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a4x4kiwi
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Post by a4x4kiwi » Tue, 23 Dec 2008, 06:13

http://yro.slashdot.org/article.pl?sid= ... 7&from=rss

The testing shows voltages of up to 5000V. It might need a very special inverter to use the energy in the rage of 0 to 5000V

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Post by AMPrentice » Thu, 25 Dec 2008, 01:07

Umm could this be the next DeLorean?

I hope Im wrong but it seems to hold so much energy, so much capacity with such a long lifetime it seems to good to be true.

If it is true it will need a hell of a charger, a hell of a motor and a hell lot of money to make it available to EVeryone.

If it does happen it will be in luxury and expensive sports cars, aircraft and sea craft only the wealthy could rub in our faces.
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Post by acmotor » Thu, 25 Dec 2008, 02:28

Interesting posts on slashdot.
EEstore may be patenting "where they would like to be" with research but I would not doubt the potential (no pun intended) of where they are heading.

It is still interesting that fast recharge rates (minutes) are being entertained. EVers are already very aware that the specific power of a battery pack is a function of both the ESR of the cells and the capacity of the wiring that interconnects them.
e.g. for a 50kWh pack at say 200V, if your emotor demand is 100kW peak then current is 500A peak for seconds with an average of less than 100A

The current to charge in one hour is 250A. This is already 2.5x the average current, and it is a continuous current.

To charge in 6 minites is 2500A. This is 25x the average current.
I am not certain that even if you had off vehicle energy bank to charge from that you will be prepared to overbuild the vehicle wiring (and battery internal construction) 25x to cater for this fast charge.
This also requires contactors and fuses etc rated at 25x. The mind boggles. Just be patient... take 12 minutes ! Image

I would really like to see ultracaps compete in EVs.
One issue that will come up though is the safety factor.
In a chemical battery (this includes fuel), the energy is stored by change of chemical state and this energy is possibly less prone to catastrophic release as the energy requires a reation to take place before it is released. True, this release can be violent but typically progressive and not all chemicals will end up reacting.
Check out zebra battery crash test.zebra
more zebra This is one fairly tame battery (apart from being at 300deg C already). It can be shut down to cold and continues to store its energy quite inertly. Energy is again available when heated up.

An ultracap will require careful design on the other hand, as the energy is already in electrical form and able to discharge very rapidly with the only end product being bulk heat. Once there is heat you can be certain that all insulation will fail, so all energy will very likely and very quickly end up as heat and maybe some Christmas lights.

I still wish EEstore et. al. all the best.

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Post by bga » Thu, 25 Dec 2008, 20:03

Hi AC,

Well said, I'm expecting to hear of another delay from EEStor sometime near the proposed release day. The 3500+ Volt capacitor at 1mF is a tall order. They are coy about leakage currents. The patent discusses connecting a large number of individual capacitors in an array. The number stated (31353) doesn't factorise very well (3 x 7 x 1493 hmmm). It is used as an example in the patent.

A large number or parallel high voltage elements is interesting from a reliability aspect. Many could be disabled (fuse themselves out of the circuit) before significant degredation occurs. The eestor arrangement looks like an extension on the usual dual layer capactor in a layered stack of super-plates. They discuss this as a monolithic block (thermal coefficients)!

I'm sure that they haven't thought about the implications of extreme fast charging. The 6 minutes is more likely to be from a time and motion study of a petrol station. The power and currents are so high that the the battery pack will be impossible to be made 'safe' by internal fusing and would likely suffer internal heating issues.

General comment on the capacitor voltage-energy relationship:
It's actually not a lot different to a normal battery because the energy is proportional to V squared, the range 2500-5000V contains 3/4 of the energy. This is kind of like 4V to 2.5V in a Lion or NiM-H battery, maybe a bit more dynamic range needed.

Cheers

BGA


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Post by juk » Fri, 24 Apr 2009, 06:14

From Green car Congress 22/04/2009:

EEStor, Inc. issueda short press release announcing that a third-party has certified that EEStor’s patented and patent pending Composition Modified Barium-Titanate Powders have met and/or exceeded a relative permittivity of 22,500.

