Energy controlling system for time shifting electric power use

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This invention relates to a system for controlling the use of power by power consumers so as to limit the amount of the power being used during periods of peak power usage, particularly as applied to electric water heaters.

BACKGROUND OF THE INVENTION

Electric utilities need to have a power generating capacity sufficient to supply the peak load on the power generating system. The peak load varies both daily and seasonally and the cost of providing power has a direct relationship with the peak daily load as well as the peak seasonal load. To reduce costs, it is highly desirable, to the extent possible, to transfer power use on a daily basis from the periods of peak load to periods of off-peak load. One electrical appliance which is particularly suitable for shifting the time that it is energized is the electrical water heater. Conventional electrical water heaters are equipped with a thermostat which turn the heating element of the water heater on and off in accordance with the temperature of the water in the tank and accordingly, are turned on and off without any regard to the periods of peak load intervals for power use. On the other hand, the use of electrical power to energize the heating element and heat the water in the water heater can be delayed with little or no inconvenience to the consumer. The reason for this fact is that when hot water is used from a hot water tank, it is replaced by cold water in the bottom of the tank, but the cold water does not mix with the hot water. As a result, most of the hot water can be drawn from the tank without any noticeable drop in the temperature of the hot water being drawn off. Thus, a time shifting of the energization of the heating element to an off-peak time period will in most instances, not inconvenience the user who can still draw an amount of hot water during the peak period approaching the capacity of the water heater tank. This fact is particularly true when the water heater tank is of thermal storage type, which has a large capacity.

SUMMARY OF THE INVENTION

The present invention provides a system for automatically controlling the power applied to an electric water heater so that on week days, power will not be applied to the water heater at certain times during the day determined by the power company to be times of peak load. As soon as the peak load period ends, the power is restored to the water heater and the thermostat will resume control of the heating of the water in the water heater in accordance with water temperature. Thus, on week days the energization of the water heater is time shifted to off-peak load periods. On weekends and holidays the water heater is controlled by the thermostat in the conventional manner and power is not interrupted to the water heater by the system of the invention. As pointed out above, since the temperature of the hot water coming from the tank, does not drop appreciably until the amount of hot water drawn from the tank approaches the capacity of the tank, this shifting of the energization of the water heater in most instances will not inconvenience the user. To further reduce any chance of inconvenience, each unit is provided with an override button by which the energy controller can be overridden and power applied to the thermostatically controlled water heater for a predetermined time interval regardless of whether the period is a peak load period or not. The user is permitted by the system to perform this override function only once during each 24 hour day.

The energy controller will be mounted on or near the water heater. In order to facilitate the monitoring and changing of status data in the energy controller such as the holidays, the starting and ending of subyearly intervals, peak power schedules for the subyearly intervals, or correct the time or date, the energy controller is connected to a remote outdoor module. The outdoor module contains a signal light which is caused to blink by the energy controller signalling that the controller is operating. The outdoor module contains an infrared signal light interface connectable to a portable programing unit. The portable programming unit contains means to compare the status data stored in the energy controller with status data contained in the programming unit and provide an indication of whether or not the comparison is correct. Alternatively, the programming unit may be operated to substitute the status data contained in the programming unit for that in the energy controller and in this manner, change the status data in the energy controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating the system of the invention;

FIG. 2 is a perspective view of an external module employed in the system of the invention;

FIG. 3 is a perspective view of a portable programming unit employed in the system of the present invention;

FIG. 4 is a block diagram illustrating the circuitry employed in the programming unit shown in FIG. 3;

FIG. 5 is a block diagram illustrating the circuitry employed in the energy controller of the system of the invention;

FIG. 6 illustrates a flowchart of the computer program employed by the energy controller of FIG. 6;

FIGS. 7a and 7b illustrate a flowchart of a time keeping routine employed in the program of FIG. 6;

FIG. 8 is a flowchart of a routine employed in the program of FIG. 6 when power fails; and

FIG. 9 is a flowchart illustrating a routine employed in the program of FIG. 6 to carry out communications between the energy controller and the programming unit.

