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from the seawater-is-more-than-just-salty-water dept.
There are many ways to generate electricity—batteries, solar panels, wind turbines, and hydroelectric dams, to name a few examples... and now, there's rust.
New research conducted by scientists at Caltech and Northwestern University shows that thin films of rust—iron oxide—can generate electricity when saltwater flows over them. These films represent an entirely new way of generating electricity and could be used to develop new forms of sustainable power production.
Interactions between metal compounds and saltwater often generate electricity, but this is usually the result of a chemical reaction in which one or more compounds are converted to new compounds. Reactions like these are what is at work inside batteries.
In contrast, the phenomenon discovered by Tom Miller, Caltech professor of chemistry, and Franz Geiger, Dow Professor of Chemistry at Northwestern, does not involve chemical reactions, but rather converts the kinetic energy of flowing saltwater into electricity.
https://phys.org/news/2019-07-ultra-thin-layers-rust-electricity.html
More information: Mavis D. Boamah et al. Energy conversion via metal nanolayers, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1906601116
(Score: 2) by RS3 on Wednesday July 31 2019, @05:53PM (36 children)
I don't see the problem. Could you please elaborate?
(Score: 0) by Anonymous Coward on Wednesday July 31 2019, @06:03PM (15 children)
Have you tried a mirror?
Facetiousness aside, he is mixing energy and power units. "A few kilowatts per hour" would be a linearly increasing power source. After 1000 hours it would be a few megawatts. Give it a few decades and it could power the entire USA. Indeed, wait long enough and it will outshine the Sun.
(Score: 2) by RS3 on Thursday August 01 2019, @03:23AM (14 children)
I really don't see the problem. It may be because I'm an EE and had to study the stuff out the wazoo. The really enlightening thing was that I didn't know I even had a wazoo.
It may be that you don't understand "watt". Watt is a unit of measurement of "power", which is an instantaneous measurement. Simply volts times amps. You have to produce power over time to have energy, measured in "joules", which are defined as "watt seconds".
Exactly the same as "horsepower", which is used in the US, and KW (kilowatts) are often used in EU, etc. It's an instantaneous measurement- no time unit involved. To do actual work, you have to make horsepower for some amount of time to move a load.
A battery will have a rating of how many watt-hours it can store. Or maybe amp hours.
I dunno if that makes sense, but I'm glad to explain more clearly if not.
(Score: 1, Informative) by Anonymous Coward on Thursday August 01 2019, @09:48AM (1 child)
No no no, energy is not power over time... To define energy in terms of power is basically the same thing as defining position in terms of velocity. This is like saying "you have to move over time to have position" -- no! Velocity is a rate of change change in position. Likewise, power is a rate of change in energy. You can absolutely have energy without power.
When energy moves from one place (or form) to another you have work, and the speed at which that happens is power.
(Score: 1, Redundant) by RS3 on Thursday August 01 2019, @01:55PM
You're a tiresome pedant. How about: power for a period of time.
(Score: 1, Troll) by Sabriel on Thursday August 01 2019, @10:16AM (7 children)
AC was rude but is right about the unit mixup in what was quoted:
"For perspective, plates having an area of 10 square meters each would generate a few kilowatts per hour—enough for a standard US home,"
Watt is indeed an instantaneous measurement, as you say, yet the quote is claiming that plates would generate a few kilowatts _per_ hour - which is not the same thing as a few kilowatt hours.
The article may have since been corrected, since when I read it just now it uses "kilowatt-hours". Which is better but still annoying in that no time frame is given for how long it takes to generate that amount. An hour? A week? A century?
(Score: 1, Troll) by RS3 on Thursday August 01 2019, @01:58PM
I forgot I was in the land of cowardly anonymous pedants.
(Score: 1, Offtopic) by RS3 on Thursday August 01 2019, @02:47PM
If you downmodded me, uncool. I referred to the ACs, right? They're a scourge.
