Slashdot Mirror


Hemp Fibers Make Better Supercapacitors Than Graphene

biodata (1981610) writes "BBC News is reporting findings published in the journal ACS Nano by Dr David Mitlin from Clarkson University. Dr. Mitlin's team took waste hemp stems and recycled the material into supercapacitors with performance as good, or better, than those built from graphene, at a fraction of the raw materials cost. "We're making graphene-like materials for a thousandth of the price - and we're doing it with waste. The hemp we use is perfectly legal to grow. It has no THC in it at all - so there's no overlap with any recreational activities," Mitlin says.

44 of 178 comments (clear)

  1. suitable for home use? by russejl · · Score: 5, Informative

    This is potentially exciting... no pun intended :-)

    The article abstract says:
    The nanosheets are ideally suited for low (down to 0 C) through high (100 C) temperature ionic-liquid-based supercapacitor applications: At 0 C and a current density of 10 A g–1, the electrode maintains a remarkable capacitance of 106 F g–1. At 20, 60, and 100 C and an extreme current density of 100 A g–1, there is excellent capacitance retention (72–92%) with the specific capacitances being 113, 144, and 142 F g–1, respectively. These characteristics favorably place the materials on a Ragone chart providing among the best power–energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor: At a very high power density of 20 kW kg–1 and 20, 60, and 100 C, the energy densities are 19, 34, and 40 Wh kg–1, respectively. "

    Which possibly suggests that the materials are suitable for indoor use (but not in cars unless you happen to operate in a non-freezing climate) which could have some very practical applications. Solar panels are becoming attractive and I'd like a storage bank but would like to avoid batteries because of the slow charge, expense, and maintenance. A super capacitor, of course, is attractive. Off the top of my head, I don't know what the power density of this type of capacitor is relative to lead acid deep cycle batteries. Still, I smile though :)

    1. Re:suitable for home use? by cbhacking · · Score: 5, Informative

      The power density is really nowhere close to a battery. Supercaps make sense for things where you actually need really massive charge and/or discharge spikes, over very short times. Think railguns, or a camera flash that can fire multiple times without needing to recharge between shots (if it charged enough to begin with), or possibly a smoothing system for charging batteries from a very spiky power source (hypothetically, this could scale to things like harvesting lightning, though at present that's not at all practical). They aren't practical for long-term storage, either due to energy density or due to their tendency to lose power over time pretty quickly.

      A sufficiently large battery bank will have no problem with the charge speed of a photovoltaic array (which is actually rather slow). A small bank might reach saturation voltage - where the batteries are still charging but can't charge any *faster* or they'll take damage from overvolting - fairly quickly if fed by a large array, but that's not the real problem with a small bank; the real problem is not having enough storage capacity.

      Expense is considerable, especially if you go with the low-maintenance options like gel-cells. However, supercaps are, at this time, not something you can buy a huge bank of at any price (certainly not the hemp-based ones). If you could get a meaningful capacity of the graphene ones it would probably cost many times as much. Maybe the hemp ones will change that, but don't hold your breath.

      Maintenance is much less than it sounds. Wet-cells (typical lead-acid batteries) need topping up with water periodically, and occasionally may need equalization charges; the first can be done by a reminder to go do so every month, and the latter doesn't even need to be that often. Pretty much every other aspect of maintenance should be handled by a good enclosure for the batteries and a good charge controller. The controller costs a bit but you want one of the good ones anyhow; they perform DC-DC voltage conversion to take the output of the solar cells (which can easily be at least 25% higher voltage than the batteries will charge at) and down-convert it, extracting some extra current in the process (some energy is lost in this process, but it's typically a 10%-20% net positive for the 12V gel-cells my family uses). Speaking of gel-cells, those will save you on maintenance (at a cost of more money up front and a more severe voltage sensitivity that limits charge rate a bit harder). Such batteries are basically install-and-forget, but you'd need to be tremendously lazy for them to be worthwhile for a home installation; they are typically for marine usage (as my parents do) where never needing to open the cells (to add water) is a significant plus.

      --
      There's no place I could be, since I've found Serenity...
    2. Re:suitable for home use? by geoskd · · Score: 3, Informative

      The power density is really nowhere close to a battery. Supercaps make sense for things where you actually need really massive charge and/or discharge spikes, over very short times.