DESCRIPTION OF A SPECIFIC EMBODIMENT

In the system of the invention as shown in FIG. 1, the energy controller 11 maintains a calendar clock and controls the energization of a relay 13 via a triac 15. The relay 13 controls the application of power to a conventional thermostatically controlled electric water heater 17. When the relay 13 is energized, power is applied from the electric power source 19 to the water heater 17, and the turning on and off of the element of the water heater will be under the control of the thermostat of the water heater in accordance with the water temperature. When the energy controller 11 from the calendar clock determines that it is a peak period of power use on an appropriate day, it will produce a power off output signal on line 24 to the triac 15, which will deenergize the relay 13 to interrupt the power supply to the water heater, so that the heating element of the water heater cannot be energized. As soon as energy controller determines that the peak power period has ended, the energy controller 11 will produce a power on signal on line 24, and the triac 15 will energize the relay 13 to again apply power from the source 19 to the water heater, which at that time may apply the power to the heating element depending upon whether the thermostat of the water heater calls for heating The energy controller 11 is provided with an override button 21. If the energy controller 11 determines that the override button 21 has been actuated and that this is the first time that the override button 21 has been actuated during that day, the energy controller 11 will produce a power on signal on line 24 to energize the relay 13 so that power is applied to the water heater 17, regardless of the calendar clock time, for a predetermined time period set by the power company. If the power company does not want to provide the consumer with the override option, the predetermined override time period is set to zero.

The electric meter in the preferred embodiment of the invention is a two rate meter wherein the consumer is charged at a higher rate for power consumed during peak load periods and charging at a lower rate during off-peak load periods. To achieve this variation in charge, the electric meter 23 receives a signal from the energy controller 11 on output line 26 which may be either a high charge signal or a low charge signal, and the meter 23 responds to this signal to charge the consumer at the high charge rate or low charge rate. The energy controller applies the high charge rate signal to the meter on line 26 whenever it produces the power off signal on output line 24 or whenever it is in an override period in response to the override button being actuated. At all other times, the energy controller will apply the low charge rate signal to the meter 13.

The water heater will normally be within the dwelling enclosure 22 of the consumer and the meter 23 will be outside the dwelling enclosure on a wall of the dwelling. Also outside the dwelling enclosure 22 adjacent to the meter 23 is an external module 25 having a signal lamp, an infrared photodetector, and an infrared signal light beam transmitter. The energy controller causes the signal lamp to blink on and off whenever the energy controller is operating, at two different blink rates. It causes signal lamp to blink on and off at a slow rate when the energy controller 11 is applying the low charge rate signal to the meter 23 and causes the signal lamp to blink at a fast rate whenever the energy controller is applying the high charge rate to the meter. Thus, the rate of blinking of the signal lamp 27 will indicate whether the meter 23 is running at the high charge rate or the low charge rate with the higher frequency blinking indicating the higher charge rate.

A portable programming unit 27 has a recess adapted to receive and fit with the external module 25. The recess is provided with an infrared light beam transmitter and an infrared photodetector and when the module is received in the recess, the infrared light transmitter in the recess will line up with the infrared photodetector in the external module 25 and the infrared photodetector in the recess will line up with the infrared light beam transmitter of the module 25. A serial digital pulse signal can be generated by the portable programming unit 27 to energize the infrared beam signal transmitter in the recess and cause corresponding pulses to be generated by the photodetector in the external module 25 and be transmitted to the energy controller 11. In this manner, data can be transmitted from the portable programmer 27 to the energy controller 11. Similarly pulses generated by the energy controller 11 can energize the infrared light beam transmitter in the module 25, to cause corresponding pulses to be generated by the infrared photodetector in the recess and to be received by the portable programmer 27. In this manner, messages generated by the energy controller 11 are transmitted to the portable programmer 27.

