1. Field of the Invention
The present invention relates generally to solar panels and more particularly to an interconnection system in which an electrical connection length between adjacent panels during field installation is minimized irrespective of orientation of such panels within an array.
2. Description of the Related Art
A typical solar panel includes a plurality of individual solar cells aggregated and electrically interconnected so that the electrical current developed by each individual cell in response to solar energy incident thereon is ultimately conducted to a current collector node, which may exemplarily be a bus bar, within the panel. The details of various methods for and systems of the aggregation and interconnection of each cell within the panel are well known and need not be further described herein.
The typical solar panel may include a tap accessible at the exterior of the panel to facilitate electrical connection to the current collector node of the panel. The solar panel may also include another tap accessible at the exterior of the panel to facilitate electrical connection to a common reference node, which may exemplarily be another bus bar, within the panel. The tap to the current collector node may be indicated by a (+) polarity and the tap to the common reference node may be indicated by a (−) polarity.
A single solar panel of the type presently commercial available for commercial and residential installations generally provides a relatively low power output, typically in a range of 150-200W at 15-20VDC and 5-10A. Accordingly, in a residential or commercial installation, many such panels must be used to provide a useful amount of power.
The panels in any such installation are typically mounted to a roof top rack and disposed in a two dimensional array. The plane of the array is oriented to maximize the collection of solar energy in each panel so that upon its conversion to electrical energy the maximum power output available from each panel can be obtained, thus maximizing the power output from the array as a whole. To maximize the effective surface area of the array, this generally being the sum of the active surface area for all of the panels in the array, the panels are mounted edge to edge with the smallest gap possible between adjacent panels being provided to compensate for thermal expansion. It is also recognized that the active surface area of each panel is less than its total surface area as the solar cells therein cannot extend completely to the edges at which there is provided sealing of a typical panel laminate structure, and further that non-active space exists between individual cells or submodules of cells within the panel.
Most such panels come in a variety of sizes, and typically are rectangular with a width generally between 50-60% of the length. Of course, to construct any two dimensional array having the maximum effective surface area, all panels in the array must have the same length and width. At the time of field installation of the panels into an array, a simple calculation based on the overall dimensions of the installation site and the dimensions of the panels to be used readily determines if a landscape or portrait orientation of each of the panels provides for the maximum number of panels that can be utilized to obtain the maximum effective surface area of the resultant array.
Because of the relatively low power output of each panel, and the number of panels required to achieve usable amounts of power, substantial efforts in the art have been directed to the minimization of electrical losses both within the internal circuitry of the panels and the external interconnections between panels and of the arrays to external loads. Every connector and each length of cable used in the array has associated therewith a resistance. When current flows through any such connector or cable, a voltage drop occurs across such connector or cable and some power is lost through its resistance as dissipated heat.
To provide the above mentioned taps needed to interconnect adjacent panels, many such commercially available panels have a junction box providing access to such taps disposed on the bottom surface of the panel so as not to interfere with solar energy collection. The installer may then run appropriate weather resistant cables between each junction box on two adjacent panels, for example in a series connection from the (+) tap of one such panel to the (−) tap on the next adjacent panel in a row or column in the array. If the panels are disposed in a portrait configuration relative to the electrical connection to be made between adjacent panels, the distance between each junction box on each of adjacent identically manufactured panels is substantially commensurate with the width of the panel. Conversely, if the panels are disposed in a landscape configuration relative to the electrical connection to be made, the distance between each junction box on each of these same panels is substantially commensurate with the length of the panel.
If the interconnection cables are installed during field installation, then the cable lengths between identically manufactured panels can be minimized by mounting the panels in the portrait configuration. However, as stated above, the installation site may require that these panels be array mounted in the landscaped configuration to maximize the number of panels in the array. Although the overall power output the entire array is increased, the increase is less than the sum total of the power of the additional panels due to the increased resistive losses in the longer cables needed for panel interconnection.
