DE202009018167U1 - photovoltaic module - Google Patents

Abstract

Photovoltaic module (1) with a number of solar cells (4) and with a solar glass pane (8), characterized by a lichteinstrahlseitig arranged functional layer (2), which is interchangeable between a substantially transmissive to solar radiation state and eifern impermeable state.

Description

The invention relates to a photovoltaic module with a number of solar cells and with a solar glass pane. The invention further relates to a method for operating such a photovoltaic module.

A solar cell works on the principle of the photovoltaic effect and converts light directly into electrical energy. In a solar cell, free charge carriers are generated by light irradiation. An internal electric field, which is formed by a p-n junction in the solar cell, causes a steering of the charge carriers between an n-doped layer and a p-doped layer. The electric field accelerates electrons to the p-type material and holes to the n-type material. During the movement, some of the charge carriers recombine, producing heat. The remaining charge carriers generate a photocurrent.

A photovoltaic module (PV module) with solar cells arranged therein is part of a photovoltaic system (PV system). The photovoltaic module has a carrier plate, which may be foamed or molded or molded from a layer of elastomeric plastic. Instead of or in addition to the support plate, the photovoltaic module with a weather-resistant plastic composite film, for example, polyvinyl fluoride or PET, be laminated. Lichteinstrahlseitig the photovoltaic module with a transparent substrate, z. B. a solar glass cover.

The solar cells are arranged on the carrier plate and embedded in a transparent plastic layer, for example of EVA (ethylene vinyl acetate). The solar cells are enclosed by a holding frame between the solar glass cover and the carrier plate and laterally along the outer edges of the photovoltaic module. The support frame may for example consist of aluminum or also of an elastomeric plastic. Between the frame and the support plate and between the frame and the solar glass cover a sealing material is introduced. The solar cells are closed by this environmental protection.

Furthermore, the solar cells are interconnected within the photovoltaic module. By interconnecting the individual solar cells, a voltage range and current range characteristic of the photovoltaic module is generated at a connection point of the photovoltaic module under solar irradiation.

Individual photovoltaic modules are usually connected to so-called strings, to which an inverter is typically connected via DC voltage lines. The inverter converts the direct current generated in the photovoltaic module into alternating current and feeds it into the public power grid. Depending on the application, it is also the practice to connect strings in an island system to an energy storage system with batteries or directly to machines, such as pumps.

In Photovoltaikanlangen both a DC side between the photovoltaic module and the inverter and the AC side between the public grid and the inverter, a circuit breaker is installed. By using the circuit breaker, for example, maintenance or installation work on the inverter can be performed without voltage and without flowing current.

The problem, however, is that in solar radiation to a photovoltaic module is generally applied a voltage and possibly a current flows. Defective components of the photovoltaic system, such as cable lines, connectors or junction boxes, can cause dangerous arcs and voltages of several hundred volts. Arc flashes can cause a fire and make firefighting work harder. Conversely, a fire can change individual components of the photovoltaic system in their function and structure in such a way that arcing faults occur. High voltages on defective parts of the photovoltaic system are a potential hazard during assembly, repair and extinguishing work.

Various protective measures against unwanted voltages and arc faults are provided in the prior art. If necessary, the safety device prevents, in particular, that arcing arcs occur on the photovoltaic module side and voltages are present.

From the DE 10 2005 018 173 B4 it is known to short-circuit the photovoltaic module if necessary. The short-circuiting takes place by means of a thyristor which operates in the passband until the photovoltaic module, z. B. at nightfall, tension is free. In this case, the thyristor is ignited via an additionally laid two-wire control line from a control switch.

In the WO 2009/073868 is proposed a solution in which outputs of the photovoltaic module by means of a 100 Hz PWM signal (pulse width modulation) are enabled. A microcontroller at the output of the photovoltaic module constantly checks whether the 100 Hz signal is present and switches off the output as soon as the signal fails. This method has the advantage that no further Lines are needed because the information signal can be transmitted via the DC voltage lines.

In general, a measure is always provided in the prior art, in which at a point between the (public) power grid and a photovoltaic module of the solar system, the electrical connection is disconnected or the photovoltaic module is short-circuited. In the case of those solutions in which electrical connections are disconnected, a voltage is still applied from a point or at a point in the photovoltaic system and / or a current flows when light is incident on the photovoltaic module. In the solution in which each photovoltaic module is short-circuited, so far a danger point is given as permanently a short-circuit current in the amount of about 1.4 times the nominal module current flows.

The invention has for its object to provide the safest and most reliable protection for photovoltaic systems, so that dangers and destruction due to applied voltages and arcing arcs are avoided.

