Method for operating an HVAC system
View Patent ↗A method for operating an HVAC system of a building is provided. The method includes providing a model for an indoor temperature of the building, a model for an operating cost of the HVAC system, and predicted future outdoor temperatures. Utilizing at least the models for the indoor temperature and the operating cost of the HVAC system and the predicted future outdoor temperatures, future operating states of the HVAC system can be calculated.
1. A method for operating an HVAC system, the HVAC system configured for cooling air within a building, heating air within the building, or both, the method comprising:
providing a model for an indoor temperature, y, of the building, the model for y comprising
y k =a k−1 +a 2 y k−2 +b 1 v k−1 +b 2 u k−1
where
y k is an indoor temperature of the building at time k,
y k−1 is an indoor temperature of the building at time k−1,
y k−2 is an indoor temperature of the building at time k−2,
v k−1 is an outdoor temperature at time k−1,
u k−1 is an operating state of the HVAC system at time k−1, and
a 1 , a 2 , b 1 , and b 2 are constants;
providing predicted future outdoor temperatures;
calculating future operating states of the HVAC system with a controller of the HVAC system utilizing at least the model for y, the model for J, and the predicted future outdoor temperatures; and
activating the HVAC system during the future operating states of the HVAC system from said step of calculating.
2. The method of claim 1 , wherein said step of providing the model for J comprises providing the model for J based at least in part on a utility cost of the HVAC system, a comfort cost of the HVAC system, and a state change cost of the HVAC system.
3. The method of claim 2 , wherein the model for J comprises
J ( X 0 ) = J e +J d +J p
where
J(X 0 ) is a total cost of operating the HVAC system;
J e is the utility cost of the HVAC system,
J d is the comfort cost of the HVAC system, and
J p is the state change cost of the HVAC system.
4. The method of claim 3 , wherein the utility cost of the HVAC system is determined with the following:
J
e
=
∑
k
=
0
N
-
1
u
k
g
(
k
)
where
u k is the operating state of the HVAC system at time k, and
g(k) is a unit price for energy at time k.
5. The method of claim 3 , wherein the comfort cost of the HVAC system is determined with the following:
J
d
=
∑
k
=
0
N
-
1
d
(
y
k
-
r
k
)
2
+
d
(
y
N
-
r
N
)
2
where
d is a constant greater than zero,
y k is the indoor temperature of the building at time k,
r k is a user selected temperature at time k,
y N is the indoor temperature of the building at a terminal time N, and
r N is the user selected temperature at the terminal time N.
6. The method of claim 3 , wherein the state change cost of the HVAC system is determined with the following:
J
p
=
∑
k
=
1
N
-
1
p
(
u
k
,
u
k
-
1
)
where
p
(
u
k
,
u
k
-
1
)
=
{
w
p
if
u
k
≠
u
k
-
1
0
if
u
k
=
u
k
-
1
u k is the operating state of the HVAC system at time k,
u k−1 is the operating state of the HVAC system at time k−1, and
w p is the cost of changing the operating state of the HVAC system.
7. The method of claim 1 , wherein said step of calculating future operating states of the HVAC system comprises calculating future operating states of the HVAC system in order to minimize future operating costs of the HVAC system.
8. The method of claim 7 , wherein said step of calculating future operating states of the HVAC system comprises calculating future operating states of the HVAC system with the following:
J
N
(
X
N
,
U
N
-
1
)
=
d
(
y
N
-
r
N
)
2
and
J
k
(
X
k
,
U
k
-
1
)
=
min
u
k
u
k
g
(
k
)
+
d
(
y
k
-
r
k
)
2
+
p
(
u
k
,
u
k
-
1
)
+
J
k
+
1
(
AX
k
+
BU
k
,
U
k
)
where
d is a constant greater than zero,
y N is the indoor temperature of the building at a terminal time N,
r N is the user selected temperature at the terminal time N,
u k is the operating state of the HVAC system at time k,
g(k) is a unit price for energy at time k,
y k is the indoor temperature of the building at time k,
r k is a user selected temperature at time k,
p
(
u
k
,
u
k
-
1
)
=
{
w
p
if
u
k
≠
u
k
-
1
0
if
u
k
=
u
k
-
1
,
u k is the operating state of the HVAC system at time k,
u k−1 is the operating state of the HVAC system at time k−1, and
w p is the cost of changing the operating state of the HVAC system.
