I would like to know how to calculate the energy density and the power density for a capacitor using these 2 equations: E (Wh/Kg) = 1/8 C (F/g) / V²(volt) P (W/Kg) = E (Wh/Kg) x scan rate (Volt/sec) / V (volt).
I tried to calculate it, but I don't know how to convert these different units.
My problem is units conversion, if any body could help me.
for example c = 400 farad/g Volt V = 2.5 Volt Scan rate 1 mV/sec
What would be the power and energy density in that case?
As far as the energy storage goes, farad is a coulomb per volt, an ampere is a coulomb per second, and a Joule is an amp volt second. You can divide it by mass or area to get an energy "density." See for instance the link below for various units and formula. The power is another matter. Capacitors can charge and discharge quite rapidly, but not instantaneously. Besides the capacitance and area, it depends on the load.
http://en.wikipedia.org/wiki/Farad
http://en.wikipedia.org/wiki/Capacitor
Thanks Dr. Dudley J Benton
I have calculated it by the way as follow:
Energy (joule) = ½ x Capacitance (Farad) x Voltage2 (Volts)
as: joule = C (Coulomb) x V (Voltage) and C (coulomb ) = Farad x Volt
http://en.wikipedia.org/wiki/Joule
then Energy (Wh) = Energy (Joule) / 3600 (sec)
(http://www.ultracapacitor.co.kr/ultracapacitor/comparison.html)
Then, Energy Density (joule/kg) = ½ x Capacitance (Farad/kg) x Voltage2 (Volts)
and Energy density (Wh/kg) = Energy (Joule/kg) / 3600 (sec)
are these conversions correct ??
Thanks
1.stored energy in capacitor is Est = (1/2)C v^2 joules [ c in farads ; v in volts ]
2. energy density =Est/ mass = joules/ kg [ mass in Kg ]
= (1/2)[ C/mass ] [ v^2 ] ...[ farads /kg * volts^2 ]
sometimes conversion of units such as farads /kg to farads/ gm is confusing
e.g. 4 farads/kg = 4/ 1000gms = 4*10^-3 farads /gm
3.lhs and rhs of " Energy density (Wh/kg) = Energy (Joule/kg) / 3600 (sec)"
is dimensionally not correct perhaps lhs is meant as power = W/kg ?
good luck
Cheers
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