Generating and implementing thermodynamic models of a structure

• US 10,545,517 B2
• Filed: 02/22/2018
• Issued: 01/28/2020
• Est. Priority Date: 04/19/2013
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Matsuoka, Yoky, Malhotra, Mark, Minich, Allen J., Ruff, Joseph A.
• Primary Examiner(s): Ciric, Ljiljana V.
• Assistant Examiner(s): Cox, Alexis K
• Application Number:
  US15/902,290
• Publication Number:
  US 20180181149A1
• Time in Patent Office: 705 Days
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/58 using Internet communication
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: G05B 2219/2614 HVAC, heating, ventillation, climate control
• CPC Class Codes: G05B 2219/2642 Domotique, domestic, home control, automation, smart house
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

In controlling the HVAC system, a need to determine an expected indoor temperature profile for a particular schedule of setpoint temperatures may arise. To make such a determination, a thermodynamic model of the structure is used. The thermodynamic model is generated by fitting weighting factors of a set of basis functions to a variety of historical data including time information, temperature information, and HVAC actuation state information. The set of basis functions characterize an indoor temperature trajectory of the structure in response to a change in HVAC actuation state, and include an inertial carryover component that characterizes a carryover of a rate of indoor temperature change that was occurring immediately prior to the change in actuation state.

Claims

1. An intelligent network-connected thermostat for controlling an operation of an HVAC system in a smart home environment, the thermostat comprising:

HVAC control circuitry operable to actuate one or more elements of the HVAC system;

one or more sensors for measuring characteristics of the smart home environment; and

a processor coupled to the HVAC control circuitry and the one or more sensors and operable to cause the thermostat to perform operations including;

acquiring time information, temperature information, and HVAC actuation state information for a period of time during which the HVAC system controls a thermal environment of a structure;

determining a plurality of weighting factors corresponding to a respective plurality of predetermined basis functions, the weighted combination of basis functions characterizing an indoor temperature trajectory of the structure in response to a change in the HVAC actuation state, the basis functions including an inertial carryover component that characterizes a carryover of a rate of indoor temperature change that was occurring immediately prior to the change in actuation state; and

providing a thermodynamic model including the determined plurality of weighting factors corresponding to the respective plurality of predetermined basis functions.

2. The thermostat of claim 1, wherein the basis functions further include a current stage effect component that characterizes an effect that a current stage has on the indoor temperature trajectory of the structure.

3. The thermostat of claim 2, wherein the current stage effect component begins at zero, reaches a maximum after a certain period of time, and diminishes thereafter.

4. The thermostat of claim 1, wherein the plurality of weighting factors are determined using only information that is available local to the thermostat except for an externally provided weather forecast and an externally provided clock signal.

5. The thermostat of claim 1, wherein the HVAC actuation state is:

a first state characterized by a relatively high first energy consumption, or a second state characterized by a relatively low energy consumption.

6. The thermostat of claim 1, wherein the basis functions comprise at least one basis function that has associative mathematical significance on the indoor temperature trajectory.

7. The thermostat of claim 1, wherein the inertial carryover component that characterizes a carryover of a rate of indoor temperature change that was occurring immediately prior to the change in actuation state is represented by:

8. The thermostat of claim 7, wherein the plurality of basis functions further include a current stage effect component that begins at zero, reaches a maximum at 2×

t^steady-state, and diminishes thereafter.

9. The thermostat of claim 1, wherein the plurality of basis functions further comprises a basis function characterizing an effect of a difference between an outdoor temperature and an indoor temperature.

10. The thermostat of claim 1, wherein the operations the processor is configured to perform further include estimating a temperature of the structure by:

setting an initial temperature of the structure to an indoor temperature at a first time; and

for each of a plurality of times after the first time, determining the temperature of the structure as a weighted combination of a previous indoor temperature and a previous outdoor temperature.

11. The thermostat of claim 1, wherein the plurality of basis functions further comprises a basis function characterizing an effect of a difference in a temperature of the structure and an indoor temperature.

12. The thermostat of claim 1, wherein the plurality of basis functions further comprises a basis function characterizing an effect of a time-of-day approximating an effect of sunlight.

13. The thermostat of claim 12, wherein the basis function characterizing the effect of the time-of-day approximating the effect of sunlight comprises a sinusoidal term having a period of 24 hours.

14. The thermostat of claim 1, wherein the plurality of basis functions further comprises a basis function comprising a constant representing energy changes not affected by environmental factors.

15. The thermostat of claim 1, wherein the operations the processor is configured to perform further include:

using a required level of specificity for the thermodynamic model.

16. The thermostat of claim 15, wherein the operations the processor is configured to perform further include:

searching a plurality of existing thermodynamic models for one or more candidate thermodynamic models that satisfy the required level of specificity for the thermodynamic model.

17. The thermostat of claim 16, wherein providing the thermodynamic model that predicts the temperature trajectory of air inside the structure in response to the actuation of the HVAC function comprises:

failing to identify one or more candidate models; and

in response to failing to identify the one or more candidate models, generating the thermodynamic model.

18. The thermostat of claim 1, wherein the processor is further configured to predict the temperature trajectory of air inside the structure by calculating a time-wise series of temperature changes beginning at a current indoor temperature.