In the few public statements made by the company several years ago, it had said that it anticipated that the relative permittivity of its then current powder would either meet and/or exceed 18,500, the previous level achieved when EEStor produced prototype components using it engineering level processing equipment. ( Earlier post.)

The third party certification tests were performed by Texas Research International’s Dr. Edward G. Golla, PhD., Laboratory Director.

EEStor said that it feels this is a “ huge” milestone which opens the advancement of key products and services in the electrical energy storage markets of today. The automotive and renewable energy sectors are a few of the key markets that would benefit greatly with the technology.

EEStor, Inc. is working to develop solid-state electrical energy storage units (EESU’s) in the form of batteries and capacitors. The EEStor EESU—a high-power-density multi-layered barium titanate ceramic ultracapacitor—is expected to provide energy densities of more than 450 Wh/kg and more than 700 Wh/L; charge in minutes; and have extremely long life. ( Earlier post.)


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Post by woody » Wed, 29 Jul 2009, 15:15

EEStor founder interview

On EESU status: “I’m already out there putting EESUs together and I’m still in June. I’m ahead of schedule.” Says ZENN will get pre-production prototypes by the end of this year. “Once I do that, all hell is going to break loose for ZENN as well as EEStor.”
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Post by acmotor » Fri, 31 Jul 2009, 03:25

I really really believe in the future of ultra capacitors, but why is it something on that site puts me off ??? Image
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Post by Johny » Fri, 31 Jul 2009, 04:31

Hmm. Yes I left a negative comment in the responses section and it didn't make it through moderation.
There is something about all the hype that makes it sound just to good to be true.

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Post by Electrocycle » Fri, 31 Jul 2009, 15:54

Does anyone know what limits the energy storage of a capacitor?

Is it a simple "this much charge per area" thing?

I imagine most of the development in capacitors is based on getting more surface area, and the plates closer together while maintaining isolation.

Big claims are being made... hopefully at least some of them are true :)
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Post by Johny » Fri, 31 Jul 2009, 16:08

Short answer is yes but EEStor essentially concentrated their effort in getting the voltage higher. For the same capacity, if you double the voltage you have doubled (actually quadrupled - see later posts) the stored energy. Ultracaps as we have seen them for car hi-fi are generally very low voltage. 2.5V units in series.
EEStor claim to have 5000 Volts insulation happening with lower but similar Farad capacities as the low voltage ones.

It means that the EEStor devices will need a lot of high power electronics to support their use. A buck/boost convertor that handles 5000 down to 500 (or lower) volts and outputs whatever equivalent traction pack voltage required - say 300 VDC.

In theory it also opens up a whole new area where the motor/motor controller and buck/boost convertor are designed in a more holistic fashion to run on the changing voltage as the "pack" discharges.

Time will tell.

Edit: Short is spelt short.
Edit: Appended fix for physics error.
Last edited by Johny on Tue, 01 Sep 2009, 06:36, edited 1 time in total.

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Post by Electrocycle » Fri, 31 Jul 2009, 16:25

yeah I definitely think controller are going to become more of a buck / boost bidirectional device to handle all the possible conditions.
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Post by vince » Fri, 31 Jul 2009, 16:42

Is it safe to say that ultra-capacitors store dc volts?

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Post by Johny » Fri, 31 Jul 2009, 16:46

Electrocycle wrote: yeah I definitely think controller are going to become more of a buck / boost bidirectional device to handle all the possible conditions.
Whoops - forgot about the regen. You are right - need buck/boost converter.
vince wrote: Is it safe to say that ultra-capacitors store dc volts?
In that they are require DC to charge them, and provide DC, yes.

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Post by vince » Fri, 31 Jul 2009, 19:53

I'm not sure how accurate this is but from what i read-ultra capacitors can handle greater loads from ac/regen setup.If this is correct then how will this compare to present percentages of efficiencies using lead acid/l-ion batts?

