SWITCHABLE GLASS WINDOW WITH AUTOMATIC CONTROL OF THE TRANSMISSION
The present invention concerns a switchable glass window whose light and energy transmission are altered when voltage is applied comprising, An electrochromic (EC) glazing unit whose light transmission, TL, of light, is altered between a minimum value, TLmin, and a maximum value, TLmax, upon variation of a voltage applied to the electrochromic glazing unit, des A source of electrical power for varying the voltage applied to the electrochromic glazing unit, A sensor ( 5 s ) for measuring values of a parameter representative of the irradiance, Is, of the sun on the outer surface of the electrochromic glazing unit, A controller ( 5 c ) for controlling the voltage applied to the electrochromic glazing unit, said controller being configured for carrying out the following steps: Dividing a range comprised between a lowest boundary, Is 1 , and a highest boundary, ls(N+1), of the irradiance, Is, into N intervals, Ri=[Isi, ls(i+1)[. For a value of the irradiance, Is, comprised in an ith interval, Ri=[Isi, ls(i±1)[, of the N intervals, R 1 to RN, a voltage yielding a value, TL(Ri), of the light transmission is applied as a function of the value of i which is comprised within the range defined by Equation (1), as follows: Wherein ε is comprised between 0 and 1, Ai=1 when i=1 or N+1, and Ai is comprised between 0.8 and 1.2 for i=2 to N. TL ( Ri ) = Ai × ( TL min + ɛ ) × ( T L max T L min + ɛ N - 1 ) N - i - A i × ɛ × i - 1 N - 1 ( 1 )
1 . Switchable glass window whose light and energy transmission are altered when voltage is applied comprising,
(a) An electrochromic (EC) glazing unit comprising an outer surface and an inner surface and whose light transmission, TL, of light of wavelength comprised between 380 and 780 nm, is altered between a minimum value, TLmin, and a maximum value, TLmax, upon variation of a voltage applied to the electrochromic glazing unit,
(b) A source of electrical power for varying the voltage applied to the electrochromic glazing unit,
(c) A sensor ( 5 s ) for measuring values of a parameter representative of the irradiance, Is, of the sun on the outer surface of the electrochromic glazing unit,
(d) A controller ( 5 c ) for controlling the voltage applied to the electrochromic glazing unit, said controller being configured for carrying out the following steps:
(i) Determining values of the irradiance, Is, based on the values of the parameter measured by the sensor,
(ii) Dividing a range comprised between a lowest boundary, Is 1 , and a highest boundary, Is(N+1), of the irradiance, Is, into N intervals, Ri=[Isi, Is(i+1)], wherein the values of Is 1 , Is(N+1), and N are predefined, and wherein i=1 to N+1.
(iii) For a value of the irradiance, Is, lower than or equal to the lowest boundary, Is 1 , a voltage yielding the maximum value, TLmax, of the transmission is applied (if Is≤Is 1 ⇒TL=TLmax),
(iv) For a value of the irradiance, Is, higher than or equal to the highest boundary, Is(N+1), a voltage yielding the minimum value, TLmin, of the transmission is applied (if Is≥Is(N+1)⇒TL=TLmin),
(v) For a value of the irradiance, Is, comprised in an i th interval, Ri=[Isi, Is(i+1)], of the N intervals, R to RN, a voltage yielding a value, TL(Ri), of the light transmission is applied as a function of the value of i which is comprised within the range defined by Equation (1), as follows:
T
L
(
R
i
)
=
A
i
×
(
TL
min
+
ɛ
)
×
(
T
L
max
T
L
min
+
ɛ
N
-
1
)
N
-
i
-
A
i
×
ɛ
×
i
-
1
N
-
1
(
1
)
Wherein ε is comprised between 0 and 1, Ai=1 when i=1 or N+1, and Ai is comprised between 0.8 and 1.2 for i=2 to N.
2 . Switchable glass window according to claim 1 , wherein ε=0 for values of TLmin>1%, yielding Eq. (1a):
T
L
(
R
i
)
=
Ai
×
TL
min
×
(
T
L
max
TL
min
N
-
1
)
N
-
i
(
1
a
)
and wherein ε=1 for values of TLmin≤1% yielding Eq. (1b):
T
L
(
R
i
)
=
A
i
×
(
TL
min
+
1
)
×
(
T
L
max
TL
min
+
1
N
-
1
)
N
-
i
-
A
i
×
ɛ
×
i
-
1
N
-
1
(
1
b
)
3 . Switchable glass window according to claim 1 , wherein the values of the transmission, TL, of a glazing are as defined in Equations 1 to 3 for simple, double and triple glazing of § 5.2 of EN410 (2011).
4 . Switchable glass window according to claim 1 , wherein the range comprised between the lowest boundary, Is 1 , and the highest boundary, Is(N+1), of the irradiance, Is, is divided into N intervals, Ri=(Isi, Is(i+1)), as follows,
I
s
i
=
I
s
1
+
I
s
N
-
I
s
1
N
×
(
i
-
1
)
5 . Switchable glass window according to claim 1 , wherein the parameter measured by the sensor is the Direct Normal Irradiance (DNI), which is measured normal to a surface of the sensor.
6 . Switchable glass window according to claim 1 , wherein the controller is configured for carrying out the steps (i) to (v) for two or more switchable glass windows.
7 . Switchable glass window according to claim 5 , wherein the controller is configured for carrying out the steps (i) to (v) for two or more switchable glass windows based on the values of the parameter representative of the irradiance (Is) measured by a single sensor.
8 . Switchable glass window according to claim 6 , wherein the controller is configured for determining the values of the irradiance parameter, Is, based on the values of the parameter measured by one or more sensors ( 5 s ) as a function of specifications of each of the two or more switchable windows (LS,n, LE,n, . . . ), including a spatial position and/or an orientation of the outer surface of each of the two or more switchable windows.
9 . Switchable glass window according to claim 8 , wherein the occurrences of fixed obstacles hiding the sun from the outer surface of the electrochromic glazing unit as a function of time of day and year are entered into the controller, and wherein the determination of the values of the irradiance parameter, Is, takes said occurrences into account for determining a value of the irradiation reaching a given EC glazing unit, based on the measurement of the parameter by the one or more sensors.
10 . Switchable glass window according to claim 1 , wherein the controller is configured for determining the values of the irradiance parameter, Is, based on a set of historical values measured by one or more sensors.
11 . Switchable glass window according to claim 1 , wherein the variation of a voltage applied to the electrochromic glazing unit alters the light and energy transmission, TL, by varying the light absorption and/or the light reflection.