DE102018222585A1 - Method and device for reducing the potential induced degradation of solar cells - Google Patents

Abstract

The invention relates to a solar module for generating electrical current, comprising a plurality of photovoltaic cells (13) which are electrically connected to one another, a photovoltaic cell (13) having two electrodes and a material between the two electrodes containing free charge carriers can be generated by an electromagnetic wave, as well as one or more adjacent components (10) on photovoltaic cells (13), characterized in that an electrical device (15, 30, 31) is present, by means of which a electrical potential difference between one side of a photovoltaic cell (13) and an adjoining component (10) is reduced. The invention also relates to a method for operating the solar module. The invention can provide a durable and powerful solar module.

Description

The invention relates to a solar module and a method for operating the solar module.

A solar module consists of a plurality of photovoltaic cells. A photovoltaic cell can convert radiation energy, in particular light, into electrical energy. A photovoltaic cell, also called a solar cell, comprises a material, for example a semiconductor material, in which free charge carriers are generated by electromagnetic radiation. Two electrodes are adjacent to the material mentioned. The material mentioned is then between the two electrodes. For example, an electric field, such as an internal electric field of a pn-type semiconductor, leads the free charge carriers generated out of the material mentioned. The electrical current thus generated can be supplied to an electrical consumer via the adjacent electrodes.

The photovoltaic cells of a solar module are electrically connected to each other, usually in series. The photovoltaic cells of a solar module can be protected, for example, by a glass cover. Alternatively or in addition, one or more other protective layers, for example made of plastic, may be present. A solar module can include an anti-reflective layer. For reasons of protection, a solar module can include a frame. The frame can be electrically grounded.

During the operation of a solar module, one side of the photovoltaic cells is at a positive potential and an opposite side of the photovoltaic cells is at a negative potential. Adjacent components such as glass, other layers or frames are at zero potential or close to zero potential. Potential differences therefore occur during operation between surfaces of photovoltaic cells and adjoining components. Such potential differences can cause ions, for example Na ⁺ ions, to migrate from the components mentioned to the solar cells and damage them. This negative effect, which is called potential-induced or voltage-related degradation, can cause large power losses.

From the WO 2015/191699 A1 It is known to arrange an electrically insulating material between the frame of a solar module and photovoltaic cells of the solar module in order to avoid potential-induced degradation.

From the US 7,554,031 B2 It is known to apply a conductive layer to a dielectric passivation layer of a solar cell in order to avoid potential-induced degradation. Since the conductive layer is to be applied on the incident side for light, the incidence of light is reduced by the conductive layer and thus also the efficiency of the solar module.

It is an object of the invention to create powerful and long-lasting solar modules.

The object is achieved by a solar module according to claim 1 and by a method according to the independent claim. Advantageous refinements result from the claims which refer back to them in each case.

To solve the problem, a solar module for generating electrical current is provided, which comprises a plurality of photovoltaic cells. Each module can comprise more than 10 photovoltaic cells, for example more than 50 photovoltaic cells.

The photovoltaic cells of a solar module are electrically connected to one another, preferably in series, so that a solar module can provide a higher voltage compared to the voltage that a single photovoltaic cell can generate.

A photovoltaic cell has two electrodes. There is a material between the two electrodes in which free charge carriers can be generated by an electromagnetic wave. The material can be crystalline, polycrystalline or amorphous silicon, for example. The material can be a III-V semiconductor, such as GaAs. The material can be a II-VI semiconductor such as CdTe. The material can be an I-III-VI semiconductor such as copper indium gallium diselenide. The material can be based on organic hydrocarbon compounds or organic dyes. The material can be doped.

The electrodes consist of an electrically conductive material, for example of metal such as copper or silver. An electrode is transparent on a light-incident side and consists, for example, of indium tin oxide, fluorine-tin oxide, aluminum-zinc oxide or antimony-tin oxide.

Components such as a glass pane or a layer made of plastic adjoin photovoltaic cells.

There is an electrical device through which an electrical potential difference between one side of a photovoltaic cell is generated during the generation of electrical current and an adjoining component is reduced. If a component borders the side of a solar cell that is at negative potential during power generation, then this adjacent component is also brought to a negative potential, for example by the electrical device, in such a way that the potential difference is reduced. If a component borders on the side of a solar cell that is at positive potential during power generation, then this adjacent component is also brought to a positive potential, for example by the electrical device, in such a way that the potential difference is reduced.

