Solar module

A solar module comprising a sheet; a plurality of solar cells electrically connected in series between first and second conductor lines, and arranged on a first side of the sheet, wherein the first and second conductor lines each extend along a length on the sheet; a first conductor lead in electrical connection with the first conductor line and a second conductor lead in electrical connection with the second conductor line; and a through-hole in the sheet through which the first conductor lead extends to a second side of the sheet and a further through-hole through which the second conductor lead extends to the second side of the sheet.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is the US national stage of International Application PCT/EP2009/052813 filed on Mar. 11, 2009 which, in turn, claims priority to European application EP08102493.7, filed on Mar. 11, 2008.

The present invention relates to a solar module.

A solar module typically contains a plurality of solar cells connected in series, since each cell only produces a limited voltage that is lower than required as output voltage from the module. The output voltage that is generated between the first and last solar cell, and is typically withdrawn by means of conductor lines, such as in the form of metal ribbons, which are also referred to as bus bars. The conductor lines are arranged on one side of a sheet, such as a glass plate, and the electrical current needs to be guided from the conductor lines to one or two connection boxes, also referred to as junction boxes, to which an electrical load can be connected.

Even in designs with a single series connection per module, guiding leads laterally out of a laminate structure, such as e.g. with so-called edge connectors, is not ideal as it can impair the electrical performance and long-term stability of the module.

U.S. Pat. No. 5,578,502 discloses a solar module of superstrate type. Cells are connected in series, of which the first and last are each fitted with a bus bar. In the superstrate design, the substrate forms the light-receiving side of the solar module. A back cover is provided, and a junction box is arranged over a hole in the back cover, through which hole leads from both bus bars may extend, which leads can be connected to contacts of the junction box.

Other solar modules of superstrate design are disclosed in EP 1 041 647 A1 and EP 1 220 329 A2.

In connecting the connector box to the conductor lines, several technical requirements have to be met and taken into account. One such requirement is sufficient insulation between current-conducting parts of the module and its frame or the surroundings, both under dry and wet conditions, e.g. as put down in standard IEC 61646. An issue in meeting this requirement is the ingress of moisture at the edges of the module, which can potentially lead to increased conductivity, leak currents and sparkovers. Another requirement is a sufficiently high maximum back current with which the module can be operated without damage in forward direction, with regard to the diode characteristic of the solar cells. This is for example a subject of standards DIN EN 50380 and IEC 61730. The maximum back-current can be highest there, where the conductor lines are led to the rear side of the sheet. On the other hand, it is desired to keep the cross-section of conductor lines minimum, because thick conductor lines result in a more difficult and expensive encapsulation, and wide conductor lines result in a decrease of active photovoltaic area of the module. Meeting these requirements in modules of substrate type is of particular interest. In superstrate-type modules there is generally more flexibility in arranging the electrical connections at the back side after arranging the solar cells.

It is an object of the present invention to provide an improved solar module, in particular of the substrate type.

In accordance with the invention there is provided a solar module comprisinga substrate, forming or being part of a sheet;a plurality of solar cells electrically connected in series between first and second conductor lines, and arranged on a first side of the sheet, wherein the first and second conductor lines each extend along a length on the sheet;a first conductor lead in electrical connection with the first conductor line and a second conductor lead in electrical connection with the second conductor line; anda through-hole in the sheet through which the first conductor lead extends to a second side of the sheet and a further through-hole in the sheet through which the second conductor lead extends to the second side of the sheet.

The sheet will hereafter also be referred to as a connection sheet.

The first and second conductor lines extending on the sheet and are spaced apart from each other. The spacing between the first and second conductor lines is the minimum spacing that can be measured between them along their length. The invention allows to maximise the active photovoltaic area on a module, without needing to compromise on other technical requirements such as sufficient insulation and maximum back current

In one embodiment the first and second conductor lines are spaced apart from each other by a spacing; and the solar module further comprisesa connection box with a first connector in electrical connection with the first conductor line and a second connector in electrical connection with the second conductor line,

wherein at least one of the first and second connectors is in electrical connection with the respective conductor line by the respective conductor lead extending through the sheet, and which conductor lead extends along the second side of the sheet for a distance of at least 25% of the spacing.

