Research on harvesting electricity from humidity in the air | Hacker News Reader

Research on harvesting electricity from humidity in the air

techxplore.com

95 pointswglb89 comments

The article does not say much, and I would urge magazine editors that report these things to hire journalists with at least some knowledge of physics. Articles like this should say at least what kind of energy (in watts) has been achieved experimentally in what type of device so that we know how close to being realistic the device is and whether it is in the range where it's energy generation may actually be just an error of the measuring instruments.

Also, the article should have some kind of explanation as to where the energy actually comes from. Saying it comes from humidity is not saying much. In order for the thing to get energy out it has to change the environment it is in somehow. How does the device change the humidity in order to get the energy out? Solar panels for example flat out absorb photons and get energy from them. Wind turbines slow down the movement of the air around them and get energy from that.

How does this thing change the humidity? Does it rely on change of potential energy of water droplets as they drop through the holes. If that is the case, it is doubtful it would get much power out for reasonably sized device. Or is it something to do with electrostatic charges around water droplets? This would be much more interesting. But if that is the case, it would not be a very good idea to stack multiple layers of the thing to make a high power device. If one layer strips the energy from the water droplets, then the next layer would have much less energy to strip.

Regardless, these are the sort of things one should talk about if one wants to make a better article on this subject.

I would urge magazine editors that report these things to hire journalists with at least some knowledge of physics.

Place an ad for a COBOL developer and an ad for a journalist with knowledge of physics, and see which one you fill first.

90% of journalists are generalists. That's just how journalism school works, since the reporters don't know where they'll end up working.

Most of the remainder are people who were experts or have degrees in a particular field, and ended up becoming journalists.

That said, the second group are often the best at their job. I know journalists who were in the psychiatry, IT, health, and other fields before they started reporting. They all excel at their craft.

I think your job as a journalist should be to interview experts, not be one.

there’s a difference between being an expert and knowing what sorts of questions will sniff out bullshit.

i think you just described a good journalist vs a not good journalist. one way that typically makes a good journalist (other than natural talent) is time working with experienced editors. since we've pretty much eliminated the editorial role at most publications (i use that word loosely), that avenue is pretty much no longer available.

how do you validate the interviewee's level of expert, especially when the interviewer is not one themself?

You cross reference their answers with answers from others in their field. This is in fact something you learn in journalism school.

In the days of single source anonymous attribution sources, I think what's accepted in practice varies greatly from the book learning in journo school

Ask a reputable college professor from a reputable college.

If a MIT professor confirms it, gives a comment about what is this useful for, etc, there's at least a 90% chance the answer will be correct and on point.

It's a stupid example, but the easiest person to find.

It's a stupid example, but the easiest person to find.

Not a stupid example at all. Many colleges, even small colleges, have systems set up to refer journalists with questions with the right professor.

In smaller colleges, it might just be someone inside the college's Communications or PR department. In big universities, it's often a "media bureau" or something similar, with multiple staffers.

That's part of the reason why you see so many academics quoted in newspaper articles. They're a good place to start, and can often send you to even better sources.

There are many physicists who write. Books or other content. This job wouldn't need a full time employee, an external ad-hoc editor/consultant would do.

Watts measures power, not energy.

This appears to build off of earlier research: https://www.nature.com/articles/s41586-020-2010-9

"Here we show that thin-film devices made from nanometre-scale protein wires harvested from the microbe Geobacter sulfurreducens can generate continuous electric power in the ambient environment. The devices produce a sustained voltage of around 0.5 volts across a 7-micrometre-thick film, with a current density of around 17 microamperes per square centimetre. We find the driving force behind this energy generation to be a self-maintained moisture gradient that forms within the film when the film is exposed to the humidity that is naturally present in air. Connecting several devices linearly scales up the voltage and current to power electronics."

It's interesting, but 10^9 devices of about 1m^2 each would require an energy input to manufacture that likely far outstrips the device's generation capability over it's projected lifespan. So unless they can make these extremely durable, resistant to oxidization and all manner of pollution I think that this will never make it to market in any usable form. But it is very interesting from an applied physics perspective and at the smallest scales there may well be some use for this (energy scavenging like applications for sensors that report infrequently).

