Flat Tile Solar Panels

Abstract

An earth mount enabled utility scale solar photovoltaic array having a plurality of solar panels is supported on the ground at edge portions of the solar panels. The panels are interconnected in at least one series-connected string, in which said at least one series-connected string extends along adjacent or closely adjacent solar panels along at least two rows so that the string has a distance between terminal ends of the series connection less than a lengthwise dimension of the solar panels constituting the string.

Claims

1-58. (canceled)

59. A utility-scale photovoltaic plant comprises arrays having PV modules located at a site, wherein a spacing between the modules is smaller than an average spacing between racked panels.

60. The plant of claim 59, wherein the utility-scale photovoltaic plant is a plant with a capacity of 1 MW of solar energy.

61. The plant of claim 60, wherein at least some of the modules have support regions in which the site surface (the ground) supports the modules.

62. The plant of claim 61, wherein free air is air bounded by an intermediate structure having top and bottom portions and single or adjacent side portions, the module's photovoltaic substrate comprises a downward face having a non-contact surface and a contact surface, the contact surface is defined as a portion of the downward face that touches one or more, 1.0 mm or thicker, solid substances other than the ground and other than the photovoltaic substrate, a contact region is defined as the region between the contact surface and the ground, perpendicular to the contact surface, and some parts of the contact region do not contain a region of free air.

63. The plant of claim 62, wherein the contact region does not contain free air.

64. The plant of claim 63, wherein the plane of the array is parallel to the plane of the earth.

65. The plant of claim 64, wherein the modules of an array are flexibly joined in two dimensions.

66. The plant of claim 65, wherein the two dimensions correspond to array rows and columns.

67. The plant of claim 66, wherein the spacing between modules in an array row is approximately the same as the spacing between modules in an array column.

68. The plant of claim 67, wherein the ground includes material naturally present at the site and material added to the site by human activity.

69. The plant of claim 68, wherein the retainers electrically bond some module frames to adjacent module frames.

70. The plant of claim 64, wherein solar panel trackers or other racking do not sit between the support regions and the ground.

71. The plant of claim 70, wherein the spacing between modules causes the plant to use less than 250% of the land area that a similarly sized traditional utility scale solar PV power plant uses.

72. The plant of claim 71, wherein the spacing between modules is greater than or equal to 217 mm.

73. The plant of claim 64, wherein the modules are joined in two dimensions.

74. The plant of claim 73, wherein the two dimensions correspond to array rows and columns.

75. The plant of claim 74, wherein the spacing between modules in an array row is approximately the same as the spacing between modules in an array column.

76. The plant of claim 75, wherein solar panel trackers or other racking do not sit between the support regions and the ground.

77. The plant of claim 76, wherein the spacing between modules causes the plant to use less than 250% of the land area that a similarly sized traditional utility scale solar PV power plant uses.

78. The plant of claim 77, wherein the spacing between modules is greater than or equal to 217 mm.

79. The plant of claim 78, wherein the spacing between modules is greater than or equal to 17 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic diagram showing a corner bracket used for attachment to a solar panel.

[0033] FIG. 2 depicts corner bracket 101 attached to solar panel.

[0034] FIGS. 3A-3D are schematic diagrams showing solar panels connected using individual corner brackets and a hold-down clamp. FIG. 3A shows a hold-down clamp. FIG. 3B shows the clamp engaging the corner brackets. FIG. 3C shows the clamp anchored and FIG. 3D is a top view.

[0035] FIG. 4 is a cross-sectional view of the clamping arrangement of FIGS. 1- 3.

[0036] FIGS. 5A and 5B are schematic diagrams showing a configuration of corner brackets, in which horizontal support is used to secure panels. FIG. 5A shows a configuration for a clamp. FIG. 5B shows a configuration in which a bracket extends in a straight line connecting two modules.

[0037] FIGS. 6A and 6B are schematic diagrams showing a solar panel with its edge frame resting on the ground. FIG. 6A shows a furrow placement. FIG. 6B shows an end stop or curb member positioned at the edge of an array.

[0038] FIGS. 7A-7F are schematic diagrams showing configuration of corner brackets, in which a single disk supports four panels at corners of the panels.

