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possibly a massive electricity storage breakthrough  RSS feed

 
Daniel Shultz
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Hi,

I didn't see an alternative energy storage sub-forum so I hope I posted this in the right place.

the gist of how i tend to feel about electricity.
Electricity = yay! potentially clean!
Storing Electricity = boo! batteries yuck!

The video below is about a new discovery in science called a graphene supercapacitor.
I think you'll be pleasantly amazed. I nearly jumped out of my chair in excitement thinking "I must be missing something... this can't be real"

http://vimeo.com/51873011

for those who don't care to watch the video:
a graphene supercapacitor charges in a fraction of the time that a normal battery takes to charge, stores electricity, and is biodegradable.

is this real? it seems too good to be true.

Daniel

...my first post on permies btw.
 
Cj Sloane
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I think I've heard about using capacitors as batteries but not graphene based. Seems legit.
 
William Donald
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awesome! that is great news for solar power, and subsequently all of us!!
 
S Bengi
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Batteries cost about $1 per watt that it stores, and the last about 8years, I wonder what the price is for super capacitors.
So if these super capacitors last 25 years and cost 3 times the price they would be ok, Even if it was 6 times the price it would be ok.
However I fear that it is 1000 times the price of a Lead battery. Hopefully in a few decades that will not be the case.
 
Cj Sloane
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I doubt it would cost 1000x lead acid.

The good thing about capacitors is they are scalable (as I understand it). Maybe I should say I think they scale better than batteries.
 
S Bengi
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Daniel Shultz
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I'm curious how the prices here will reflect the prices of a super capacitor which is made with graphene.
I think it might make more sense to look up the price of graphite oxide.

I found this video as well while looking up graphite oxide.
it was uploaded 3 months before the one above and credits Rice University.

http://www.youtube.com/watch?v=3O4YV0mrkfQ

It also doesn't really get into the storage aspect of it. It more focuses on the capacitor aspect.

btw a brief google search shows that 500mg of graphite oxide is $160
http://www.acsmaterial.com/product.asp?cid=27&id=16

I don't have time at the moment, but I think it might be worth checking out the wiki on graphene if all this seems to you as mysterious as it does to me.
http://en.wikipedia.org/wiki/Graphene
 
Cj Sloane
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S Bengi wrote:It seems the price is only 33x.


I think this price is a little misleading. As far as I can tell, there aren't any off the shelf models that replace a regular battery. When they become available to replace AA batteries the price will drop dramatically. The same would be true for the large batteries needed for an off grid house.

I do wonder if they'll end up in appliances to cut energy use. Something like a freezer that has a high start up load would be far more efficient if a capacitor kicked in for the 2 seconds the extra power is needed.

We might still run into Jevons paradox.
 
Morgan Morrigan
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They just figured out how to use a Lightscribe DVD player to "print" supercapacitors with graphene on substrate. Cheap and easy, and can stack as many as you need.

The problem is the patents on all this stuff.

there are also some on demand hydrogen fuel cells coming.
 
S Bengi
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For a 3.3kWhr battery pack I would need 1,000 of these. There is no off the shelf product but I dont think that it is that hard to stick 1,000 of these in a PCB.
The biggest problem would be how to deal with 4,000 Amps of current trying to discharge all at once. esp if I am the one touching it after it is charge, yikes.
I am not too sure how inverter would hold up to so much amps, all at once.
The good news is that I would actually be able to do a 5 minutes wielding job with a tiny off-grid solar system, but that might be the Jevons paradox that you mention, lol

Cj Verde wrote:
S Bengi wrote:It seems the price is only 33x.


I think this price is a little misleading. As far as I can tell, there aren't any off the shelf models that replace a regular battery. When they become available to replace AA batteries the price will drop dramatically. The same would be true for the large batteries needed for an off grid house.

I do wonder if they'll end up in appliances to cut energy use. Something like a freezer that has a high start up load would be far more efficient if a capacitor kicked in for the 2 seconds the extra power is needed.

