Patent Application
20180076758
The present invention relates to photovoltaic cell assemblies and more particularly to three-dimensional elongated photovoltaic cell assemblies.
Photovoltaic cells, also known as solar cells are increasingly being utilized as a source of clean renewable energy. Photovoltaic cells can convert radiant sunlight energy into direct current electrical energy.
Photovoltaic cells comprise layers of conducting and semi-conducting materials and are typically constructed as wafers having flat structures that can be connected together to form flat photovoltaic modules or panels. Modules can in turn be connected to form photovoltaic arrays or assemblies. Photovoltaic modules of the prior art are commonly mounted on flat supporting structures providing flat assemblies with overall two-dimensional configurations. Elongated photovoltaic cells are also known and can comprise cylindrical conductor and photovoltaic layers encasing an elongated core electrode. Elongated photovoltaic cells of the prior art are usually assembled in parallel arrangements as two-dimensional structures.
The surface of photovoltaic cells must face the direction of the sun in order to absorb sunlight and produce the desired electricity. Electric output from a photovoltaic cell is greatest when the cell faces directly towards the sun, that is, the sun is at a 90 degree angle to the cell surface (0 degree angle of incidence), and output decreases as the cell faces further away from the sun (increasing angle of incidence). Thus, flat photovoltaic cell assemblies installed in a fixed position can suffer from significant daily electric output variability. Daily electric output variability can be a significant issue facing the incorporation of photovoltaic assemblies into existing electric grids. To minimize daily output variability, flat photovoltaic assemblies can be placed on motorized platforms (trackers) that track the movement of the sun throughout the day. Trackers, however, can be expensive to install and maintain.
Thus, there is a need to reduce daily solar electric output variability in order to facilitate integration of photovoltaic assemblies into the electric grid. Efficient and cost effective means of reducing variability caused by daily movement of the sun are needed that do not involve the use of trackers.
Furthermore, since the amount of electricity generated by photovoltaic assemblies is directly related to the total photovoltaic cell surface area or footprint covered by flat photovoltaic assemblies, large assembly footprints are required when attempting to produce large quantities of electricity. Thus, there is also a need for increased photovoltaic electric power output from a given assembly footprint.
An object of the present invention is to provide three-dimensional elongated photovoltaic cell assemblies with reduced daily solar electric power output variability than flat two-dimensional assemblies of the prior art. Three-dimensional elongated photovoltaic cell assemblies of the present invention are comprised of a plurality of elongated photovoltaic modules configured to project radially outward from a central trunk in a plurality of spatial directions. In some embodiments, an elongated photovoltaic module comprises an elongated body such as a multi-sided prism having a module basal end, a module distal end and a polygonal cross-section parallel to the module basal end, wherein the lateral sides of the elongated body define non-parallel elongated rectangular panels. Each elongated photovoltaic module further comprises a module electric circuit with means of conducting electricity between the module basal end and the module distal end. Photovoltaic cells are mounted on at least two of the lateral sides or panels of the elongated body and electrically connected to the module electric circuit. The elongated body can be solid, hollow or tubular. The basal end of each elongated photovoltaic module is physically attached to the lateral surface of the central trunk while the distal end is oriented to project radially outward from the central trunk. The central trunk comprises a trunk body having a first trunk end, a second trunk end and a trunk lateral surface. The central trunk functions as a central attachment hub for the elongated photovoltaic modules and is provided with a central electric circuit with means of conducting electricity between the first trunk end and the second trunk end. A means of connecting the module electric circuit of the plurality of elongated photovoltaic modules to the trunk central electric circuit is provided and a means of connecting the trunk central electric circuit to an external circuit is also provided. The exact shape of the central trunk body is not critical to the present invention and can be for example cylindrical, pyramidal, conical, spherical or prismatic. Possible shapes for the central trunk include cylinders, pyramids, pyramidal frustums, spheres, spherical frustums, cones, and conical frustums. A cross-section parallel to the base of the central trunk can describe a circle, semi-circle, oval, oblong, parabola, curvilinear polygon, ellipse, polygon or an irregular shape.
