Factors influencing the rate of evaporation
* Concentration of the substance evaporating in the air: If the air already has a high concentration of the substance evaporating, then the given substance will evaporate more slowly.
* Concentration of other substances in the air: If the air is already saturated with other substances, it can have a lower capacity for the substance evaporating.
* Flow rate of air: This is in part related to the concentration points above. If fresh air is moving over the substance all the time, then the concentration of the substance in the air is less likely to go up with time, thus encouraging faster evaporation.
* Concentration of other substances in the liquid: If the liquid contains other substances (such as salts), it will have a lower capacity for evaporation. This is due to Raoult's law.
* Temperature of the substance: If the substance is hotter, then evaporation will be faster.
* Inter-molecular forces: The stronger the forces keeping the molecules together in the liquid state the more energy that must be input in order to evaporate them.
* Surface Area: A substance which has a larger surface area will evaporate faster due to the fact that there are more surface molecules which are able to escape.
There is more information, charts and formula for evap rate there too.
Good ideas but I'm not sure the copper or greenhouse will help. The greenhouse will keep relative humidity high which prevents evaporation(which I think is the point of a greenhouse?).
The copper in the water probably will not help much. You have a certain area of sunlight and absorb a certain amount of that light (which is why many people use black tarps). Unless the copper helps absorb more of the light, it's not increasing the energy of the system. If the copper is outside of the water area, then you are increasing the area of light you're absorbing, but then you have to ask why are you increasing the area with copper instead of with the water, which would probably give a better return in the first place. Also it could hurt you, acting as a heat sink for your water system. As you've probably noticed before, water in a dark container can get very hot in the sun. Adding surface area to the wind could actually leave your copper cooler than your water system and cool it. It could be done, but you'd probably have better results by just adding another bucket holding water.
The lens has the same problem with surface area. It's only taking in energy from it's cross sectional area facing the sun. If that interferes with light that would normally hit the water, there will be no net gain. The way you could get this to work, is that you can take a small amount and make it hot locally. The hotter you get the water the faster the increase in evaporation rate
. So if your system is small relative to the lens, you could get an increase worth your while. Coupled with a float and fill system you might have a really efficient system.