> In the natural world, evaporation occurs when sunlight warms the surface of the Earth, breaking the bonds which hold water molecules together.
Which is... sort of not inaccurate, but feels like it implies a misleading concept, and makes me think the author copied it without understanding it.
Really? Do puddles not dry up at night?
My impression was that evaporation occurs because that's just the way liquid behaves. It's more important that water molecules are really small than that they experience sunlight. Temperature-based evaporation is "boiling", and sunlight doesn't make a meaningful difference there, as far as water goes...?
That's almost worse than the original! :)
Water evaporates because their energy (heat) causes the molecules to bounce around and sometimes escape the cohesive attraction of their friends and into the air. More energy, more evaporation.
This works well with small water molecules, less well with larger and heavier liquids.
Hmm, could you call this mysterious "cohesive attraction"
> the bonds which hold water molecules together.
...? If not, then please do describe this cohesive attraction.
I've come to realize some people just like to complain on the internet.
Evaporation does not break those bonds, it's just the intact molecules energetically escaping the surface tension of the liquid.
(Disclaimer: My high school chemistry books have not left their shelves in many years, except when moving.)
Surface tension is a bond that binds water mold together similar to how mortar holds bricks together in a wall.
Mortar doesn't make the brick solid, but it holds the bricks together.
People are reading bond in two different ways. Bond within a molecule vs bond between molecules.
1. https://www.usgs.gov/media/images/surface-tension-forms-a-st...
I don't think that's true for naming, but regardless warmer water evaporates quicker.
And the statement doesn't say evaporation doesn't occur for other reasons, though the wording feels like it implies it.
1) Breaking the covalent bonds that hold individual water molecules together, preventing them from splitting into two hydrogen and one oxygen atom. That's clearly not true.
2) Breaking the hydrogen bonds that stick one water molecule to another, keeping the water in liquid form. That's true.
In any case, it's poorly phrased.
Cooking oil, notably, will not evaporate the way water will -- if you spill it somewhere, the oil will mostly just stay wherever you left it until you clean it up -- but my understanding was that this is because oil molecules are huge and heavy while water molecules are tiny.
I am very skeptical how much usable power could be generated using the 'drinking bird' approach. Show me the engine or generator that the drinking bird powers . . .
I will never understand how insanely ignorant the average person is about electricity when every single electrical object in the US comes with label that concisely and accurately describes how much voltage and current it uses, and you get billed by the kWh, and the equation that pulls all this together is literally a simple multiplication, and I've struggled to put two transistors together in a circuit every single time I've tried to learn analog electronics!
It feels like watching that early internet video of the lady that couldn't figure out that if you are driving 60 mph, you drive one mile a minute. I want to be clear, I'm saying this as someone who struggles with doing basic dimensional analysis in high school physics. I cannot comprehend the willful and purposeful ignorance that most people seem to carry throughout their lives.
I don't think people do enough recreational math or unit conversions. My STEM trained friend recently expressed surprised at how much chicken "2 kg" is, and I just don't get it. 1 pound is close enough to 500 grams as to not care about the actual conversion! Same as 1 meter = 1 yard, and 1 qt damn near equals 1 liter. I know my brain is broken compared to most, but how do you live without figuring these things out?
39 inches to the meter.
3.79 liters to 4 quarts.
1.6 km to the mile.
* 9/5 and + 32 for C to F.
I think those are correct? I think I was made to memorize those at some point, but of note, I am also an immigrant to the US from a wacky metric system nation.
Solar power, geothermal power, hydro power, are effectively perpetual motion, for our purposes. Heat pumps kind of violate the "you can't get something for nothing" principle too, since you can get >100% return on the electricity you put into them. The more we look into renewables, the more we can find ways to "cheat" by using "preprocessed" goods where the sun or the earth already did the hard part for us.
There's no thermodynamic reason you couldn't have a small device on your desk that uses ambient heat, moisture, light, etc to store energy that you can use to do work, just engineering and chemical reasons it's hard to do this on a scale that's relevant. https://en.wikipedia.org/wiki/Crookes_radiometer is over 100 years old and, if kept in sunlight, can provide "perpetual motion" for "free".
> Solar power, geothermal power, hydro power, are effectively perpetual motion, for our purposes.
I get solar power and hydro [also solar] power, but isn't geothermal power a closed part of the system? Where does solar input feature in that?
> The more we look into renewables, the more we can find ways to "cheat" by using "preprocessed" goods where the sun or the earth already did the hard part for us.
This is also a closed part of the system. If the argument you're making is "the planet is not a closed system", then you need to be using energy that comes from outside, not energy that is already contained in the system.
Agreed, ‘output of 100 volts’ is meaningless without knowing the current.
Edit: Looks like it puts out 3.6 microwatts (0.0000036 watts) at 100v, or (assuming single-phase) 0.000000036 VA
> Until now, previous attempts to convert evaporation energy into electricity have suffered from a low-conversion efficiency. But using the drinking bird method, scientists have managed to generate an output of 100 volts using just 100 millilitrers of water, enough to power small electronic devices.
I would take it with a huge grain of salt.