Patent ID: 7590472

Claim:
A computer-assisted method of electrical energy load shifting utilizing an electrical energy storage device connected to receive electrical energy from an electrical power grid, comprising the steps of: establishing a budget of unreserved cycles of discharging and charging the electrical energy storage device for load shifting purposes within a given time period; establishing a schedule for load shifting within sub-parts of said time period, based upon said budget and input data regarding multiple rate levels applicable to electrical energy available from the electrical power grid during the sub-parts of said time period; and executing load shifting cycles within one or more of said sub-parts of said time period, in accordance with said schedule, by discharging electrical energy stored in said electrical energy storage device in a first interval for which a first rate is applicable to energy available from the grid, and charging said electrical energy storage device with electrical energy obtained from the grid during a second interval for which a second rate lower than said first rate is applicable to energy obtained from the grid; wherein said budget is computed by a data processor based at least in part on of at least one: an input indicating a cycle life of the electrical energy storage device; an input indicating a time life of said electrical energy storage device; and an input reflecting a number of cycles reserved for purposes other than load shifting; wherein the step of establishing a schedule for load shifting comprises splitting the time period into rate periods, and calculating values of P−(O/E) for days within each rate period, where P is a peak rate applicable to energy obtained from the grid during a first time interval of any given day, O is an off-peak rate applicable to energy obtained from the grid during a second time interval of the given day, and E is a measure of the efficiency of the electrical energy transfer during a cycle of discharging and charging the electrical energy storage device; wherein a rate schedule applicable to the rate periods has energy usage level-based tiers, said method further comprising calculating the values P−(O/E) for days within each rate period so as to account for increased rates applicable to electrical energy usage above a tier boundary representing a maximum energy usage within a rate period before crossing into the next tier, wherein said calculating comprises: recording an expected energy usage for each rate period apart from any load shifting; calculating an additional amount of energy that will be used by a load shifting cycle; calculating for each rate period the number of cycles Y of load shifting that can be executed before crossing into the next tier; sub-dividing the rate periods into days corresponding to number of cycles Y, and days remaining; and calculating the quantity P−(O/E) for days remaining with values for the next highest tier.