[0039] FIG. 7A is a perspective view of the corner bracket supporting four panels, with the panels in cut-away view. FIG. 7B shows the arrangement of the corner bracket.

[0040] FIG. 7C shows a bottom support. FIG. 7D shows a cross-section of the corner bracket with a cinch pin. FIG. 7E shows the corner bracket and cinch pin gripping an anchor cable. FIG. 7F shows the corner bracket with the cinch pin securing panels.

[0041] FIGS. 8A-8C are schematic diagrams showing configuration of a spring clip arrangement used to link panels with a minimal gap between panels. FIG. 8A shows the spring clip in profile. FIG. 8B shows the spring clip in an elevation view. FIG. 8C shows the spring clip engaging one solar panel.

[0042] FIGS. 9A and 9B are schematic diagrams showing the spring clip of FIGS. 8A-8C gripping panels. FIG. 9A shows two adjacent panels held by a spring clip. FIG. 9B shows the gripping arrangement of the spring clip.

[0043] FIGS. 10A and 10B are schematic diagrams showing a wiring connection layout for adjacent solar panels.

[0044] FIG. 11 is a graphic diagram showing a sample output for a single clear sky day of the operation of a solar power plant. The horizontal axis represents time. The vertical axis on the left represents the available sunlight, or “solar insolation”. The vertical axis on the right indicates the power output of the power plant.

[0045] FIGS. 12A-12D are schematic diagrams showing a layout of a solar array for a commercial solar power plant. FIG. 12A shows a partial string array of three strings of panels arranged in six rows. FIG. 12B expands 12A to show a string array comprising 18 strings with a string inverter depicted in the center. FIG. 12C further expands 12B to show 6 string arrays further co-located to one another. FIG. 12D further expands 12C to show a complete solar array.

DETAILED DESCRIPTION

Overview

[0046] The disclosed technology provides a technique for generating electricity using either commercially available, utility scale, solar PV (e.g., CSi, CdTe, CIGS, CIS) modules, or new and novel adaptations of commercially available, utility scale, solar PV modules, or new module technologies, a plurality of which are mounted in such a way as to be both in direct contact with the earth's surface and parallel to the same. This establishes an earth orientation of the solar PV modules, as distinguished from a solar orientation, although contouring of the soil and other mounting considerations will consider the angle of the sun.

[0047] The modules are placed in a grid pattern both edge to edge and end to end as if tiles on the floor of a house. The “utility scale” nature of the modules limits the application of said system to voltages exceeding 600 volts DC which ensures the system is placed “behind the fence” whereby limiting access to trained professionals. There can be variations in the threshold voltage, as it is possible to design arrays that can safely operate at higher voltages in unprotected environments, a non-limiting example being 800-volt arrays for unprotected areas. The method of attachment of the modules to one another or to the earth is not limited by this application. This arrangement of modules substantially reduces wind loading effects of the modules. The arrangement of the modules electrically is in such a way as to allow for both series and parallel connections, and eliminates, but does not preclude the need for discrete wiring harnesses and harness supporting means used by traditional utility scale solar plant PV power plant systems. This arrangement of modules provides for significant advantages with the use of commercially available string/micro inverters but does not preclude the use of industry standard central inverters or alternate power conversion and transmission technologies.

[0048] This arrangement of modules in conjunction with the use of active electrical protective devices such as ground fault interruption and arc fault interruption, fully eliminates the need and subsequent use of electrical grounding and bonding of the modules to the structure for purposes of personal protection per code compliance. In contrast, these devices, when used in conjunction with conductive module support structures do not meet the protection levels necessary for code compliance, and thusly require the use of bonding and grounding of the modules.

[0049] This arrangement of modules fully eliminates the need and subsequent use of steel and steel structures in the power plant thereby reducing and/or eliminating the natural weathering effects of corrosion while enhancing life expectancy of the power plant from a minimum requirement of 25 years to greater than 40 years. This system does not preclude the use of steel, coated or otherwise for site-specific applications.

[0050] The arrangement of modules allows for both commercially available and new techniques for module cleaning and/or dust removal from the modules surface, increasing the effective energy production rate of the modules.