In an aspect of this embodiment, the invention provides an improved interconnection between the conductor lines and a single connection box. By guiding the conductor lead (or both conductor leads) along the second side of the connection sheet, which will typically be the rear side of the solar module opposite its light-facing side, the active area of the module is maximised, while a convenient single connection box is provided.

In a particular class of embodiments, a contact point between at least one of the conductor leads and the respective conductor line is located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof. By arranging the contact point away from an end portion of the conductor line, ohmic losses in the conductor line are minimized, because the average length for the current to travel along the conductor line is shortened. This allows lowering the cross-sectional area of the conductor line, such as decreasing the thickness and/or width, with advantages for encapsulation and/or active surface. In particular, contact points between both the first conductor line and the first conductor lead, and the second conductor line and the second conductor lead, can be located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof.

Accordingly, this aspect of the invention is actually also achieved in any solar module comprisinga sheet;a plurality of solar cells electrically connected in series between first and second conductor lines, and arranged on a first side of the sheet, wherein the first and second conductor lines each extend along a length on the connection sheet and are spaced apart from each other by a minimum spacing; anda connection box with a first connector in electrical connection with the first conductor line and a second connector in electrical connection with the second conductor line, for connecting an electrical load to the first and second conductor lines,

wherein at least one of the first and second connectors is in electrical connection with the respective conductor line by a conductor lead, and wherein a contact point between the conductor lead and the respective conductor line is located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof.

A solar module comprisinga sheet;a plurality of solar cells electrically connected in series between first and second conductor lines, and arranged on a first side of the sheet, wherein the first and second conductor lines each extend along a length on the sheet; anda connection box with a connector in electrical connection with one of the first and second conductor lines,

wherein the connector is in electrical connection with the respective conductor line by a conductor lead, and wherein a contact point between the conductor lead and the respective conductor line is located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof.

Suitably the connection box is arranged at a second side of the sheet opposite the first side where connection lines are arranged, which second side will typically be the rear side of the solar module opposite its light-facing side.

The connection box with a connector in electrical connection with one of the first and second conductor lines serves for connecting an electrical load to the respective conductor line. In particular the first and second contacts serve for connecting an electrical load to the first and second conductor lines. Several solar modules are often connected in series by their contacts to form a module array, and in that case the load is a load of the module array.

In one embodiment a single connection box is provided. Instead of a single connection box, also two connection boxes can be employed without departing from the invention. Then, the two connection boxes suitably are a first connection box with a first connector in electrical connection with the first conductor line and a second connection box with a second connector in electrical connection with the second conductor line, for connecting an electrical load to the first and second conductor lines. The electrical load can be connected to both contacts of both connection boxes.

In one embodiment the connection box has two connectors, a first connector in electrical connection with the first conductor line and a second connector in electrical connection with the second conductor line. An electrical load can be connected to the first and second conductor lines. Moreover in this embodiment each of the connectors is in electrical connection with the respective conductor line by a conductor lead, and wherein a contact point between the conductor lead and the respective conductor line is located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof.

In one embodiment, the first and second conductor lines are substantially parallel, such as along the long sides of a rectangular module. Suitably further at least one connection box or the connection box is arranged substantially at a position along a virtual middle line between the first and second conductor lines.

Also, the first and second conductor leads can extend through the connection sheet at positions that substantially lie on a virtual perpendicular line crossing the first and second conductor lines, and wherein the connection box is substantially arranged along that virtual perpendicular line. In this case the length of the conductor leads along the rear side to a single connection box can be minimized.

In one embodiment the connection box can be arranged near an end portion of at least one of the first and second conductor lines.