      That is the definition of power density. You're thinking energy density. The fact that you would get the two confused casts aspersions on your knowledge in the field.

      It should also be noted that almost all types of batteries have leakage current which renders them unsuitable for long term energy storage. Most super caps have a higher than normal leakage current due to the lower operating resistance of the devices (the same trait which allows them very high power density).

      --
      I wish I had a good sig, but all the good ones are copyrighted
    3. Re:suitable for home use? by mlts · · Score: 5, Interesting

      I'd love these for a solar array where energy stored for unit volume is important, but not critical (like it is in a car or RV) for a number of reasons:

      1: Hemp is a lot less nasty for the environment than graphene.

      2: This could be used as a buffer for the chemical batteries, since you don't have to worry about limiting amps coming in. Come "shoulder hours", the supercaps can be charging the batteries at exactly the amperage rate they need even after the sun is down, greatly improving the system's efficiency.

      3: The lifespan of a capacitor is a lot longer than a battery because electricity is stored physically, not chemically. So, if space is less of an issue, large supercaps can be used without worrying about replacement every 5-10 years (or 2-3 years with Li-ion) batteries.

      So, for an off-grid circuit (one that never goes near mains power and pretty much acts as a UPS), having this technology would go far.

    4. Re:suitable for home use? by Dr_Barnowl · · Score: 3, Interesting

      Asbestos is just silicate rock. Structure makes a difference..

      Graphene is just a sheet of carbon, but it's structure gives it novel properties - it wouldn't be a super-material if it didn't, just because it's all cool and awesome doesn't mean it's also inert and harmless.

    5. Re:suitable for home use? by schlachter · · Score: 2

      The Mazda 6 uses capacitors for it's regenerative braking system...so they are relevant for hybrid car systems...for short term energy storage.

      --
      My God can beat up your God. Just kidding...don't take offense. I know there's no God.
  2. Gives new meaning... by ilsaloving · · Score: 5, Funny

    This will give new meaning to the term 'magic smoke'.

    ( http://en.wikipedia.org/wiki/M... for those that don't know)

    1. Re:Gives new meaning... by Ellis+D.+Tripp · · Score: 2

      Actually, Washington's diaries talk about his hemp crop, and include this passage:

        "Began to separate the Male from the Female hemp ⦠rather too late."

      The only reason to separate the male and female plants is to prevent pollination, and thereby increase (psychoactive) resin production. This is still done to this day among pot growers. It seems pretty clear that Washington had at least some interest in the medicinal/psychoactive qualities of his crop.

      --
      Remember "News for Nerds, Stuff that Matters"? Help make it a reality again! http://soylentnews.org
    2. Re:Gives new meaning... by Grishnakh · · Score: 4, Insightful

      The pro pot crowd points to Washington and hemp so they can point out how stupid our marijuana laws are, because these laws, in banning marijuana, also ban hemp, even though hemp does suck for getting high. It's a versatile and useful plant (but not for smoking), good for making rope, paper, clothing, etc., but we can't have it because of these stupid pot laws.

    3. Re: Gives new meaning... by Anonymous Coward · · Score: 2, Informative

      That's not the only reason, and you pinched that idea from Robert Anton Wilson. The Straight Dope has something to say about it:

      But let's not give up too quickly. In his diary for August 7, 1765, Washington writes, "Began to separate the Male from the Female hemp ⦠rather too late." Female marijuana plants are the ones that contain enough THC to be worth smoking. Some take this to mean Washington was cultivating the plant not just for fiber. Of course, two days later Washington says he put the hemp in the river to soak and separate out the fibers, and later in September that he started to harvest the seed. That suggests he divided the plants because the males made stronger fiber while the female plants produced the seed needed for the next year's crop. Jefferson in his Farm Book wrote that a female plant would produce a quart of seed, and a bushel of seed was enough to plant an acre.

  3. Gives new meaning... by Stolovaya · · Score: 3, Funny

    Have you ever made hemp fiber supercapacitors...on weed?

  4. Legal... sort of by michael_cain · · Score: 3, Informative

    "The hemp we use is perfectly legal to grow."

