Dc building system with energy storage and control system

Abstract

A DC building electrical system includes a DC power consuming device connected to a DC bus. A source of DC power is connected to the DC bus and powers the DC power consuming device. An energy storage device is connected to the DC bus and to a DC emergency load. The energy storage device powers the DC power consuming device in conjunction with the source of DC power, and powers the DC emergency load when source of power other than the energy storage device is available to the DC power consuming device.

What is claimed is: 
     
         1 . A DC building electrical system comprising:
 a DC bus;   a DC power consuming device connected to the DC bus;   a source of DC power connected to the DC bus and configured to power the DC power consuming device;   a DC emergency load; and   an energy storage device connected to the DC bus and to the DC emergency load, the energy storage device being configured to:
 power the DC power consuming device in conjunction with the source of DC power; and 
 power the DC emergency load when no source of power other than the energy storage device is available to the DC power consuming device. 
   
     
     
         2 . The system of  claim 1 , wherein the source of DC power comprises:
 a photovoltaic array producing a DC voltage on the DC bus; and/or   a DC power supply producing DC voltage on the DC bus from AC voltage received from a utility grid.   
     
     
         3 . The system of  claim 1 , wherein the energy storage device is configured to power the DC emergency load for a predetermined period of time when no source of power other than the energy storage device is available to the DC power consuming device. 
     
     
         4 . The system of  claim 3 , further comprising a renewable energy DC power source connected to the DC bus and configured provide power to the DC emergency load in conjunction with the energy storage device when no source of power other than the energy storage device is available to the DC power consuming device. 
     
     
         5 . The system of  claim 1 , wherein the DC emergency load is included in the DC power consuming device and is configured to draw less power than the DC power consuming device. 
     
     
         6 . A DC building electrical system comprising:
 a DC bus;   a DC power consuming device connected to the DC bus;   a source of DC power connected to the DC bus and configured to power the DC power consuming device;   a motorized vehicle; and   an energy storage device connected to the DC bus and to the motorized vehicle, the energy storage device being configured to:
 power the DC power consuming device in conjunction with the source of DC power; and 
 power the motorized vehicle. 
   
     
     
         7 . The system of  claim 6 , wherein the energy storage device is configured to be an only source of power for the motorized vehicle. 
     
     
         8 . The system of  claim 6 , wherein the motorized vehicle comprises a golf cart or a fork lift. 
     
     
         9 . A DC building electrical system comprising:
 a DC bus;   a DC power consuming device connected to the DC bus;   a source of DC power connected to the DC bus and configured to power the DC power consuming device;   an energy storage device connected to the DC bus and configured to power the DC power consuming device in conjunction with the source of DC power; and   a DC power control system configured to selectively charge and discharge the energy storage device based on a current state of charge of the energy storage device and a predetermined target state of charge of the energy storage device.   
     
     
         10 . The system of  claim 9 , wherein the DC power control system is configured to charge the energy storage device during time periods in which the source of DC power is operable and discharge the energy storage device during time periods in which the source of DC power is inoperable, the predetermined target state of charge being a state of charge that is sufficient to solely power the DC power consuming device for a predetermined duration of time while the source of DC power is inoperable. 
     
     
         11 . The system of  claim 9 , further comprising a renewable energy DC power source connected to the DC bus, wherein the DC power control system is configured to charge the energy storage device by using excess power from the renewable energy DC power source. 
     
     
         12 . The system of  claim 9 , further comprising a renewable energy DC power source connected to the DC bus, wherein the DC power consuming device is variable, the DC power control system being configured to respond to the current state of charge of the energy storage device dropping below the predetermined target state of charge by adjusting the variable DC power consuming device such that a level of current drawn by the variable DC power consuming device is less than a level of current sourced by the renewable energy DC power source, and such that the energy storage device is charged to the predetermined target state of charge by the renewable energy DC power source. 
     
     
         13 . The system of  claim 9 , further comprising a renewable energy DC power source connected to the DC bus, wherein the DC power consuming device is variable, the DC power control system being configured to respond to the current state of charge of the energy storage device dropping below the predetermined target state of charge by adjusting a discharge current rate of the energy storage device by selectively reducing or discontinuing operation of the variable DC power consuming device dependent upon a building ambient condition and a corresponding predetermined building condition. 
     
     
         14 . The system of  claim 13 , wherein the building ambient condition comprises a level of sunlight. 
     
     
         15 . The system of  claim 13 , wherein the corresponding predetermined building condition comprises a desired emergency interior lighting level. 
     
     
         16 . The system of  claim 9 , further comprising a renewable energy DC power source connected to the DC bus, wherein the DC power consuming device is variable, the DC power control system being configured to respond to the source of DC power being inoperable for a threshold period of time by adjusting the variable DC power consuming device such that a level of current drawn by the variable DC power consuming device is thereby reduced. 
     
     
         17 . The system of  claim 9 , wherein the DC power consuming device is variable, and wherein the DC power control system is configured to selectively reduce or discontinue operation of the variable DC power consuming device dependent upon a length of time during which the source of DC power has been inoperable. 
     
     
         18 . The system of  claim 9 , wherein the DC power consuming device comprises a motor or a generator, the DC power control system being configured to charge the energy storage device by discontinuing power to the motor or generator and operating the motor or generator in a regenerative mode in which kinetic energy of the motor or generator is converted to DC power. 
     
     
         19 . A microgrid system arrangement comprising:
 a photovoltaic array producing a DC voltage on a DC bus;   a DC power supply producing DC voltage on the DC bus from AC voltage received from a utility grid;   a DC power consuming device connected to the DC bus; and   a controller configured to control amounts of DC power provided to the DC bus by the photovoltaic array and by the DC power supply.   
     
     
         20 . The arrangement of  claim 19 , further comprising an energy storage device connected to the DC bus, the controller being configured to cause the energy storage device to:
 power the DC power consuming device in conjunction with the photovoltaic array and/or the source of DC power; and   be an exclusive provider of power to the DC power consuming device when the photovoltaic array and the DC power supply are inoperable.   
     
     
         21 . The arrangement of  claim 20 , wherein the controller is configured to selectively charge and discharge the energy storage device based on a current state of charge of the energy storage device and a predetermined target state of charge of the energy storage device, the predetermined target state of charge being a state of charge that is sufficient to solely power the DC power consuming device for a predetermined duration of time while the photovoltaic array and the DC power supply are inoperable. 
     
     
         22 . The arrangement of  claim 19 , wherein the controller comprises a first controller, the arrangement comprising a second controller configured to respond to the photovoltaic array and the DC power supply being inoperable for a threshold length of time by reducing a level of power drawn by the DC power consuming device.