US 7,590,472 B2
Energy arbitrage by load shifting
David B. Hakim, Rockville, Md. (US); Douglas Ricardo Danley, Germantown, Md. (US); and Michael Caplan, London (United Kingdom)
Assigned to GridPoint, Inc., Arlington, Va. (US)
Filed on Nov. 09, 2006, as Appl. No. 11/558,068.
Prior Publication US 2008/0114499 A1, May 15, 2008
Int. Cl. G06F 17/00 (2006.01); H02J 15/00 (2006.01)
U.S. Cl. 700—295  [700/291; 705/412] 16 Claims
OG exemplary drawing
 
1. 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.