HK40002481B - Emergency elevator power management - Google Patents

Description

Emergency elevator power management

Background Art

Elevator systems can be used to transport passengers between floors in a building. A typical traction-based elevator system includes an elevator car and a counterweight associated with a corresponding machine responsible for moving the elevator car. Some elevator machines are capable of operating in two modes. In motoring, or power-consuming, mode, the machine draws power from the utility grid or an emergency generator, such as when the elevator car begins moving or lifts a positive load. In regenerative mode, the machine operates as a generator, producing power that can be provided back to the utility grid, the emergency generator, or an energy storage device. Regenerative mode can occur, for example, when stopping a moving car or lifting a negative load based on the movement of the elevator car, as appropriate.

Many elevator systems include a backup power supply to allow the elevator system to operate even if the main power supply becomes unavailable, such as during a utility power outage. The amount of power drawn by a typical elevator system requires a large number of backup power supplies. When using a backup power supply, many existing elevator systems have constraints or restrictions on the number of elevator cars that can be in operation. For example, in these situations, some elevator systems only allow one car to be in operation. Occupant Evacuation Operation (OEO) protocols require sufficient backup power to supply all Occupant Evacuation Elevators (OEE) in a building. One way to meet OEO requirements is to include multiple large-capacity emergency generators, but this introduces significant costs.

Summary of the Invention

An exemplary example embodiment of an elevator system includes: a plurality of elevator cars; a plurality of elevator machines, respectively associated with the elevator cars, to selectively cause the associated elevator cars to move, at least some of the elevator machines operating in a first mode comprising consuming power and a second mode comprising generating power, respectively; a power source, the power source providing power for movement of the elevator cars, the power source having a power output threshold and a power intake threshold; and at least one controller configured to determine when the power source provides power to the elevator system and dynamically adjust how the plurality of machines move the elevator cars to maximize the number of the plurality of cars used to move passengers while maintaining power consumption of the elevator system below a power output threshold and power generation of the elevator system below a power intake threshold.

In an example embodiment having one or more features of the elevator system of the previous paragraph, the controller dynamically adjusts how the plurality of machines moves elevator cars to maximize the number of the plurality of cars used to move passengers during an evacuation operation.

In an example embodiment having one or more features of the elevator system of any preceding paragraph, the controller controls the timing of the one or more power peak events to minimize a number of power peak events within a predetermined time interval.

In an example embodiment having one or more features of the elevator system of any preceding paragraph, the power peak event includes acceleration of an elevator car, movement of an elevator car from a stop, and stopping an elevator car that is moving in a manner that generates power for an associated elevator machine.

In an example embodiment having one or more features of the elevator system of any of the preceding paragraphs, the controller controls timing to avoid more than one power peak event occurring simultaneously.

In an example embodiment of an elevator system having one or more features of any preceding paragraph, the controller dynamically adjusts how the plurality of machines moves the elevator car by controlling the timing of at least one of elevator car starting from a stop, elevator car stopping, elevator car speed, elevator car acceleration, and elevator car deceleration.

In an example embodiment of the elevator system having one or more features of any preceding paragraph, the controller dynamically adjusts how the plurality of elevator machines moves the elevator car by scheduling at least one of the elevator machines to operate in a first mode while at least one other of the elevator machines operates in a second mode.

In an example embodiment having one or more features of the elevator system of any preceding paragraph, the controller schedules movement of the plurality of elevator cars to maximize the number of passengers brought to predetermined destinations per unit time.

In an example embodiment of the elevator system having one or more features of any of the preceding paragraphs, the predetermined destination corresponds to a location where passengers may exit a building in which the elevator system is located.

In an example embodiment having one or more features of the elevator system of any preceding paragraph, the controller balances an amount of power consumed by any of the elevator machines operating in the first mode with an amount of power generated by any of the elevator machines operating in the second mode during a time interval.

An illustrative example embodiment of a method of operating an elevator system includes determining when a power supply provides power to the elevator system and dynamically adjusting how a plurality of machines moves a plurality of associated elevator cars to maximize the number of the plurality of cars used to move passengers while maintaining power consumption of the elevator system below a power output threshold of the power supply and power production of the elevator system below a power intake threshold of the power supply.

An example embodiment having one or more features of the method of the preceding paragraph includes dynamically adjusting how a plurality of machines move elevator cars to maximize the number of the plurality of cars used to move passengers during an evacuation operation.

