Computerized peak-shaving system for alleviating electric utility peak loads

• US 3,906,242 A
• Filed: 08/16/1974
• Issued: 09/16/1975
• Est. Priority Date: 08/16/1974
• Status: Expired due to Term

• Current Assignee: Megatherm Incorporated
• Original Assignee: Robert H. Stevenson
• Inventors: Stevenson, Robert H.
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Ginsburg, M.
• Application Number:
  US05/497,967
• Time in Patent Office: 396 Days
• Field of Search: 307/40,35,38,39,62,140 219/485 235/151.21 340/31A
• US Class Current: 307/38
• CPC Class Codes: H02J 2310/60 Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
• CPC Class Codes: H02J 3/144 Demand-response operation of the power transmission or distribution network
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

A system for lowering electrical energy peak demand while minimizing service disruption allows instantaneous dropping of a plurality of interruptible thermal storage devices with predictable reserve capacity. At the time the loads are dropped, a central computer establishes a plurality of permissible offtimes for corresponding mutually exclusive groups of loads in similar installations based on characteristic projected energy consumption profiles predicted from past statistical history for the groups. At the end of each off-time interval, a central transmitter transmits reconnect signals to which the devices in the corresponding group are responsive. The groups of units are thus reconnected sequentially avoiding the possibility of generating a secondary peak by indiscriminate, simultaneous reconnection. The reconnection sequence is determined according to changing priorities which take into account the customer'"'"''"'"'s needs at the time of disconnection. The system provides electric utilities with a controllable equivalent peak load capacity in excess of the total connected load of all non-controlled devices. Employing load limiters at individual locations permits use of established commercial and industrial rate structures in concert with increased economy in the use of power by way of programmed peak load reduction.

Claims

1. A method of lowering peak electrical energy demand on a central electrical distribution network to alleviate a power emergency while minimizing the impact of service disruption, comprising the steps of sensing the approach of an excessive demand peak, in response thereto remotely disconnecting simultaneously a plurality of similar interruptible loads powered via said network, said loads being divided into a plurality of mutually exclusive groups based on similar reserve-capacityversus-time characteristics, indicating time-varying permissible off-times for corresponding ones of said groups based on characteristic projected energy consumption profiles predicted from past statistical records for said groups, and remotely reconnecting said loads automatically, one-group-at-a-time, in accordance with said permissible off-times, whereby said loads are reconnected on a changing priority basis projected by customer needs.

2. The method of claim 1, wherein the step of disconnecting takes place at time t1, said permissible off-times for said groups being different functions of t1.

3. The method of claim 1, wherein said steps of disconnecting and reconnecting are accomplished by transmitting control signals to which said loads are responsive.

4. The method of claim 1, further comprising the step of postponing reconnection of an individual load in one of the groups being reconnected where reconnection on schedule according to said permissible off-time would interfere with the rate the customer was being charged for energy.

5. The method of claim 1, wherein said interruptible loads are energy storage loads.

6. The methods of claim 1, wherein said loads are thermal storage loads.

7. The method of claim 1, wherein said loads are water heaters.

8. The method of claim 1, wherein said loads are thermal storage water heaters.

9. A system for lowering peak electrical energy demand on a central electrical distribution network to alleviate a power emergency while minimizing the impact of service disruption, comprising a plurality of similar interruptible loads powered via said network, a plurality of receiver control means associated respectively with said loads for disconnecting and reconnecTing respective ones of said loads in response to corresponding signals, centralized transmitter means for generating said corresponding signals on command, first control means for causing said transmitter means to generate said signals such that said loads are simultaneously disconnected at one time from said network in response to a power energency, data storage means for indicating a plurality of time-varying permissible off-times for corresponding mutually exclusive groups of said loads based on characteristic projected energy consumption profiles predicted from past statistical records for said groups, said groups being composed of loads having similar reserve-capacity-versus-time characteristics, and second control means operatively interconnected with said data storage means for causing said transmitter means to generate a sequence of signals after operation of said first control means to reconnect said loads one-group-at-a-time on a changing priority basis in accordance with the permissible off-times for said groups as of said one time.

10. The system of claim 9, further comprising means for postponing reconnection of one of said loads on schedule according to said permissible off-time where reconnection would interfere with the rate the customer was being charged for energy, said one load having extra reserve capacity to meet maximum demand over the extended period of disconnection.

11. The system of claim 9, wherein said loads are energy storage loads.

12. The system of claim 9, wherein said loads are thermal storage loads.

13. The system of claim 9, wherein said loads are water heaters.

14. The system of claim 9, wherein said loads are thermal storage hot water heaters.

15. The system of claim 9, wherein said groups include respectively commercial installations having distinct usage characteristics, the types of commercial installations identified respectively with said groups having a predetermined variety.

16. The system of claim 9, wherein said receiver control means associated with each said group of loads is responsive to a uniquely corresponding signal from said transmitter means.

17. The system of claim 16, wherein said receiver control means and transmitter means operate on radio frequencies, said receiver control means in each group being responsive to a uniquely corresponding frequency signal, said first control means including means for causing transmission of all of said uniquely corresponding signals, said second control means including means for causing transmission of one uniquely corresponding signal at the expiration of each respective permissible off-time.

18. The system of claim 9, wherein said second control means includes a plurality of comparator means corresponding to said groups and operatively receiving the outputs of said data storage means for producing an output when the elapsed time from said one time matches the respective permissible off-times.

19. The system of claim 18, wherein said first control means includes load sensing means producing a control output to said transmitter means in response to an excessive demand peak.