In the green energy systems use renewable energy sources to produce electricity. Batteries are used to store the energy. The life of batteries is short and they produce lot of wast. This wast is harmful to the environment. How can the use of batteries be avoided?
Dear Muhammad Shafiq
Batteries can be replaced by capacitors.Even super capacitors are available in the market.But the problem is, Super capacitors are temperature dependent and normal capacitors discharge very fast but batteries don't. Cost of capacitors is quite high when compared with lead acid batteries.
To my understanding the capacitor technology is not yet suitable. what are the future prospects ? will they be environment friendly?
Capacitor bank not able to provide long term storage and adequate for fast transients. Cost of capacitor banks also hinders its usability.
Energy E joules stored in a capacitor of C farads charged to E volts is :
E = 1/2 * C * V^2
The output power into a load depends on the charge voltage. So as the capacitor discharges into a constant resistance the power drops very rapidly. This effect is much reduced in a battery where the energy stored depends largely on the charge Q put in at sensibly constant voltage. So batteries are much easier to interface with in most situations.
Capacitor Banks and Batteries are entirely different scope of Technology. A Capacitor Bank is primarily used in a renewable system as mentioned by Mr Shafiq especially in Wind generators as mostly induction generators are used which sucks out the active and reactive VARs which may affect the connected grid as the same grid has to supply VARs to connected induction motors in the system. Hence capacitors are used to compensate VARs in the grid.
Batteries only stores energy for a arising out of migration of electrons from anode to cathode via the electrolyte which can be used to discharge when needed.
Therefore capacitors can never replace a battery and in no case will it be so.
Capacitors largely rely on a physical change in a dielectric in order to store electrical energy. Batteries rely on a chemical change in a (usually) electrolyte/cathode/anode system to store energy. Interestingly lithium ion batteries store their charge by means of an ionic interaction between the ions and the electrode lattices - so they are arguably both a capacitor and a battery together! Maybe soon we will have a supercapacitor that works more like an Li-ion battery and is cheaper and more effective than either.
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