A new Form of Green Energy

[swansont]

First, I don't believe humidity will be 100% at any temperature. Can you provide backup for that claim?

 

 

Relative humidity can be 100%. It occurs at (or below) the saturation temperature, aka the dew point.

https://en.wikipedia.org/wiki/Dew_point

 

It is an easy calculation. Just water weighs 18g per mole, 3785grams/gallon, 210moles per gallon, 1 gallon weighs 8.3 lbs, 1 footpound =1.36 Joules. So, if we had a hygroscopic substance that absorbed twice it's weight in water and we

started with 100lbs of the substance, it would absorb 200lbs of water. If we had it at 1000ft, we would get 100,1000 foot pounds of energy or 136,000 joules. That would be 1000 watts for over 2 mins. At 10,000 ft, we would have a hair dryer running for 20 mins.

 

 

I don't think you get watts from your calculation; you don't have a rate in your energy calculation. 100,1000 foot-pounds? (200 lbs at 1000 feet would be ~270,000 J)

 

Further, I don't see any justification that the numbers you are using are reasonable.

 

At 20ºC, you have a little less than 15g of water per kg of air.

http://www.engineeringtoolbox.com/humidity-ratio-air-d_686.html

 

So, for 1 kg of water (2.2 lbs) you would need 66.7 kg of air. At 22.4 L/mole, and ~ 29 g/mole, that's 51,500 liters of air. That's 51.5 cubic meters. And you want to have almost 100 kg (so 5000 m^3, at absolute minimum), with no realistic expectation that the hygroscopic material would draw all of the water out, so you would need several times that volume.

[robinpike]

Another way of looking at this process could be to consider a condensing system where vanes in each box are chilled at the bottom and the box opened at the top, allowing water in the air at the top to condense onto the vanes and cause the box to increase in weight and drop. At the bottom, the water could be poured out before re-chilling the vanes, etc.

 

So in this variation the question is: could enough energy be extracted from the falling boxes to drive the chilling of the vanes and leave some energy left over? And if so, would it grind to a halt anyway, ending up with a pool of cold water at the bottom and no evaporated water at the top?

[swansont]

Another way of looking at this process could be to consider a condensing system where vanes in each box are chilled at the bottom and the box opened at the top, allowing water in the air at the top to condense onto the vanes and cause the box to increase in weight and drop. At the bottom, the water could be poured out before re-chilling the vanes, etc.

 

So in this variation the question is: could enough energy be extracted from the falling boxes to drive the chilling of the vanes and leave some energy left over? And if so, would it grind to a halt anyway, ending up with a pool of cold water at the bottom and no evaporated water at the top?

 

 

You would need a way to re-heat the condensed water, and a way to chill the vanes. It all boils down (excuse the pun) to the gravitational potential energy vs the thermal energy, and whether or not any of this can be grabbed from some external source like the sun. Reheating the condensation water could be done for free with solar, for example.