Example embodiments having one or more features of the method of any preceding paragraph include controlling the timing of one or more power peak events to minimize the number of power peak events within a predetermined time interval.

In an example embodiment having one or more features of the method of any preceding paragraph, the power peak event includes acceleration of an elevator car, movement of an elevator car from a stop, and stopping an elevator car that is moving in such a way that an associated elevator machine generates power.

Example embodiments having one or more features of the method of any preceding paragraph include controlling timing to avoid more than one power peak event occurring simultaneously.

An example embodiment having one or more features of the method of any preceding paragraph includes dynamically adjusting how a plurality of machines moves an elevator car by controlling the timing of at least one of elevator car starting from a stop, elevator car stopping, elevator car speed, elevator car acceleration, and elevator car deceleration.

An example embodiment having one or more features of the method of any preceding paragraph includes dynamically adjusting how a plurality of machines moves an elevator car by scheduling at least one of the elevator machines to operate in a power consuming mode while at least one other of the elevator machines operates in a power regenerating mode.

An example embodiment having one or more features of the method of any preceding paragraph includes scheduling the movement of a plurality of elevator cars to maximize the number of passengers brought to a predetermined destination per unit time.

In an example embodiment having one or more features of the method of any of the preceding paragraphs, the predetermined destination corresponds to a location where passengers may exit a building in which the elevator system is located.

An example embodiment having one or more features of the method of any preceding paragraph includes balancing an amount of power consumed by any of the elevator machines operating in the power consumption mode with an amount of power generated by any of the elevator machines operating in the power regeneration mode during a time interval.

The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description, which includes drawings that accompany the detailed description and can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates selected portions of an elevator system designed according to an embodiment of the present invention.

FIG2 is a flow chart summarizing an example control strategy designed according to an embodiment of the present invention.

DETAILED DESCRIPTION

Example embodiments of the present invention facilitate maximizing the number of elevator cars that can be used to move passengers within the power limits of the power supply used for the elevators. Embodiments of the present invention are particularly well-suited for controlling elevator system operation in situations where emergency or backup power is required to operate the elevator system. The manner in which the elevator machine moves the elevator cars is dynamically adjusted to maximize the number of cars used while maintaining the power limits within the capacity of the backup power supply. Predicting, monitoring, and controlling the drive and regenerative power of the elevator system according to embodiments of the present invention allows the peak drive and regenerative power of the elevator system to be maintained within desired limits while maximizing the number of elevator cars that can be used during an evacuation operation (OEO).

FIG1 schematically illustrates selected portions of an elevator system 20 within a building. A plurality of elevator cars are located within respective hoistways. For discussion purposes, sixteen elevator cars and associated machinery are shown. Other details of the illustrated example elevator system, such as the counterweight and roping arrangements, are not shown, as these aspects of elevator systems are understood by those skilled in the art and are not necessary to provide an understanding of embodiments of the present invention. Elevator systems designed in accordance with embodiments of the present invention may include more or fewer cars.

While the elevator system shown is a traction-based elevator system, other elevator system configurations that do not require a counterweight or ropes are also included in some embodiments. In such embodiments, the machine would not be a traction machine, but would include some motive power source (such as a motor) for moving the associated elevator car when needed, as well as brakes for controlling the movement and position of the associated elevator car. For discussion purposes, a traction-based elevator system is used as an example system in the remainder of this description. Those skilled in the art who have the benefit of this description will be able to apply the features of the present invention to other elevator system configurations.

The example shown in Figure 1 includes a group of elevator cars dedicated to serving a floor zone indicated as SZ ₁ in Figure 1. The elevators serving the floors in SZ ₁ include cars 22, 24, 26, 28, 30, and 32. Each of these cars has a corresponding machine 42, 44, 46, 48, 50, and 52.

A second set of elevator cars 60, 62, 64, 65, 66 and 68 are dedicated to serving floors through the middle section of the building. The service area of the second set of cars is indicated at SZ ₂ in Figure 1. The cars 60-68 have corresponding machines 70, 72, 74, 75, 76 and 78.

A third group of elevator cars 80, 82, 84 and 86 and their respective associated machines 90, 92, 94 and 96 are dedicated to serving a group of floors near the top of the example building. Service zone SZ ₃ includes the only floors served by elevator cars 80-86.