Moreover, some commercially available panels are manufactured with weather resistant cables leading from the junction box with mating weather proof connectors, which may further be provided in (+) and (−) polarity configurations, provided at the free end thereof. The length of the preinstalled cable must accordingly be sufficient to mate with the corresponding cable of the adjacent panel irrespective of the portrait or landscape orientation of the panels. Thus, the maximum length of cable must always be used, resulting in maximum resistive losses in the cables, to allow landscape orientation even if the panels are array mounted in a portrait configuration.
In the co-pending application above referenced, it is disclosed that each solar panel may have a pair of junction boxes, wherein each junction box is disposed adjacent a respective one of opposite edges of the panel along a line normal to such opposite edges. If the edge chosen is the short edge along the width of the panel, then as the panels are array mounted edge to edge in a landscape configuration the junction boxes on facing edges of two adjacent panels will accordingly be aligned and proximate to each other, thereby minimizing the electrical connection distance between the junction boxes on facing edges of the panels and thus minimizing the length of cable needed. As the length of all such cables used to connect each panel in each landscaped configured row is minimized, resistive losses due to cable lengths is accordingly minimized.
Another advantage of using two junction boxes per panel is that each junction box on a single panel can have a respective one of the (+) or (−) polarity taps associated therewith. As the panels are array mounted edge to edge in the landscape configuration the tap of the junction box on the edge of one panel will have the opposite polarity to the polarity of the tap of the junction box at the facing edge of the adjacent panel.
By providing on each panel two junction boxes, each respectively associated with one of the (+) or (−) polarities, the internal bus bars in each panel for common reference and the current collector node may then advantageously have a minimal length by obviating the need to extend each of these bus bars across the total length of the panel to provide connection thereto at each junction box or, as in the case of the commercially available panels described above, to the single junction box wherever located on the panel. The common and current collector bus bars need only extend across the width of the panel in this example, assuming that individual solar cells along a common row along the length are series connected for maximum output voltage. Since any conductor has a resistance per unit length, this decreased length thereby decreases resistive losses within the panel. A further advantage arises from the savings of material and fabrication costs of each panel.
However, if those same panels need to be mounted edge to edge in a portrait configuration, then the junction boxes of adjacent panels that need to be interconnected become separated by a distance substantially commensurate with the dimension of the diagonal of the panel. As this diagonal has a dimension greater in magnitude than the length of the panel, the length of the cable required becomes even longer, and the resistive losses due to cable length even greater, than the cable required for a portrait configuration in the commercially available panels with one junction box.
Similarly, if the two junction boxes are configured for minimal interconnect distance between portrait oriented panels, in which each of the junction boxes is mounted along a respective one of the long edges along a line normal to the opposite long edges, then should a landscape orientation be necessitated the cable length required is again substantially commensurate with the dimension of the diagonal of the panel. Even if the junction boxes are placed at a corner of the panel, but at opposite ends of the long edge for optimal landscape orientation or at opposite ends of the short edge for optimal portrait configuration, then the use of such panels in their respective non-optimized configuration will always result in a cable length substantially commensurate with the dimension of the diagonal of the panel.
Another consideration, in addition to resistive losses incurred through excessive cable lengths, is the cost of the cable itself. Cable that is typically used during field installation of solar panels generally costs between $0.20-0.25 per foot. Clearly, should maximum cable lengths for panel to panel interconnection, as in the examples set forth above, be required for a typically sized array the cost of the cable would be significantly increased as compared to adjacent panels having closely disposed junction boxes on the edges thereof.
Accordingly, a need exists to provide a solar panel interconnection system in which the electrical interconnect distance between panels is always optimally minimized irrespective of whether such panels are oriented in a portrait or landscape configuration.