We might still run into Jevons paradox.
 
nustada adatsun
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"
The biggest problem would be how to deal with 4,000 Amps of current trying to discharge all at once. esp if I am the one touching it after it is charge, yikes.


The current is still dependent on voltage and total circuit resistance\impedance. Battery internal resistance is also small enough that it often ignored when designing simple circuits.
 
allen lumley
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Hi all!: While there are many uses for super capacitors, they are mainly used today as a way to store a large amount of energy that needs almost zero maintenance,
and can then bleed of that energy to match a sudden increase in 'load' on the system ! The systems that monitor and control most appliances use very very little
electricity, and can decide to charge up the capacitor rapidly, to be instantly ready or slowly in time to (statistically) meet the next spike, It might even 'talk' to other
appliances/machines to smooth out the load to keep the Electrical meter spinning slowly ! Power hogs and volt vampires will slowly get dealt with, as kilo watt use
become mini watt use !

We must look to the energy used by the process or work load of the appliance to find major savings. We all 'KNOW" that a chest type refrigerator uses a fraction of
the Electricity of the 2-door upright !

I leave you with a thought! Who is looking into connecting this new mini Super Capacitor to a joule thief ?
 
Len Ovens
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The only thing I haven't seen mentioned is the leakage rate. Some people call this efficiency... Just to give some examples... a capacitor with an air dielectric seems to hold a charge forever... but even with quite large plates it is not much of a charge. Electrolytic caps used to be the high end capacity wise, but leaked like crazy. A fully charged electrolytic could self discharge in a few hours... (a CRT could get charged just by using compressed air to clean the dust off) Batteries have the same problem. One of the reasons nickel iron batteries are not used more is that the amount of output for 100% charge is less than the flooded lead cells even though they can cycle many more times. Lots of e-cars use batteries with caps already. The battery charges the caps for high amp use and then the batteries take over for cruise speed. There are lots of super cap toys and the charge does not seem to last from one day to the next.

The other thing is weight/size per energy storage unit. How big does it have to be to store the same as a deep cycle lead acid battery?

And one more... what is the mttf (mean time to failure- AKA time to replacement)? Electrolytic caps are starting to have issues by the time they are ten years old if they are in a warm box (like most electronics). The average person may not hear the difference it makes in an amp for their stereo, but people who are picky do and will swap them out. That is as used for smoothing and the leakage may not even show up at all in the sound, the unit just runs hotter and draws more power. If used for power storage, leakage of any amount would show up much sooner.

In the end there is not that much difference from caps to batteries. They share may of the same problems when used for power storage. Not a silver bullet for sure.

With regard to life times of manufactured stuff... No one is trying to create much of anything that lasts for more than 10 years. Some things just do, like solar cells and LEDs, but that is not because the maker has designed for that property, it is a byproduct of other design targets. Generally, these parts are part of a whole that does have other bits that will fail sooner. For example, a LED lamp has LEDs that should last for 30 years, but the power supply used to match the input voltage to the LED voltage and smooth the ripple to a point we don't see flicker needs capacitors which have a much shorter life span, maybe 10 years. (so it may be worth while scavenging the LEDs from failed LED lamps)
 
Dave Turpin
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I don't understand how we are comparing batteries to capacitors here? How did we come up with 20x cost for an equivalent supercapacitor? From the link I see, a single 3000F, 2.7V supercap is $58. The energy in this supercap is then 1/2(3000F)(2.7v)^2 (Joules) x (2.77777777.. x 10-7) (kWh/Joule) = 0.00304 kWh. So to make an equivalent circuit to replace a 10kWh battery bank, it would cost $190,947, not even including all the interconnecting buswork... Now a 10kWh battery bank is about $1800. That's 107x as expensive for the caps, not 20x....

 
Len Ovens
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Since my last post I have done some research and a couple of things stand out to me. First, yes there is some leakage in super caps, but not any greater than the rechargeable AA batteries everyone uses (which are 1% per day) maybe less. A very small 1 watt solar cell was able to keep a capacitor pack used for car starting fully charged without any problem.