As shown in more detail in FIG. 2, the external module 25 comprises a base 31 in which the blinking signal lamp 28 is mounted. Also mounted on the base 31, is an infrared light beam transmitter 33 and an infrared photodetector 35. The top of the base 31 is covered with a transparent layer 37 which encapsulates the signal lamp 28, the infrared transmitter 33 and the infrared photodetector 35. As shown in FIG. 3, the front wall of the programming unit 27 has a recess 40 defined therein shaped to receive and fit with the transparent layer 37 of the module 25. The recess 40 has on its sidewalls semicircular ribs 42 which, line up with the semicircular recesses 39 and fit in the recesses 39. The module 25 and recess 40 are shaped so that the module will fit in the recess in only one orientation. When the programming unit 27 is coupled to the external module 25 in this manner, an infrared light beam transmitter 46 in recess 40 will be aligned with the photodetector 35 so that when the transmitter 44 is energized, the light beam pulses will be transmitted through the transparent layer 37 to the photodetector 35. Similarly an infrared photodetector 44 in the recess 40 will be aligned with the infrared transmitter 33 and when the transmitter 33 is energized, light beam from the transmitter 33 will be transmitted through the transparent layer 37 to the photodetector 44.

The portable programming unit 27, as shown in FIGS. 1 and 4, is provided with a serial signal plug 41 which is designed to plug into a socket in the energy controller 11 so that the portable programming 27 can transmit and receive information directly instead of transmitting and receiving through the remote outside module 25. As shown in FIG. 4, the portable programming unit comprises a microprocessor 45, which is controlled by a program stored in an EPROM 43, which is a reprogrammable read only memory. The portable programming unit has a random access memory or RAM 47 and the microprocessor 45 can store information or read out information from the RAM 47 under the control of the program in the EPROM 43. In addition, the programming unit has a calendar time keeper 49 which keeps the calendar time The calendar time keeper 49 is an off-the-shelf item sold under the name "Smart Watch" available from Dallas Semiconducter.

As shown in FIG. 3, the programming unit 27 has two panel buttons 51 and 53 labelled "program" and "verify" respectively. When the portable programmer 27 is connected to the energy controller either via the external module 25, or by the plug 41 and the button 53 is actuated, the microprocessor 45 will send a message to the energy controller 11 requesting the status data from the energy controller 11. In response to receiving this message, energy controller 11 will send back to the portable programmer 27, all of its status data, which as pointed above will include all of its calendar time information. In addition, the status data includes a list of holidays stored in the energy controller, the dates for changing between daylight savings time and standard time, the starting and ending days for each yearly subinterval, the peak power schedule for each yearly subinterval, and the length of the override interval. All of this status data is compared with corresponding information stored in the RAM 47 or kept by the calendar time keeper 49. If the status data received from the energy controller 11, other than the time of day, is identical to that kept in the programming unit and the time of day received is within 12 minutes of the time kept by the calendar time keeper, the microprocessor 45 determines that the status data in the energy controller 11 has been verified and accordingly, energizes a signal lamp 55 on the top panel of the programming unit 27 labelled "passed". If the status data received from the energy controller 11, with the exception of the time of day, is not identical to the corresponding status data in the programming unit, or if the time of day received from the energy controller 11 is not within 12 minutes of the time of day kept in the programming unit, the microprocessor 45 will energize a lamp 57 on the top panel of the program labelled "error".

At the completion of the verify program, for reasons which will be explained below, the microprocessor 45 will send a message to the energy controller 11 to replace the time of day in the energy controller 11 with the time of day derived from that kept in the programming unit. The status data in the RAM 47 are stored in the RAM 47 by connecting the microprocessor 45 via an input terminal 59 to a PC computer 61 as shown in FIG. 1. The PC computer 61 is connected to the input terminal 59 of the portable programming unit 27 via an interface 63, which converts the PC output signals to a form compatible with the microprocessor of the portable programming unit 27. To condition the programming unit 27 to receive data from the computer 61 both panel buttons 51 and 53 are pressed simultaneously for five seconds. The status data is entered into the memory of the computer 61 by means of the keyboard of the computer 61 and then transmitted to the microprocessor 45 which stores the data received from the PC computer 21 in the RAM 47.