[0051] The arrangement of modules and disclosed technology significantly reduce the negative effects of high wind forces on the modules. These wind forces, which in certain geographies reach hurricane force strength, often preclude the construction of solar power plants in those regions, or significantly increase the expense of doing so. In addition, the modules themselves are easily damaged by high winds requiring significant repair and replacement expenditures. By removing the modules from the direct forces of wind, the negative effects of cyclic loading, the “micro-cracking” is effectively eliminated.

[0052] The disclosed technology allows for both commercially available and new or novel methods for module cooling from the backside of the modules' surface including evaporative cooling, alternate high emissivity coatings, the addition of “air vents” on the edge of the module frame, the addition of various enhanced heat transfer materials and or methods, thereby increasing the effective energy production rate of the modules. The positioning of the modules on the ground results in avoiding indirect sunlight and heat from ground exposed to sunlight from heating the backsides of the modules. As a result, rather than being a source of additional heat, the ground beneath the modules becomes more of a heat sink. To take further advantage of this, the modules are coated on the backside with a dark or heat transmitting coating to promote radiant heat transfer to the ground or airspace beneath the modules.

[0053] The disclosed technology increases the power density per acre of land. The quantity of acres used per unit of power production is reduced by more than 50% from traditional utility scale solar plant PV power plants.

[0054] The disclosed technology allows the PV array to follow the existing contour of the land whereby the need for land preparation such as mass grading, plowing, tilling, cutting, and filling as is typically needed for utility scale solar plant PV power plants can be significantly reduced and even eliminated.

[0055] The disclosed technology inherently results in an effective decrease in annual module performance yield as measured in kWhrs per kWp as compared to traditional solar PV power plant systems because of not being oriented to the sun as are the trackers and racks. While the energy performance is significantly reduced, the reductions in electrical losses due to wiring, energy losses due to module cleaning, costs materials and construction, construction schedule and risk result in an overall reduction in produced energy price (LCOE) of greater than 10% over current technologies.

[0056] The disclosed technology provides a system for a solar PV module directly mounted to the earth. In one non-limiting configuration, a bracket assembly utilizes the module frame as the structural support system by securing the four corners of the solar PV module frame directly to the earth leaving no air gap between the earth, frame corners, and bracket assembly. Earth mounting with no air gap reduces wind loading and uplift forces, and eliminates shading from panel to panel, has zero or minimal row spacing requirement, and increases the ground coverage ratio. This earth mounted PV system orients the PV panels parallel to existing topography and the solar panel arrays can be positioned at any azimuth angle.

[0057] Solar panels, sometimes called solar modules, are configured as tiles suitable for installation directly on the earth and are configured to take advantage of the cooling and heat sinking effects of the earth. In placing the panels, attachment brackets may be used. The panels are snapped into or otherwise secured to the attachment brackets, retaining a solar array on the ground or near the ground. The ground placement allows a low-cost configuration in that it avoids the requirements for mounting the panels on racks and avoids shadows and the consequential need for spacing between rows.

[0058] Since the panels are not mounted on racks, the requirements for wind tolerance are significantly reduced. This also reduces the need to anchor the panels because there are no racks to mount, and since the panels are on the ground, there is substantially less lifting due to wind conditions.

[0059] The mounting may use attachment brackets which connect adjacent panels together. While it is possible to anchor the brackets to the ground, the anchoring requirements, meaning anchoring force, is greatly reduced because the panels are not supported above-ground in the wind at an angle to the horizontal. Instead, the panels rest substantially flat on the ground or near the ground.

[0060] The brackets secure the panels to each other and maintain a fixed positioning of the panels to stabilize the panels in a desired position. Anchor stakes augment this stability but need only secure the panels against forces experienced when laid flat on the ground, which is substantially lower than the force incurred in rack-mounted or tracker mounted configurations.

[0061] The lack of shadows is in part the effect of the panels not being tilted. This results in reduced power conversion as compared to panels oriented toward the sun, but if the total costs of the array without racks compares favorably with the loss of output from flat placement, flat placement can be cost-effective.