Yes super Caps are expensive, but that will change.

Battery sizing is not cap bank sizing. A cap bank has characteristics that are totally different from a battery. The Cap bank can be totally (100%) discharged without lowering the life of the device. The average car battery can only be 10% discharged and so has to be 10 times the needed power of the same capacitor. Then the battery has to be over sized by about half, because even 2 or 3 years down the road a battery's charge capacity is almost down to half. So for car starting, a Capacitor that is one twentieth the the capacity of the battery would be effectively equivalent. A capacitor that is down to 9v will still start a car, a battery won't turn it over at that voltage.

Ok, but deep cycle batteries can handle 50% discharge right? Yes, but if you discharge a deep cycle battery to 50% every time... it will not last 8 to 10 years. Lucky to make 5 years. A capacitor can take full discharges every time at a fast rate even, indefinitely. To make a battery last 8 to 10 years it has to only get discharged 25% or so. A capacitor could still be one eighth the size and give the same performance.

Back to the car battery, why do we use a light cycle battery? We use a light cycle battery that is 10 times over size because of another of the battery's failings. Available current draw. A battery can only give up current so fast, but the car starter needs a lot of current in a short time, so the battery is over sized 10 times in order that it can give those "cold cranking amps". A capacitor can give up its charge almost instantly. There is some internal resistance and because of internal lead size, over drawing could melt some of these leads. Even the older electrolytic caps were slower than other caps, filtering often had two caps, one for low frequency filtering and another for high frequency noise. In any case, a capacitor power storage can be smaller than a battery storage where part of the battery sizing has to do with peak draw such as motor starts.

There are some other differences between the two as well. The battery has a cell voltage, a 12 volt lead acid battery will work from 11 to 15 volts and the charge controller has to take whatever the input voltage is and convert it to this range. Both wind and solar receivers output a wide range of voltages depending on wind and sun. Capacitors have a maximum voltage, but are happy with any voltage so long as it is less than this maximum (running them near that voltage can shorten their life, so a system maximum below that unit maximum would be advisable).

System testing. A battery UPS testing procedure is to run the system with power out till it quits. That is the only way to know how long you will get from your battery back up. There are some other ways for approximating life of a battery bank, but testing is standard at least for computer backup. Only one problem, full discharge for testing is hard on the battery and shortens it's life. A capacitor doesn't have that problem.

Other things... all our inverters are designed for the failing of batteries... They shut off at a voltage to keep the battery from over discharge for example. All of our off grid battery stuff is designed around the characteristics of lead acid batteries and will need some redesign to work with the shiny new capacitor banks. This bad news for the consumer, but good news for the experimenter who would like to sell stuff in small quantities. There is room for small scale innovation.

Anyway. batteries do not equal capacitors. Sizing will be wildly different. Battery charging systems will work with capacitors, but new designs could make better use of the incoming charge power. Capacitors will work with current battery uses as a "drop in" replacement and will do so at a much smaller size, however, even better use of the capacitors storage could be made with better inverter/load design.

So in general, when comparing batteries to capacitors, the battery has to be at least 8 times larger for similar performance. It would not be unrealistic to use a capacitor size of 1/10 when comparing cap to batteries.
 
S Bengi
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I found these 2.25Whr (3000F,2.7V) supercapacitors for $40 each.
Assuming I only need 1kWhr for night time use (14 hours in the winter).
It would cost me $12,200 (306*$40).
I have seen used ones for as low as $10 each but that would still be $3,060.

I will probably use 5kWhr in the day, with 4hr of sunshine per day in the winter.
A 2000W solar panel array will give me 8kWhr (2kW*4hrs of sunlight).
Solar panels cost about $1/W for a total of $2000

Now we still need a Charge Controller and an Inverter.
We can use a regular Charge Controller for about $1000

Now for the hard part an Inverter that can deal with low voltage and high current.
To maintain a power output of say 200W. At first with a full charge of 29V it will be easy with only 6.7Amp DC needed.
However as the night progress and I drop down to 1V I would then need 200Amp DC, the capacitors have no problem doing this and it does not harm them.
But does anyone know of an Inverter than can do all of that.