In one embodiment, at least one of the conductor leads and at least one of the conductor lines are integrally formed, i.e. integrated, rather than interconnected, so they can both form part of the same lead. The conductor line, such as in the form of a metal ribbon, can be provided with sufficient length so that it extends through the connection sheet as conductor lead to the connection box. This obviates the need for interconnecting the conductor line with the conductor lead, in particular in the area of a through-hole in the connection sheet.

In one embodiment, one or both connectors are a terminal of the connection box.

In another embodiment, one or both connectors comprise a connection lead extending from the connection box. The connection leads and the respective conductor leads can be integrally formed, i.e. they can both form part of the same lead.

A particular embodiment is as follows.

A solar module comprising

a connection sheet;a plurality of solar cells electrically connected in series between first and second conductor lines, and arranged on a first side of the connection sheet, wherein the first and second conductor lines each extend along a length on the connection sheet and are spaced apart from each other by a minimum spacing; anda connection box with a first connector in electrical connection with the first conductor line and a second connector in electrical connection with the second conductor line, for connecting an electrical load to the first and second conductor lines,

wherein at least one of the first and second connectors is in electrical connection with the respective conductor line by a conductor lead extending through the connection sheet, and along the second side of the connection sheet for a distance of at least 25% of the minimum spacing.

The connection sheet can form part of the encapsulation of the solar module.

Like reference numerals are used in different Figures to denote the same or similar objects.

Reference is made toFIG. 1, which schematically shows an embodiment of a solar module1according to the present invention.

The solar module1, shown in cross-section, is of the substrate type, which means that the connection sheet5forms the substrate on which the solar cells7,8are arranged, before they are encapsulated by a lamination foil10, such as polyvinyl butyral foil or ethylene vinyl acetate foil, and a front cover11, such as a front glass. The connection sheet5can in particular be a glass substrate, such as of float glass. For providing some mechanical stability, which is desired for example for the substrate during the arrangement of the solar cells, the sheet can have a thickness of 0.5 mm or more, e.g. from 0.5 mm to 20 mm, such as from 1 to 6 mm, in particular the sheet, e.g. of float glass, can be of 1-4 mm thickness. The front cover11forms the light-receiving side of the module.

For simplicity, in this schematic embodiment only two solar cells7,8are shown in series connection. The number of serially connected solar cells can typically be between 2 and 500, preferably between 50 and 200, such as about 100.

The present invention is applicable to all types of solar cells, including conventional crystalline silicon solar cells and thin-film solar cells, including those based on the following non-exhaustive list of silicon-based thin film, chalcopyrite compounds, II-VI compounds and analogues, III-V compounds and analogues, organic materials, and dye-sensitized solar cells. Thin-film solar cells are preferred, in particular chalcopyrite based solar cells.

The term chalcopyrite compound is herein employed as a genus term that covers materials formed of a group I-III-VI2semiconductor or a group II-IV-V2semiconductor, including a p-type semiconductor of the copper indium diselenide (“CIS”) type. Special cases are sometimes also denoted as CIGS or CIGSS. It covers at least the following species: CuInSe2; CuInxGa(1-x)Se2; CuInxGa(1-x)SeyS(2-y); CuInxGazAl(1-x-z)SeyS(2-y), and combinations thereof; wherein 0≦x≦1; 0≦x+z≦1; and 0≦y≦2. The chalcopyrite compound may further comprise a low concentration, trace, or a doping concentration of one or more further elements or compounds, in particular alkali such as sodium, potassium, rubidium, caesium, and/or francium, or alkali compounds. The concentration of such further constituents is typically 5 wt % or less, preferably 3 wt % or less.

The term II-VI compounds is herein employed as a genus term that covers compounds wherein any number of group II elements from the periodic system and any number of group VI elements from the periodic system are present. Amongst examples are ZnSe, ZnS, ZnSxSe1-x, ZnSx(OH)1-x, CdS, CdSe, CdTe. Other elements may be present in such compounds, such as for instance doping elements and trace elements.