(Score: 0) by Anonymous Coward on Thursday August 01 2019, @10:28PM (4 children)
hehehe, lol. now i get it "watt per hour" translated is "w/h" but watt-hour is "w*h".
i am sure the writer has stumbled upon something on the internet often enough to know that watt or even kilo watt is not energy.
so for good measure threw in hours too ...
(Score: 2) by RS3 on Thursday August 01 2019, @11:36PM (3 children)
Yes, thank you. It's a matter of English, terminology, plainspeak, etc. The word "per" does NOT exclusively mean "divide by", but some ACs here have limited brain cells, and they're way overly proud of the few they have that work, so that's all they can handle.
Fortunately, as an engineer, one of my jobs, which makes me pretty good, is to understand and interpret "plainspeak". If everything I designed, configured, etc., was spelled out for me, I would not be functioning as an engineer, but more as an assembler / technician. And sometimes we have to spend quite a bit of time with customers, process engineers, sales / marketing people, etc., to understand what they really want, and make sure they understand what we believe is the correct design / process to give them the working design. And when we run into people like many (most?) of the other ACs here, we do everything we can do bypass them.
(Score: 0) by Anonymous Coward on Sunday August 04 2019, @03:37AM (2 children)
Please give an example, in a natural sentence, of using the word "per" where it does NOT mean "divided by".
(Score: 2) by RS3 on Sunday August 04 2019, @03:51AM (1 child)
"I built the bicycle per the instructions". I guess I could say "I built the bicycle divided by the instructions", but it wouldn't make sense.
"Per" is a prepostion, one definition (you can look it up too) is: "by means of".
How about "take one pill per day". Would you say "take one pill divided by day"? Doesn't make sense, does it?
Is that enough to convince you, or do you expect me to google some more?
I don't understand the pedantry here. I need to consult a social psychologist. I've come into boards like this fairly late in the game and some things baffle me. Why all the flame wars and downmodding? It's sad how this could have been a great website.
(Score: 0) by Anonymous Coward on Monday August 05 2019, @03:08PM
For perspective, plates having an area of 10 square meters each would generate a few kilowatts per hour—enough for a standard US home
For perspective, plates having an area of 10 square meters each would generate a few kilowatts by means of hour—enough for a standard US home
Doesn't really work in that context does it?
Maybe you meant the meaning "each"
For perspective, plates having an area of 10 square meters each would generate a few kilowatts each hour—enough for a standard US home
Nope. Although given your apparent disregard of units you probably think that's fine.
(Score: -1, Troll) by Anonymous Coward on Thursday August 01 2019, @10:55AM (3 children)
As sabriel says, I may be rude, but I would never hire you as an EE if you can't see the problem in what was quoted. It would be bad enough to miss it in the original, but to still not see it when it is pointed out...
Have you considered remedial classes? Or maybe a job where you say "would you like fries with that?"
(Score: 2) by RS3 on Thursday August 01 2019, @01:42PM (2 children)
As an EE I use numbers and formulas, not words. If you hire technical people based on pedantry, you're a hated boss, and likely constantly complaining that you can't find good people.
(Score: -1, Troll) by Anonymous Coward on Thursday August 01 2019, @07:03PM (1 child)
If I was hiring an E.E. I doubt that I would consider one who did not know the difference between power and energy to be a "good people". Using numbers and formulas is fine when you use the right ones, but if you don't understand what they represent then at some point you are going to use the wrong one and whatever you built is going to burst into flames.
(Score: 2) by RS3 on Thursday August 01 2019, @11:43PM
More platitudes. You're good at something afterall.
(Score: 2) by DannyB on Wednesday July 31 2019, @06:03PM (4 children)
> would generate a few kilowatts per hour
Ah!, there's the problem!
But you hear this kind of incomprehensible nonsense from YouTube videos about electric cars.
And . . . Han Solo claimed that his Millennium Falcon "made the Kessel Run in less than twelve parsecs"
And . . . you might have to wait for ten light years to get to that star!
Every performance optimization is a grate wait lifted from my shoulders.
