Power Density of energy sources

[dave_dj88]

Hi,

What limits power density of a source (eg: battery, supercapacitor)?

My line of thinking took me to a simple case of a source V, with no internal resistance, and a load R. Now, power to load is V²/R. Thus, smaller the R, higher the power delivered. As R --> 0, P --> infinity.

Then, I modified the case to include the internal resistance of the source (see pic attachment).
I found that the total power from the source and the total power to the load had limits which depend on the value of the internal resistance.

So, am I correct in saying that the internal resistance limits the power density of a source?
Are there any other reasons for the limits on power densities of supercapacitors, capacitors, batteries?


Thanks

 

[dknguyen]

POwer density or energy density? THere is a difference. As far as energy sources that output current, I would say that, yes, internal resistance does play a role in limiting power density. It's probably the most prominent and most talked about factor but almost certainly not the only thing limiting the power density of batteries (though I am just speculating here). IR would not limit energy density though.

THe limits of the energy and power density can't really be generalized since it's totally based on the mechanism used to store the energy. It's different between gasoline, alcohol, super capacitors, and batteries (and even different kinds of batteries).

 

[Hero999]

Of course it does, maximum power transfer will occure when the load impedance equals the source impedance but the efficiency will be very poor, only 50%.

 

[sniper007]

https://en.wikipedia.org/wiki/Maximum_power_theorem

 

[dave_dj88]

Thanks for the clarifications!

cheers!