The term III-V compounds is herein employed as a genus term that covers compounds wherein any number of group III elements from the periodic system and any number of group V elements from the periodic system are present. Amongst examples are GaAs, AlxGa1-xAs, InxGa1-xAs, GaP, InxGa1-xP, InxGa1-xAszP1-z(wherein 0≦z≦1). Other elements may be present, such as for instance doping elements and trace elements.

The term absorber layer is intended to cover multiple layers, in particular multiple thin film layers, and moreover other layers may be located between the back electrode layer and the front electrode layer in addition to the absorber layer. As an example, in the case of a chalcopyrite absorber layer, a window layer or buffer layer may be present. An example is a layer of a II-VI compound such as for example CdS, such as at the interface with a front electrode comprising e.g. zinc oxide.

The embodiment ofFIG. 1will be discussed at the hand of solar cells7,8having a chalcopyrite type absorber layer.

A back contact comprises a metal layer14deposited upon substrate5. Layer14, in a preferred embodiment, typically comprises or consists of a highly conductive metal. Of specific importance are considered copper, aluminium, molybdenum, tungsten, and silver. Often applied are molybdenum layers that are deposited by sputtering to a thickness of about 0.2 to 2 microns.

On top of the back electrode14a chalcopyrite type semiconductor layer16(also referred to as CIS type layer) is arranged, having a thickness of about 0.2 to 2 microns, and being for example of p-type.

The CIS type layer16can be formed by any method available in the art. A preferred method includes sputter deposition of a sequence of layers comprising the metal constituents of the CIS type layer, optionally depositing a Se layer by vapour deposition, followed by rapid thermal processing. A preferred process is described in J. Palm, V. Probst and F. H. Karg, “Second generation CIS solar modules” Solar Energy, vol. 77, p. 757-765, 2004, incorporated by reference.

Between the substrate5and back electrode layer14a diffusion barrier layer (not shown) can be arranged, which serves to suppress diffusion of alkali metals from the glass substrate into the CIS layer16. If such a layer is arranged, it clearly forms part of the substrate before the solar cells are arranged. Further, the CIS type layer preferably contains a controlled amount of Na, as disclosed in U.S. Pat. No. 5,626,688, included by reference.

On top of the CIS layer a buffer layer and/or window layer can be deposited, such as of CdS, or of a Cd-free material.

The solar cells further comprise a front electrode layer20. The layer20can in particular be a transparent conductive oxide (TCO), such as zinc-oxide (ZnO) or indium-tin-oxide (ITO), preferably ZnO. The TCO layer can e.g. be deposited by means of sputtering. The layer is doped opposite to the semiconductor type of the absorber layer, such as n-type when the absorber layer is p-type. Sputtering can for example be done by DC sputtering from an ZnO:Al target, or by reactive sputtering from a metallic target. The layer is appropriately doped to provide relatively low resistivity, for example, better than about 2.0 times 10−3Ohm·cm, and preferably better than 1.0 times 10−3Ohm·cm. The thickness of the layer20is suitably 0.5 to 2 microns.

The back electrode layer14, absorber layer16and front electrode layer20are patterned such that separate solar cells7,8are formed, which are connected in series. In particular, the front electrode layer20of solar cell7is in electrical connection with the back electrode layer14of solar cell8. The front electrode layer20of the last solar cell8of the series is in electrical connection with the back electrode layer14in a region26adjacent solar cell8. The back electrode layer of the first cell of the series, solar cell7, also extends to a region27adjacent the first cell. Suitably the back electrode layer14stays clear of an edge region28along the edges of the module1. On the regions26and27and in electrical contact therewith, conductor lines31and32are arranged, which will be referred to as first and second conductor lines, respectively, hereafter. The conductor lines can e.g. be metal ribbons such as of copper, aluminium, molybdenum, optionally coated with e.g. nickel, palladium, tin or silver. The first and second conductor lines in this example are parallel and therefore also linear, and have a spacing L.