    Yeah, if you're properly affiliated with a university or state department of agriculture, are doing it for research purposes, and have agreed to all of the terms and conditions that the feds and your local state require. If you or I try to do it commercially, it's a federal felony.

    1. Re:Legal... sort of by GrahamCox · · Score: 5, Insightful

      Which is nuts, actually. Hemp is a brilliant raw material with hundreds of practical uses which *should*, if people had any sense of balance, far outweigh the small issue of the cannabinoids. It could probably even be selectively bred to eliminate that aspect, but no, concern about a few potheads sends legislators into a tailspin. This is why we can't have nice things.

    2. Re:Legal... sort of by TapeCutter · · Score: 4, Informative

      It could probably even be selectively bred to eliminate that aspect

      That's been available for a very long time, it's what they used in this experiment and is grown commercially to make hemp clothing. Getting permission to grow those species is unreasonably difficult in many countries for no other reason than it looks like the smokeable stuff. Historically hemp is as important as cotton, George Washington once decreed every land holder set aside a portion of land for growing hemp to supply the colonial navy with rope. It's said that the invention of nylon spurred the original US government propaganda and the prohibition drive, hemp was a direct competitor in many markets and the nylon makers had powerful friends in congress. The propaganda avoided the word "hemp" and used the Mexican name "Marijuana" in a cynical attempt to appeal to the racist dogma of the day that branded Mexicans as lazy and untrustworthy.

      --
      And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
    3. Re:Legal... sort of by dbIII · · Score: 3, Informative

      It's one of the reasons France gave the USA the finger and you guys decided to hate the nation that used to be admired - France still has a large and legal hemp industry for fibre production. They refused to shut it down as part of the "war on drugs". India grows a vast amount of the stuff for fibre. There's a few other places that didn't decide to wipe out an industry as collatoral damage in the "war on drugs" distraction.

    4. Re:Legal... sort of by Anonymous Coward · · Score: 2, Interesting

      No. There is no replacement yet for hemp cloth that is as good or better in hot weather. Flax comes close but isn't as durable. The ridiculous state of the law makes flax cheaper than hemp which would otherwise outperform it in all aspects including price. Synthetic fibers are trash for clothing if you have to do anything beyond sitting in an air-condition room.

  5. No overlap with recreational activities? by kruach+aum · · Score: 5, Insightful

    What about basket weavers, you insensitive clod!

  6. No THC? by msobkow · · Score: 2

    Sorry, but every cannabis sativa plant, whether of the recreational, medicinal, or hemp varieties produces some THC. Granted, hemp is a miniscule fraction of a percentage THC, but it does have THC.

    --
    I do not fail; I succeed at finding out what does not work.
    1. Re:No THC? by dbIII · · Score: 2

      Friend of a friend story but probably true.
      A friend of mine, his sister and his sister's stoner boyfriend went to Latvia after the Russians moved out and they could reconnect with family etc. The stoner was astonished with hemp growing all over the place and he collected and dried a lot of it. It turns out that with the variety there and the short growing season he was effectively just smoking rope because whatever process forms THC just didn't get time to happen.

    2. Re:No THC? by sound+vision · · Score: 2

      The concept of dirtweed or ditchweed is well-known to US stoners as well - if you find it growing naturally there is a good chance it's a hemp strain, not suitable for smoking. It's not that the these plants don't contain any THC, it's that they don't contain appreciable THC in doses large enough to get high. It's a minor distinction, and probably good not to mention it lest the government try to clamp down on supercapacitor research. But, I would expect the scientist in the article to be more precise.

  7. That tears it, Bailing Twine? by bobbied · · Score: 4, Funny

    Dang it folks, I left the farm to be an electrical engineer and it keeps following me! I ran away from the farm for a reason, and bailing twine was wrapped all around it.

    Now we are going to be making capacitors from bailing twine? NOOOOOO!! I won't do this again!

    I have to retire before they start sending me out to pickup packages of dried grass and haul them to the barn again.

    --
    "File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
  8. Marijuana... by geekd · · Score: 4, Interesting

    Marijuana. Is there anything it CAN'T do?

    1. Re:Marijuana... by fyngyrz · · Score: 2

      Make donuts?