According to the present invention, a solar panel interconnection system in which electrical interconnection distance is minimized irrespective of one of a first panel orientation and a second panel orientation includes a first solar panel having first diagonally opposed corners, a first edge, a second edge and a tap adapted to provide electrical connectivity to the first solar panel, and a second solar panel having second diagonally opposed corners, a first edge, a second edge and a tap adapted to provide electrical connectivity to the second solar panel. The first edge and the second edge of the first solar panel extend from one of the first diagonally opposed corners and the tap on the first solar panel is disposed at the same corner thereof. The first edge and the second edge of the second solar panel extend from one of the second diagonally opposed corners and the tap on the second solar panel is disposed at the same corner thereof.
Upon the first solar panel and the second solar panel each being disposed in a selected one of the first orientation and the second orientation in which for the first orientation the first edge of the first solar panel and the first edge of the second solar panel are proximately disposed in a facing relationship to each other and in which for the second orientation the second edge of the first solar panel and the second edge of the second solar panel are proximately disposed in a facing relationship to each other, the first diagonally opposed corners and the second diagonally opposed corners mirror image each other with the one of the first diagonally opposed corners being proximate the one of the second diagonally opposed corners. As the tap on the first solar panel and the tap on the second solar panel are also disposed at these proximately disposed corners, the taps also become proximately disposed to each other. The electrical interconnection distance between the tap on the first solar panel and the tap on the second solar panel is therefore minimized irrespective of whether the first orientation or the second orientation is selected.
A feature of the present invention is that when such first and second solar panels are disposed in an array, taps to be connected to each other in any one row or column of the array are always proximate each other thereby advantageously minimizing cable lengths between panels. Accordingly, the total resistive losses due to electrical interconnection cables and also the cost of such cables in the array are also advantageously minimized.
These and other objects, advantages and features of the present invention will become readily apparent to those skilled in the art from a study of the following Description of the Exemplary Preferred Embodiments when read in conjunction with the attached Drawing and appended Claims.
Referring now to
The first solar panel 10 further has a tap 22 disposed thereon at one of the first diagonally opposed corners 14a, 14b from which each of the first edge 16a and the second edge 16b of the first solar panel 10 extends, exemplarily shown herein as corner 14a. Similarly, the second solar panel 12 has a tap 24 disposed thereon at one of the second diagonally opposed corners 18a, 18b, from which each of the first edge 20a and the second edge 20b of the second solar panel 12 extends, exemplarily shown herein as corner 18a. The tap 22 on the first solar panel 10 and the tap 24 on the second solar panel 12 each provide electrical connectivity respectively thereto.
When the first solar panel 10 and the second solar panel 12 are disposed, for example during field installation, in the first orientation of
As readily seen in
As a result of this mirror image, the tap 22 at the corner 14a on the first solar panel 10 and the tap 24 at the corner 18a on the second solar panel 12 are proximately disposed to each other. Accordingly, irrespective of orientation, the electrical connection distance between the tap 22 on the first solar panel 10 and the tap 24 on the second solar panel 12 is minimized, thus minimizing electrical resistance due to the electrical interconnect cable used in such connection.
Utilizing the principles of the present invention as described in conjunction with the first solar panel 10 and the second solar panel 12 of
Referring now to
It is to be noted that the exemplary row 28a of the array 26a as seen in
Each of the first solar panels 10 further has a third edge 16c and a fourth edge 16d extending from the other one of the diagonally opposed corners 14a, 14b, exemplarily shown herein as corner 14b. More particularly, in each of the first solar panels 10 the third edge 16c is opposite the first edge 16a and the fourth edge 16d is opposite the second edge 16b. Similarly, each of the second solar panels 12 further has a third edge 20c and a fourth edge 20d extending from the other one of the diagonally opposed corners 18a, 18b, exemplarily shown herein as corner 18b. More particularly, in each of the second solar panels 12 the third edge 20c is opposite the first edge 20a and the fourth edge 20d is opposite the second edge 20b.