Notes
I can connect 18 in series for 48V (18*2.7v), I would then connect 17 of these in parallel for a total of 306 supercapacitor.
To prevent back flow I would connect a 47ohms resistor in parallel to each supercapacitor or I could get fancy and make a active system, but that would be too much to describe in one post.

All I really use in the night would be
1) laptop*4 30W/hr. They have their own 8hr battery pack so it does count towards energy usuage
2) led light 4hrs/night, 6 bulbs at 20W/hr each, about 500W
3) Fridge filled with ice made in the day and not opened in the night with the temperature raised at night and lowered in the day, about 200W/night total
4) Not too sure where the other 300W will be used but it will.

If there is a real emergency, earthquake, storm or I need to use a welder or some powertool a generator will be used.
I dont use a welder/powertool or such everyday not even once a month.
But if I have to breakout the generator 12 times a year to "check" if it is working. That is OK in my book.








 
S Bengi
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Between the Supercapacitor "battery" array and the inverter, I could put a DC to DC Boost Converter.
Then connect the Inverter to the DC to DC Boost converter.
The DC to DC Boost converter has a 97% efficiency so while I will be losing some power it will not be much.

The quest now is to find one with the following specs
Output Voltage: 48V
Output Current: 0.1A-200A
---------------------------
Input Voltage: 0.1V-47V
Input Current: 0.1A-1000A

It looks relatively simply to build one, I will have to figure out how to get the desired specs.
However it would be even easier if I found one already made.


So far this is what I have found

Output Voltage: 9V-90V
Output Current: 0-28A
---------------------------
Input Voltage: 9V-90V (hard 5V-100V)
Input Current: 0A-28A
http://www.synqor.com/datasheets/NQ90W90HGx26_Datasheet.pdf

They can be configured in parallel at the same output voltage to give more current.
So with 10 of them
max current is 28*10=280A
At 95% discharge the biggest load it could handle is 1,400W (5V*28A*10)
At full charge the biggest load it could handle is 20,000W (2000W*10)

 
Len Ovens
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S Bengi wrote:I found these 2.25Whr (3000F,2.7V) supercapacitors for $40 each.
Assuming I only need 1kWhr for night time use (14 hours in the winter).
It would cost me $12,200 (306*$40).
I have seen used ones for as low as $10 each but that would still be $3,060.


I guess that is the price of using "new" technology. They should last forever, but... it is new tech and if one goes in a series bank, it could take that bank with it as caps are as likely to fail to short as open. This means I am not ready to try this technology yet, at least not that much of it.



Now for the hard part an Inverter that can deal with low voltage and high current.
To maintain a power output of say 200W. At first with a full charge of 29V it will be easy with only 6.7Amp DC needed.
However as the night progress and I drop down to 1V I would then need 200Amp DC, the capacitors have no problem doing this and it does not harm them.
But does anyone know of an Inverter than can do all of that.

Because it would be a "one off" it would cost a lot. They aren't there yet. Home built may be the other way to go, but that would likely loose on the efficiency end.


 
Len Ovens
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S Bengi wrote:Between the Supercapacitor "battery" array and the inverter, I could put a DC to DC Boost Converter.
Then connect the Inverter to the DC to DC Boost converter.
The DC to DC Boost converter has a 97% efficiency so while I will be losing some power it will not be much.


There is switching to add in too, I think. When fully charged the cap bank would be fed direct to the inverter. At a lower voltage through the boost... maybe switching the configuration as the voltage drops. Being able to use an off the shelf inverter would be a good start I agree.
 