On the rear side of the connection sheet5a connection box36is arranged. The connection box36is provided with two connectors41and42, which will hereafter be referred to as first and second connectors, respectively. To the connectors41,42an electrical load (not shown) can be connected.

The first connector41is in electrical connection with the first conductor line31, by a conductor lead46. The conductor lead46extends through a hole48in the connection sheet5, and continues along the second side50of the connection sheet5.

In this embodiment, the second connector42is connected to the second conductor line32in an analogous and symmetrical manner, by second conductor lead51that extends through the connection sheet5via hole52. In this embodiment, the distance between the hole48and the connector41is at least 25% of the spacing L, and therefore also the distance between the holes48and52is at least 25% of the spacing L.

According to an aspect of the invention, the first connector41is in electrical connection with the first conductor line31by the conductor lead46, and the contact point at the hole48between the conductor lead46and the respective conductor line31can be located at a distance of from 20% to 50% of the length of the respective conductor line31, counted from an end thereof, i.e. along the respective conductor line. Suitably, also the contact point at the hole52between the second conductor lead51and the respective conductor line32is then located at a distance of from 20% to 50% of the length of the second conductor line32, counted from an end thereof. Such embodiments are shown inFIGS. 3d-3h,4,5a, and further detail will be discussed with reference to these Figures.

It shall be clear that an expression in the specification and in the claims that a component such as a solar cell, conductor line, connection box etc. are arranged on a particular side of the connection sheet and/or substrate, it does not necessarily mean that such component is directly on the particular side. It is however possible that the component is directly arranged on that side.

The connection box36can be provided in various arrangements as shown inFIGS. 2-5.

InFIG. 2an embodiment of the module1is schematically shown in a view on the connection sheet5(i.e. from below inFIG. 1).FIG. 1represents a cross-section along line I-I. For the sake of clarity, only the bus bars31,32, and not the solar cells between them are indicated. In this view it becomes clear that the parts of the conductor leads46,51running along the rear surface of the module between the holes48,52and the connectors41,42do not cover any surface on the light-receiving side. So, in this embodiment there is no active surface consumed by the interconnection between conductor lines31,32and the connection box36.

It will often be preferred to arrange the junction box symmetrically between the conductor lines31,32as shown, i.e. at a position along the virtual middle line55between the first and second conductor lines31,32.

The width of the connector box, measured perpendicular to middle line55, is typically less than 25% of the minimum spacing L. A typical minimum spacing is e.g. in the range of from 10 to 100 cm, in particular 40-80 cm.

In the embodiment as shown inFIG. 2, the holes48,52through which the first and second conductor leads extend through the connection sheet lie on a virtual perpendicular line60, crossing the first and second conductor lines31,32and the virtual line55at right angles. In this embodiment, moreover the conductor leads46,51extend along that line60, and the connection box36is arranged along that line60as well.

The connector box is shown here at an end portion61of the conductor lines31,32, which is here near a short side of the rectangular module1, but could also be arranged further away from an edge, or even at the centre of the module.

Preferably the distance between a through-hole for a conductor lead and the edge of the module is chosen such that sufficient insulation is achieved. The maximum voltage of the module is of influence here. For example, good insulation is achieved when the edge region28inFIG. 1is free of thin films and forms together with the polyvinyl butyral lamination foil10, having conductivity of 1.10−12(Ohm·cm)−1, an insulation zone. The edge region can e.g. be between 5 and 50 mm wide, preferably between 10 and 20 mm, such as 15 mm. A maximum system voltage of up to 1000 V can be achieved, or even more.

Each of the conductor leads46,51can be an integral extension of the conductor lines31, or32, respectively. The conductor leads can extend to connectors in the form of terminals66,67in the connection box. The connectors can also extend as connection leads extending from the connection box36, indicated in the Figure as71,72.

A connection lead71,72and a respective conductor lead46and/or51can be integrally formed.

