I want to know about the difference as I don't understand what these parameters mean in real world application of the batteries
Energy density (Wh/kg) can be given as the amount of energy stored per unit ( mass (kg) , area (cm2) , or volume (L)) and corresponding power density (W/ kg) means amount of energy flow per unit (mass, area, volume) per unit time (s).
Just think about water tank with the fixed tap at its bottom.
More simply saying, energy density can be taken as volume of the water tank and power density can taken as rate of water flow from the tap.
Normally batteries has high energy density due to their red-ox nature. For such a redox reactions take a little long time, therefore, the power density is low. but for a capacitors (EDLC) their aren't any red-ox reactions, only static charges accumulations, that means low energy density. But static charges separation happens very short time that means large power density can be seen.
Hello Kishore Mallela
Energy density describes how much energy the device can store for a given mass/volume. Therefore a device with a higher energy density can supply an electronic load for longer than one with a low energy density and the same mass/volume.
Power density describes how quickly the device can deliver energy. It is equivalent to the maximum current you can draw from a device of a given mass/volume.
Typically capacitors offer very high power density but low energy density. They are good for short bursts of very high current. On the other hand, batteries are good at providing lower currents for extended periods of time. See attached figure.
Energy density (Wh/kg) can be given as the amount of energy stored per unit ( mass (kg) , area (cm2) , or volume (L)) and corresponding power density (W/ kg) means amount of energy flow per unit (mass, area, volume) per unit time (s).
Just think about water tank with the fixed tap at its bottom.
More simply saying, energy density can be taken as volume of the water tank and power density can taken as rate of water flow from the tap.
Normally batteries has high energy density due to their red-ox nature. For such a redox reactions take a little long time, therefore, the power density is low. but for a capacitors (EDLC) their aren't any red-ox reactions, only static charges accumulations, that means low energy density. But static charges separation happens very short time that means large power density can be seen.
Energy density mainly refers to the energy storage ability of a technology batteries can store energy. Power density usually implies to the running power production of a technology, it has no relation with storage of energy. Fuel cells are examples of devices that are related more with power density, since they do not store energy.
Regards
Waqas
If you are running in a 100meter race... You need quick power to accelerate yourself... So you need high power density... Likewise if you are running in 1000 meter race... You need constant energy for longer time and hence your energy density should be higher... So energy density is the ability of how long you can store energy... And power density is how quickly you can release it...
@Mohit, devices can still keep on giving power density as long as they are given the right fuel. Recently SOFCs have shown power densities for untill 5000hrs with a degradation rate of less than 2%.
Think of it also in these terms: an energy harvesting system, as long as it does not fail, has infinite energy density. It’s power density may be quite small. I think you can apply similar thinking to batteries, depending on their ability to provide large currents over a short time.
Somebody has given a much simpler definition for energy density and power density by correlating it with a vehicle. Energy density decides how far you can travel while power density decides how fast you can travel. Hope this helps..
In Energy Storage Systems:
- "Energy Density" refers to the amount of energy that the system can store.
- "Power Density" refers to the rate of energy that the system can release.
Both of them may be presented per unit of weight or volume.
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