S Bengi
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I was worried that I needed a DC to DC converter that accept a huge voltage range to ensure that I drain most the energy in a capacitor.
However it turns out that a 50% drop in voltage means that 99% of the energy is gone.
This makes it so much easier to source the components. Now that I know I only need a 2:1 ratio for Vmax:Vmin
 
Len Ovens
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S Bengi wrote:I was worried that I needed a DC to DC converter that accept a huge voltage range to ensure that I drain most the energy in a capacitor.
However it turns out that a 50% drop in voltage means that 99% of the energy is gone.
This makes it so much easier to source the components. Now that I know I only need a 2:1 ratio for Vmax:Vmin


I am used to thinking about integrators that work constant current and have a linear slope (or at least the designer tries to make it so), but here we are working for constant power out, so the current rises as voltage falls. As the current rises so does the discharge rate. I am surprised it is as high as 99%. However, I have forgotten how to calculate this stuff (it has been over 35 years) I can draw a simple line drawing though that shows at least 80% and can see where my inaccuracies would make that on the low side. A properly designed inverter should be able to deal with that range no problem and with no efficiency penalty but, will cut out at 70 to 75% to "save the lead acid batteries". I do not know if it is easier to design a switch for two (or three) inverters depending on voltage, design a DC to DC inverter or to see if the inverter can be programed on the fly for different "battery" voltages as the bank voltage drops. Some inverters are made to work with more than one battery bank voltage. If the steps are not too far apart, that could work. Also it may be worth while seeing if the battery voltage cutout is programmable.

The upside of a dc to dc converter is it is easier to swap out the the AC inverter if it dies or you need a new size.
 
Barry Fitzgerald
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Ok, I still remember my high school electricity. Capacitors in series, total capacitance = 1/ C1+C2+C3 etc. but as all the capacitors have an equal value we can simplify this to total capacitance = C/the number of capacitors.
The problem here is the 2.7 volt rating, to get 24 volts you would have to put 10 of these in series (with no safety factor). That would reduce the total capacitance by 90% of the value of 1 capacitor.
When they build a supercapacitor with a 50 volt rating it would be more practical.
 
S Bengi
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Barry Fitzgerald wrote:Ok, I still remember my high school electricity. Capacitors in series, total capacitance = 1/ C1+C2+C3 etc. but as all the capacitors have an equal value we can simplify this to total capacitance = C/the number of capacitors.
The problem here is the 2.7 volt rating, to get 24 volts you would have to put 10 of these in series (with no safety factor). That would reduce the total capacitance by 90% of the value of 1 capacitor.
When they build a supercapacitor with a 50 volt rating it would be more practical.



Let us compared the amount of energy stored in series and also "individually".


Energy stored in series=1/2*C*V*V
=1/2*(3000/10)*(2.7*10)*(2.7*10)
=1/2*300*27*27
=1/2*300*729
=1/2*218700
=109350J

Energy stored individually =1/2*C*V*V
=1/2*3000*2.7*2.7
=1/2*3000*7.29
=1/2*21870
=1/2*21870
=10935J
Now if we multiply the energy stored individually by 10 we end up with the same number as in series.

Total Energy=Energy in Each CAP times Amount
W=10935J*10
W=109350J


Both of those numbers are the same
 
Barry Fitzgerald
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Let us compared the amount of energy stored in series and also "individually".




Both of those numbers are the same


Yes the numbers are the same. My point was that they are only a fraction of what you want for efficient energy storage.
The issue is the voltage rating and the Farad rating reduces the total stored energy by putting them in series to a tenth. You have shown that if you increase the applied voltage 10X , you get the same storage. Remember the 50% energy loss in charging a capacitor?
I will stick with batteries for now.
 
S Bengi
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Whether the capacitors are in series or not does not make a difference in the amount of energy that they store.
It is true that in series the voltage is higher and then that voltage is squared so it is even higher but the capacitance is lower and we end up with the same number(amount of energy stored)

NOW it is true that capacitors has an efficiency of 50% thus the half in W=1/2*C*V*V
Whereas batteries has an efficiency of 76%.
http://evbatterymonitoring.com/WebHelp/Section_1.htm

Note:
a battery is 100% efficient at charging until it get to 70% charge once it reaches 70% it becomes less efficient,
To go from 70% to 100% requires twice as much energy to be supplied compared to what is stored.
So if 70% to 100% comes out to 30kWHr of energy stored, the charger would have to supply about 60kWHr.