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Post by JackM » Fri, 31 Jul 2009, 20:30

I am concerned about the charging heat and its affect on the bonded dissimilar materials in the solid state "electrolyte". As you know dissimilar materials have different coefficients of expansion. Could this cause the components to flex, like a thermostat, and crack after many charges. (Ceramics don't like to be flexed).

Here is something I found at Ultracpacitors.org. Someone told me that these guys won an award for their technology from a large, intenational tech research firm. This stuff has a large energy and power density. With some tweaking, it could compete with EEStor Read this:

[ Edit Coulomb: original paper here:
http://www.ct-si.org/publications/proce ... /70364.pdf ]

Use of Reticle Carbon in Supercapacitors
Dr. Carl C. Nesbitt
Reticle Inc., 334 State Street; Suite 204; Los Altos, CA, USA, cnesbitt@mtu.edu

ABSTRACT

Supercapacitors can be used to augment chemical
batteries, in rapid-pulse battery rechargers, with fuel cells,
electric motors, turbines, computers and in many other
applications. Inasmuch, Reticle Carbon, an inexpensive,
high surface area carbon, may lead to a resurgence of
interest in electric double-layer (EDL) supercapacitors.
Reticle Carbon is a unique, consolidated material that has
low electrical resistivities (0.04-0.130 Ω-cm), demonstrated
high surface areas (1250-1750 m²/g), and the highest
reported specific capacitance (200-310 F/g). It is produced
by consolidating granular activated carbon that has been
selected for its properties. The manufacturing process is
single-stage in which parameters can be varied to tailor the
properties to make the perfect supercapacitor material. This
paper shows the wide range of properties that the material
possesses with the underlying theory to store energy in the
massive available surface area of the material. We have
demonstrated the energy storage and discharge capability of
the material in leveling the electric load of a small electric
motor.

Keywords: supercapacitors, carbon electrode, energy
storage, load leveling

1 BACKGROUND

Capacitors are fundamental devices used in electric and
electronic circuits. In their simplest form, capacitors use
two plates separated by a distance. The concept is simple,
just charge the plates and the energy is stored. The
capacitance (C), a quantitative measure of energy storage
capacity, has the standard unit known as a farad (F).
Capacitors typically have high power densities in small
bursts, they recharge and discharge very quickly (often in
seconds), they can be cycled over 300,000 times without
loss of capacity, and they cannot be overcharged.

As an example of the utility of these devices, let’s look
at electric motors. Engineers size a motor to the peak
power output required for start-up, when the power demand
to create momentum from a dead stop is greatest. After this
initial surge requirement, the power draw is significantly
lower to maintain the inertia. So what if you could attach a
power supply on the side that could give that boost of
energy required at start-up, but then shut off when not
needed? The motor could be sized to the lower load—a
concept known as load-leveling.

This is not a new idea, but the methods for supplying
the extra energy for motor startups vary. Some use
chemical batteries, while others use auxiliary motors that
“kick in” when needed. Recently, the idea of large capacity
energy storage devices (supercapacitors) has appeared as a
logical solution.

While the load leveling concept for a motor is
understandable, the same theory applies for any electrical or
electronic device. For instance, computer hard drives and
screens, CD-ROM drives, cell phones, DVD players, fans
in furnaces and air conditioners, and refrigerator
compressors are examples of things that operate in an ‘onoff
cycle’ which could use this same type of energy storing
device. Placing a small capacitor in computers, for
instance, would reduce the high peak draw on the battery,
which would extend its charge-life. On a larger scale,
supercapacitors can augment solar panels, wind turbines or
other intermittent power generation systems.
Supercapacitors could be used to store this energy until
peak demand (when most sources are not generating
power.) Now all we need are reliable, high-capacity
materials in capacitors that can store large amounts of
energy. That is where Reticle Carbon can make a sea
change in the technology.