In the illustrated embodiment, each of the elevator machines is capable of operating in two different modes. The first mode, or drive mode, involves consuming power during a first type of elevator car movement. For example, when the elevator machine moves the associated elevator car in a manner that requires drawing power from the power supply, the elevator machine operates in the first mode, consuming power in these circumstances. Given that counterweights are typically designed to have a mass roughly equal to the mass of the elevator car plus between 45% and 55% of the car's rated load, there are times when the counterweight weighs more than the car, and in these circumstances, power is required to raise the counterweight to lower the elevator car. Alternatively, when the car is sufficiently loaded to be heavier than the counterweight, power is required to raise the elevator car. Depending on the acceleration of the elevator car, there are situations in which drive power (i.e., power consumption) is required to initiate downward movement of a heavily loaded car or to move an empty car upward. These and other power consumption scenarios are taken into account when determining the power consumption of a particular machine or group of particular machines.

Each of the elevator machines in the illustrated example is capable of operating in a second mode, which involves generating power during a second type of elevator car movement. This second mode may be referred to as a regenerative mode. For example, when an elevator car is fully loaded and traveling downward, the elevator machine associated with that car does not need to draw power from a power source to accomplish such movement. Instead, the elevator machine can operate in a regenerative mode, during which the elevator machine acts like a generator and supplies power back to a power source, such as the utility grid or an emergency generator, or otherwise to an energy storage device. For example, hoisting an empty car does not require drawing power, as a counterweight heavier than the empty car will descend as the machine allows. Another scenario in which the machine operates in the second, or regenerative, mode is lowering a fully loaded car that is heavier than the associated counterweight. Depending on the deceleration of the elevator car, there are situations in which the machine generates a small amount of regenerative power when decelerating a heavily loaded car moving upward or an empty car moving downward. Such effects are taken into account when determining the total regenerative power for the elevator system.

The elevator system includes an emergency or backup power supply 100 for providing power to a plurality of elevator machines during situations in which a primary power supply (not shown) is unavailable. The backup power supply 100 has a power output threshold corresponding to the maximum power capacity of the backup power supply 100. In this example, the backup power supply 100 also has a power intake threshold corresponding to the maximum amount of power that the backup power supply 100 can absorb or receive from an elevator machine operating in a regenerative mode.

Controller 102 controls the operation of elevator system 20 when backup power source 100 is in use. Controller 102 includes at least one processor or computing device and associated memory. Controller 102 is schematically shown as a single device or component, however, the features and functions of controller 102 may be implemented by multiple devices. Furthermore, controller 102 may be a dedicated device or may be implemented as part of multiple other controllers associated with the elevator system. Those skilled in the art, having the benefit of this description, will understand how to arrange the components to implement controller 102 that meets their specific needs. Furthermore, those skilled in the art, having the benefit of this description, will be able to appropriately program the controller to function in accordance with embodiments of the present invention.

The processor or computing device is programmed so that the controller 102 is configured to dynamically adjust the manner in which the elevator machine causes the corresponding elevator cars to move to ensure that the power threshold of the backup power supply 100 is not exceeded, while maximizing the number of elevator cars that can be used to transport passengers when the backup power supply 100 is in use.

One situation in which the example elevator system 20 is useful is during an OEO, which may correspond to an emergency evacuation situation in which people should evacuate at least some floors of the building in which the elevator system 20 is located. In some embodiments, the controller 102 schedules or controls the movement of the elevator cars to maximize the number of passengers carried to their intended destinations per unit time. In some example embodiments, all elevator cars of the elevator system 20 can be used during an OEO without exceeding the power threshold of the backup power supply 100. For example, in a situation in which the cars are fully loaded and all traffic is in the downward direction, all elevators are utilized. The controller 102 utilizes information about the power requirements of each elevator machine and its associated elevator car and dynamically adjusts the operation of the elevator machines as needed to ensure that the power threshold of the backup power supply 100 is not exceeded. The techniques used in the illustrated example embodiments allow a relatively low-cost backup power supply to be sufficient to enable movement of most or all of the elevator cars in the elevator system, without requiring multiple or expensive backup power supplies.

During evacuation operations, most passenger traffic will be from the upper floors of the building down to the lobby, ground level, or some lower exit level so that individual passengers can exit the building. When the elevator car is fully loaded, such downward movement will typically be associated with the elevator machine operating in a regenerative mode. In the example shown, the elevator machine will operate in a second mode that includes generating power during the type of elevator car movement described. Similarly, moving the empty car upward to gather more passengers allows the associated machine to operate in the second regenerative mode because the counterweight (not shown) is heavier than the car and, in this case, is lowered. Therefore, during evacuation operations, the power intake threshold of the backup power supply 100 is more likely to be exceeded than the power output threshold. The controller 102 controls the operation of the elevator machine in a manner that reduces or eliminates the likelihood of exceeding the power intake threshold.