When a conductor lead is not an integral extension of a conductor line, it can be electrically connected to the conductor line by known means, such as by soldering, welding, or by mechanical means such as a spring contact. The electrical connection can in particular be provided in the holes and/or the surrounding area. The holes48,52are suitably sealed against ingress of moisture, such as by butyl or epoxide. It shall be clear that the electrical connection forms part of the conductor leads.

The connection box can for example be glued to the rear side of the connection sheet5. In the connection box other electrical or electronic components can be arranged, such as one or more bypass diodes. The connection box can have a lid that can be opened, such as for the installation and/or connection of a load. It can also be sealed, while having external connectors and/or conduction leads (so-called one-piece junction cap).

Reference is made toFIG. 3, showing schematically and by way of example various embodiments of the present invention.FIGS. 3a-3crelate to embodiments wherein through-holes48and52are provided at an end portion61of the module, andFIGS. 3d-3hrelate to embodiments wherein the through-holes are provided at a central portion75of the module.

FIG. 3ais a further simplified version of the embodiment ofFIG. 2. In the other Figures only the parts relevant for discussing the respective modification will be indicated by reference numbers, all other parts as indicated are the same or similar as inFIGS. 2 and 3a.

InFIG. 3b, terminals66,67at the connection box36are provided instead of connection leads71,72.

InFIG. 3c, the connection box36is arranged away from the middle line55. Conductor line46is longer than 25% of the spacing L, in fact longer than 40%, more in particular longer than 50% of the spacing L. Conductor line51may be shorter than that.

InFIG. 3d, through-holes48and52are provided in the central portion75of the module, substantially in the middle of each conductor line31,32. The conductor leads46,51run skewed from contact points at the through-holes to the connection box36at the end portion61of the module. The end portion with respect to a length or width of a module can be the area within the first or last 20% of that length or width. Skewed leads provide the shortest connection, but is shall be clear that the conductor leads can also be arranged along other pathways.

FIG. 3eshows a variant in which the conductor lines31,32are also contacted via holes48,52in the central portion75of the connection sheet5, be it not exactly in the middle of the busbars. The central portion with respect to a length or width of a module can be the area within the central 20% of that length or width. Also the connection box36is outside the end portion, and the conductor leads46,51run skewed.

The embodiment ofFIG. 3fcombines features fromFIGS. 3aand3d. The through-holes and contact points48,52, as well as the connection box36are all provided in the central portion75. The conductor leads run perpendicular to the parallel conductor lines31,32.

The embodiment inFIG. 3gdiffers from that in3fin that the connection box36is arranged in the central portion75, and near one of the conductor lines. In fact, the connector42is arranged very close to the through-hole52, which is covered by the junction box36.

InFIG. 3h, the connection box36is centrally arranged, and the holes48,52are arranged at either side in longitudinal direction, somewhat away from the middle of the conductor lines31,32, but within 20-50% of the length K, counted from an end78,79of the conductor lines31,32. It would also be possible that one of the holes46,51is arranged at an end portion, less than 20% of the length K away from an end78or79.

FIG. 4shows the embodiment ofFIG. 3f) in the detail ofFIG. 2. The through-holes48and52are arranged in the middle, or substantially in the middle, of the conductor lines31,32, i.e. contact points between the first and second conductor leads and the respective conductor lines are both located at a distance of from 20% to 50% of the length of the respective conductor line, counted from an end thereof. The connector box is shown here in the central portion75of the module, but could also be arranged further away from the centre.FIG. 1is again a cross-section along lines I-I.

Instead of a single connection box, also two connection boxes can be employed without departing from the invention. The invention then still gives flexibility in choosing the location for the connection boxes without sacrificing active area of the module. Reference is made toFIG. 5a, showing schematically and by way of example a further embodiment of the present invention, where two connection boxes36a,36bare applied. The same reference numerals as inFIGS. 1-4are used to refer to the same or similar parts. Each connection box36a,36bin this embodiment is arranged above a through-hole48,52, respectively. Both through-holes are provided in the central area75, such as in the middle of the busbars.

