HVAC control system and method

1. A method of controlling the heating, ventilation and air conditioning (HVAC) system of a building, the method comprising the steps of:

(a) developing an initial thermal model of the building, and continuously updating this thermal model substantially daily;

(b) utilising the thermal model to continuously develop a daily HVAC operating plan for the building wherein the daily HVAC operating plan includes the aggregate impact of multiple heating/cooling sources on a series of zone temperatures in said building, with the daily HVAC operating plan being recalculated substantially every 5 minutes; and

(c) continuously examining a current HVAC operating plan and optimising the alignment of the current HVAC operation with the current HVAC operating plan substantially on the basis of seconds.

2. The method of claim 1 , wherein said thermal model utilises a series of parameters, fitted to historical thermal data for the building.

3. The method of claim 1 , wherein said thermal model is a piecewise polynomial model.

4. The method of claim 1 , wherein said optimising the alignment of said current HVAC operation with the current HVAC operating plan is attempted substantially every 10 seconds.

5. The method of claim 1 , wherein the thermal model has substantially the following form:

T

int

⁡

(

z

)

=

F

amb

⁡

(

z

)

⁢

T

amb

⁡

(

z

)

-

10

P

coolTyp

⁢

F

Pcool

⁡

(

z

)

⁢

P

cool

⁡

(

z

)

+

1

P

heatTyp

⁢

F

Pheat

⁡

(

z

)

⁢

P

heat

⁡

(

z

)

+

B

⁡

(

z

)

Where:

T int (z) is an average internal building temperature;

T amb (z) is an ambient temperature;

P cool (z) is a HVAC cooling power consumption;

P coolTyp is a typical HVAC cooling power consumption;

P heat (z) is a HVAC heating power consumption;

P heatTyp is a typical HVAC heating power consumption;

F amb (z) captures an internal building temperature response to the ambient temperature;

F Pcool (z) captures an internal building temperature response to the HVAC cooling power consumption;

F Pheat (z) captures an internal building temperature response to HVAC heating power consumption;

B(z) is a baseline fucntion and captures factors other than those captured by F amb (z), F Pcool (z) and F Pheat (z); and

10 is a scaling factor.

6. The method of claim 5 , wherein the baseline function changes depending on the day of the week.

7. The method of claim 6 , wherein the baseline function is formed of a combination of triangular basis functions that are estimated at specific fixed points throughout a day.

8. The method of claim 1 , wherein said optimising the alignment of the current HVAC operation with the current HVAC operating plan is attempted substantially in increments of seconds.

9. The method of claim 1 , wherein the thermal model has substantially the following form:

T z = F A ( s )· T Amb +Baseline Fcn−F T ( s )·Δ T SS

where:

T z is a modelled aggregate zone temperature;

T Amb is an outside ambient air temperature;

ΔT ss is a steady state difference in zone temperature that would result from the current HVAC cooling and heating powers;

BaselineFcn is a learnt function of time, accounting for at least one of people, equipment, or sun;

F A (s) and F T (s) are linear time invariant filters, accounting for system dynamics.

10. The method of claim 9 , wherein ΔT ss has the form of an equation:

Δ T ss =∝ c ·μ c ·max{0 ,P cool −P cb }−∝ h ·μ h ·max{0 ,P Heat −P hb }

where:

the first part of the equation is an effective cooling temperature (ΔT cool );

the second part of the equation is an effective heating temperature (ΔT Heat );

P cool and P Heat are estimates of actual cooling power and actual heating power, respectively;

P cb and P hb are baseline cooling power and actual heating power, respectively;

∝ c , and ∝ h are nominal scaling for HVAC power effectiveness; and

μ c and μ h are HVAC efficiency de-ratings as a function of external temperature.