In addition to the tap 22, each of the first solar panels 10 has a further tap 30 disposed thereon at the other one of the first diagonally opposed corners 14a, 14b from which each of the third edge 16c and the fourth edge 16d of the first solar panel 10 extends, exemplarily shown herein as corner 14b. Similarly, in addition to the tap 24, each of the second solar panels 12 has a further tap 32 disposed thereon at the other one of the first diagonally opposed corners 18a, 18b from which each of the third edge 20c and the fourth edge 20d of the second solar panel 12 extends, exemplarily shown herein as corner 18b.
When the plurality of the first solar panels 10 and the second solar panels 12 are alternatingly disposed along the exemplary row 28a in the landscape orientation of
Alternatively, when the plurality of the first solar panels 10 and the second solar panels 12 are alternatingly disposed along the exemplary row 28b in the portrait orientation of
In either the landscape orientation of
As a result of this mirror image similarly as described above, the tap 22 at the corner 14a on the each of the first solar panels 10 in any ith position and the tap 24 at the corner 18a on each of the second solar panels 12 in the next adjacent ith+1 position are proximately disposed to each other and the tap 30 at the corner 14b on the each of the first solar panels 10 in any ith position and the tap 32 at the corner 18b on each of the second solar panels 12 in the previously adjacent ith-1 position are proximately disposed to each other. Accordingly, irrespective of orientation, the electrical connection distance between the tap 22 on each of the first solar panels 10 and the tap 24 on the next adjacent one of the second solar panels 12 and between the tap 30 on each of the first solar panels 10 and the tap 32 on the previously adjacent one of the second solar panels 12 is minimized. Therefore, the electrical resistance due to electrical interconnection cables in either the landscape array 26a or the portrait array 26b, as well as the costs of such cables used, is also minimized.
Exemplarily, for an electrical connection along any row as described above, the tap 22 on each of the first solar panels 10 may have a (+) polarity associated therewith and the proximately disposed tap 24 on the next adjacent one of each of the second solar panels 12 may have a (−) polarity associated therewith. In such example, the tap 30 on each of the first solar panels 10 would then have a (−) polarity associated therewith and the proximately disposed tap 32 on the previous adjacent one of each of the second solar panels 12 would then have a (+) polarity associated therewith.
By mirror imaging only the corners at which the afore described taps are located in adjacent panels, the internal circuitry of the first solar panel 10 and the second solar panel 12 can advantageously be of identical manufacture. Only the internal reference bus bar and current collector bus bar need be tapped at the appropriate corner of the identically manufactured panels to construct either the first solar panel 10 or the second solar panel 12 and provide the polarity to be associated with the tap at such corner.
With reference now to
The material of the front layer 34 may typically be glass as glass is transparent to solar energy and weather resistant. The material of the back protective layer may also be glass, however, other materials such as lightweight flexible materials and laminates are well known for providing the requisite sealing of the front layer 34 and the back protective layer 36 to each other to isolate the interior of the solar cell panel from external ambient conditions. The sealant layer 38 may exemplarily be a polymeric sealant. The second solar panel 12 is of similar construction such that the details of the construction described herein with specific reference to the first solar panel 10 apply equally to the corresponding elements of the second solar panel 12.
The tap 22 is made accessible at an opening in the first solar panel 10 proximate the corner 14a thereof. This opening, which may be any type of bore, cut, slice, knockout or the like, may be disposed with the void in the planar surface of either the front layer 34 or the back protective layer 26 of the first solar panel 10, disposed with the void along the first edge 16a or second edge 16b interstitially or within either or both of the of the front layer 34 and the back protective layer 26, or disposed with the void being removing part of such planar surface and the contiguous edge thereto. This opening may also either expose a portion of an underlying bus bar within the first panel 10 or such bus bar may be extended through any such opening. The integrity of the sealant between the front layer 34 and the back protective layer 26 is nonetheless maintained at any such opening. The other diagonally opposed corner 14b of the first solar panel 10, and both of the diagonally opposed corners 18a-b of the second solar panel 12, may be constructed identically as described for the corner 14a herein.