I think this is going nowhere, but even if you only get 80% of the manufacturing energy back, that might be competitive with other forms of long term energy transport and storage.

For storage you'd have to have the current leakage down to next to nothing for that to be effective. Think about it: 10^9th devices in one meter, that's one micrometer thickness per device. At that surface area and thickness you'd have to have an extremely high grade insulator between the layers or the leakage current (essentially a parasitic resistor of 10^9 meter area with a thickness of a fraction of a micrometer electrically in parallel with the device) will kill any storage application.

Another thing I'm missing very much in this discussion is the equivalent of Betz for this device: it only works if the air has a way to exchange with the surface which would greatly increase the required volume. Without air exchange (and thus humidity exchange) it would eventually just stop working. Unless Brownian motion alone is enough to make it work but I find that hard to imagine. Come to think of it: moving the air through a sandwich of layers that thin would require considerable power!

The point is it doesn't leak because it doesn't actually store energy. It takes 100k joules to make a box that will generate 80k joules over its lifetime. But you can make it here, where and when energy is plentiful, and put it there, where energy is scarce. That's effectively energy storage, if not technically.

If that works out to the same physical size then at 22 Wh that would be a complete waste of space and money. It would likely also cost a very large multiple of that to transport it to the location where energy is scarce. A nice high quality battery with plenty of reserve power would likely be much cheaper, easier to interface to and easier to transport. There are batteries with a 20 year shelf life.

Maybe energy transporter…

Right so looking at the paper here and the proposed mechanism, it looks like basically they've built a plate-less super-capacitor.

In short; a normal capacitor is two conductive plates with a dielectric separator. In a super-capacitor you have an electrolyte and a porous membrane which can absorb it to allow the ions to build up an even bigger charge separation layer.

It seems like what happens here is that their porous material does the same thing, but the "charge" is the incidental charge on the ambient humidity in the air. The nano-pores are basically small enough that you make the likelihood of a being able to strip that charge from a collision very high, and thus get a current as you discharge the capacitor.

Which answers one of my questions: no this doesn't actually remove humidity from the air, so that's disappointing but expected.

But my second question is whether what they've really found is a new class of super-capacitor separator materials - since you'd get a lot more current if you intentionally jammed a lot of charged ions into close-proximity. Or at least a mechanism by which these can be optimized.

Do these devices have the effect of cooling the air? The energy has to come from somewhere… If so, that would potentially serve two purposes for the price of one: cooling and power generation. Or, is the side effect to make the air less moist. Also a useful function, particularly in humid places where drying the air is desired.

I have a pet theory that in the future air conditioning will generate small amounts of electricity rather than requiring a great deal of it. I think perhaps a large volume of these, self powering a fan could fit the bill.

Under what atmospheric conditions is that possible while preserving conservation of energy?

Something like this looks promising. If you can remove humidity and get a little power you might for example power an ultra efficient heat pump with that power then use say a peltier device to charge your phone off the hot side.

Edit: another idea use this to reduce the humidity in the air, then use the captured moisture to enable a swamp cooler.

It requires improvements in the efficiency of everything but I think it's possible in say a few hundred years.

Not if some of those improvements have reach bona fide >100% efficiency.

Whatever you do, you will be adding heat/entropy to the system somewhere. Even the most efficient heat pumps heat things up on the net - they cool by moving heat around, and then they add their own waste heat on top.

The trick is, and always has been, to make sure your waste gets dumped somewhere you don't care about. A heat pump will dump its waste heat along with the heat it moves out of the place you care about, like inside your house, to the place you don't care about, like the ground beneath your house or the air outside. Other such tricks include dumping heat into rivers and lakes (see: most power plants), routing it where you need things heated up (see: combined heat and power plants), or just dumping it to space (Earth's atmosphere happens to be transparent at certain IR wavelengths, allowing you to use the universe as your heat sink).

There's space for more sophisticated trickery, trying to minimize waste by reusing everything as part of some process elsewhere. But the net entropy still has to grow, so the main question is the same as it always has been: where do you dump waste heat?

> There's space for more sophisticated trickery, trying to minimize waste by reusing everything as part of some process elsewhere. But the net entropy still has to grow, so the main question is the same as it always has been: where do you dump waste heat?