2 RETICLE CARBON—THE ADVANTAGE
OF SURFACE AREA

The unique properties of Reticle Carbon are the result
of the patented manufacturing process and the precursor
carbon properties. Reticle Carbon is manufactured from
any granular activated carbon in a simple, one-step
consolidation process. The process can be tailored to give
Reticle Carbon unique properties, such as macroporosity
ranging from 10-40%, electrical resistivity ranging from
0.04 – 0.13 Ω.cm, and thermal conductivity measured at a
low 0.1 W/m.K. However, the most unique property of the
material is the demonstrated high surface areas, ranging
from 1250 to over 1750 m²/g. Compared with other
activated carbon materials, this is an exceptionally high
surface area range.

Samples of Reticle Carbon have been used to
investigate improvements to capacitive energy storage, as
well as many other applications. Laboratory and pilot-scale
experiments have been performed using the material to
desalinate, or deionize water, as well as recover metal from
electrolytes. For these tests, several different samples of
Reticle Carbon have been made with a wide range of
surface areas as determined by BET method [1].

Table I shows the range of properties of Reticle Carbon
compared with the properties of other materials being used
in supercapacitors—Aerogel carbon (from Lawrence
Specific Attribute Reticle Carbon

Properties

Aerogel Carbon
Properties [3-4]
Carbon Nanotube
Properties [5-7]
Surface Area (m^2/g) 950 – 1750 100 – 800 125 – 250
Specific Capacitance (F/g) 80-390 100-180 30-90
Bulk Density (g/cm^3) 0.75 – 1.0 0.78 1.3 – 1.4
Est. Mfg. Cost <$100/kg $250/kg >$10,000/kg

TABLE I: Range of properties of Reticle Carbon as compared with Aerogel Carbon and Carbon Nanotubes

Livermore National Laboratory) and carbon nanotubes (as
those being studied at MIT). Although the performance of
the carbon material is dependent on many properties, the
surface area is the standard metric used to differentiate
between the samples. Notice that Reticle Carbon has
significantly higher proven surface areas than the other
“best-in-class” materials, and at significantly lower
estimated cost.

The importance of surface area can be illustrated by
considering the electric double-layers formed at the solidliquid
interface [1]. The only way to increase the amount
of ions in diffuse double-layers would be to (a) increase the
charge of the solid (as by an applied potential), or (b)
increase the surface area of the interface between the
electrolyte and the solid. Both of these are easily
accomplished with Reticle Carbon, which has the highest
reported surface area and the highest electrical conductivity
(inverse resistivity) reported for any activated carbon
material.

Let’s try to quantify this impact. Capacitance is
defined by Equation (1) as:
4 d
C
(1)

where, C = capacitance per unit area (F/cm²)
ε = dielectric constant of the medium
d = thickness of the double layer (cm)

Using typical values [2], Equation (1) can be used to
calculate an average specific capacitance:

<equation> C = 17.6 μF/cm²

This is in agreement with the reported range of 10 and 20
μF/cm² for carbon materials. Consider just 1-g of Reticle
Carbon with more than 1250 m² of available interfacial
surface area, or 12,500,000 cm². A simple capacitor with
this material will have 220 F of total capacitance. Onegram
of the 1750 m²/g carbon will have over 300 F!

That is precisely the level of capacitance we have
found in Reticle Carbon. Table II shows the properties of
three Reticle Carbon samples manufactured from the same
granular activated carbon precursor. Notice that the
specific surface areas range from 930 to 1240 m²/g (66-
90% of the precursor area), while the specific capacitance
of the material varied from 80 to 212 F/g. If we combine
these values, the average specific capacitance was
15μF/cm², which demonstrates that nearly all of the
available surface area contributed.

We have made and tested capacitors with Reticle
Carbon (as diagramed in Figure 1). These simple devices
are just sandwiches of the Reticle Carbon electrodes with
an electrolyte permeating the space between them. The
electrolyte can be any aqueous solution or conductive
organic electrolyte. A glass wool separator is used to keep
the electrodes from contacting each other. Graphite was the
current collector used to attach the leads to the power
source. We have measured 53 F/g specific capacitance in
capacitors made from the Sample I carbon. This is
outstanding considering the previous best-in-class Aerogel
carbon electrodes have reported a 40 F/g specific
capacitance [3]. Even higher capacitances will be achieved
when we incorporate Reticle Carbon that has 1750 m²/g.
The capacitor was not optimized to minimize the overall
weight, so we anticipate even better performance with
higher surface areas and lower weight capacitors.