[0062] The lack of shadowing between adjacent rows of panels falls into this economic balance. The reason there is no shadowing is that the shadowing is created by the racking, and more specifically, from the angled positioning of the racked panels. Since racking is not used, there is no shadowing, which allows configurations which close the gaps between sequential rows. Elimination of the gaps establishes a two-dimensional connection array, meaning closely adjacent panels extend in a row-wise direction as well as across sequential rows because sequential rows are also adjacently positioned. In other words, gaps between sequential panels from row-to-row closely approximate gaps between sequential panels along the rows.

[0063] This adjacent positioning allows wiring connections or harnesses to take advantage of the adjacent relationships across two or more rows, thereby reducing the need for harness connections. In a particular arrangement, “home run” harness connections, commonly referred to as “whips”, are significantly reduced because adjacent rows can be connected without “skip stringing” or “leapfrog wiring”. In an alternate arrangement, sequential connections can be made with “next” panels in adjacent rows, thereby reducing the length of connections required for “skip stringing” or “leapfrog wiring”.

[0064] The elimination of racking affords an additional advantage when it comes to harnessing. Since there are no racks, the need to extend the length of racks is reduced to the need to limit the voltages of the strings, without consideration of the costs of the racks, or in the case of trackers, the cost of tracker drive mechanisms. This, in turn, allows the strings to terminate at both ends of the strings close to the inverters. In this respect, having multiple strings terminate close together allows inverters to be positioned close to the end terminations of the strings.

Mounting System

[0065] FIG. 1 is a schematic diagram showing a corner bracket 101 used for attachment to a solar panel. Depicted are flat body 111, inner panel attachment flange 112 outer panel attachment flange 113 and linking flange 114. Inner and outer attachment flanges 112, 113 are formed to mate with an outer frame of a solar panel (201, FIG. 2). Outer panel attachment flange 113 is in a middle position because linking flange 114 is intended for attachment outside of outer attachment flange 113.

[0066] Also depicted in FIG. 1 is frame grip 122, which is depicted as an angled or wedge portion of inner attachment flange 112. It is noted that the configuration of frame grip 122 is dependent on the physical configuration of the solar panel's frame to which corner bracket 101 mates.

[0067] FIG. 2 depicts corner bracket 101 attached to solar panel 201.

[0068] FIGS. 3A-3D are schematic diagrams showing solar panels 201 connected using individual corner brackets 101 and a hold-down clamp 301. Hold-down clamp 301 is used to link corner brackets 101, with clamp flanges 314 on clamp 301 engaging linking flanges 114 on brackets 101. Clamp flanges 314 may also closely fit against outer attachment flanges 113 for added stability, according to design choice. Also depicted is anchor bolt or pin 321 (FIG. 3C), which is used to secure hold-down clamp 301 to the ground or other supporting surface. Anchor bolt or pin 321 is given as a non-limiting example, as any suitable anchoring mechanism can be used, provided corner brackets 101, hold-down clamp 301 or another part can be secured to the anchoring mechanism.

[0069] A cross-section of the arrangement is depicted in FIG. 4. While adjacent corner brackets 101, 101 are depicted as abutting, in the depicted arrangement, corner brackets 101, and hence panels 201 have lateral play, as the primary function of corner brackets 101 and hold-down clamp 301 is to retain panels 201 in place on the ground (vertical positioning), with lateral movement inherently limited. So long as the connecting cables or “strings” can tolerate the implied variations, the positional tolerance would not affect the assembly. Other physical variations can be employed, so long as the clamping and hold-down functions are accomplished.

[0070] FIGS. 5A and 5B are schematic diagrams showing a configuration of corner brackets, in which horizontal support is used to secure panels. FIG. 5A shows a configuration for a clamp 501 in which top and bottom corner flanges 511, 512 are used. FIG. 5B shows a configuration in which a bracket 531 extends in a straight line connecting two modules 201. By using interlocking links, opposing brackets 501-501 can be locked together, and secured by the weight of the panels 201, with or without the use of anchor bolts or pins 321 (FIG. 3C) or another suitable anchoring device.