Not OP, but wouldn't the "ideal" be to pull any excess heat (energy) out of the interior air, and use it first for electricity-needs in a home like phones, toasters, etc (which generate heat). That heat will eventually be re-captured by the heat-extractor, and can be recycled - any excess heat can still be "dumped" outdoors, and "ideally" the energy required to "move" that heat outdoors is first pulled from the spare-heat of inside.

Obviously the big question in this scenario is how to convert heat into electricity, without a temperature differential. AFAIK we haven't figured this out.

>Obviously the big question in this scenario is how to convert heat into electricity, without a temperature differential. AFAIK we haven't figured this out.

Wouldn't that mean you create energy out of nothing breaking the first law of thermodynamics or that energy goes from a colder body to a warmer body, breaking the second law?

You will find the second law of thermodynamics very disappointing.

Assuming the system is exposed to open atmosphere, and knowing that free electrons have higher energy than bound electrons, it's not clear what you're trying to imply here. Especially since entropy increasing only applies to closed systems.

Wait till you find out what people do with electricity.

I can't see how you'd avoid it. The charge on the molecule is going to be one of the things keeping it repelled from other water molecules, so as you take charge off it, there are fewer internal forces to keep them apart. That's got to be a reduction in the vapour pressure, right? In the right circumstances the water will condense out. I think that's got to be the engineering limit of the "stack of thousands of sheets" idea they mention: somewhere down the stack they short out because water droplets will condense out into liquid on the sheet.

This all assumes a net charge one way or the other on the body of water vapour. The article doesn't make it clear but I assume that's inevitable.

Need to have a $/watt-hr metric to know if this will be viable. This reminds me of the Windbelt generator from several years ago. It was a brilliant design to extract power from low speed wind, but did not find economic value with existing cheaper forms of generation.

The windbelt was a non-starter, and the idea had already been proposed in various forms decades ago. The same with all of the variations on the VAT, energy from soundwaves and many other curiosities. They are fun on the toy scale but you can't turn them into usable and net-energy positive devices (energy produced over the lifetime of the device / energy consumed by the construction and installation of the device).

So I don't care if this can harvest energy, but I care very much if it will reduce humidity without running a compressor.

Because during the summer where I live, humidity spikes and I pay about 1400W in two dehumidifiers to keep it down.

If you don't want to run a compressor, your other option is dessicants. The difficulty there is you've got to 'recharge' the dessicants, and that usually means heating them, and you probably don't want to heat your space (although increasing the temperature does reduce relative humidity). From what I've seen, the typical way to recharge dessicsants is to heat inside air, pass it over the saturated dessicant and then discharge this hot humid air outside, and I guess hope the makeup air you get back is less hot and humid?

Maybe someone with such a system can chime in? I've only got a compressor based dehumidifier for my needs (basement humidity spikes in the summer when the temperature differential between the basement and the first floor is too great)

Title should be "New Devices Generates Electricity from Thick Air"

I'm still waiting for the sound deadening paint that will also power my home by absorbing ambient vibrations.

Piezoelectric energy harvesting is cool though, even if the paint stuff is a pipe dream

We're awash in waste energy (thermal etc.), but almost every form of harvesting it is way more expensive $/watt than tapping the grid.

Yep, the second law of thermodynamics is like that.

The $/watt price from tapping the grid part might solve itself in the foreseable future. Not that I'm happy with it.

maxwell's demon for air conditioning, maxell's demon for sound absorption.

https://en.wikipedia.org/wiki/Maxwell%27s_demon

https://upload.wikimedia.org/wikipedia/en/f/fb/Blown_Away_Gu...

Static charge generated by rubbing water molecules against nanoholes. Generate charge by shifting humidity.

The real-life version of windtraps:

https://dune.fandom.com/wiki/Windtrap

This is exciting technology. If they can mass produce the nanopore material then perhaps we will see these in power production systems.

OK, I'll bite: How much energy can they harvest? While realising that this is still highly experimental, early days and bleeding edge (and also very exciting!) it would be very interesting to get some idea of the actual energy harvest, even though this will surely be an area of intense future research. I did not see any mention of it in the article, though, and the original paper seems to be paywalled.