Surface Area
(m2/g)
Mass Specific
Capacitance
(F/g)
Porosity
(%)
Bulk
Density
(g/cm³)
Electrical
Resistivity
(Ω.cm)
Sample I (light consolidation) 1238 ± 21 212 31.0 0.75 0.134
Sample II (moderate consolidation) 1026 ± 20 160 16.8 0.94 0.060
Sample III (heavy consolidation) 931 ± 15 80 11.9 1.05 0.047
Raw carbon (as received) 1400 ± 22 - 19.8 0.66 -

Table II: Range of properties of Reticle Carbon made from a single precursor carbon, demonstrating the flexibility of the
manufacturing process.

AC Electrodes
Current Collector
Separator
Casing
Electrolyte

Figure 1. Schematic of the Supercapacitor Using Reticle

Activated Carbon (AC) Electrode Material.
To understand the importance of this discovery, we can
use the basic principles. The energy stored in a capacitor is
defined in Equation (2):

Wc(t) = ... v.i dτ   (2)

Keep in mind that the voltage (v) and current (i) both vary
with time in these cells. In fact, Equation (3) represents the
time interdependence of both:

i = C dv/dt    (3)

Combining (2) and (3), and assuming the capacitor is
initially uncharged (that is, at t = -∞, v(t) = 0), we get the
following:

wc(t) = 1/2 C.V²(t)     (4)

If the capacitance (C) is in farads, and voltage (v(t)) is in
volts-DC, then the total energy stored (wc(t)) will be in
Joules. As shown in Equation (4), as the voltage changes
(an implied current change will also occur, as well), the
energy stored changes. But once the capacitor is charged at
a specific voltage, the energy will not dissipate until the
capacitor is connected to a resistance or load.

So for example, if we have a 1-F capacitor at 10-V, the
energy stored would be:

Wc(t) = ... = 50 J

That means that this capacitor will store up to 0.014 W-hr of
energy. Now let’s look at 1-g of Reticle Carbon, with 212 F
of capacitance and 1.5-V potential:

Wc(t) = ... = 0.068 Wh

In other words, we have the potential for energy densities of
68 W-hr/kg of Reticle Carbon. If 1-g of graphite is used to
make the current collectors, and 1 ml of aqueous electrolyte
is used, the overall energy density of the entire device will
be over 20 W-hr/kg of electrode, which is quite high.
Because capacitors discharge their stored energy rapidly
(often less than 3 sec), the estimated power density of these
small units would be:

... = 24 kW per kg of capacitor.

Improvements to our capacitors will improve the amount of
energy stored. Aqueous electrolytes are an obvious first
target, although they are low cost, safe, available, and are
adjustable with minor changes to salt concentrations. But it
has an electrochemical restriction—at relatively low
electrical potentials (above 1.5-V) water decomposes into
gaseous hydrogen and oxygen. However, capacitors in
series could handle much larger voltages and energy loads.

If we could double the voltage to 3-V, we would have a
four-fold increase in the energy density for the same
material. There are many commercially available organic
electrolytes that have relatively high decomposition
potentials (>5-V) that may be considered. We have
performed preliminary experiments and have not as yet
found an organic that has sufficiently high ionic strengths to
meet requirements of our capacitors. However, the
possibilities for improvement are certainly endless for the
energy storage of supercapacitors.

In a qualitative test, we incorporated a set of
supercapacitors in a toy electric car (shown in Figure 2) to
demonstrate load leveling of batteries. As you will notice,
six “AA” batteries are required to operate the car under
normal conditions—that’s 9-V from the batteries in series.

As discussed earlier, the power required for starting the
motor is significantly higher than the power required for
constant driving conditions. So to show how our
supercapacitor provides the “kick” at start up, we attached a
supercapacitor rated at 4-V in parallel with the battery bank
of the toy car as shown in Figure 3. The capacitor was
actually two capacitors in series, to avoid generating
hydrogen or oxygen under charge.

