Emulating Batteries with Deferrable Energy Demand: Fundamental Trade-offs and Scheduling Policies

We investigate the ability of a homogeneous collection of deferrable energy loads to behave as a battery; that is, to absorb and release energy in a controllable fashion up to fixed and predetermined limits on volume, charge rate and discharge rate. We derive explicit bounds on the battery capacity that can be offered, and show that there is a fundamental trade-off between the abilities of collective load to absorb and release energy at high aggregate rates. Finally, we introduce a new class of dynamic prioritydriven feedback policies that balance these abilities, and characterize the batteries that they can emulate.