9. The method of claim 1 , wherein said step of providing predicted future outdoor temperatures comprises determining predicted future outdoor temperatures based upon weather forecast data.
10. A method for operating an HVAC system, the HVAC system configured for cooling air within a building, heating air within the building, or both, the method comprising:
providing a model for an indoor temperature, y k , of the building at time k based at least in part on an interior temperature, y k−1 , of the building at time k− 1 , an exterior temperature, v k−1 , of the building at time k−1, and an operating state, u k−1 , of the HVAC system at time k− 1 ;
providing a model for an operating cost, J, of the HVAC system based at least in part on a utility cost, J e , of the HVAC system, a comfort cost, J d , of the HVAC system, and a state change cost, J p , of the HVAC system, J e being determined with the following:
J
e
=
∑
k
=
0
N
-
1
u
k
g
(
k
)
where
u k is the operating state of the HVAC system at time k, and
g(k) is a unit price for energy at time k;
providing predicted future outdoor temperatures;
calculating future operating states of the HVAC system with a controller of the HVAC system utilizing at least the model for y k , the model for J, and the predicted future outdoor temperatures; and
activating the HVAC system during the future operating states of the HVAC system from said step of calculating.
11. The method of claim 10 , wherein said step of calculating future operating states of the HVAC system comprises calculating future operating states of the HVAC system in order to minimize future operating costs of the HVAC system.
12. The method of claim 10 , wherein J d is determined with the following:
J
d
=
∑
k
=
0
N
-
1
d
(
y
k
-
r
k
)
2
+
d
(
y
N
-
r
N
)
2
where
d is a constant greater than zero,
y k is the indoor temperature of the building at time k,
r k is a user selected temperature at time k,
y N is the indoor temperature of the building at a terminal time N, and
r N is the user selected temperature at the terminal time N.
13. The method of claim 10 , wherein J p is determined with the following:
J
p
=
∑
k
=
1
N
-
1
p
(
u
k
,
u
k
-
1
)
where
p
(
u
k
,
u
k
-
1
)
=
{
w
p
if
u
k
≠
u
k
-
1
0
if
u
k
=
u
k
-
1
u k is the operating state of the HVAC system at time k,
u k−1 is the operating state of the HVAC system at time k−1, and
w p is the cost of changing the operating state of the HVAC system.
14. The method of claim 10 , wherein said step of calculating future operating states of the HVAC system comprises calculating the future operating states of the HVAC system with the following:
J
N
(
X
N
,
U
N
-
1
)
=
d
(
y
N
-
r
N
)
2
J
k
(
X
k
,
U
k
-
1
)
=
min
u
k
u
k
g
(
k
)
+
d
(
y
k
-
r
k
)
2
+
p
(
u
k
,
u
k
-
1
)
+
J
k
+
1
(
AX
k
+
BU
k
,
U
k
)
where
d is a constant greater than zero,
y N is the indoor temperature of the building at a terminal time N,
r N is the user selected temperature at the terminal time N,
u k is the operating state of the HVAC system at time k,
g(k) is a unit price for energy at time k,
y k is the indoor temperature of the building at time k,
r k is a user selected temperature at time k,
p
(
u
k
,
u
k
-
1
)
=
{
w
p
if
u
k
≠
u
k
-
1
0
if
u
k
=
u
k
-
1
,
u k is the operating state of the HVAC system at time k,
u k−1 is the operating state of the HVAC system at time k−1, and
w p is the cost of changing the operating state of the HVAC system.
15. The method of claim 10 , wherein the model for y comprises
y k = a 1 y k−1 +a 2 y k−2 +b 1 v k−1 +b 2 u k−1
where
y k is an indoor temperature of the building at time k,
y k−1 is an indoor temperature of the building at time k−1,
y k−2 is an indoor temperature of the building at time k−2,
v k−1 is an outdoor temperature at time k−1,
u k−1 is an operating state of the HVAC system at time k−1, and
a 1 , a 2 , b 1 , and b 2 are constants.
16. The method of claim 10 , wherein said step of providing predicted future outdoor temperatures comprises determining predicted future outdoor temperatures based upon weather forecast data.