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I am not sure I entirely understand, are you essentially generating electricity by evaporating water from a very concentrated solution, condensing it somewhere with no solute and then generating the power by letting it fall to the bottom of the tree, only to be lifted back up again by osmotic pressure?
If so my first reaction is that is is going to be hideously inefficient, the latent heat of vaporisation for water is 2.2MJ per kg... if you can lift the water up 300m that means you are going to get out at the most 300J/kg which gives you a thermodynamic efficiency of about .015% so if you have on average about 250W/m2 of sunlight hitting a piece of ground,you are going to generate about .04W/m2...
Dave if we have 800,000 liters of water falling 250 meters through a pipe 20 cm in diameter hitting a turbine how much electricity would we generate? And what is the optimum diameter of the pipe?
Power = ( 820.2 * 68.75 * 90% )/11.8 = 4300.8 kilowatts per hour or 71.68 kilowatts per minute
One square metre of timber when burned will give more than 1KW
Now as I said earlier this formula was the only one I could find that estimates power from falling water and it is from an American website (http://www.wvic.com/hydro-works.htm).If you know of another formula please tell me.
Now it seems that you're suggesting that a tree is doing something impossible!According to your figs 0.11g per second * 60 * 60 * 24 = 9504g or 9.5 liters a day!9.5 liters a day doesn't come close to what a tree tries NOT to do!
As I said earlier I'll go though most of the math with regards to estimating how much water we can raise. we estimated earlier than we can increase this by a factor of a hundred, recently we've begun to think than we can increase this natural evaporation rate by closer to three hundred.
Does it take the same amount of energy to evaporate 1 kg of water when it is in a cube shape as it does when it is spread out a few molecules in depth with a huge surface area?
This is in imperial units and the the '11.8' is used to convert units of feet and seconds into kilowatts per hour.If we can have kilowatts per hour why not per minute?