We investigate the ability of a homogeneous collection of deferrable energyloads to behave as a battery; that is, to absorb and release energy in acontrollable fashion up to fixed and predetermined limits on volume, chargerate and discharge rate. We derive bounds on the battery capacity that can berealized and show that there are fundamental trade-offs between batteryparameters. By characterizing the state trajectories under scheduling policiesthat emulate two illustrative batteries, we show that the trade-offs occurbecause the states that allow the loads to absorb and release energy at highaggregate rates are conflicting.
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