There are various aspects of elevator car movement that are associated with different levels of power consumption or regeneration. For example, when the elevator system is loaded to 80% or more of its rated capacity, downward movement will generate regenerative power from the associated machinery. This power often spikes when the elevator car reaches the end of its trip and stops at a landing. Larger peaks in power consumption often occur when the elevator car begins to move.

1 , several floors within a building served by an elevator system 20 are part of an evacuation zone (EZ). One or more floors within the evacuation zone (EZ) may contain a hazardous situation, such as a fire, requiring evacuation of people from at least the floors in the EZ.

As can be understood from FIG1 by comparing the different service zones SZ with the evacuation zone EZ, no one group of elevator cars is capable of performing an OEO for the entire evacuation zone EZ. Elevator cars 22-32 can only serve the lower portion of the evacuation zone, elevator cars 80-86 can only serve the upper portion of the evacuation zone, and elevator cars dedicated to service zone SZ ₂ can serve all floors except one or some lower floors within the evacuation zone EZ. In the scenario schematically shown in FIG1 , all three groups of elevator cars can be used during an OEO.

The controller 102 controls the movement of the elevator cars to ensure that the power consumption associated with the elevator machines operating in the first, or drive, mode and the power regeneration associated with the machines operating in the second, or regeneration, mode of the elevator system 20 do not exceed corresponding limits of the backup power source 100. The controller 102 is configured or programmed to account for the various ways in which elevator car movement or machine operation affects the power consumed or generated by the elevator system.

FIG2 is a flowchart 120 summarizing an example method used by the controller 102. At 122, the controller 102 determines the power of the elevator system, including the amount of power consumed by the system and the amount of regenerative power generated by the system. Each machine individually contributes to the total drive and regenerative power, depending on the current state of machine operation. The controller 102 continuously determines the total power of the elevator system as a current power level and a predicted level to proactively control power within threshold limits of the power supply.

At 124, the controller 102 determines whether the drive power exceeds the power supply output threshold. If not, the controller 102 continues to monitor the power at 122. If at 124, the drive power exceeds or will exceed the output threshold, the controller adjusts the car movement (e.g., changes the timing of starting or stopping, changes the acceleration rate, or changes the speed) to reduce the drive power or increase the regeneration power so that the total system power is within the desired limits.

At 128, the controller 102 determines the system regenerative power. If the power level is acceptable, the controller 102 continues to monitor and predict the power at 122. If the regenerative power is outside of a limit corresponding to the power intake threshold of the backup power source, or is predicted to be outside of it, the controller 102 adjusts the car movement of at least one elevator car to reduce the regenerative power or to increase the drive power to use some of the regenerative power so that the intake threshold of the backup power source will not be exceeded.

The controller 102 is programmed or otherwise has information available to it indicating which floors within the evacuation zone (EZ) can be served by which elevator cars or groups of elevator cars. This information allows the controller 102 to assess the likelihood of any stoppage of any elevator car, which could affect power consumption or power regeneration in the elevator system 20. For example, when performing an OEO to evacuate a group of people from the evacuation zone (EZ), the controller 102 need not consider any potential stoppage of any elevator car within the second group of service zones (SZ ₂₎ dedicated to evacuating the evacuation zone (EZ). Additionally, during an OEO, once a passenger enters an elevator car, the car will only move toward a discharge landing and will not service calls outside the evacuation zone. Such factors are taken into account when determining and predicting power levels.

In FIG1 , elevator car 22 is only partially loaded and descending. Therefore, machine 42 is operating in a power-consuming or drive mode for returning car 22 to the lobby or landing at floor 104 in the building. Elevator car 24 is currently moving upward, with machine 44 operating in a first or drive mode. Elevator car 26 is loaded such that the car is heavier than its associated counterweight (not shown), causing machine 46 to operate in a second or regenerative mode. As elevator car 28 descends, machine 48 also operates in a regenerative mode. Elevator car 30 is lightly loaded, causing machine 50 to operate in a first mode for lowering elevator car 30. Elevator car 32 is loaded such that machine 52 operates in a first mode for raising elevator car 32. In this example, controller 102 causes machine 52 to operate at a reduced speed compared to the designated or designed speed to reduce the amount of power consumed for operating at least a portion of elevator car 32.

