They give current solar desalination efficiency as 1.5 kilos of water per square meter. Shouldn't there be a time component?
They're using Journalist Power Units. You're lucky it's not in houses per year.
Light can make water evaporate without heat
21–30 of 198 posts
Re: Light can make water evaporate without heat
#22Why is it surprising? Light can transfer momentum into the water, which is was matters for the process of evaporation...?
> Light can transfer momentum Momentum is mass x velocity; what’s the mass of a photon?
You can't use classical physics to calculate the momentum of a photon.
https://en.wikipedia.org/wiki/Photon#Relativistic_energy_and...
Re: Light can make water evaporate without heat
#23This technology leads directly to cloud lasers. Yesss
Cloud what?
Re: Light can make water evaporate without heat
#24I can't wrap my head around this story. What does it mean in thermodynamic terms? Isn't there a fixed amount of energy per mass that it takes to convert liquid water into vapor? Why does it matter that the energy comes from light?
if you leave a container of liquid in a cold dry room, it will eventually become empty and the room will become more humid
Heat speeds up this process via excitation, photon bombardment speeds up this process also. I'm guessing its more a matter of, if you heat up stuff, you need to heat up stuff and everything around it. Light can be a lot more controllable and directed. In addition, internal reflection can happen within water against air, meaning a free second (third, fourth, fifth, etc) attempt at depositing energy somewhere.
Re: Light can make water evaporate without heat
#25I can't wrap my head around this story. What does it mean in thermodynamic terms? Isn't there a fixed amount of energy per mass that it takes to convert liquid water into vapor? Why does it matter that the energy comes from light?
Entropy favors the vapor form. It doesn't necessarily take energy to evaporate.
Re: Light can make water evaporate without heat
#26I can't wrap my head around this story. What does it mean in thermodynamic terms? Isn't there a fixed amount of energy per mass that it takes to convert liquid water into vapor? Why does it matter that the energy comes from light?
> In recent years, some researchers have been puzzled upon finding that water in their experiments, which was held in a sponge-like material known as a hydrogel, was evaporating at a higher rate than could be explained by the amount of heat, or thermal energy, that the water was receiving. And the excess has been significant — a doubling, or even a tripling or more, of the theoretical maximum rate.
Apparently it evaporates much, much more quickly than you'd expect from purely energy per mass.
Re: Light can make water evaporate without heat
#27I can't wrap my head around this story. What does it mean in thermodynamic terms? Isn't there a fixed amount of energy per mass that it takes to convert liquid water into vapor? Why does it matter that the energy comes from light?
My 8th grade understanding is evaporation doesn't always mean steam.
Re: Light can make water evaporate without heat
#28Earlier quoted context omitted.
Isn't 'transfer momentum' just a round about way of saying "heat up." I think the interesting aspect here is that the evaporation is greater than what can be explained by heat alone.
Yeh I read it as though it’s a form of catalyst. Ultimately the light is changing the threshold energy at which water can evaporate. Similar to the photoelectric effect. Similar say to an enzyme. All these environmental changes to the reaction lower the ‘action’ energy making the reaction vastly more efficient or possible in an environment that it wasn’t possible in previously.
Enzymes catalyze the breaking of molecular bonds.
The embodied energy of a phase transition does not pay attention to what path you took to cross it. There’s no “threshold” between phases of water.
For H20 to move from liquid water to vapor, energy must be added. There’s no catalyst.
So either we’ve discovered some new physics since I last studied thermodynamics, or this isn’t an accurate analogy.
Re: Light can make water evaporate without heat
#29Would this be useful for desalination or laundry?
Re: Light can make water evaporate without heat
#30I can make water evaporate too (by drinking it and making it disappear;)