Wolfram alpha says it takes ~1.3kj to change the temperature of 1m^3 of air by 1 degree C. Obviously this will vary enormously with temperature and humidity, bu

Wolfram alpha says it takes ~1.3kj to change the temperature of 1m^3 of air by 1 degree C. Obviously this will vary enormously with temperature and humidity, but it gives us a number to work with. Wikipedia, and a post by 'someone' tells us there is ~30cc of water per cubic meter of air at 100% humidity and 30c. (This could be a reasonable set of envoronmental conditions in Washington DC for example). The mass of water in 100% humidity air is 28c 27.22g http://www.wolframalpha.com/input/?i=mass+of+water+in+1+cubic+meter&f1=28+%C2%B0C&f=MoistAirMoistureContent.Tdb_28+%C2%B0C&f2=1+bar&f=MoistAirMoistureContent.P%5Cu005f1+bar&f3=100+%25&f=MoistAirMoistureContent.RH_100+%25 http://www.wolframalpha.com/input/?i=mass+of+water+in+1+cubi... 30c 30.34g http://www.wolframalpha.com/input/?i=mass+of+water+in+1+cubic+meter&f1=30+%C2%B0C&f=MoistAirMoistureContent.Tdb_30+%C2%B0C&f2=1+bar&f=MoistAirMoistureContent.P%5Cu005f1+bar&f3=100+%25&f=MoistAirMoistureContent.RH%5Cu005f100+%25 http://www.wolframalpha.com/input/?i=mass+of+water+in+1+cubi... So we can extract ~3g, or 3cc of water from saturated air, with the use of ~2.6kj (assuming 100% efficiency, which is unlikely) Some of the highest power density batteries I've handled are 5 cell, 5500mAh li-poly batteries for model aircraft use, with a total energy capacity of around 180kj, Or ~ 200g of water. I think I'd rather carry a water bottle.