If the operator wants to change the status data in the energy controller 11, the operator presses the panel button 51 labelled "program" and in response to actuation of this panel button, the microprocessor 45 under the control of the program in the EPROM 43 will transmit all of the status data in the RAM 47 and the calendar time data kept by the calendar time keeper 49 to the energy controller 11, which will replace the status data stored in this memory with the status data received from the portable programming unit 27. The last item of status data transmitted to the energy controller will be the time of day. When the portable 27 transmits the new time of day to the energy controller, it takes the time of day maintained by the calendar time keeper 49 and changes it by a random variable, ranging from minus four minutes to plus four minutes. The reason for adding this random variable to the time of day is to make the energy controllers at different consumer locations be unsynchronized, but within 8 minutes of each other. This variation in time of day avoids the energy controllers at different consumer locations from turning on the water heaters at the same time and causing an undesirable power surge, as would otherwise normally occur at the end of a peak power interval.

As shown in FIG. 4, the microprocessor 45 is energized by means of a rechargeable battery 65. The rechargeable battery also energizes the RAM 47 by means of an electronic switch 67 when the microprocessor is carrying out a program of the EPROM 45 either in response to actuation of the verify button 53, the program button 51 or actuation of both buttons simultaneously to receive information from the computer 61. The calendar time keeper 49 on the other hand, is powered by a lithium battery 69. As the last step of each program carried out by the microprocessor 45 either in response to the verify button, to verify the status data in the energy controller 11, or in response to the actuation of the program button 51 to replace the status data in the energy controller 51 with the status data in the RAM 47, or in response to actuation of both buttons simultaneously to replace the status data in the RAM 47 with status data transmitted from the PC computer 61, the microprocessor 45 opens the electronic switch 67 and then opens an electronic switch internally to disconnect the rechargeable battery from the microprocessor 47 so that power from the rechargeable battery 65 is used only when the microprocessor is carrying out a program. Actuation of one of the buttons 51, or 53, or both of the buttons will reconnect the rechargeable battery 65 to the microprocessor 45 and also close an the electronic switch 67 to reconnect the RAM 47 to the rechargeable battery 65. The lithium battery 69 is connected to the interconnection of the electronic switch 67 and the power input terminal of the RAM 47 by means of a diode 71. The lithium battery 69 will have a lower voltage than the rechargeable battery 65 and the polarity of the diode 71 will shut off current flow between the RAM 47 and the lithium battery 69 when the electronic switch 67 is closed. When the electronic switch 67 is open, power from the lithium battery 69 to the RAM 47 will be sufficient to maintain the data stored in the RAM 47 and updated by the calendar time keeper 49. With the lithium battery 69 used for only these purposes, only a small amount of power from the lithium battery is required As a result, the lithium battery 69 will last for ten years. The output voltage of the rechargeable battery 65 is sensed by a battery voltage detector 73 and when the rechargeable battery output voltage 65 drops below a level which indicates that the battery 65 needs recharging, the battery voltage detector 73 will energize a blinking signal lamp 75 on the top panel of the portable programming unit to indicate that the rechargeable battery 65 needs recharging. The signal lamp 75 is labelled "low batt".

FIG. 5 illustrates the circuitry of the energy controller 11. As shown in FIG. 5, the energy controller receives power from the household AC power supply 19 and applies it to an AC-to-DC converter 77 and also to a pulse generator 79. The AC-to-DC converter 77 converts the AC power to a DC voltage and applies it through diodes 81 and 82 to a junction 83 which is also connected to receive power from a rechargeable battery 85 through a diode 87. If the household power supply is not interrupted, the DC voltage from the AC to DC converter 77 passing through the diodes 81 and 82 will be greater than the voltage of the rechargeable battery 87 and the diode 87 will be back biased. A resistor 90 connects the junction of the diodes 81 and 82 to the rechargeable battery to recharge it when power is available from the power source 19. Power from the junction 83 is applied directly to a microprocessor 88 and to a high frequency clock pulse source 89 external to the microprocessor 88. Should the power from the household AC source 19 fail, power will be supplied from the internal battery source 85 through the diode 87 to the microprocessor 88 and to the clock pulse source 89. A lithium battery 92 is connected to the junction 83 through a diode 94 to supply power to the