This object is achieved by the features of claim 1. Accordingly, a photovoltaic module is provided with a number of solar cells and with a lichteinstrahlseitigen functional layer. In this case, the light-beam-side functional layer can be exchanged between a substantially transparent state for solar radiation and an impermeable state. The solar cells arranged in the photovoltaic module can be isolated from the solar irradiation by changing the functional layer into an opaque state. By foreclosure photovoltaic module side, a current flow and an applied voltage can be avoided.

The light transmission of a functional layer is dependent on the transmission, reflection, absorption and Streuanteilsbeiwert the functional layer against einstrahlendem light. There are various technologies available for modifying the coefficients. It is particularly advantageous to modify the light transmission with an electrochromic functional layer. Under the influence of an external electric field as a result of the external voltage, a potential difference arises due to charge displacements, which in turn leads to an electric current. In a cathodic reduction, injected cations and in anodic oxidation anions cause coloration and change of light transmission in two complementary electrochromic layers. The dyeing process is reversible, in that the ions are transported back into the ion-conducting layer by means of a voltage or an electric field.

The use of electrochromism is particularly advantageous, since even with low voltages, an ion transfer and concomitantly a change in the light transmission can be achieved. It is also advantageous that, without the voltage or electric field applied, the light transmission state in the electrochromic layer remains due to storage properties of the functional layer.

Photochromism is based on a reversible photochemical reaction of silver halides or organic compounds. The reaction products have a changed absorption behavior. The thermochromism is based on reversible temperature-dependent changes in the optical properties of a functional material, wherein the effective temperature range can be adjusted by doping the functional material. By electrical induction, orientation changes can be effected in liquid crystal systems. The crystals change between a light-scattering and transparent state.

In a particularly advantageous embodiment of the photovoltaic module, the functional layer is subsequently applied to the or each solar cell, if necessary with the interposition of a transparent insulating layer, for example a film or a lacquer layer. In this case, an ion-conducting layer is arranged between the two mutually complementary electrochromic layers. Further, a transparent electrode layer covers the opposite side of the electrochromic layers from the ion-conductive layer.

The application of the functional layer and the transparent electrode layers can take place in an in-line process. The layers can be coated directly during solar cell production or after application to the carrier plate. This particularly efficient production can save costs and avoid later complex assembly work. Furthermore, by reducing the components to be installed further cost savings can be achieved.

According to a variant, the functional layer of the photovoltaic module is arranged between two solar glass panes.

The change in the light transmission of the functional layer is suitably controlled by a modular control device associated with the functional layer. Furthermore, the controller can be assigned an energy store. This advantageous modular design allows easy replacement or retrofitting of components in case of need and an assignment of individual control modules to individual or groups of functional layers. The energy storage can also when Failure of the power supply, the control unit or the control module continue to provide power and thus allows a particularly reliable control of the functional layer.

By integrating the functional layer into an already required cover made of solar glass for the photovoltaic module, production costs can be kept low by reducing components. The coating of the solar glass can be done in an inline process on float glass. Furthermore, as required, a photovoltaic module can be equipped with conventional solar glass or with a solar glass provided with the functional layer. Another advantage of the variant with two solar glass panes is a particularly reliable protection of the functional layer from environmental influences.

In an expedient development of the photovoltaic module, a release signal is generated. If the release signal fails, the functional layer is converted into a light-impermeable ground state. In this case, the control of the functional layer can be carried out by a central control unit or by the control unit. A particular advantage of this variant is that a maximum of security is given, since in case of failure of a component or in case of a defect of a cable line, which causes the failure of the release signal, an automatic shutdown of the system takes place.

Embodiments of the invention will be explained in more detail with reference to a drawing. Show:

1 and 2 a schematic sectional view of a photovoltaic module with a functional layer in a translucent or in an opaque state,

3 Diagram representation of the transparency, the current and the voltage in different light transmission states and with a change between the light transmission states,

4 Diagram representation of the percent transparency of solar glass and electrochromic glass in translucent and opaque state in a spectral region of the light,

5 in a schematic sectional view of a photovoltaic module, in which the electrochromic functional layer is disposed on the solar cells, and

6 schematically a photovoltaic system with a number of individually controllable strings.

The 1 schematically shows a cross section through a photovoltaic module (solar module) 1 with a functional layer 2 in the translucent state. Here are on a support plate 3 a number of solar cells 4 arranged and in a transparent plastic layer 5 For example, from ethylene vinyl acetate (EVA), embedded. To the embedded solar cells 4 includes an electrochromic arrangement, which is one of the solar cells 4 facing first solar glass pane 6 and the functional layer 2 and on both sides of the functional layer 2 provided transparent electrode layers (driving electrode layer) 7 and a second solar glass pane 8th on the sun or Lichteinstrahlseite includes. The transparent drive electrode layer 7 For example, it is indium tin oxide (ITO).