Some of the other machines operate in a first, or power-consuming, mode, while still other machines operate in a second, or regenerative mode. For purposes of discussion, machines 70, 78, and 96 operate in the first mode, while machines 72, 74, 75, 76, 90, and 94 all operate in the second mode. In the example schematically shown in FIG1 , elevator car 82 is currently stopped, and the next movement of the car is delayed by controller 102 to temporarily avoid introducing additional power consumption associated with machine 92 initiating movement of elevator car 82.

Taking into account the amount of power consumed and regenerated by various machines, the controller 102 can balance the amount of power consumed and regenerated to avoid exceeding the output threshold of the backup power supply 100 and the intake threshold of the backup power supply 100.

In the illustrated example, the elevator system 20 is configured so that regenerative power from any machine is provided to the backup power source 100 to recharge the backup power source 100 or replenish its power output capacity. The controller 102 dynamically adjusts the operation of the elevator machine operating in the second mode, which includes regenerative power generation, by controlling, for example, the timing of the start of such movement, the speed of such movement, the acceleration or deceleration of such movement, and the timing of stopping the elevator car moving in the manner described. Adjusting the timing of such events allows the controller 102 to control how much regenerative power is provided to the backup power source 100 at any given time or during any time interval.

For example, the controller 102 controls the operation of the elevator machines to ensure that the associated elevator cars do not stop simultaneously to avoid a more significant regenerative power peak that must be absorbed by the backup power supply 100. In this example, the controller 102 is configured to separate the stopping times of any elevator cars moving in the second operating mode to ensure some time delay between consecutive stops of the elevator cars. In addition to controlling the timing of the elevator cars to avoid overlap in time, the controller 102 controls the timing of one or more power peak events to minimize the number of power peak events within a predetermined time interval.

Likewise, the controller 102 controls the movement of any elevator car moving in a drive or first mode (during which the associated machinery must consume power from the backup power source) to avoid exceeding a power output threshold of the backup power source 100. The initiation and acceleration of elevator car movement often require the associated machinery to consume more power, and therefore the controller 102 is configured or programmed to avoid simultaneous startup of multiple elevator cars and to avoid simultaneous acceleration of multiple cars at the same rate. Slowing the acceleration of one of the elevator cars may be sufficient to avoid a power consumption peak that could cause problems for the backup power source 100, such as exceeding a power output threshold.

One feature of the example controller 102 is that it balances power consumption and power regeneration by the machine. For example, when the situation schematically illustrated in FIG. 1 exists and some of the elevator cars are moving in a manner that causes regenerative power to be generated by the associated elevator machine, the controller 102 controls the timing of movement of these cars, as well as at least one other elevator car moving in a first drive mode, so that power consumption by the elevator machine or the other cars can utilize some of the regenerative power generated at that time. Coordinating the timing of elevator cars moving in different modes helps ensure that the power threshold of the backup power supply 100 is not exceeded. At the same time, when the backup power supply 100 is in use, the maximum number of elevator cars becomes available to transport passengers.

In one example embodiment, the controller 102 determines when the level of power consumption or power regeneration approaches a corresponding threshold for the backup power source 100. The controller 102 controls the timing of the power distribution to the elevator cars to avoid exceeding the threshold. For example, when the regenerative power that cannot otherwise be used and must be absorbed by the backup power source 100 is approximately 90% of the power intake threshold of the backup power source 100, the controller 102 delays allowing another elevator car to move in a manner in which its associated machine will provide more regenerative power until one of the elevator cars has stopped moving in that manner, or until the other elevator machine begins to consume power. Based on this description, one skilled in the art will understand how to program an appropriate controller to implement the type of power management described, which allows for economical use of backup power while maximizing the number of elevator cars that can be operated when the backup power source is in use.

While OEO operation is described above, the elevator system operation control described above can also be used in other situations where the power source is not an emergency backup power source with output limits or intake limits. The described method for controlling elevator system operation and car movement maximizes the number of elevator cars that can be used within such limits.

The foregoing description is illustrative rather than restrictive in nature. Variations and modifications to the disclosed examples will become apparent to those skilled in the art without necessarily departing from the spirit of the invention. The scope of legal protection afforded this invention can only be determined after studying the following claims.