The potential equalization prevents the solar module from being damaged by potential-induced degradation. This improves the longevity of a solar module. The electrical power that has to be used for this is extremely low. Power losses caused by this are therefore negligibly small. The technical effort can be kept low.

The electrical device is preferably set up such that the required electrical power is provided by the solar module during operation. Then the solar module can be operated independently.

The adjacent component can be a glass pane. The glass pane can rest directly on electrodes of the photovoltaic cells. The glass pane can be glued with electrodes. There may be at least one intermediate layer between the electrodes and the glass pane.

In a technically simple embodiment, the electrical device comprises one or protective contacts. Each protective contact can rest on the adjacent component. Each protective contact can be glued to adjacent components. The adjacent component can be between two protective contacts. Two protective contacts of the electrical device can rest on opposite sides of the adjacent component, for example on a glass pane. The one or more protective contacts can be attached to a glass pane, for example.

One or more protective contacts of the electrical device can be frame-like, for example rectangular or square, in order to suitably reduce a potential difference without excessively hindering the incidence of an electromagnetic wave.

One or more protective contacts of the electrical device preferably adjoin the edge of the solar module in order to further suitably reduce a potential difference without excessively hindering the incidence of an electromagnetic wave. One or more protective contacts of the electrical device then run close to the edge of a solar module and generally parallel to the edge of the solar module. The distance to a frame or edge of a solar module and a protective contact of the electrical device can then be less than 5 cm, preferably less than 3 cm, particularly preferably less than 1 cm.

The one or more protective contacts can run around the solar cells when viewed from the top of the solar cells.

One or more protective contacts of the electrical device can consist of a transparent, electrically conductive material in order to further reduce power losses. One or more protective contacts of the electrical device can consist of a metal.

At least one protective contact of the electrical device is preferably connected to an electrical resistor. When the solar module is installed, this resistor is connected to ground, i.e. grounded. The electrical resistance can be connected to an electrically conductive frame of the solar module if it is intended to ground the electrically conductive frame in the installed state. A risk to people due to an electrical current through a protective contact is thus avoided.

The resistor may include a grounding means at one end, such as a means such as an electrical connector or an electrical socket, for connecting the resistor to ground through an electrical connector. But it can also be an electrical cable that can be connected with its free end, for example with a clamp connection.

The electrical resistance can be more than 1 kΩ, preferably more than 10 kΩ, particularly preferably more than 100 kΩ.

In one embodiment, the solar module comprises a frame which, in the installed state, can be grounded for protection reasons, that is to say it is then connected to ground. To this end, the frame may include means for grounding the frame. This device is, for example, an electrical plug or an electrical socket which can be connected to a ground or to the ground by means of an electrical plug connection. But it can also be an electrical cable that comes with its free end can be connected to a clamp connection.

The invention particularly relates to a plurality of solar modules that are electrically connected in series. In this case in particular, solar modules can be damaged by the degradation, which is reliably avoided by the invention with little technical effort and with little loss of power.

During operation, electromagnetic radiation, in particular light, strikes the solar module, as a result of which the solar module generates an electrical current. During the generation of the electrical current, the electrical device approaches the electrical potential of a component to the electrical potential on which an adjoining side of the photovoltaic cell is located. The adjoining side of the photovoltaic cell is in particular of negative potential, since this case is particularly problematic.

In the following, the invention is illustrated by means of exemplary embodiments and the attached one 1 to 3rd explained in more detail, without thereby restricting the invention.

• 1: Querschnitt eines geerdeten Solarmoduls nach dem Stand der Technik mit möglichen Leckströmen;
• 2: Querschnitt eines geerdeten Solarmoduls mit erfindungsgemäßen Schutzkontakten zur Reduktion der potenzialinduzierten Degradation;
• 3: Aufsicht auf ein Solarmodul mit erfindungsgemäßem Schutzkontakt.

Show it:

• 1 : Cross section of an earthed solar module according to the prior art with possible leakage currents;
• 2nd : Cross-section of an earthed solar module with protective contacts according to the invention for reducing the potential-induced degradation;
• 3rd : Supervision of a solar module with protective contact according to the invention.

1 shows a section of a lateral cross section of a solar module in the region of its frame 14 with photovoltaic cells 13 . The photovoltaic cells 13 are in an ethylene vinyl acetate layer 12th embedded. The front of the solar module is through a glass plate 10 covered. On the back is a back wall 11 upset. The frame 14 is electrically grounded.

