Hemp Fibers Make Better Supercapacitors Than Graphene 178
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.
suitable for home use? (Score:5, Informative)
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
Legal... sort of (Score:4, Informative)
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.
not superconducting (Score:5, Informative)
A supercapacitor is not superconducting; it just stores a lot of charge.
/Oblg. Hemp for Victory ! (Score:4, Informative)
https://www.youtube.com/watch?... [youtube.com]
The hypocrisy of the government is retarded.
--
"It is the government proselytizing it is propaganda. When it is people promoting it, it is outlawed."
Re:suitable for home use? (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.
Re:Legal... sort of (Score:5, 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.
Comment removed (Score:4, Informative)
Re:Legal... sort of (Score:4, Informative)
Re:Oh, come now (Score:5, Informative)
Re:Potheads assemble! (Score:4, 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... [sane.org]
http://medicalmarijuana.procon... [procon.org]
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.
Re: Gives new meaning... (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.