There was a thread from another article on the washington post: https://news.ycombinator.com/item?id=36091615

It is essentially the usual "breakthrough" that won't likey have any practical use for many years, the experimental device is tiny and produces very little power.

It seems you need one billion of these devices to get 1 kW.

>The device, the size of a fingernail and thinner than a single hair, is dotted with tiny holes known as nanopores. The holes have a diameter smaller than 100 nanometers, or less than a thousandth of the width of a strand of human hair.

>While one prototype only produces a small amount of energy — almost enough to power a dot of light on a big screen — because of its size, Yao said Air-gens can be stacked on top of each other, potentially with spaces of air in between. Storing the electricity is a separate issue, he added.

>Yao estimated that roughly 1 billion Air-gens, stacked to be roughly the size of a refrigerator, could produce a kilowatt and partly power a home in ideal conditions. The team hopes to lower both the number of devices needed and the space they take up by making the tool more efficient. Doing that could be a challenge.

Some googling and napkin math. 1 fridge = 1 kW

A fridge is 25 cubic feet, so 40 watts per cubic foot. A Dell E2422H monitor uses 13 watts while powered on. So a box 0.325 cubic feet could power a monitor, or a cube of 8.25" edge length. Assuming it was 100% efficient and endless supply of humid air etc.

> and endless supply of humid air etc.

Floridians are getting really excited right now.

I had a 5kW gas powered generator that more than lowered out 3 bedroom 1.5 bath house for when our power would go out - sometimes for several days (1 refrigerator, HVAC unit, microwave, electric washer/dryer, two laptops, 2 large screen TV's, hot water heater - all drawing power intermittently of course, but we never exceeded). It was about the size of a small riding lawn mower.

If I could have 5 refrigerator-sized boxes in my backyard powering my house, I would be in.

>If I could have 5 refrigerator-sized boxes in my backyard powering my house, I would be in.

Yep, but that would be 5 billion "cells".

How much would a "nail sized" cell cost?

If 0.001 $ (1/1000 of a dollar), that would be a nice, round 5 million dollar.

Sure, but the first LCD tv's were $50,000, now you can get one for $100. It won't be $5m forever.

Yep, but prototypes of (small, monochrome) LCD screens were created in the '60's, your $50,000 data point would have been probably mid-1980's, and the $100 lcd tv's probably happened in the late 2010's.

I wouldn't be surprised (if this humidity device actually works and can be bettered) that working regrigerator sized units will be availably in 2040 and be actually affordable by the 2070's.

Unless I misunderstood, the fingernail sized object was just a prototype and the important thing isn't the size of the "cell" but the number of 100nm holes in the material.

I wonder if the kind of lithography used for semiconductor manufactur would be a useful way to produce this material?

huh, seems like you could realistically power a low end watch, though.

It is in the article:

Finally, because air humidity diffuses in three-dimensional space and the thickness of the Air-gen device is only a fraction of the width of a human hair, many thousands of them can be stacked on top of each other, efficiently scaling up the amount of energy without increasing the footprint of the device. Such an Air-gen device would be capable of delivering kilowatt-level power for general electrical utility usage.

That seems like something that would be insanely easy to clog up by just dust in the air

Maybe it could be pre-filtered air in a closed loop? However, this already seems like magic to me, so I am unsure if it is possible to filter/recycle the air and still come out net energy positive. Alternatively, maybe there could be some kind of washing step where the plates are washed/air forced through/voltage applied to remove debris.

Indeed, but at utility-scale you also likely have some energy to spare for powering an electrostatic dust filter at the intakes...

My parents' house had a Honeywell brand electrostatic air filter in front of the air handler that wasn't cost-prohibitive to operate, and didn't have a drip pan or anything so I don't think it stripped moisture either. We'd just toss the large metal filter cartridges in the dish-washer periodically, which barely fit. They didn't pose a significant air restriction, unlike conventional pleated physical filters.

Have they figured out how to prevent this tech from producing ozone?

apparently yes.