Figure 2. The battery powered car used for the load leveling
tests with Reticle Carbon supercapacitors.

RC CAPS

Figure 3. Schematic of the Reticle Carbon supercapacitor
attached in series with half of the required batteries to
operate a toy car.

For this test, we removed half of the batteries. Three
batteries (4.5-V) alone did not provide enough power to get
the car started. The current draw from the batteries was so
great, that the batteries potentials dipped to meet the sudden
demand for power. The drop in the potential shown in
Figure 4 was the actual voltage response of the batteries in
the car at startup. (Notice that the batteries we used only
provided 4.0-V of potential instead of the 4.5-V expected
from fresh batteries.) However, the capacitor provided the
boost to the motor to get the car started with only a
moderate voltage drop observed in the batteries. The
batteries then supplied enough power to operate the car
normally. As the car stopped, the current from the batteries
was slow to respond, and quickly recharged the capacitor,
readying it for the next start. Incorporating the capacitor
provided the power required to start the motor, but allowed
us to reduce the number of batteries required. It also helps
save battery life by minimizing the voltage drop when the
load is applied!

Without supercapacitor With supercapacitor

Figure 4. Battery response at the start of the toy electric car
with and without Reticle Carbon supercapacitor. The car
would not run without the capacitor.

3 SUMMARY

Reticle Carbon has unique properties that allow it to be
an efficient electrode material in supercapacitors. The
material has surface areas as high as 1750 m2/g, which give
the material a specific capacitance of 300 F/g.

Supercapacitors made with material with just 1240 m2/g had
energy densities of 23 Wh/kg and peak power densities of 8
kW/kg. With modification and design optimization these
levels will be exceeded in next generation Reticle
supercapacitors.

REFERENCES

[1] D.J. Shaw, Introduction to Colloid and Surface
Chemistry, 2nd Edition, Butterworths, 111-116, (1976).

[2] E.C. Potter, Electrochemistry Principles and
Applications, Cleaver-Hume Press Ltd., London, p.
156, (1956).

[3] CDT Systems, Inc. Homepage, found on-line,
www.cdtwater.com/carbonaerogel.php (2008)

[4] Richardson, et. al., “Desalting in Wastewater
Reclamation using Capacitive Deionization with
Carbon Aerogel Electrodes”, Preprint UCRL-JC-
122914, Lawrence Livermore National Laboratory,
(July, 1996).

[5] On-line pricing from www.cheaptubesinc.com

[6] A. Peigney, Ch. Laurent, E Flahaut, R.R. Bacsa, and A
Rousset, “Specific surface area of carbon nanotubes and
bundles of carbon nanotubes”, Carbon 39 (2001), 507-
514.

[7] T.A. Adams, II, “Physical Properties of Carbon
Nanotubes”, www.pa.msu.edu/cmp/csc/ntproperties,
(2008).

[8] J. Kassakian, J. Schindall, and R. Signorelli, MIT
Laboratory for Electromagnetic and Electronic
Systems,
lees-web.mit.edu/lees/projects/cnt_ultracap_project.htm,
(2008).   Image

[ Edited Coulomb: Repaired bad Unicode chars in preparation for conversion to phpBB ]
Last edited by coulomb on Sun, 25 Jun 2017, 14:45, edited 1 time in total.
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Post by antiscab » Sat, 01 Aug 2009, 08:55

Johny wrote: For the same capacity, if you double the voltage you have doubled the stored energy.


Hi Johny,

for the same capacity cap (in Farads), if you double the voltage, the energy stored is quadrupled, not just doubled.

the relationship is:

E = V^2 / C;

E is energy (J)
V is voltage (V)
C is capacitance (F)

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Post by Johny » Sat, 01 Aug 2009, 15:41

Thanks Matt. After I wrote it I started having doubts.
I had figured basically with a constant current discharging twice voltage would discharge for twice as long - forgetting that twice voltage would be four times power into a given resistance.

Anyway - it supports even more the concept that raising the insulation voltage on caps has a dramatic benefit.