      Clearly, you are unfamiliar with Marijuana. :)

      --
      I've fallen off your lawn, and I can't get up.
  9. not superconducting by penguinoid · · Score: 4, Informative

    A supercapacitor is not superconducting; it just stores a lot of charge.

    --
    Don't waste your vote! Vote for whoever you want, unless you live in a swing state it won't matter anyways
  10. /Oblg. Hemp for Victory ! by UnknownSoldier · · Score: 3, Informative

    https://www.youtube.com/watch?...

    The hypocrisy of the government is retarded.

    --
    "It is the government proselytizing it is propaganda. When it is people promoting it, it is outlawed."

    1. Re:/Oblg. Hemp for Victory ! by ganjadude · · Score: 4, Interesting

      It was a 2 fold attack from du pont, who nust created the synthetic fibre, and william henrey hurst with his timber operation, they didnt want the competition with the hemp fibre, so they started a campaign to smear it. They were blaming marijuana for black men raping white women and chinese being lazy, the convinced the government that they were both evil

      --
      have you seen my sig? there are many others like it but none that are the same
  11. Oh, come now by fyngyrz · · Score: 4, Funny

    The hemp we use... has no THC in it at all - so there's no overlap with any recreational activities," Mitlin says.

    Well, every technology has bugs and birthing pains. Keep working at it, and perhaps you can graduate to a better class of hemp, Mr. Mitlin.

    --
    I've fallen off your lawn, and I can't get up.
    1. Re:Oh, come now by Anonymous Coward · · Score: 2, Insightful

      Hemp can't replace marijuana, but I'm pretty sure marijuana can replace hemp.

    2. Re:Oh, come now by Ol+Olsoc · · Score: 2

      Hemp can't replace marijuana, but I'm pretty sure marijuana can replace hemp.

      Well sure - for baking anyhow....

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    3. Re:Oh, come now by Grishnakh · · Score: 2

      As I understand it, no. (I'm not a marijuana expert however.) From what I'm told, while the two plants are closely related, marijuana is really good for smoking, but the fibers are not very good for rope-making, whereas hemp has great fibers for rope-making and clothes and such, but sucks for smoking. So basically you can have one or the other, but not both.

      It's kinda like trying to use a Prius for hauling plywood and concrete, and a Ford F350 for daily commuting. You could probably get both those combinations to work, but the Prius is not optimized for cargo like the F350 is, and the F350 gets lousy fuel economy compared to the Prius and is much harder to maneuver and park.

    4. Re:Oh, come now by ganjadude · · Score: 4, Informative

      You are correct, the hemp plat is the rudalis plant, we smoke the indica and sativa plants. Side note, hops are also related to pot

      --
      have you seen my sig? there are many others like it but none that are the same
    5. Re:Oh, come now by Anonymous Coward · · Score: 3, Funny

      Side note, hops are also related to pot

      As are pine trees, sharks, monkeys and potatoes. But not humans, we were made by a wizard separately.

  12. Re:Potheads assemble! by PPH · · Score: 2

    but love science when it finds uses for hemp

    Because with large scale hemp agriculture, you can always sneak in a few rows of 'the good stuff'.

    --
    Have gnu, will travel.
  13. Hey! by PPH · · Score: 2

    Administrator: What are you guys doing in the lab with all those plants?

    Undergrad lab assistant: Testing them for use as supercapacitor electrodes. Yeah. That's the ticket.

    Administrator walks away satisfied.

    --
    Have gnu, will travel.
  14. Um, I have to wonder... by roc97007 · · Score: 2

    Experimenter bias?

    --
    Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
  15. Re:So no ... by roc97007 · · Score: 2

    Actually when I was in high school electronics class we had great fun charging up big capacitors then tossing them to our classmates yelling "Here, catch!". A few of us were smart enough not to catch.

    In my high school electronics class the instructor announced on the first day of class that anyone charging up a capacitor and tossing it to someone else as a joke would automatically fail the class. (Apparently this was not his first rodeo.)

    Up to that point, we'd never even realized this was possible. That Halloween was fun.

    --
    Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
  16. How unfortunate ... by angel'o'sphere · · Score: 2

    The hemp we use is perfectly legal to grow. It has no THC in it at all - so there's no overlap with any recreational activities," Mitlin says.
    A shame, isn't it?