> Note: Avoid portable air cleaners and furnace/HVAC filters that intentionally produce ozone. Ozone is a lung irritant. Note that in some cases, air cleaners that contain electrostatic precipitators, ionizers, UV lights without adequate lamp coatings, and plasma air cleaners may have the potential to emit ozone. Both the California Air Resources Board and the Association of Home Appliance Manufacturers maintain lists of air cleaners that have been tested and shown to emit little or no ozone.

from: https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaner...

following the link to the california one you get:

> Electronic: Air cleaners that are listed as "Electronic" may be capable of generating small amounts of ozone, but have been tested and found to produce an ozone emission concentration less than 0.050 parts per million. This category includes ionizers, electrostatic precipitators, PCOs, hydroxyl generators, devices with UV light components, and other electronic air cleaning technologies.

I imagine electrostatic precipitators would fall into that category

It would seem to me that surface area is the key. Fractals or similar techniques? It says the material isn't important, so maybe some sort of crystal growth could do it?

a kilowatt for a fridge is pretty good honestly, and it stacks vertically.

Or you integrate it with the underside of solar panels for better yield.

1KW/"fridge" is a lot more than I was expecting.

If they don't give a watt per square meter value I'm not interested

There was a different article reporting on this that mentioned they would have to stack many layers into a block "about the size of a refrigerator" to make kilowatt. I will try to find it.

Found it.

"Yao estimated that roughly 1 billion Air-gens, stacked to be roughly the size of a refrigerator, could produce a kilowatt and partly power a home in ideal conditions. The team hopes to lower both the number of devices needed and the space they take up by making the tool more efficient. Doing that could be a challenge."

https://www.washingtonpost.com/science/2023/05/26/harvest-en...

A device the size of a "consumer" refrigerator? Having a device like that in the garage or exterior wall of the house doesn't seem that bad to me. Tesla Powerwalls aren't too much smaller.

Having an appliance that generated even half that, 12kwh per day, would be fantastic. The issue, of course, would be cost. It would need to pay itself off within a feasible period of time.

sure, but it has to start somewhere. as a society dealing with scams and what not, i'm still not convinced that solar will pay itself off in a human life time. so it's not like this new thing is unique. even the Tesla Powerwalls + Solar is not convincing that it's paying back, but there's just something that screams "worth it anyways" about these systems. part of the issue is that in many areas, you are not allowed to cut the cord to public utilities even if you are self-sufficient, so you're never truly free of expenses.

> i'm still not convinced that solar will pay itself off in a human life time

What do you mean by that? The payoff, even factoring opportunity cost, is around 10-12 years or less in my country.

maybe I'm jaded and put off by all of the scammy/predatory lending that's prevalent in the US around solar. there's also the seemingly back and forth between ability to earn money from unused powered produced and shared with the grid. are there rebates or not, but depends on the particular time you're purchasing. things like being transferable or not also come into play. lots of things make it a complicated equation compared to buying a house/car/similar.

A report done in New Zealand in 2018 by arranging quotes for houses around the country found many quoted systems had 20+ yr paybacks.

https://i.stuff.co.nz/business/107335911/solar-power-systems...

But on the other hand if a house is ideally suited for solar, the payback will easily be 10 years.

Wind turbines?

A common misconception, wind turbines require thick air to be effective.

This device requires humid air to work, so this article title should replace "From Thin Air" to "From Thick Air"

I guess this is sort of to wind turbines as wave power is to hydro? (in that they're taking advantage of a sort of smaller effect)

But the air is very dirty - wouldn't that be a problem?

Wouldn't the water just condense inside the nanopores due to surface energy, and render them useless?

Gives new meaning to the phrase about generating something from thin air...

This is an interesting approach to generating electricity 'from thin air,' but I think I'd just rather see improvements in metal-air battery tech, especially on the recycling/remanufacturing side.

It's not an either/or situation.

this doesn’t necessarily need to produce net positive energy to be net positive. Think solar cells on calculators in the 90s

Why is the air always so thin? Why never thick air? And why does it matter?

I’ve heard of a similar device leading to the creation of a fascinating enclave of libertarian inventors. I can’t wait to see how this plays out in the public world.

I'll wait till Thunderf00t debunk it

Anyone else find thunder foot to be intolerably smug and self righteous? That combined with the fact he never addresses some of his considerable factual errors means I'll pass.

It's fine (and good) to be a skeptic, but you should also understand your own knowledge gaps and be curious. Thunder foot fails here.

same there is always something to it

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