[0071] In addition to simpler mounting, the flat mounting system makes some maintenance tasks easier. By way of non-limiting example, cleaning equipment can be operated across the tops of the panels, as will be described.

Furrow Mounting

[0072] The earth-oriented mounting lends to directly placing the panels on the ground without the use of corner brackets or other external bracing. In the case of solar panels with frames, the frame can be rested on the ground, which, in turn, provides mechanical support for the panels. FIGS. 6A and 6B are schematic diagrams showing a solar panel 601 with its edge frame 611 resting on the ground.

[0073] Referring to FIG. 6A, the ground is prepared by generally smoothing the ground to desired contours for the panels 601. Furrows 621 are dug by mechanical means, and the panels 601 are placed on the ground with their edge frames 611 resting against the sides of furrows 621. Furrows 621 serve to positionally stabilize the panels 601 and provide the mechanical support for the panels 601. While it is possible for the panels 601 to directly rest on the ground on parts of the panels 601 other than the edge frames 611, the support by the frames 611 reduces mechanical force applied to the active parts of the panels 601 and leaves additional room for electrical connections. Thus, the furrows 621 are formed as grooves, depressions or channels dug into the ground to receive the edge frames 611.

[0074] While smoothing and prior ground preparation is described, it is possible in some circumstances to avoid some of the grading and contouring steps. It is also possible that some ground conditions allow direct placement of the edge frames 611 with the edge frames 611 securing the panels 601 to the ground without a specially prepared furrow. The smoothing facilitates orienting the panels substantially parallel to the ground.

[0075] FIG. 6B shows an end stop or curb member 635 positioned at the edge of an array. Curb 635 can be made of any convenient low-cost material and serves to retard movement of the panels along the edges of the array. Since adjacent panels within the array abut one another or are otherwise near each other, the only place for lateral movement would be along the edges of the array, which is prevented by curb 635. Curb 635 also directs surface water over the tops of the panels 601, which reduces the potential for washout of the soil and lifting of the panels 601 caused by surface water. Additionally, causing surface water to flow over the tops of panels 601 has some benefit in keeping the panels 601 clean. These advantages are also useful in installations in which corner brackets or other brackets are used to support solar panels.

[0076] The depiction of FIG. 6B shows water flow on the upslope side of the array, in which water may have sufficient velocity to flow upward over to top, as indicated by the arrows. Water that pools at curb 635 would be able to flow laterally parallel to curb 635 or percolate into the ground.

[0077] Furrows 621 are given by way of non-limiting example. In many installations, it is possible to directly support the panels 601 or the edge frames 611 directly on the ground without digging furrows. In some soil conditions, the edge frames 611 will sink into the soil, whereas in other conditions, the edge frames 611 will remain substantially at the top surface of the ground. It is further expected that the panels 601 will rest against the ground without the use of the edge frames 611, either because the edge frames 611 can sink below a level at which the panels will rest on the ground, or in cases in which panels are constructed without edge frames.

Alternate Mounting Systems

[0078] FIGS. 7A-7F are schematic diagrams showing configuration of corner brackets, in which a single disk supports four panels at corners of the panels.

[0079] FIG. 7A is a perspective view of the corner bracket supporting four panels, with the panels in cut-away view. FIG. 7B shows the arrangement of the corner bracket. FIG. 7C shows a bottom support. FIG. 7D shows a cross-section of the corner bracket with a cinch pin. FIG. 7E shows the corner bracket and cinch pin gripping an anchor cable. FIG. 7F shows the corner bracket with the cinch pin securing panels.

[0080] The configuration of FIGS. 7A-7F allows simplified mounting, and further facilitates the use of anchor cables. The anchor cable can be any convenient anchoring system, such as a cable anchoring system produced by American Earth Anchors of Franklin, Mass. (US), one variation being the Model 3ST60QV anchor system, which uses a pivoting spade attached to wire rope. The wire rope is swaged or cinched by a swage fitting such as an American Earth Anchors Quickvice QV18 swage fitting (Quickvice is a trademark of American Earth Anchors). The anchor system sold by American Earth Anchors is given by way of non-limiting example, as a wide variety of convenient anchoring systems can be used.

