Flow-based energy management

A method of managing energy for an energy storage device, which includes an energy storage medium, an energy converter configured to add energy to the medium, a device temperature sensor configured to detect a temperature of the energy storage medium, and a device controller configured to control the energy converter based on a temperature signal from the device temperature sensor, the method comprising:

• generating at least one energy input signal using an energy input sensor indicating heat energy input to the energy storage medium from the energy converter;
• generating at least one energy output signal using an energy output sensor indicating heat energy output from the energy storage medium;
• and
• estimating a charge level of the energy storage medium based on an initial charge level of the energy storage medium and a change in the charge level of the energy storage medium, which is based on the at least one energy input signal and the at least one energy output signal, using a system controller.

An energy management system for a water heater, the water heater including an energy storage medium comprising water contained in a tank, an energy converter configured to heat the water, a device temperature sensor configured to detect a temperature of the energy storage medium, and a device controller configured to control the energy converter based on a temperature signal from the device temperature sensor, the system comprising:

• an energy input sensor configured to detect one of electrical power delivered to the energy converter and an exchange of heat energy between a fluid flow and the energy converter, and generate at least one energy input signal indicating heat energy input to the energy storage medium from the energy converter, wherein the energy input sensor comprises at least one an electrical power sensor configured to detect the electrical power, and a heat flow sensor comprising flow sensor configured to measure a flow rate of the fluid flow and a temperature sensor configured to measure a temperature of the fluid flow;
• an energy output sensor configured to generate at least one energy output signal indicating energy flow from the device, the energy output sensor comprising a first flow rate sensor configured to generate a first flow rate signal indicating a flow rate of the water delivered to or discharged from the tank, and the at least one energy output signal includes the first flow rate signal;
• and
• a system controller configured to estimate a charge level of the energy storage medium based on an initial charge level of the energy storage medium and a change in the charge level of the energy storage medium, which is based on the at least one energy input signal and the at least one energy output signal.