Claims (20)

1. An elevator system comprising: Multiple elevator cars; A plurality of elevator machines, each associated with an elevator car, for selectively causing the associated elevator car to move, wherein at least some of the elevator machines operate in a first mode including consuming power and a second mode including generating power. A power source that provides power for the movement of the elevator car, the power source having a power output threshold corresponding to the maximum power capacity of the power source and a power intake threshold corresponding to the maximum amount of power the power source can absorb from the elevator machine operating in the second mode; and At least one controller, the at least one controller being configured to: Determine when the power source supplies power to the elevator system; and The elevator system dynamically adjusts how the multiple elevator machines move the elevator cars to maximize the number of elevator cars used to move passengers, while keeping the power consumption of the elevator system below the power output threshold and the power generation of the elevator system below the power intake threshold. 2. The elevator system of claim 1, wherein the controller dynamically adjusts how the plurality of elevator machines move the elevator cars to maximize the number of the plurality of elevator cars used to move passengers during personnel evacuation operations. 3. The elevator system of claim 1, wherein the controller controls the timing of one or more power peak events to minimize the number of power peak events within a predetermined time interval. 4. The elevator system according to claim 3, wherein the power peak event includes: The elevator car accelerates; The elevator car begins to move from a stop; and To stop the elevator car that is moving in a manner powered by the associated elevator machinery. 5. The elevator system of claim 3, wherein the controller controls the timing to avoid more than one power peak event occurring simultaneously. 6. The elevator system of claim 1, wherein the controller dynamically adjusts how the plurality of elevator machines move the elevator car by controlling the timing of at least one of the following: The elevator car starts from a stop; The elevator car has stopped; Elevator car speed; Elevator car acceleration; and The elevator car slows down. 7. The elevator system according to claim 1, wherein the controller dynamically adjusts how the plurality of elevator machines move the elevator car by scheduling at least one of the elevator machines to operate in the first mode while at least one other of the elevator machines operates in the second mode. 8. The elevator system of claim 1, wherein the controller schedules the movement of the plurality of elevator cars to maximize the number of passengers carried to a predetermined destination per unit time. 9. The elevator system of claim 8, wherein the predetermined destination corresponds to a location where the passenger can leave the building, and the elevator system is located within the building. 10. The elevator system of claim 1, wherein the controller balances the amount of power consumed by any elevator machine operating in the first mode with the amount of power generated by any elevator machine operating in the second mode over a time interval. 11. A method of operating an elevator system, the elevator system comprising a plurality of elevator cars, a plurality of elevator machines, and a power source, wherein the elevator machines are associated with the elevator cars to selectively cause the associated elevator cars to move, wherein the power source provides power for the movement of the elevator cars, and wherein the power source has a power output threshold corresponding to the maximum power capacity of the power source and a power intake threshold corresponding to the maximum amount of power that the power source can absorb from the elevator machines operating in power regeneration mode, the method comprising: Determine when the power source supplies power to the elevator system; and The elevator system dynamically adjusts how the multiple elevator machines move the elevator cars to maximize the number of elevator cars used to move passengers, while keeping the power consumption of the elevator system below the power output threshold and the power generation of the elevator system below the power intake threshold. 12. The method of claim 11, further comprising dynamically adjusting how the plurality of elevator machines move the elevator cars to maximize the number of the plurality of elevator cars used to move passengers during a personnel evacuation operation. 13. The method of claim 11, further comprising controlling the timing of one or more power peak events to minimize the number of power peak events within a predetermined time interval. 14. The method of claim 13, wherein the power peak event comprises: The elevator car accelerates; The elevator car begins to move from a stop; and To stop the elevator car that is moving in a manner powered by the associated elevator machinery. 15. The method of claim 13, further comprising controlling the timing to avoid more than one power peak event occurring simultaneously. 16. The method of claim 11, further comprising dynamically adjusting how the plurality of elevator machines move the elevator car by controlling the timing of at least one of the following: The elevator car starts from a stop; The elevator car has stopped; Elevator car speed; Elevator car acceleration; and The elevator car slows down. 17. The method of claim 11, further comprising dynamically adjusting how the plurality of elevator machines move the elevator car by scheduling at least one of the elevator machines to operate in a power consumption mode while at least one other of the elevator machines operates in a power regeneration mode. 18. The method of claim 11, further comprising scheduling the movement of the plurality of elevator cars to maximize the number of passengers carried to a predetermined destination per unit time. 19. The method of claim 18, wherein the predetermined destination corresponds to a location where the passenger can leave the building, and the elevator system is located within the building. 20. The method of claim 11, further comprising balancing the amount of power consumed by any of the elevator machines operating in power consumption mode with the amount of power generated by any of the elevator machines operating in power regeneration mode over a time interval.