In 1 As an example, two possible paths for leakage currents are drawn in, which can cause a potential-induced degradation. A first possible leakage path 20 can of photovoltaic cells 13 through the ethylene vinyl acetate layer 12th and through the glass plate 10 through along the top of the glass plate 10 to the frame 14 and then run to ground. A second possible leakage current path 21st can from the photovoltaic cells 13 through the ethylene vinyl acetate layer 12th along the bottom of the glass plate 10 wander and from here along the bottom of the glass plate 10 to the frame 14 and then run to ground.

2nd shows accordingly 1 also a section of a lateral cross section of a solar module in the area of the frame 14 of the solar module. The solar module includes photovoltaic cells 13 that are in an ethylene vinyl acetate layer 12th are embedded. There is a glass plate on the front 10 and a back wall on the back 11 . The frame 14 also has a ground.

In 2nd are two examples for the attachment of protective contacts according to the invention 15 shown, each with a protective contact 15 for preventing or reducing leakage current 20 , 21st out 1 is arranged. According to the invention, protective contacts 15 in the area of the frame 14 arranged, each with a protective contact line 30th , 31 connected. To the protective contacts 15 is via the protective contact lines 30th , 31 created a potential that is close to the potential of the adjacent side of the solar module and less close to the potential of the frame 14 . This can cause leakage currents 20 , 21st be avoided. There can be leakage currents 22 , 23 occur by protective contacts 15 to the frame 14 flow. Such leakage currents 22 , 23 however, they are negligibly small and harmless.

3rd shows a plan view of a solar module with a rectangular protective contact arranged according to the invention 15 on the front of a glass pane. There may also be an electrical protective contact running on the back of the glass pane. In this embodiment, the one or more protective contacts 15 arranged so that these around the photovoltaic cells 13 run around. Such protective contacts 15 can be arranged both above and below a layer of the solar module or only above or only below the layer. In particular, there is an external protective contact 15 with one in the 3rd electrical resistance not shown connected. This electrical resistance is grounded during operation of the solar cell.

The invention can damage solar cells 13 can be avoided in solar modules. To one or more protective contacts 15 a potential is created during the generation of electricity which is closer to the neighboring potential of the photovoltaic cells 13 lies as the potential of the frame 14 .

Reference list

10:

Glass plate on the front

11:

Rear wall of the solar module

12:

Ethylene vinyl acetate layer (EVA)

13:

photovoltaic cell

14:

frame

15:

Protective contact

20:

Leakage current path

21:

Leakage current path

22:

Leakage current path

23:

Leakage current path

30:

Protective contact line

31:

Protective contact line

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2015/191699 A1 [0005]
• US 7554031 B2 [0006]

Claims (10)

Solar module for generating electrical current comprising a plurality of photovoltaic cells (13) which are electrically connected to one another, a photovoltaic cell having two electrodes and a material between the two electrodes in which free charge carriers can be generated by an electromagnetic wave , and at least one component (10, 12) adjacent to photovoltaic cells (13), characterized in that an electrical device (15, 30, 31) is present, by means of which an electrical potential difference between one side of a photovoltaic cell (13) and the adjacent component (10) is reduced. Solar panel after Claim 1 , characterized in that the adjacent component is a glass pane (10). Solar module according to one of the preceding claims, characterized in that the electrical device comprises one or more protective contacts (15) in the adjacent component (10). Solar module according to the preceding claim, characterized in that one or more protective contacts (15) of the electrical device are frame-like. Solar module according to one of the two preceding claims, characterized in that one or more protective contacts (15) of the electrical device are adjacent to the edge of the solar module and / or to a frame (14) of the solar module. Solar module according to one of the three preceding claims, characterized in that one or more protective contacts (15) of the electrical device are connected to an electrical resistor. Solar module according to the preceding claim, characterized in that the electrical resistance is more than 1 kΩ, preferably more than 10 kΩ, particularly preferably more than 100 kΩ. Solar module according to one of the preceding claims, characterized in that the solar module comprises a frame (14) and a device for grounding the frame. Method for the operation of a solar module according to one of the preceding claims, characterized in that electromagnetic radiation impinges on the solar module and the solar module thereby generates an electrical current and during the generation of the electrical current the electrical device (15, 30, 31) the electrical Potential of a component approximates the electrical potential on which an adjoining side of the photovoltaic cell is located. Method according to the preceding claim, characterized in that the adjoining side of the photovoltaic cell (13) is at negative potential.

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