The functional layer 2 is on the first solar glass pane 6 facing electrode layer 7 arranged and comprises a first electrochromic layer 9 For example, nickel (II) oxide (NiO), to which an ion-conducting polymer layer 10 followed. The functional layer 2 closes with a second electrochromic layer 11 , for example of tungsten (VI) oxide (WO ₃ ), on the Einstrahlseite of the arrow (incident light beam) 12 symbolized sunlight. On the second electrochromic layer 11 is the light-beam-side drive electrode layer 7 applied. On the side is the photovoltaic module 1 from an aluminum frame 13 enclosed.

Schematically this is the photovoltaic module 1 incident sunlight (incident light beam) 12 of which a small portion as a reflected light beam 14 lichteinstrahlseitig from the electrochromic arrangement of the photovoltaic module 1 exit. Much of the incident light beam 12 radiates the electrochromic arrangement and strikes the solar cell 4 , Another, not shown here portion of the incident light beam 12 is absorbed or scattered. The functional layer 2 is permeable to light or sunlight in this state.

The 2 shows the photovoltaic module 1 in a light or sunlight impermeable ground state. The two complementary electrochromic layers are 9 . 11 the functional layer 2 previously by applying a voltage to the electrode layers 7 has been placed in an opaque state. Much of the incident light beam 12 is doing as a reflection light beam 14 thrown back and enters the Lichteinstrahlseite from the photovoltaic module 1 out. Only a small portion of the incident light beam 12 penetrates the electrochromic arrangement with the solar glass panes 6 . 8th and the functional layer 2 and the transparent electrode layers 7 ,

3 shows one above the other three diagrams with the transparency τ, the current I and the voltage U as functions of time t in a change between the opacity state and the light transmittance state of the functional layer 2 , At an initial time t ₀ is the functional layer 2 essentially translucent. In a first interval j ₁ , a voltage U of (+) 1 V is applied to the electrode layers 7 created. In this case, a current I flows, in which cations and anions between the electrochromic layers 9 . 11 and the ion-conducting layer 10 be transferred and thereby changing the light transmission in the functional layer 2 cause. With the achievement of the then opaque state, the current I decreases under constant voltage U.

In a following second interval j ₂ no voltage is applied and no current flows. This leaves the functional layer 2 in the opaque state. In a following third interval j ₃ is a voltage U of -1 V between the electrode layers 7 created. The result is a current I, in which anions and cations opposite to the direction of the first interval j ₁ in the functional layer 2 hike. This increases the light transmission of the functional layer 2 , At constant voltage U between the electrode layers 7 and increasing transparency τ of the functional layer 2 the current falls off. In a following fourth interval f ₄ are the electrode layers 7 de-energized and no current flows while the functional layer 2 remains in the translucent state. A following fifth interval j ₅ is identical to the first interval j ₁ .

4 shows a graph of the light transmission properties, ie the transparency τ of solar glass and of the electrochromic arrangement with the solar glass panes 6 . 8th and the functional layer 2 and the transparent electrode layers 7 in the translucent and in the opaque state as a function of the wavelength λ for a spectral range. The solar glass characteristic 15 shows that the transparency τ of solar glass in a wavelength range λ of 400 nm to 2200 nm is about 90%.

The transparency characteristic 16 for the electrochromic device 2, 6, 7, 8 in the light-transmitting state shows a strongly increasing transparency τ up to a wavelength λ of 500 nm, in which a transparency τ of about 80% is achieved. This transparency τ remains up to a wavelength λ of 2100 nm. in the wavelength range λ over 2100 nm, the transparency τ drops steeply. The transparency characteristic 17 for the electrochromic arrangement 2, 6, 7, 8 in the opaque state substantially describes the course of a Planck radiation distribution curve, wherein a peak transparency 18 of τ of 30% at a wavelength λ of 520 nm is achieved. At a wavelength λ of 750 nm, the transparency τ is about 5%.

5 shows a schematic representation of a cross section through the photovoltaic module 1 in an alternative embodiment. Here are on the carrier plate 3 turn into a plastic layer (EVA) 5 embedded solar cells 4 arranged. Immediately after that into the plastic layer 5 embedded solar cells 4 is the transparent drive electrode layer 7 made of indium tin oxide. Below directly, an arrangement is understood in which between the solar cells 4 and the electrode layer 7 a thin transparent insulating layer, for example a lacquer layer is introduced, in order to short-circuit the connections of the solar cells 4 to avoid each other.