(Score: 1, Funny) by Anonymous Coward on Wednesday July 31 2019, @06:10PM
And . . . Han Solo claimed that his Millennium Falcon "made the Kessel Run in less than twelve parsecs"
And . . . you might have to wait for ten light years to get to that star!
In both cases it's a matter of routing. As long as that star is closer than 10 light years away, waiting ten light years(or 5 miles to get to the next rest area) only indicates that you may not be taking the optimal route. Similarly, with the assumption that most pilots take a distance greater than 12 parsecs to go from the beginning to the end of the Kessel Run, and assuming that the Kessel Run is not a specific route, but rather an indication of 2 end points, it may be impressive that he cut the corners faster and finised the 500 mile race while only traveling 498 miles.
(Score: 5, Interesting) by tangomargarine on Wednesday July 31 2019, @06:47PM (2 children)
I don't know what the current canon explanation is since they jettisoned all the "legacy" continuity, but in the Expanded Universe they explained that the Kessel Run is a route around a cluster of black holes, so measuring the trip in distance rather than time indicates that you skirted closer to the black holes. So instead of just having a faster ship, a shorter route indicates you "have more chest hair" since you flew it more dangerously.
Pretty sure this was a thing in the books easily 10+ years ago.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 2) by DannyB on Wednesday July 31 2019, @06:51PM
Then the bragging should be about the pilot's chest hair rather than the ship, should it not?
Every performance optimization is a grate wait lifted from my shoulders.
(Score: 2) by JoeMerchant on Wednesday July 31 2019, @07:42PM
They even go into this pretty clearly in the Solo movie, showing him take a "shortcut" to avoid being blasted to bits.
🌻🌻 [google.com]
(Score: 3, Insightful) by JoeMerchant on Wednesday July 31 2019, @07:40PM (14 children)
10 square meters is ~108 square feet, a little over a 10'x10' plate. That's a lot of iron, and a lot of flowing saltwater, granted for a lot of power, but imagining this being implemented on a houseboat (someplace that has ready access to flowing saltwater), the friction generated by that plate in the water - even without an electrical generation load - would make it more efficient to just run a fuel powered generator rather than trying to tow this thing in the water to make the same power.
Then we get into questions of lifetime: how long does a rusty plate last in a saltwater environment?
🌻🌻 [google.com]
(Score: 2) by deimtee on Wednesday July 31 2019, @07:54PM (1 child)
They don't give a required speed, but there are places where the tidal flow can reach several knots. If the speed is low enough and it can handle pulsed power, it might even be an efficient way to recover wave energy.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by JoeMerchant on Wednesday July 31 2019, @11:15PM
Tidal flows are a good source, still questionable how much energy is required to create, install and decommission the plate vs how much energy it produces in its useful lifetime.
🌻🌻 [google.com]
(Score: 2) by Immerman on Thursday August 01 2019, @03:21AM (2 children)
>That's a lot of iron,
Not really, they use vapor deposition to create a layer of iron oxide 10nm thick. 10m^2*10nm = 0.1 mm^3 of iron oxide - or basically nothing. Of course they don't mention what the substrate is, but even if it's iron it could presumably be a thin foil laminated to something light and rigid.
(Score: 2) by JoeMerchant on Thursday August 01 2019, @02:41PM (1 child)
Iron isn't the greatest electrical conductor, on something with a span of 10's of feet I'd expect significant losses if they're using thin iron as the wires. I'd expect bigger problems if they're trying to get bonding between iron oxide and something like copper or aluminum.
🌻🌻 [google.com]
(Score: 2) by Immerman on Thursday August 01 2019, @07:34PM
Even a thin iron foil is actually a decent conductor when 10 feet wide - resistance is proportional to the cross-sectional area, and being 10 feet wide really helps with that. It'll need to be almost 6x thicker than a copper foil to get the same conductance, but it's hundreds of times cheaper, so it'd probably still be an obvious choice.
(Score: 2) by RS3 on Thursday August 01 2019, @03:28AM (1 child)
You just invented perpetual motion! Connect the rusty plate battery to a propeller motor! Voilà!! Cruise around the world!
