there's got to be a refrigerator making it happen? No, there just needs to be a temperature differential, and the heat sink acts like a cold window. The hot, moist air from your shower should be considered ambient. Your window is colder than that ambient temperature. Hence the water condenses. Let me explain further because this is clearly a sticking point. The air your shower is generating is roughly 40C at 100% humidity. You don't have to put in any work to condense this water on the window because you already put work in to heat it. "Ah ha!" you say. "They're heating the water vapor up inside the container! Just like my shower!" Except no the two are not equivalent. Heating up 25C air at 100% humidity to 40C would decrease its humidity. I.e. no condensation. Cooling 40C air at 100% humidity to 25C would result in condensation (your shower)! It is a one way process. The source of the water vapor MUST be hotter than the condenser! When your source is the atmosphere that means your condenser has to have a lower temperature than the exterior conditions. > Except it's "yes" if you define "ambient temperature" as the temperature inside the shed on a sunny day The temperature is higher in the shed but the humidity is lower! Lowering the temperature of the shed to the outside temperature will not produce condensation! Edit: Sidenote. Greenhouses generate their own water vapor (transpiration). Their absolute humidity will be higher than the outside. Edit2: I also want to emphasize that if you're adding water to the system you're doing it wrong. We're trying to harvest water not supply it. Showers and greenhouses are not apt comparisons. |
Could mean that this would be ineffective in the tropics where the temperature between day and night varies less. And presumably the device may 'stop working' part way through the afternoon if the previous night was too warm relative to daytime temperature.