Bob Flint
The idea could work, but the surface area/vs power of fan and distillation rate seems far less than what an average person expels in sweat, & skin surface area evaporation alone. I don't think this could come close to delivering the amounts of clean water you would need to survive just sitting under a tree, much less cycling in the sun..
Vaporwear at it's finest...
Maybe a wearable T-shirt style or full body suit evaporative/ recuperative/cooling solution? Pretty sure astronauts suits take this into account somehow..
reasonablyskeptical
Yes, the "ultimate in vaporware" is a fitting description for this device. On their web page and other sites they claim that it should produce 500ml per hour AND that it will produce up to one drop of water per minute... wouldn't you think that there are more than 60 drops of water in a half litre? Note that just the latent heat of vaporization for water is 2260kJ/kg so 500ml requires the transfer of 1130kJ or 314 Watt-hours. To condense this much water in say one hour, the device would have to move a continuous 314W! With a high end Peltier device, coefficient of performance is about 3.0 for their claimed 50% humidity and 68F (20C) minimum requirements meaning you'd still need about a 100W solar panel to run it. This doesn't even include cooling the air by 19F to get to the dewpoint in the first place... On an ironic note, it's also interesting that in the promotional video the mountain-biker rides right through a pristine freshwater stream.
jeffbloggs
@Reason Hitting the dew point means the water condenses by itself without the need to dissipate all of the the latent heat. You have not included any temperature nor humidity values into your calculation to cover all operating conditions.
I think the "vaporware" in the story was meant to be more tongue in cheek. Out of interest where does it say 1 drop per minute on their website?
reasonablyskeptical
@jeffbloggs Pick up any thermodynamics book and read about freezing and evaporation, reversible processes where the fluid doesn't actually change temperature while energy is transferred but a phase change happens instead. For water, this amounts to LOTS of energy - about the same energy as changing the temperature of liquid water by 80C for freezing/thawing (at a constant 0C) but equivalent to changing the temperature by 540C for evaporating/condensing. Think of how much energy you have to put into a kettle to boil it dry (after you heat it up to 100C). You have to remove that same amount of energy to condense it again. Water does not condense "by itself" - it requires removal of energy. Google "fontus one drop per minute" (without quotes) for hundreds of claims about the device's performance on various websites. In these claims, 20C and 50% humidity is given. This means that the air temp must be reduced to the dew point (9.5C for those initial conditions) which causes the RH to be 100%. Further removal of energy causes condensation but as water is removed from the air the dew point goes down and as the temperature difference increases the Peltier device COP becomes lower, much less than one. There's no way that tiny solar panel could power this process - you'd need at least hundreds of Watts to condense 500ml per hour.
MartinMansour
@reasonablyskeptical your logic is on point except for one point. You state that "as water is removed from the air the dew point goes down". While lowering the relative humidity does reduce the dew point therefore requires more energy, i presume this product cycles the air and therefore the relative humidity is approximately constant as we are working with a large volume of air. Therefore, I reckon the dew point will be constant.
JøhP
@reasonablyskeptical, I fully agree with you, that the thermodynamics of this device sounds literally incredible.
But the "one drop per minute" claim, is from a description of the first prototype, and so there is no relation between it and the 500 ml/h claim.
FabianLamaestra
If this works, wouldn't it put bottled water out of business? Couldn't you just leave this thing working in your home 24/7 filling up gallons of water, sort of like those portable air conditioning units like Movincool?
reasonablyskeptical
In order to remove any water from the air, the temperature must be below the dewpoint so that water will condense out and the resulting air will stabilize at the new dewpoint, at 100% humidity but at a lower temperature. With a 10C temperature difference, Peltier devices can have a coefficient of performance of about 3 but if the cold side temperature needs to be even lower, the COP goes down dramatically. Add to this that the hot side of the Peltier device not only has to dissipate the energy from the humid air but also the energy put in to run the device and you've got a major heat dissipation problem. The heatsink on the hot side would have to be gigantic to radiate several hundred Watts and maintain a very small temperature difference above ambient. Sadly, this product becomes more and more improbable the more I think about it...
reasonablyskeptical
In order to remove water from the air, the temperature must be below the dewpoint so that water will condense out and the resulting air will stabilize at the new dewpoint, at 100% humidity but at a lower temperature. With only a 10C temperature difference, Peltier devices can have a coefficient of performance of about 3 but if the cold side temperature needs to be even lower, the COP goes down dramatically. Add to this that the hot side of the Peltier device not only has to dissipate the energy from the humid air but also the energy put in to run the device and you've got a major heat dissipation problem. The heatsink on the hot side would have to be gigantic to radiate several hundred Watts and maintain a very small temperature difference above ambient. Sadly, this product becomes more and more improbable the more I think about it...
tempcommentaccount
@reasonablyskeptical Your understanding of thermodynamics is flawed. To remove X amount of energy from something, you don't *provide* X amount of energy to it. Ever wondered why your winter heating bill is higher than your summer cooling bill?