And you answered your own question- you'll get extra power because the saltwater will, what, make the plate clean? No no no, it will rust MORE, and you'll generate MORE POWER!!
(Score: 0) by Anonymous Coward on Thursday August 01 2019, @10:33PM
imagine a hydrodam with a rusty impeller: it makes soo much energy it can pump more water up then used down! soon all ocean will be dry!
(Score: 0) by Anonymous Coward on Thursday August 01 2019, @09:09AM (6 children)
The article has been corrected to say that you will get "a few kilowatt-hours" which gives no information whatsoever about the power generated by this thing, because kilowatt-hours is a unit of energy and power is a rate of energy output over time... and the time is not specified (so I suppose it must be the total produced over the lifetime of the device?)
And "a few kilowatt-hours" is not very much energy at all.
(Score: 2) by JoeMerchant on Thursday August 01 2019, @02:43PM (4 children)
I can buy a kWH for about $0.11 at retail, seems like a 10'x10' plate of anything is going to cost many multiples of $0.11 just to get it placed in a saltwater environment, even if the material it is made of is free.
🌻🌻 [google.com]
(Score: 2) by Immerman on Thursday August 01 2019, @07:41PM (3 children)
That's the difference between buying power, and buying generating capacity. Hint - the coal plant you're probably buying most of your power from cost a LOT more than 10 cents per kilowatt to build.
Buy 1kWh of power, and it's keep your 1kW load running for one hour, and then you have to buy another kWh.
Buy 1kW of generating capacity and (assuming it runs 24/7 with no fuel consumption) it'll run your 1kW load indefinitely, producing about 9000 kWh per year
(Score: 2) by JoeMerchant on Thursday August 01 2019, @09:19PM (2 children)
This circles back to the question posed earlier: are they telling what the generating capacity is, or are they actually quoting the total generating capacity of the device over its lifetime (as the units implied...)
One would hope they just flubbed the units in the usual fashion and they really meant generating capacity (in kW) instead of total lifetime generating capacity (in kWh).
🌻🌻 [google.com]
(Score: 2) by Immerman on Friday August 02 2019, @03:05AM (1 child)
I'm not paying to skim the paper, and the top several results from Google all have the exact same quote:
>"For perspective, plates having an area of 10 square meters each would generate a few kilowatts per hour -- enough for a standard U.S. home" Miller said.
Heck, they might all be republishing the exact same press release - I just searched for "watts"
I'm confident it was a units flub. Though I've heard that in the power industry (and perhaps researchers?), where "kWh" is the "normal" unit to be discussing, and is often shortened to just "kW" when speaking, in which case "kW/h" would in fact be the correct way to converse about instantaneous power - doubly so since it's pretty much a nonsense unit so that it won't confuse anyone (except outsiders, but how often do you talk to them about your work?)
At any rate, lets get to the meat of the claim: assume that Miller at least knows what they're talking about, and that "enough for a standard U.S. home" is correct. The average U.S. home consumes about 10,000kWh per year, or an average of a bit over 1 kW-hour per hour. Of course peak load will be a few times higher than that. So "a few kW hours per hour" would in fact provide for the average U.S. home, with a generous window for individual variability (or leaving out the batteries), and is almost certainly what he meant actually.
So this technology could supposedly produce a few hundred watts per square meter, which would put it roughly on par with solar panels in terms of peak generating potential per unit area. And I would presume this could be "stacked" in all sorts of interesting ways - how much surface area is in a car's radiator? If it could be made cheaply enough this might be a huge boon to seaside communities. Of course there is the question of how it actually stacks up to other forms of wave and tidal power. The lack of moving parts would seem to be a huge boon, but that's an awful lot of delicate surface area to keep clean and undamaged
(Score: 2) by hendrikboom on Friday August 02 2019, @11:52AM
Love the unit! It's probably what the original article needed in the first place!
(Score: 2) by Immerman on Thursday August 01 2019, @07:36PM
They say that it's "enough to power a house", so presumably that's per-day, or *maybe* per-hour (though that would be a heck of a high-power house)