Patent ID: 8227937

Claim:
An uninterruptible power supply comprising: a power bus; mains circuitry configured to rectify electrical energy received from a mains supply system into rectified electrical energy and to provide the rectified electrical energy to the power bus; photovoltaic circuitry configured to convert solar energy into converted electrical energy and to provide the converted electrical energy to the power bus; a battery system configured to receive electrical energy from the power bus to charge a battery of the battery system and to discharge electrical energy to the power bus; an inverter configured to provide electrical energy from the power bus to a load; a controller configured to monitor the photovoltaic circuitry and to implement at least one operation of the uninterruptible power supply using the monitoring; wherein the controller is configured to implement the at least one operation comprising calculating a remaining period of time the uninterruptible power supply can provide the electrical energy from the power bus to the load during an emergency mode of operation when electrical energy is unavailable from the mains supply system; and a sensor configured to provide information regarding an amount of light present at the photovoltaic circuitry, and wherein the controller is configured to use the information regarding an amount of light present at the photovoltaic circuitry to determine the remaining period of time.