In one embodiment a bypass diode can be arranged between the contacts41,42, so as to carry away current in the case of partial shading of the module. Shading of one or several individual solar cells in a module consisting of a larger number of series connected solar cells may lead to reverse biasing of the shaded cell(s). In the embodiment ofFIG. 4, the bypass diode may be arranged in one of the connection boxes36a,b. Connection wiring80between the junction boxes runs along the back side of the module. In a particularly advantageous embodiment the connection wiring is covered by a frame element which serves for increasing mechanical stability of the module. In the embodiment schematically shown inFIG. 5the frame can be formed of a frame around the four sides of the module and a connection bar running along the wiring80. The connection bar can be hollow and/or have a recess such as at the side of the module so as to cover the wiring80.

In the further embodiment inFIG. 5bthe two through-holes and connection boxes36a,bare arranged in the end portion61, at the ends of the bus bars31,32. Optionally a bypass diode and wiring80as inFIG. 5amay be provided between the connection boxes.

FIG. 6shows schematically a conventional layout of a module with busbars31,32as well as conductor leads91,92. These conductor leads have substantially the same shape as busbars extending over the light-facing side of the sheet, in particular at the side of the solar cells in substrate design. The connectors66,67are connected to the conductor leads91,92via a common through-hole94. The area underneath91,92is not available as active area.

A calculation of ohmic losses in various configurations of a module was done, for rectangular modules of 165 cm×65 cm size, with aluminium busbars of 0.2 mm thickness and 2 mm width. For the conventional layout shown inFIG. 6, an ohmic loss of 0.83% was determined, wherein the connector leads91,92had a width and thickness identical to the bus bar.

For the layout ofFIG. 5b, the ohmic loss was 0.53%. By guiding the conductor leads separately through the sheet, ohmic losses along the leads91,92are accumulated. That would be the case also when a single junction box like inFIGS. 3a-3cwas employed, since at the rear side much thicker conductor leads can be used.

For the arrangement ofFIG. 5a, an ohmic loss of 0.14% was calculated. In this case with the contact points and through-holes in the middle of the conductor lines, current is only transported over half the length of a bus bar. It shall be clear that this benefit of the invention can also be exploited by dimensioning the busbars smaller than e.g. needed for the conventional arrangement ofFIG. 6, without higher than conventional ohmic losses.

The invention is also applicable to modules comprising a plurality of series-connections of solar cells. In that case, at least third and fourth, and optionally further pairs of conductor lines are present on the first side of the connection sheet, with a series connection of solar cells between each pair. Each pair of conductor lines has a respective minimum spacing. Each conductor line can be connected to a connection box at the second side of the conductor lead extending through the connection sheet. In a particular embodiment at least one of the conductor lines extends along the second side for a distance of at least 25% of the respective minimum spacing for that conductor line. In particular, the distance can be at least 25% of a width of the module (for a rectangular module the width is shorter or equal to the length). In such a design according to the invention, an additional advantage can be achieved when the parallel connection of the different series is provided in the connection box, so that no separate circuit board is needed.

The through-holes in the connection sheet are suitably provided underneath the conductor lines (bus bars), for easy contacting, and also no substantial area outside the bus bars is consumed for the conduction leads. It shall however be clear that a conductor lead can also be led through the connections sheet some distance from the conductor lines, in which case the conductor line can consume a limited amount of active area. Suitably, the through-holes are arranged within 5 cm from the conductor lines, and/or within 5% from the spacing between the conductor lines.

The invention has been discussed at the hand of examples using the so-called substrate design, whereby the substrate on which the solar cells are arranged during manufacture forms, or is part of, the connection sheet. The invention has particular advantages in combination with a substrate design; since in a superstrate design it is generally easier to arrange wiring and connections between bus bars, without substantially sacrificing active area of the module.