So 130kWHr supplied and 100kWHr stored for a 76% efficiency

Now given the fact that a battery should not go below 50% it really works out to be 50kWHr stores and 80kWHr supplied.
This makes battery efficiency fall to 62% still better than the 50% efficiency of capacitors but not by much more.
And a lot of people well even recommend to not let a batter fall below 75% if you want your battery to last the 10 years that they are rated for.
If we go with that 75%-100% figure then the efficiency falls even lower, much lower than 50%.

All that said batteries are 20x cheaper than capacitors. So like you stated for now batteries are the BEST option.
Hopefully with all the research going on they can bring the price of capacitors down to battery price
 
Len Ovens
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Barry Fitzgerald wrote:
Yes the numbers are the same. My point was that they are only a fraction of what you want for efficient energy storage.
The issue is the voltage rating and the Farad rating reduces the total stored energy by putting them in series to a tenth.


No. That is a false assumption. First a question to think about:

Why use 220v for hot water heaters, stoves, baseboards heaters, driers etc.?

It is the same with batteries or capacitors. Instead of 10 in series, lets start with two. For any capacitor with a capacitance of C, putting them in series gives C/2, but the voltage is now V2. This means that the capacitor will now be able to provide the same current for the same time as one capacitor at V.

So for one cap I*V=P
for two in series I*V2=2P

Hmm, but we still have c/2 to deal with, yes. That means if the load stays the same, it will discharge twice as fast. In all of this we have not talked about load. With more caps in series the load decreases for the same power. This is the reason we use 220v for baseboard heaters. A 1k heater at 100 v draws 10Amps and a 1k heater for 200v draws 5 amps, but the two are not interchangeable. If the heater for 200v is connected to 100v the power out is not half... The heater has a resistance of 200/5 = 40ohms and 100v/40ohms is only 2.5 amps* 100v is only 250watts.

So the energy stored in a cap remains the same no matter how it is connected, in parallel the current used must be twice as high for the same power and in series half as high (again with two capacitors, but the numbers work for other amounts too). The capacitors will take just as much time to discharge for the same power out, but in series we have much more useful voltages.
 
Barry Fitzgerald
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Len Ovens wrote:
Barry Fitzgerald wrote:
Yes the numbers are the same. My point was that they are only a fraction of what you want for efficient energy storage.
The issue is the voltage rating and the Farad rating reduces the total stored energy by putting them in series to a tenth.


No. That is a false assumption. First a question to think about:

Yes, I get what you are saying. I just got hung up on the idea of reducing total capacitance in order to get to an acceptable working voltage.
 
S Bengi
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With a constant voltage (unlimited peak current and instantaneous charge) the energy lost in a capacitor is 50%.
However with a constant current (via source voltage at 1/2 cap voltage and an inductor in series with a diode to prevent backflow) we can bring that energy lost down to only 10% if we move away from instantaneous recharge and spread out the charge time. The longer the charge time the less energy that is lost and the lower the current has to be. http://www.olino.org/us/articles/2006/11/22/charge-efficiency-capacitor
 
Chris Badgett
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Interesting video Daniel. Thanks for sharing.

It makes sense as a battery, but I'm still trying to understand where the original energy source comes from. Does graphine have a limited supply of energy in the material itself?

 
S Bengi
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Chris Badgett wrote:Interesting video Daniel. Thanks for sharing.

It makes sense as a battery, but I'm still trying to understand where the original energy source comes from. Does graphine have a limited supply of energy in the material itself?



The graphene works like any other battery/capacitors. It has to be originally charged by an outside source, in the same fashion that it is recharged later.

BUT what does make graphene special is the fact that it forms a compound that has 100x more surface area when compared to regular materials.
What this means is that it has more places to hold charges, it also has a really low resistance to the flow of electrons. So it can recharge and discharge quickly.
 
I am going to test your electrical conductivity with this tiny ad:
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