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Post by coulomb » Sat, 01 Aug 2009, 15:46

antiscab wrote: For the same capacity cap (in Farads), if you double the voltage, the energy stored is quadrupled, not just doubled.
Right.
the relationship is:

E = V^2 / C;
Actually, it's ½ C V².

From Wikipedia:
Image

They use W for Work (= energy). The more the capacitance, the more energy that you can store (which makes sense).

The capacitance C is affected by area and closeness of the plates, but also by the dielectric constant. This is a factor that varies with how effectively the material between the plates can "trap" charge. For air, the relative dielectric constant is 1; they have the constant up in the thousands.

This is the electric charge equivalent of iron, which has a relative permeability of thousands, so it traps magnetic fields very effectively.

The combination of the high dielectric constant, and the ability to withstand high voltages (high dielectric strength, so they can withstand over a thousand times more voltage than present ultra capacitors) makes this so promising. Present ultracapacitors get their high capacitance from very large surface areas at the nanometre scale, but that limits them to some 2.5 V. This new technology won't have the large surface area, but more than makes up for that with the voltage and the fact that stored energy is proportional to the square of the voltage.
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Post by coulomb » Sat, 01 Aug 2009, 15:57

Johny wrote: I had figured basically with a constant current discharging twice voltage would discharge for twice as long - forgetting that twice voltage would be four times power into a given resistance

True, but that's not really why the energy is proportional to the square of the voltage. It's because you provide the voltage for twice as long, but also the average voltage is twice what it was before, you you have on average 4 times the energy for twice the voltage.

You can think of the voltage verses time as a straight line, and the energy is proportional to the area of the right angled triangle under the V vs t line. By doubling the voltage, you double the length of the triangle (along the t axis), but also the height of the triangle (the V axis). Doubling the sides of a triangle (or any two dimensional shape) quadruples its area.
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Post by antiscab » Sat, 01 Aug 2009, 22:47

good catch coulomb.
sometime after i wrote that i realised i also had it wrong....just hadn't had a chance to correct it.

Good thing you (and many others) on this forum catch mistakes before people take what is written as gospel.

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Post by Richo » Mon, 03 Aug 2009, 05:10

JackM wrote: I am concerned about the charging heat and its affect on the bonded dissimilar materials in the solid state "electrolyte". As you know dissimilar materials have different coefficients of expansion. Could this cause the components to flex, like a thermostat, and crack after many charges. (Ceramics don't like to be flexed).


Maybe should have just given a link to the info.

In an AC system the regen might be say 100A.
Currently supercaps are around 0.8mR.
So the power in the cap:
P=I^2 x R
P=100^2 x (0.8/1000)
P= 8 Watts
So currently it is unlikely that 8W heating will cause too much heat problems.

Even if the supercaps became even better the internal resistance would drop.
This means that under typical load for an eV the heat would be even less.

However if using to fast charge a fan might be needed.
Tests can be done on individual caps to test for endurance under high stress.
So it is likely that cap life can be estimated before use.
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Post by Johny » Tue, 01 Sep 2009, 16:34

More "leaks" from EEStor.
Make sure that you read the comments below the article as well.
http://www.fcnp.com/commentary/national ... logy-.html

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Post by coulomb » Tue, 01 Sep 2009, 17:29

This would appear to be the website referred to ("There is even a web site devoted to watching EEStor and parsing every scrap of information that becomes available"):

http://theeestory.com/

It seems to be very low signal-to-noise ratio. A pity; I'd like to see a good site devoted to sifting out nuggets of fact amongst all the noise.
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Post by coulomb » Sun, 18 Jun 2017, 04:59

JackM's post from 2009 is of interest because it appeared to translate rather badly from Web Wiz to phpBB. But that appears to be because it's mostly a paste from a PDF file. Unfortunately, much of the formatting and symbols is lost that way.

For anyone interested in this, the original PDF article is (as of mid 2017) available here, found by a Google search (place quotes around the search terms) :

http://www.ct-si.org/publications/proce ... /70364.pdf
Last edited by coulomb on Sat, 17 Jun 2017, 19:05, edited 1 time in total.
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