I’m aware of the method where people stretch a small sheet of plastic over a pool of water and collect the condensate that drips off the plastic. But how about some more active methods, each utilizing a 1 meter square flexible solar cell array. Figure full sunlight at 1000w/square meter.
Method 1. Use the electricity to heat, hopefully boil, water and collect the condensate in a downward sloping copper tube.
Method 2. Hook the panel output to 2 electrodes in the pool of water, collect the hydrogen and oxygen and combine them to burn and produce water vapor. Don’t fret the details for now. Condense like the 1st method.
Why do you want to boil the condensate which is distilled water? Flexible solar cells are progressing but they do have problems with sunlight and weather exposure over time. This is not really a long term operation so it’s not like putting these things on your roof but they are still not as efficient as rigid panels so you might as well use rigid panels to collect condensate. New inexpensive IR flexible panels that keep producing electricity from heat could if efficient enough outperform conventional visible light cells and produce enough power to simply run filtration pumps without collecting condensate and operate 24/7. Where it’s very cold there’s usually ice to collect for your water needs though it may still require purification.
Both of those methods are terribly inefficient ways of purifying water. Your Method 1 is essentially distillation, which requires losing energy to the enthalpy of vaporization (the energy required to cause a water molecule to break free of liquid and become a vapor) which is not recoverable. If you want absolutely pure water this is the process to use but it is not necessary to produce potable water, and in fact you generally want some small amount of minerals in drinking water for taste.
Method 2 is dissociation of oxygen and hydrogen via electrolysis; aside the hazard of dealing with diatomic hydrogen, there is just a lot of energy that goes into this as well, although it is roughly 50% recoverable (not counting for additional thermal and mechanical loses) if you then combust hydrogen and oxygen in an efficient heat engine to do work.
Reverse osmosis is the most energy efficient method of removing impurities from water even accounting for the water that has to be reserved to backflush filtration systems. Most municipal water systems, however, just filter water to remove large particles and reduce dissolved solids to some acceptable level, and then treat with some combination of chemical and UV sterilization to eliminate pathogens.
Also, there is no way that solar cells on the ground are going to get anything like 1000 W/m2 for a significant portion of the day. Phoenix, AZ, for instance, gets an average of about 6.6 kWh/m2/day, which assuming your solar cells can maintain perfect alignment with the Sun works out to a mean of about 825 W/m2 over an 8 hour effective day, and that’s basically the most ideal insolation condition.
The plastic sheet method has the practical advantage of simplicity. I mean obviously it’s more efficient to gear a bicycle to a rotary saw, but a handsaw is a hell of lot simpler.
To clarify: the 1000w is just the solar input. The exact amount of electricity the array puts out is not important. What I wondered is simply which method would make the most water. I don’t know how to calculate the amount of electricity used by method 2.
Using the solar cell to heat the water and this induce increased evaporation has the drawback that you still need a cooler environment to trigger the condensation, and you need a means of collecting the output without contaminating it by the original source.
Using electrolysis to split water and then burn it in a container to collect the water means having containers to collect the gases without them escaping and then a combustion chamber that collects the output, preferably without match debris in it.
I don’t have numbers for the percentage of recovery from either method, but I can’t think either is very high.
I’m also left wondering why you stipulate a flexible sheet solar array. I suspect you may be considering some kind of emergency water purification system. I suspect that existing water filtration kits are going to be much lower volume and weight to whatever contraption that could be devised for either of your methods.