Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
1999-09-17
2001-11-27
Chapman, Mark (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
Reexamination Certificate
active
06323415
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a light concentrator photovoltaic module and a light concentrator photovoltaic system.
A light concentrator photovoltaic module, which includes photovoltaic elements and a light reflecting plane, has been disclosed in, for example, JP-A-60-128678 (laid open on Jul. 9, 1985).
FIG. 1A
illustrates substantially the same structure as that illustrated in this reference. A portion of a light reflecting plane
75
composed of aluminum protrudes between photovoltaic elements
74
toward a module light-receiving plane
72
. This protruding portion includes two inclined planes. A reflection light beam of a light beam
71
incoming onto an inclined plane on the right side is caused to enter the photovoltaic element
74
existing on the right side of the inclined planes. Similarly, a reflection light beam of a light beam
71
incoming onto an inclined plane on the left side is caused to enter the photovoltaic element
74
existing on the left side of the inclined planes. These operations concentrate, onto the photovoltaic elements
74
, the light beams incoming into the region where the photovoltaic elements
74
do not exist in the module.
FIG. 2
illustrates substantially the same structure as that of a light concentrator photovoltaic module disclosed in JP-A-60-116180 (laid open on Jun. 22, 1985). Pits and projections are provided in a portion between photovoltaic elements
84
of a light reflecting plane
85
composed of a metal. Incident light beams
81
undergo irregular reflection by the pits and projections, and the resultant scattered light beams are collected into the photovoltaic elements
84
. This operation concentrates, onto the photovoltaic elements
84
, the light beams incoming into the region where the photovoltaic elements
84
do not exist in the module. An example similar to this where the scattered light beams are used are disclosed also in “Sharp Technical Report”, April 1998, No. 70, pp. 69-70.
SUMMARY OF THE INVENTION
Referring to
FIG. 1B
drawn for explaining the conventional technique illustrated in
FIG. 1A
, the light beams that have entered the module light receiving plane
72
include light beams
71
-
3
,
71
-
4
,
71
-
5
incoming directly into the photovoltaic element
74
and light beams
71
-
1
,
71
-
2
incoming into the solar photovoltaic element
74
after reflection on the light reflecting plane
75
. The light beams
71
-
3
,
71
-
4
,
71
-
5
incoming directly enter all the regions (i.e., region a and region b) on the photovoltaic element
74
. Meanwhile, the light beams
71
-
1
,
71
-
2
incoming after reflection enter only the region b that is situated farther from the light reflecting plane
75
.
Accordingly, it is desirable to enhance a light collection efficiency of the entire photovoltaic element
74
that include the region a and the region b.
Here, the light collection efficiency and a concentration ratio are defined by the following formulae (1) and (2), respectively.
light collection efficiency=amount of incident light into photovoltaic element/amount of incident light into module light receiving plane (1)
concentration ratio=area of module light receiving plane/light receiving area of photovoltaic element (2)
Here, for example, solar batteries identical with each other or different solar batteries having almost equal spectral sensitivities are located at a setting position of the module light-receiving plane
72
and at a setting position of the photovoltaic element
74
. Values of short-circuit currents in these solar batteries at the time of the light irradiation may be employed as the amount of incident light in the formula (1). At this time, a light reflectance on the surface of any one of the solar batteries differs, depending on whether the surface is in contact with the air or in contact with a medium with a refractive index larger than that of the air. Thus, the substantial spectral sensitivity is varied. Consequently, at the measurement of the short-circuit currents, it is desirable to correct the variations in the spectral sensitivities of the solar batteries.
Also, concerning the light receiving area of the solar photovoltaic element in the formula (2), when the photovoltaic element is flat board-shaped, the light receiving area is assumed to be equal to the area of the flat board. When the photovoltaic element is rectangular parallelepiped, rod-shaped, or spherical, the light receiving area is assumed to be equal to the projection area of the light receiving plane thereof onto the module light-receiving plane. Consequently, in a double-sided light receiving type photovoltaic element on the front and the back of which light receiving planes with an equal area are formed, the light receiving area thereof does not become equal to a summation of the areas of the front and the back light receiving planes but becomes equal to one-half of the summation.
Incidentally, in
FIG. 1B
, in order for the light beams reflected by the light reflecting plane
75
to undergo total internal reflection on the module light-receiving plane
72
and then to enter the photovoltaic element
74
, the following condition will have to be met: Making large enough an angle &thgr;3, i.e. an angle which a plane
78
parallel to the module light receiving plane
72
forms with the inclined plane of the light reflecting plane
75
, so that incident angles onto the module light receiving plane
72
of the light beams reflected on the inclined plane will become equal to the critical angle (&thgr;5) or larger. A refractive index of a glass or a transparent plastic commonly used as a medium
73
is about 1.5, and accordingly the critical angle is about 42°.
In the conventional technique illustrated in
FIG. 2
, since the incident light beams undergo the irregular reflection on the light reflecting plane
85
, reflection angles of the scattered light beams
81
are not fixed and equal. Accordingly, light beams which, out of the scattered light beams
81
, enter a module light receiving plane
82
include light beams the incident angles of which are smaller than the critical angle. These light beams, in some cases, undergo no total internal reflection on the module light receiving plane
82
, then passing through into the outside of the module light receiving plane
82
. This phenomenon prevents enhancement of the light collection efficiency.
In this way, in the conventional technique illustrated in
FIG. 2
, it is intended to collect, into the photovoltaic elements
84
, the incident light beams
81
incoming into the portion between the photovoltaic elements
84
with an intention of simply not wasting the incident light beams. No consideration, however, has been given to enhancement of the light collection efficiency. No consideration has been given to the concentration ratio, either.
It is an object of the present invention to provide a light concentrator photovoltaic module, in which a light receiving area of a photovoltaic element is comparatively small and which is capable of enhancing a light collection efficiency and/or a light concentration ratio, and a method of manufacturing the module, and a light concentrator photovoltaic system.
According to one aspect of the present invention, the light concentrator photovoltaic module includes
a flat module light receiving plane upon which sunlight is incident, a plurality photovoltaic elements, a light reflecting member, and a medium for transmitting the sunlight to the photovoltaic elements and the light reflecting member,
wherein the module light receiving plane is formed by a surface of the medium upon which the sunlight is incident, and the medium and the light reflecting member are joined with each other so that their interface forms a light reflecting plane;
wherein, with the module light receiving plane and the photovoltaic elements being located at a relatively upper level and at a relatively lower level, respectively, the light reflecting plane includes, between adjacent two photovoltaic elements, at
Minemura Junko
Miyamura Yoshinori
Muramatsu Shin-ichi
Ohtsuka Hiroyuki
Tsutsui Ken
Antonelli Terry Stout & Kraus LLP
Chapman Mark
Hitachi , Ltd.
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