Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
1999-11-30
2001-12-18
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S251000, C136S255000, C136S259000, C136S261000, C136S293000, C136S291000, C060S641800, C323S906000, C323S221000
Reexamination Certificate
active
06331670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solar cell module comprising a plurality of photovoltaic elements (or solar cells) having an overvoltage preventive element and a sunlight power generation system using said solar cell module.
2. Related Background Art
A solar cell has such a property that because of its characteristics, the voltage is varied depending on a given load factor. For instance, the open-circuit voltage of a solar cell in a non-loaded state is always greater than the optimum operating voltage at which the output of the solar cell becomes maximum. In order for a solar cell to be efficiently used as a power generation device, the purpose can be achieved by actuating the solar cell at an optimum operating point (that is, by imparting an optimum load resistance to the solar cell). However, in the case where the load is lightened (that is, the load resistance value is enlarged), the voltage of the direct current circuit of the solar cell is increased, where when the solar cell is in a stopped state, the voltage is increased up to aforesaid open-circuit voltage. In this connection, for a power converter or the like to be connected to the direct current circuit of the solar cell, it is necessary to withstand against said voltage.
Incidentally, in the case of an ordinary amorphous silicon (a-Si) solar cell whose semiconductor layer comprises an a-Si material, it is known that the fill factor (F.F.) of the a-Si solar cell is inferior to that of a single crystal silicon solar cell whose semiconductor layer comprises a single crystal silicon material, and when the optimum operating voltage at which the output of the a-Si solar cell becomes maximum is the same as that at which the output of the single crystal silicon solar cell becomes maximum, the open-circuit voltage of the a-Si solar cell is greater than that of the single crystal silicon solar cell, and wherein when the open-circuit voltage is excessively large, overvoltage is generated.
In this connection, in the case of a sunlight power generation system in which such a-Si solar cell is used, an electric device such as a power converter or the like used therein is necessary to withstand against an increased voltage.
As a measure to comply with overvoltage which is generated when the open-circuit voltage is large as above described, an overvoltage preventive means is described in Japanese Patent No. 2580185 (issued Nov. 21, 1996)[hereinafter referred to as document 1].
Description will be made of the overvoltage preventive means described in document 1 with reference to FIG.
1
. In
FIG. 1
, reference numeral
101
indicates a solar cell panel, reference numeral
102
a reverse current preventive diode, reference numeral
103
a voltage limit element, reference numeral
104
a constant-voltage D.C. power source, reference numeral
105
a compressor driving-motor, reference numeral
106
an inverter power module, and reference numeral
107
an inverter air-conditioner.
As shown in
FIG. 1
, to a serialized body (that is, a solar cell array) comprising the solar cell panel
101
and the reverse current preventive diode
102
, the voltage limit element
103
is connected in parallel connection, and the paralleled circuit is connected to the compressor driving-motor
105
as a load. In the case where the quantity of solar radiation is large and the load is small, by making a dump power caused in the solar cell panel
101
to be consumed in the voltage limit element
103
, occurrence of overvoltage is prevented.
Besides, another overvoltage preventive means is described in Japanese Patent Publication No. 89302/1995 (hereinafter referred to as document 2). Description will be made of the overvoltage preventive means described in document 2 with reference to FIG.
2
. In
FIG. 2
, reference numeral
201
indicates a solar cell, reference numeral
202
an inverter, reference numeral
203
a control circuit, reference numeral
204
a short-circuiting switch, reference numeral
205
a voltage-dividing circuit, and reference numeral
206
an induction motor.
As shown in
FIG. 2
, a plurality of solar cells
201
are electrically serialized into a solar cell array, where the switch
204
for short-circuiting part of the solar cell array (the serialized solar cells) and the control circuit
203
for controlling the opening and closing of the switch
204
are provided. In the case where the generated voltage of the solar cell array becomes excessive, the control circuit
203
is actuated to close the switch
204
thereby to short-circuit part of the solar cell array, whereby overvoltage is prevented from occurring.
However, for these overvoltage preventive means, there are problems as will be described below.
In the case described in document 1, because the voltage limit element
103
is connected to the solar cell array (the serialized body) in parallel connection, the dump power caused in the solar cell array is entirely consumed in the voltage limit element. In this connection, there are such problems as will be described in the following. That is, the more the output of the solar cell array is increased, the more the power consumed in the voltage limit element is increased, where, for instance, when the output of the solar cell array becomes some hundreds wattage (W) or more, the power consumed in the voltage limit element is markedly increased and as a result, the voltage limit switch is extremely heated. Therefore, it is necessary to establish a large space for radiating heat from the voltage limit switch to cool the voltage limit switch.
In the case described in document 2, there are problems such that in order to short-circuit part of the solar cell array, extra short-circuiting wires which are extending from a prescribed position of the solar cell array, the specialized switch for the short-circuiting, the specialized control circuit for controlling the opening and closing of the short-circuiting switch, and the specialized power source for driving the control circuit are necessitated, and because of this, the system involved is unavoidably complicated.
SUMMARY OF THE INVENTION
The present invention is aimed at solving the problems found in the prior art and providing an improved solar cell module free of such problem.
Another object of the present invention is to provide a solar cell module comprising a plurality of photovoltaic elements (solar cells) electrically connected with each other, wherein each of said plurality of photovoltaic elements is provided with an overvoltage preventive element electrically connected thereto in parallel connection, and said overvoltage preventive element comprises an element which exhibits one-way continuity and has a minimum operating voltage (hereinafter referred to as “Vmin”) which is smaller than an open-circuit voltage (hereinafter referred to as “Voc”) of said photovoltaic element but is greater that an optimum operating voltage (hereinafter referred to as “Vpm”) of the photovoltaic element.
A further object of the present invention is to provide a sunlight power generation system comprising aforesaid solar cell module and a system interconnection inverter for reverse-flowing a D.C. output from the solar cell module into an alternating-current circuit.
A further object of the present invention is to provide a sunlight power generation system comprising aforesaid solar cell module and a system in which a D.C. power outputted from the solar cell module and a D.C. power obtained from the commercial alternating-current circuit by way of rectification are connected in parallel to supply into a load.
According to the present invention, it is not necessary to externally add a specialized overvoltage-preventing apparatus to a solar cell module, where it is not necessary to establish a particular place for such overvoltage-preventing apparatus to be arranged and therefore, the flexibility for the installation of the solar cell module is improved. In addition, in the present invention, the overvoltage preventive element is provide
Manabe Naoki
Takehara Nobuyoshi
Canon Kabushiki Kaisha
Diamond Alan
Fitzpatrick ,Cella, Harper & Scinto
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