[0081] Advantageously, since the panels are resting on the ground, they are not generally exposed to sufficient upward force to lift them upward. Therefore, the soil anchoring system need only provide intermittent anchoring support, for example when exposed to weather events resulting in strong winds.

[0082] FIGS. 8A-8C are schematic diagrams showing configuration of a spring clip arrangement used to link panels with a minimal gap between panels using spring clip 801. FIG. 8A shows spring clip 801 in profile. FIG. 8B shows spring clip 801 in an elevation view. FIG. 8C shows spring clip 801 engaging one solar panel. Spring clip 801 comprises a flat sheet 811, folded to outer frame support 813 (for the outer frame sides of solar panels), with raised retainer lips 814, and two inner frame supports 817 (for inner frame edges of the solar panels), with raised retainer lips 818. As can be seen in FIG. 8C, solar panel 201 is retained with its outer frame resting against outer frame support 813 and held down by retainer lip 814. The corresponding inner frame support 817 is hidden from view in FIG. 8C. Stake holes 823 (FIGS. 8B and 8C) facilitate anchoring spring clip 810 to the ground, for example by use of an anchor stake or an alternate anchoring system such as the above-mentioned cable anchoring system produced by American Earth Anchors.

[0083] FIGS. 9A and 9B are schematic diagrams showing the spring clip of FIGS. 8A-8C gripping panels. FIG. 9A shows two adjacent panels 201 held by spring clip 801. FIG. 9B shows the gripping arrangement of spring clip 801. As can be seen in FIG. 9A, the arrangement is such that adjacent solar panels 201-201 fit closely together, which reduces the gap between the adjacent solar panels and reduces the tendency of the solar panels 201 to lift when exposed to strong winds.

[0084] To install solar panels 201 into spring clip, the panels are positioned in place and downward pressure is applied to cause the panels 201 to snap into place.

[0085] It is further possible to restrain the panels by other techniques. By way of non-limiting example, adjacent panels can be linked together. Other linkages include cables or rods routed through support edges of the panels. The cables or rods can extend across multiple panels or across the length or width of the array,

Backside Cooling

[0086] A further advantage of mounting the modules on the ground or just above the ground is that cooling from the backside of the modules' surface is easily accomplished. Cooling techniques can include, by way of non-limiting example, evaporative cooling, alternate high emissivity coatings, the addition of “air vents” on the edge of the module frame, and the addition of various enhanced heat transfer materials and or methods. The increased cooling, by reducing the operating temperature, increases the effective energy production rate of the modules. The positioning of the modules on the ground results in avoiding indirect sunlight and heat from ground exposed to sunlight from heating the backsides of the modules. As a result, rather than being a source of additional heat, the ground beneath the modules becomes more of a heat sink. To take further advantage of this, the modules are coated on the backside with a dark or heat transmitting coating to promote radiant heat transfer to the ground or airspace beneath the modules. By way of non-limiting example, the dark or heat transmitting coating is provided as black-pigmented Tedlar® PVF, sold by EI duPont de Neumours, of Wilmington, Del., or a dark Tedlar® coating sold as “Tedlar® Charcoal”.

[0087] Ventilation of the backside can be accomplished by a variety of techniques. By way of non-limiting example, outlet vents can connect to one or more vertical stacks to use convection to remove warm air. Alternatively, DC power can be used to operate fans either when power is produced or when peak power is sensed. Inlet vents can use separate supply tubing or louvers cut into edge frames of the modules.

Stringed Panels

[0088] FIGS. 10A and 10B are schematic diagrams showing a wiring connection layout for adjacent solar panels 201. FIG. 10A shows an array of three strings of panels arranged of in six rows. FIG. 10B shows connection details. Adjacent panels 301 within a row are series-connected. At one end of the row, the series connection extends to the next row, and then returns to the starting end. The end connections are in turn connected to inverter 1015. Inverter 1015 converts the power for downstream power use in the usual manner. While one inverter 1015 is shown, multiple inverters 1015 can be used, to place the inverter connection closer to the terminal ends of the rows.