In the embodiment shown in
With respect to the tap 22 at the corner 14a of the first solar panel 10 and the tap 32 at the corner 18b of the second solar panel 12, if these taps 22, 32 are to be associated with the (+) polarity, the tap 22 exposed by the cut edge 40 at the corner 14a and the tap 32 exposed at the corner 18b are each extensions of or otherwise connected to the current collector bus bar in the respective first solar panel 10 and second solar panel 12. Similarly, with respect to the tap 30 at the corner 14b of the first solar panel 10 and the tap 24 at the corner 18a of the second solar panel 12, if these taps 30, 24 are to be associated with the (−) polarity, the tap 30 exposed by the cut edge 40 at the corner 14b and the tap 24 exposed at the corner 18a are each extensions of or otherwise connected to the reference bus bar in the respective first solar panel 10 and second solar panel 12.
In some field installations, it may be desirable to protect the opening in the back protective layer 36 from environmental elements with a simple junction box disposed over the opening. The junction box also provides an enclosure for electrical connections made to the tap disposed within its enclosure.
Referring now to
The junction box 44 further has a second generally rectangular portion 52 extending inwardly from the triangular portion 46 over an outer surface 54 (
Coextensive with the sidewalls 56a, 56b and the end wall 58, the rectangular portion 52 has a lower edge 60 may be sealed to the outer surface 54 of the back protective layer 36. The lower edge 60 of the rectangular portion 52 is offset from the lower edge 50 of the triangular portion 46 by a dimension commensurate with the thickness of the back protective layer 36, thereby exposing an offset edge 62 between the lower edge 60 of the rectangular portion 52 and the lower edge 50 of the triangular portion 46. The offset edge 62 may be sealed to the cut edge 40.
When mounted and sealed as above, the junction box 44 forms a weatherproof chamber 64 in which electrical connection may be made to the tap 22. The end wall 58 may include an opening 66 for access to the tap 22. The connection of the external cable to the tap 22 with the chamber 64 may be made by any conventional means such as lugs and the like.
Other junction boxes identical in construction to the junction box 44 may also be mounted to the respective corners 18a, 14b, 18b as described for the junction box 44 with respect to corner 14a. In such case an external cable may be field installed, for example between the proximately disposed junction boxes each of the first solar panels 10 and the adjacent one of the second solar panels 12. For example, one such cable would be connected by conventional means to the tap 22 accessible at the corner 14a of the first solar panel 10 and extend through the opening 66 preferably using known weatherproof connectors for cables and junction boxes. Using an identical junction box 44 at the corner 18a of the second solar panel, the cable would be installed through the opening 66 and connected by conventional means to the tap 24 accessible at the corner 18a of the second solar panel 12.
With further reference to
The junction box 44b at the second solar panel 12, which is proximate the junction box 44a on the first solar panel 10, may then have disposed in the opening 66 a socket 74 adapted to receive the electrical connector 72. The socket 74 is electrically connected by conventional means to the tap 24 accessible at the corner 18a of the second solar panel 12. Conventional mating male and female electrical connectors disposed respectively in one of the connector 72 and the socket 74 complete the electrical connection when the connector 72 is received within the socket 74. The cable 68 may be bare cabled or further have a conductive core 68a and an insulator layer 68b.
There has been described herein novel apparatus and techniques for providing electrical connection between adjacent solar panels to minimize electrical connection distances and hence minimize resistive losses. Those skilled in the art may now make numerous uses of and departures from the herein above described embodiments without departing from the inventive concepts disclosed herein. Accordingly, the present invention is to be defined solely by the lawfully permitted scope of the appended Claims.
The present application is a continuation-in-part of commonly owned application for Solar-Cell Module with In-laminate Diodes and External-Connection Mechanisms Mounted to Respective Edges, Ser. No. 12/121,602, filed May 15, 2008, the specification of which is incorporated herein as if fully set forth.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12121602 | May 2008 | US |
| Child | 12544984 | US |