Electrical energy storage system with battery resistance estimation

1. An electrical energy storage system comprising:

a battery container comprising one or more batteries configured to store and discharge electrical energy;

one or more temperature sensors configured to measure one or more temperatures associated with the battery container; and

a controller configured to:

estimate a rate of heat generation by the one or more batteries based on the measured temperatures;

monitor an electric current provided to the one or more batteries; and

estimate a resistance of the one or more batteries based on the estimated rate of heat generation and the electric current.

2. The electrical energy storage system of claim 1 , wherein the controller is configured to calculate one or more operating parameters of the batteries based on the estimated resistance, the operating parameters comprising at least one of:

a maximum state-of-charge of the batteries;

a maximum charging/discharging power of the batteries;

a power storage efficiency of the batteries; or

a health of the batteries.

3. The electrical energy storage system of claim 2 , wherein the controller is configured to use the calculated operating parameters to generate battery power setpoints for the one or more batteries.

4. The electrical energy storage system of claim 1 , wherein the controller is configured to:

monitor the estimated resistance of the one or more batteries over time; and

detect a fault in the electrical energy storage system in response to the estimated resistance crossing a resistance threshold.

5. The electrical energy storage system of claim 1 , wherein the controller is configured to:

apply the estimated resistance of the one or more batteries as an input to a battery life model; and

use the battery life model to predict a remaining life of the one or more batteries as a function of the estimated resistance.

6. The electrical energy storage system of claim 1 , wherein the controller is configured to estimate the rate of heat generation by the one or more batteries by:

calculating a rate of heat flow into the battery container;

calculating a rate of heat flow out of the battery container; and

subtracting the rate of heat flow into the battery container from the rate of heat flow out of the battery container to determine the rate of heat generation by the one or more batteries.

7. The electrical energy storage system of claim 1 , wherein the one or more temperature sensors comprise:

a supply air temperature sensor configured to measure a temperature of supply air provided to battery container; and

a return air temperature sensor configured to measure a temperature of return air returning from the battery container.

8. The electrical energy storage system of claim 7 , wherein the controller is configured to:

calculate a rate of heat flow into the battery container based on the measured temperature of the supply air;

calculate a rate of heat flow out of the battery container based on the measured temperature of the return air; and

estimate the rate of the heat generation by the one or more batteries based on a difference between the rate of heat flow out of the battery container and the rate of heat flow into the battery container.

9. The electrical energy storage system of claim 1 , further comprising an HVAC system configured to provide cooling for the battery container;

wherein the controller is configured to estimate the rate of heat generation by the one or more batteries based on a rate at which heat is removed from the battery container by the HVAC system.

10. The electrical energy storage system of claim 1 , wherein the controller is configured to:

estimate the rate of heat generation by the one or more batteries at each of a plurality of time steps within a time horizon;

determine the electric current provided to the one or more batteries at each of the plurality of time steps;

generate an integrated heat generation value and an integrated electric current value by integrating the estimated rates of heat generation and the determined electric currents over the time horizon; and

estimate the resistance of the one or more batteries based on the integrated heat generation value and the integrated electric current value.

11. A method for operating an electrical energy storage system, the method comprising:

storing and discharging electrical energy in one or more batteries within a battery container;

measuring one or more temperatures associated with the battery container;

estimating a rate of heat generation by the one or more batteries based on the measured temperatures;

monitoring an electric current provided to the one or more batteries; and

estimating a resistance of the one or more batteries based on the estimated rate of heat generation and the electric current.

12. The method of claim 11 , further comprising calculating one or more operating parameters of the batteries based on the estimated resistance, the operating parameters comprising at least one of:

a maximum state-of-charge of the batteries;

a maximum charging/discharging power of the batteries;

a power storage efficiency of the batteries; or

a health of the batteries.

13. The method of claim 12 , further comprising using the calculated operating parameters to generate battery power setpoints for the one or more batteries.

14. The method of claim 11 , further comprising:

monitoring the estimated resistance of the one or more batteries over time; and

detecting a fault in the electrical energy storage system in response to the estimated resistance crossing a resistance threshold.

15. The method of claim 11 , further comprising:

applying the estimated resistance of the one or more batteries as an input to a battery life model; and

using the battery life model to predict a remaining life of the one or more batteries as a function of the estimated resistance.

16. The method of claim 11 , wherein estimating the rate of heat generation by the one or more batteries comprises:

calculating a rate of heat flow into the battery container;

calculating a rate of heat flow out of the battery container; and

subtracting the rate of heat flow into the battery container from the rate of heat flow out of the battery container to determine the rate of heat generation by the one or more batteries.

17. The method of claim 11 , wherein measuring the one or more temperatures associated with the battery container comprises:

measuring a temperature of supply air provided to battery container; and

measuring a temperature of return air returning from the battery container.

18. The method of claim 17 , wherein estimating the rate of heat generation by the one or more batteries comprises:

calculating a rate of heat flow into the battery container based on the measured temperature of the supply air;

calculating a rate of heat flow out of the battery container based on the measured temperature of the return air; and

estimating the rate of the heat generation by the one or more batteries based on a difference between the rate of heat flow out of the battery container and the rate of heat flow into the battery container.

19. The method of claim 11 , further comprising operating an HVAC system to provide cooling for the battery container;

wherein the rate of heat generation by the one or more batteries is estimated based on a rate at which heat is removed from the battery container by the HVAC system.

20. The method of claim 11 , further comprising:

estimating the rate of heat generation by the one or more batteries at each of a plurality of time steps within a time horizon;

determining the electric current provided to the one or more batteries at each of the plurality of time steps;

generating an integrated heat generation value and an integrated electric current value by integrating the estimated rates of heat generation and the determined electric currents over the time horizon; and

estimating the resistance of the one or more batteries based on the integrated heat generation value and the integrated electric current value.