[0089] This arrangement limits the length of the series connection, and thereby limits output voltage of the array itself to permissible levels. A typical voltage limit for a string of arrays is 1500 volts, although in residential installations and other installations where non-qualified personnel are present are typically limited to lower voltages, such as 600 volts. The arrangement conveniently limits the voltage to the series output by limiting the length of the respective strings (i.e., the number of panels connected in series).

[0090] The stringing technique works because, without racking or trackers, the length of the rows can be made shorter. Additionally, since there is no separate pathway between adjacent rows, running harnessing between rows is less complicated. By way of non-limiting example, the length of the rows can be several panels to produce half the maximum design voltage (to accommodate the return run). The individual panels are provided with terminal leads or pigtails, which are directly connected to each other. This arrangement eliminates the need to provide “home run” harness connections to link the end of a string of panels to an inverter connection at the end of the row. The end-of-row connection must still be connected to the nearest inverter if the inverter is not situated immediately at the end of the row, but the intermediate connections required to extend a string to the end of a much longer row are eliminated. Additional reduction in harnessing connections can be achieved using individual inverters at the ends of the respective pairs of rows.

Power Outlet

[0091] FIG. 11 is a graphic diagram showing a sample output for a single clear sky day of the operation of a solar power plant. The horizontal axis represents time, specifically a sample of daylight hours from roughly 7 a.m. to roughly 7 p.m., where “solar noon” is represented by the peak of the graph. The vertical axis on the left represents the available sunlight, or “solar insolation” as measured in watts per meter squared (W/m2) or the typical amount of energy available from the sun during a given day. The curve which peaks out at 1000 W/m2 is representative of a typical day of sunlight. The peak, as represented by “noon” is solar noon, not to be confused with the 12 o'clock hour, which typically varies from solar noon. The vertical axis on the right indicates the AC power output of the power plant, as well as the DC power potential of the power plant, on common scales of MW, or megawatts. The actual AC power output of the plant is represented by the two lower curves. The curve characterized by the double hump is a typical sample of a tracker type solar plant, with a maximum delivered power of 1 MW (in this example). The sharp dip in the tracker curve is emblematic of a cloud moving across the power plant between the plant and the sun. The other lower curve represents the earth-oriented power plant power curve, also with a maximum delivered power of 1 MW. The two dotted lines extending above the power curves represent the additional unused portion of DC power available. The smaller of the two curves, which peaks out at 1.25 is the tracker power plant, while the taller curve, peaking out at 1.45 is the earth-oriented power plant.

[0092] The AC power output of the power plant is intentionally limited for practical reasons, mostly related to grid capacity to absorb large amounts of power during a small part of the day. Therefore, the AC power output shows a flat peak at 1.00 MW on this graph. The excess power is either not used or applied to alternative uses such as energy storage. If alternative energy storage is limited or not available, then it is possible to use the additional energy to support the grid in volt-ampere reactive units (vars, sometime given as VARs), or other power functions other than direct increases in power output (MW). Alternatively, the excess power con be purchased as surplus power by the grid utility or transported across the grid for use at a remote location.

[0093] An economic advantage of the earth-oriented arrangement of the solar modules results from the relative economics of the DC power generation components as opposed to the total cost of operations of the power plant. As depicted in FIG. 11, the two power curves have an arbitrary limit of 1 MW. This limit is set by the utility company, to which the power is sold. This limit is a function of the needs of the utility company at the point of interconnection of the power plant and cannot be exceeded by contract nor design. An important point of note is that the available DC power from the earth-oriented power plant is greater than the available DC power from the tracker power plant as is depicted in FIG. 11. This fact is a result of the difference in power plant design, function, and economics. The earth-oriented power plant has more DC power available because it has more modules in use for the same size AC. This is due to the elimination of the additional physical hardware required to hold the modules in space as well as the amount of land required to house the quantity of modules mounted on racks sufficiently spaced apart as to not shade one another. The earth-oriented plant has an intrinsic advantage over the tracker and fixed title plant in that it can contain more DC as a percentage of the design output which translates to the AC size. The additional DC power in the power plant has intrinsic value when available. This is true for any solar plant sized with a DC:AC ratio greater than 1.0. Since it cannot be used to deliver real power to the grid (the delivery of which results in revenues for the power plant owner), it is maintained as potential power, waiting to be dispatched when and if needed. There are multiple ways this intrinsic value is captured and can bring value to the asset owner.