On the drive electrode layer 7 is in turn the functional layer 2 with the first electrochromic layer 9 made of nickel (II) oxide (NiO), to which the ion-conducting polymer layer 10 followed. The functional layer 2 closes again on the solar irradiation side with the second electrochromic layer 11 from tungsten (VI) oxide (WO ₃ ). On the second electrochromic layer 11 is the transparent second drive electrode layer 7 applied. The photovoltaic module 1 closes lichteinstrahlseitig turn with a solar glass 8th from. Laterally, the photovoltaic module 1 from the aluminum frame 13 enclosed with the support plate 3 and the solar glass pane 8th connected and sealed with a sealing material. The in photovoltaic module 1 arranged functional layer 2 and the solar cells 4 are protected by the seal against environmental influences, especially from moisture.

6 shows a schematic representation of a photovoltaic system 19 with a number of photovoltaic modules 1 that with bypass diodes 20 provided and interconnected to a plurality of strings S _n . The strings S _n are connected to a common inverter 21 connected, that of the photovoltaic modules 1 produced direct current into alternating current and this into a (public) power grid 22 feeds.

Each photovoltaic module 1 is a functional layer 2 assigned. The functional layers 2 of each string S _n are from one or more controllers or control modules 23 controlled and placed in a desired light transmission state. The control modules 23 are each connected to an energy store 24 connected. A central control unit 25 constantly sends an enable signal F to the control modules 23 , In case of failure of the enable signal F by switching off or a defect transfer the modular control units 23 automatically the functional layer 2 from translucent state in the opaque ground state.

Also, each control device or control module 23 independently certain signals or parameters, such. B. the phase current I _n and the phase voltage U _n monitor and in case of failure, the functional layer 2 from the translucent state to the opaque state. The controllers 23 In addition, a corresponding error message can be sent to the central control unit 25 send.

In the opaque state are those in the photovoltaic module 1 arranged solar cells 4 isolated from solar radiation. By the partitioning of the solar cells 4 from solar radiation are the photovoltaic modules 1 current and voltage-free. As a result, the generation of a module-side voltage or an arc fault is safely avoided.

LIST OF REFERENCE NUMBERS

1

Photovoltaikmodu

2

functional layer

3

support plate

4

solar cell

5

Plastic layer (EVA)

6

Solar glass / disk

7

electrode layer

8th

Solar glass / disk

9

first electrochromic layer

10

ion-conducting layer

11

second electrochromic layer

12

Incident light beam

13

aluminum frame

14

reflected ray

15

Solar glass characteristic

16

Transparency characteristic

17

Transparency characteristic

18

tip transparency

19

photovoltaic system

20

bypass diode

21

inverter

22

power grid

23

control unit

24

energy storage

25

Central control unit

F

enable signal

I

electricity

I _n

phase current

S _n

string

U

tension

U _n

phase voltage

j _n

interval

t ₀

Start time

τ

Transpatenz

λ

wavelength

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 102005018173 B4 [0010]
• WO 2009/073868 [0011]

Claims (11)

Photovoltaic module ( 1 ) with a number of solar cells ( 4 ) and with a solar glass pane ( 8th ), characterized by a lichteinstrahlseitig arranged functional layer ( 2 ), which is interchangeable between a substantially permeable to solar radiation condition and eifern impermeable state. Photovoltaic module ( 1 ) according to claim 1, characterized in that the functional layer ( 2 ) a first electrochromic layer ( 9 ), an ion-conducting layer ( 10 ) and one to the first electrochromic layer ( 9 ) complementary second electrochromic layer ( 11 ). Photovoltaic module ( 1 ) according to claim 1 or 2, characterized in that each electrochromic layer ( 9 . 11 ) of a transparent electrode layer ( 7 ) is covered. Photovoltaic module ( 1 ) according to claim 1 to 3, characterized in that the functional layer ( 2 ) on the or each solar cell ( 4 ) is arranged. Photovoltaic module ( 1 ) according to claim 1 to 3, characterized in that the functional layer ( 2 ) between two solar glass panes ( 6 . 8th ) is arranged. Photovoltaic module ( 1 ) according to claim 1 to 5, characterized by a control device ( 23 ) for controlling the functional layer ( 2 ). Photovoltaic module ( 1 ) according to claim 6, characterized in that the control unit ( 23 ) an energy store ( 24 ) assigned. Photovoltaic module ( 1 ) according to claim 6 or 7, characterized by a central control device ( 25 ) for controlling the functional layer ( 2 ) and / or the control unit ( 23 ). Photovoltaic module ( 1 ) according to claim 1 to 8, characterized in that the functional layer ( 2 ) is impermeable to light in a ground state. Photovoltaic module ( 1 ) according to any one of claims 1 to 9, characterized by an enable signal (F) whose failure the transfer of the functional layer ( 2 ) in the impermeable state causes. Use of an electrochromic functional layer ( 2 ) for a photovoltaic module ( 1 ).

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