    --
    Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
    1. Re:How unfortunate ... by sound+vision · · Score: 2

      The good part is, instead of throwing the stems out I can now recycle them!

  17. Cotton lobby by rsilvergun · · Score: 3, Insightful

    there's more to it than just Mary Jane. You don't think the cotton lobby has noticed the wonder material that is hemp?...

    --
    Hi! I make Firefox Plug-ins. Check 'em out @ https://addons.mozilla.org/en-US/firefox/addon/youtube-mp3-podcaster/
  18. Re:Potheads assemble! by alvinrod · · Score: 3, Insightful

    You wouldn't want to though. Your marijuana plants would end up getting cross-pollinated and the quality would go to hell. No one would want to buy the crap. That and cultivating the plants indoors in a more controlled environment is going to provide a much better yield.

  19. Re:So no ... by TehZorroness · · Score: 2

    My high school instructor told us that when he was in high school electronics, the kids would toss a charged capacator at you if they saw you trying to sneak in after the bell rang. Either you try your best to catch it, or you let it drop and the professor turns around from the chalk board and notices you walking in.

  20. Re:Potheads assemble! by BlackHawk-666 · · Score: 3, Informative

    Marijuana doesn't have the same dramatic effects as meth, and there are people who are long-term users who suffer very few side effects from this drug. There is however a small chance that it can lead to temporary or even permanent psychosis. There is still some debate over this issue, but I can assure you it's quite real.

    http://www.sane.org/informatio...
    http://medicalmarijuana.procon...

    A while ago I spent some time in a mental facility and one of the patients there was that unlucky 1 in 700,000 who was vulnerable to the psychotic effects that marijuana could cause. He was a good student who was just starting university. Intelligent, articulate, and with excellent grades - he had good prospects for a long and happy life.

    His mother worked as a nurse at that hospital so she could spend time with her son, and I received this information directly from her. At uni he tried marijuana, just a few times. I get the impression he was just a typical uni kid enjoying his new freedom and he started to smoke it because his new social circle were smoking it. Pretty typical stuff. He had an adverse reaction (I think over a short time period of maybe week or so) and had to be hospitalised due to psychosis.

    By the time I met him, he had been in hospital for 12 years. He had no teeth left, since he couldn't look after them they had to all be removed. He was heavily medicated but was still liable to fits of anger and hitting other patients for something simple like sitting in his chair. He was barely able to speak and never managed more than a couple of mumbled, often unintelligible words. There was a rec room where we could watch a TV which was behind a plexiglass panel we needed to lift up to change channels. He had a tic that meant every 1-2 minutes he needed to get up, walk to the TV, life the plexiglass, run his hand over the top of the TV, then sit down again. He might do this 100+ times in a day.

    While it's easy to think there's no dangers using marijuana, and admittedly, they are few and low - it's not totally without cost or risk. This man will spend the rest of his short life in that mental institution, unable to read, play games, go outside, speak to others, share friendships or talk about the good old days. He will never experience any of the myriad of things that you and countless others can - and that is directly attributed to a fairly small quantity of weed he smoked - he wasn't trying any other drugs at the time.

    Certainly, he had a disposition towards this happening, but it was marijuana that pushed it over the limit and completely fucked his entire life.

    We have a decent welfare system and free hospitalisation in Australia, so he is getting the care he needs. You could argue that as taxpayers who are shouldering that cost we do get a say in whether people consume the drug or not...but, I'm not going to bother with that argument, it's not the important one.

    Enjoy the smoke if you can amd avoid it if that's that you prefer. Just bear in mind, however small, there is a chance of psychosis that may in same rare cases be permanent - and weed is a known contributor to this condition.

    Role your dice, move your mice.

    --
    All those moments will be lost in time, like tears in rain.
  21. Re:Potheads assemble! by Anonymous Coward · · Score: 4, Insightful

    1/700,000 has an adverse reaction to marajuana
    how many people in the US can die from eating a peanut? almost no non-essential substance is innocuous to everyone.

  22. Maybe get monsanto to get involved? by thieh · · Score: 2

    to see if it is possible to get both ends of the world?