[0094] First, during periods of intermittent cloud cover, the clouds may only cover portions of the power plant. The balance of the plant is available to run full power. The potential power of the additional DC has the effect of allowing the plant to ride through lower light conditions from clouds while still delivering 100% of the AC power plant capacity allowed by the grid connection. If there is greater DC potential, the power plant can ride through larger clouds, and slower moving clouds without going below 100% capacity. This effect is currently not calculated in the industry as it is currently impossible to make these measurements. As such, approximations are used. The accuracy of these approximations can only be determined by empirical means. What can be said is that the additional DC potential will result in some amount of benefit that is greater than zero.

[0095] Second, the utility operator receiving real power from the power plant has developed the means to use the potential DC power to the benefit of their system. This benefit comes in the form supplemental voltage, and frequency regulation of the grid by adjusting the power factor control capabilities of the connected set of inverters. Modem solar power operators have become aware of this benefit and are now selling this portion of the available power in the form of vars to the utility. The additional DC potential of the earth-oriented plant brings additional vars available to be sold as compared to a non-earth-oriented solar plant of the same AC power rating.

[0096] Third, as the use of solid-state batteries or other energy storage or conversion means have become more financially viable, the ability to convert the potential DC power from the solar plant into potential DC energy, stored in the storage means, allows for the direct transfer of the potential DC power into the sale of real energy to the grid at times when the sun is not available or other valuable use of the energy. The additional DC potential of the earth-oriented plant brings additional energy potential available to be sold as compared to a non-earth-oriented solar plant of the same AC power rating.

Solar Plant Layout

[0097] FIGS. 12A-12D are schematic diagrams showing a layout of a solar array for a commercial solar power plant. FIG. 12A shows a partial string array of three strings of panels arranged in six rows. FIG. 12B expands 12A to show a string array comprising 18 strings with a string inverter depicted in the center. The inverterl015 is connected to the strings for purposes of converting the DC power from the strings to AC power. FIG. 12C further expands 12B to show 6 string arrays further co-located to one another. FIG. 12D further expands 12C to show a complete solar array 1220 comprised of 18 string arrays, 18 string inverters, 324 strings, and a single medium voltage transformer which receives power from the six sets of three series-connected string inverters. A utility scale solar power plant typically comprises one or more of these arrays.

Cleaning

[0098] The flat orientation of the panels also provides advantages as far as cleaning is concerned. Panels in a flat arrangement can easily be cleaned by an automated warehouse street sweeper. Such cleaning devices, such as the FyBot ‘L’ (trademark of FyBots of Voisins-le-Bretonneux, France), a commercially available fully autonomous warehouse sweeping robot, similar in operation to home-use robotic vacuum cleaners such as the Roomba (trademark of iRobot Corporation), and the automated cleaning technique was tested with a Roomba 690-type cleaner. While cleaning is more important for earth-oriented solar panels, the ability to use low-cost automated cleaning allows frequent cleaning at significantly less cost than would be incurred in if one were to institute a regimen for cleaning rack-mounted arrays. The implementation of a low-cost cleaning regimen on earth-oriented arrays results in soiling loss reductions from typically 6% for fixed tilt and 3.5% for trackers, non-cleaned, down to less than 1% for the cleaned earth-oriented array.

[0099] Referring again to FIGS. 12A-12D, to traverse gaps between the portions of the arrays, bridges 1233 are provided to connect gaps within the array to allow the automated warehouse street sweeper to automatically traverse the gaps. Similar bridges can be provided between arrays as well, to allow the cleaning operation to continue automatically across multiple arrays.

[0100] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated to explain the nature of the subject matter, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

[0101] In some embodiments, the spacing between adjacent modules is 11/16 inch (17.5 mm) or greater. The Solar Energy Industries Association (SEIA), a leading trade group for solar developers, defines a solar project as utility-scale if it generates greater than 1 megawatt (MW) of solar energy.