Supercapacitor energy storage in solar application: A design approach to minimize a fundamental loss issue by partitioning the load and the storage device

摘要

When an ideal voltage source is used to replenish an electro-chemical battery with an open circuit voltage of V and a charge of Q coulombs, it stores an energy of QV in the battery, if the charging loop is ideal with no losses. However, if the electro-chemical battery is to be replaced by a capacitor, the energy stored will be ½QV and the loop resistance will dissipate ½QV of energy creating an overall charging efficiency of only 50%. In a solar type application if a supercapacitor (SC) bank replaces a battery, due to its long life and its ability to deliver high power bursts into a load, the designer has to be concerned about this fundamental charging efficiency limitation. However, by splitting the load and the SC bank into two identical halves, and using a series charging scheme where in any given charging process the load and the SC bank comes into series mode, this fundamental loss can be circumvented. The other half of SC bank can deliver energy to the other part of the load.