Static structures (e.g. – buildings) – Combined – With a sunlight activated device
Reexamination Certificate
1999-10-22
2001-11-06
Brown, Peter R. (Department: 3636)
Static structures (e.g., buildings)
Combined
With a sunlight activated device
C359S592000, C359S593000
Reexamination Certificate
active
06311437
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A MICROFICHE INVENTION
Not applicable
BACKGROUND OF THE INVENTION
Panes with Horizontal Prismatic Ribs
Panes with horizontal prismatic ribs for vertical windows which are directed to the south and which reject or transmit direct solar radiation depending on the actual solar elevation angle are known since 1980 (French patent application no. 8017364, publication no. 2463254). Adequate dimensioning of the cross-section of the rib (
FIG. 1
) causes the refraction of rays when penetrating the upper surface of the ribs and then—in case—the total internal reflection of rays at the rear surface of the pane in such a way that the direct solar radiation is rejected in summer and transmitted in winter. The basic prism angle &thgr; is determined such that the equation
sin(&eegr;
G
−&thgr;)=n·sin(&kgr;−&thgr;) (1)
with n: the refractive index of the pane material which is about 1.5 for common mon window glass and for acrylic glass,
&eegr;
G
: the chosen limiting value of the solar elevation angle &eegr;
S
at 12 o'clock local time—i.e. the solar rays impinging at an angle &eegr;
S
<&eegr;
G
are to be rejected and those impinging at an angle &eegr;
S
<&eegr;
G
are to be transmitted—and
&kgr;=arcsin(1
), the critical angle of total reflection,
holds. If the window with the prismatic pane is directed to the south, the vector of solar radiation at the local time t
v
=12 o'clock is located within the cross-sectional planes of the ribs, is perpendicular to the longitudinal axes of the ribs and the horizontal prismatic ribs are parallel to the equator plane. Therefore, the direction of the prismatic pane to the south has the consequence that the functional dependency on local time of the incident angle &ggr;
2
of the rays impinging on the rear surface of the pane—&ggr;
2
being decisive for reflection or transmission—is symmetrical to the local time t
v
=12 o'clock. For radiation which is irradiated with identical incident angles from the clear or the overcast sky this reflective property of the prismatic ribs is, of course, the same as for radiation incident from the sun. In summer time, therefore, the room temperatures remain in acceptable limits, whereas in winter time the energy of solar radiation contributes to the reduction of heating energy. However, this prismatic pane offers no clear view and is applicable for vertical windows only which are essentially directed to the south. In comparison to common glass panes this prismatic pane offers a better protection from glare of direct solar radiation at locations in the vicinity of a window, but does not achieve an improved daylighting of the deeper parts of a room.
Panes with Non-Horizontal Prismatic Ribs
A later development (European patent application no. 97113294.9-2205) describes, how panes with prismatic ribs may achieve this performance for all vertical windows with a direction between southeast by east and southwest by west. This is accomplished by prismatic ribs which are declined—depending on the deviation &Dgr;&bgr; of the window direction from the south—by a certain angle &agr; to the horizontal plane. The angle &agr; is determined by the
tan&agr;=−sin&Dgr;&bgr;/tan&lgr; (2)
with &lgr;: the geographical latitude of the application site.
For a variety of window directions the declination of the prismatic ribs relative to the horizontal plane is presented in FIG.
2
. The angle &eegr; is generally defined as the angle between the directional component of a ray within the cross-sectional plane of the rib and the intersecting straight line between the horizontal plane and the cross-sectional plane of the rib. The limiting angle &eegr;
G
between the vector of solar radiation and the intersecting straight line between the horizontal plane and the cross-sectional plane of the rib is determined for the daytime angle &bgr;
v
with the aid of the equations
&dgr;
G
=&dgr;
0
·cos(2
&pgr;·d
G
/d
J
), (3)
the limiting angle of the solar declination relative to the equator plane at the times of the year, when there is just no solar radiation to be transmitted anymore or, respectively, when there is just solar radiation to be transmitted again by the prismatic pane, with
&dgr;: the angle of solar declination relative to the equator,
&dgr;
0
=23.45°, the maximum angle of solar declination relative to the equator at the annual time of summer solstice,
d
J
=365.25 days, the period of a year,
&bgr;
v
=−arctan(tan&Dgr;&bgr;/sin&lgr;), (4)
the daytime angle at which the vector of solar radiation is within the cross-sectional planes of the ribs and is perpendicular to the longitudinal axes of the ribs, with
t: the mean local daytime,
&bgr;=&pgr;/12h·t: the daytime angle,
&eegr;
0
=−arcsin(cos&bgr;
v
·cos&lgr;cos&agr;), (5)
the angle between the vector of solar radiation and the intersecting straight line between the horizontal plane and the cross-sectional plane of the rib for the daytime angle &bgr;
v
and the solar declination angle &dgr;=0° and
&eegr;
G
=&dgr;
G
+&eegr;
0
. (6)
The basic prism angle &thgr; is calculated from the equation
tan&thgr;=(1−sin&eegr;
G
)/[(
n
2
−1)
½
−cos&eegr;
G
]. (7)
Eqn. 7 is an explicit form of eqn. 1. The maximum possible angle &eegr; between the vector of solar radiation and the intersecting straight line between the horizontal plane and the cross-sectional plane of the rib for daytime angle &bgr;
v
at the annual time of summer solstice is
&eegr;
M
=&dgr;
0
+&eegr;
0
. (8)
The angle &OHgr; of the cross-section of the ribs is determined such that
&OHgr;≧&pgr;/2−&eegr;
G
(9)
holds. If
&OHgr;≧&pgr;/2−&thgr;−arcsin[sin(&eegr;
M
−&eegr;)/
n]
is valid, which is true for great deviations of the window direction from the south and/or great solar radiation blockade periods, a saw tooth profile with specific angles is provided for the lower faces of the prismatic ribs (FIG.
3
). For a correspondingly dimensioned prismatic pane the functional dependence on daytime of the solar incident angle &ggr;
2
at the rear face of the prismatic pane which is decisive for reflection or transmission is symmetrical to the daytime t
v
, has a minimum at this daytime and the level of the angle values increases with the annual time approaching summer solstice. This functional dependence on daytime of the solar incident angle &ggr;
2
is presented for an example (&Dgr;&bgr;=45°, &dgr;
G
=11.725°, &agr;=−30.68°, &thgr;=47.87°, &bgr;
v
=127.45° or, respectively, t
v
=8:30) in FIG.
4
. It can be recognized that at the two days of the annual times with the limiting solar declination angle &dgr;
G
just no solar ray can penetrate the prismatic pane and that the solar radiation blocking effect of the prismatic pane is vanishing more and more with a decreasing solar declination angle &dgr;. As, of course, the radiation blocking effect of the prismatic pane holds for solar radiation as well as for radiation incident from the sky, the part of the sky radiation for which &ggr;
2
>&kgr; holds cannot penetrate, too. Therefore, this prismatic pane offers the protection from solar radiation and the energetic advantages of the prismatic pane described in the French patent application no. 8017364 for a wide range of window directions and, moreover, enables the individual choice of the annual solar radiation blockade time by adequate dimensioning of the prismatic ribs. However, this prismatic pane offers no clear view, too, and is applicable for vertical windows only. In comparison to common glass panes also this prismatic pane offers better protection from glare of direct solar radiation at locations in the vicinity of
Brown Peter R.
Hansen James O.
Lorenz Werner
LandOfFree
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