The plurality of elongated photovoltaic modules project radially from the central trunk in a plurality of spatial directions and can be uniformly distributed about the central trunk with adjacent modules pointing in different spatial directions. It is desirable to distribute elongated photovoltaic modules on the central trunk such that modules provide minimal shading to adjacent modules. The elongated photovoltaic modules can be attached from completely around the perimeter or circumference of the central trunk to as little as half the perimeter or circumference of the central trunk. The exact shape of the elongated body of elongated photovoltaic modules is not a critical parameter of the present invention and can be for example cylindrical, pyramidal, conical or prismatic to name a few. The three-dimensional arrangement of the elongated photovoltaic modules, in conjunction with photovoltaic cells being provided on several lateral sides of the elongated modules, can present an assembly's photovoltaic cells to the sun at a plurality of angles of incidence at any given time of the day. The average angles of incidence of photovoltaic assemblies of the present invention exhibit less intraday variability than the angles of incidence of flat assemblies of the prior art. Reduced angle of incidence variability can result in more consistent sunlight absorption and in turn more uniform electricity production throughout the day. A more uniform amount of light can be absorbed by the three-dimensional elongated photovoltaic cell assemblies of the present invention and thus alleviate the deficiency of prior art flat photovoltaic cell assemblies of having to track the sun.
Another object of the present invention is to provide three-dimensional elongated photovoltaic cell assemblies with greater power output than flat photovoltaic assemblies with the same footprint. Since the length or height of the central trunk can be increased without impacting the assembly footprint, the number of elongated photovoltaic modules and thus photovoltaic cell area of a three-dimensional elongated photovoltaic cell assembly of the present invention can be increased over what is possible for a flat assembly having an equivalent footprint. Increased photovoltaic cell area can result in increased overall power output from three-dimensional elongated photovoltaic cell assemblies of the present invention over what is possible from flat assemblies of the prior art with the same footprint.
In some embodiments of the present invention, an elongated photovoltaic module comprises photovoltaic cells electrically connected in series and/or parallel mounted on the surface of an elongated body. The elongated body can be a multi-sided prism, pyramid or pyramidal frustum with a cross-section of the elongated body being described by a polygon such as a triangle, square, diamond, rectangle, trapezoid, pentagon, hexagon, or octagon to name a few. Flat photovoltaic cells are mounted along the length of at least two of the lateral sides of the elongated body. The lateral sides of the multi-sided elongated body function essentially as non-parallel elongated panels that allow for photovoltaic cells to face in several directions; this is in contrast to flat assemblies of the prior art where all of the cells face in the same direction.
In some embodiments, the elongated body of a photovoltaic module can be cylindrical or conical with a cross-section parallel to the base of the elongated body being described by a circle, semi-circle, oval, oblong, ellipse, curvilinear shape such as a parabola, or an irregular curved shape, and curved photovoltaic cells are mounted along the length of the elongated body. Cylindrical and conical elongated photovoltaic modules can have photovoltaic cells covering from about 90 degrees to 360 degrees around the central axis of the modules allowing for the photovoltaic cells to face in a multitude of directions.
In some embodiments, a cross-section of the elongated body can describe a curvilinear polygon consisting of circular arcs and photovoltaic cells are mounted along the length of at least two of the circular arc lateral sides. With circular elongated photovoltaic modules, as with multi-sided modules, photovoltaic cells face in several directions at the same time. When elongated photovoltaic modules are not provided on all lateral sides of the elongated body, modules are oriented on the central trunk such that the lateral sides of the modules with photovoltaic cells can face up. Additionally the central trunk tilt angle can be adjusted depending on the assembly installation location, time of year, or even time of day.
Elongated photovoltaic modules can be constructed out of rigid or flexible materials, can be designed to be straight or curved, and can comprise transparent materials in order to maximize light transmission through the assemblies. Furthermore, individual elongated photovoltaic modules can be protected from the environment by a transparent weather-proof protective covering with a material being selected for optimized absorption of sunlight energy. A three-dimensional elongated photovoltaic assembly of the present invention can have elongated photovoltaic modules all of the same type, size, length or shape, or alternatively the modules can be of various types, sizes, lengths or shapes. The photovoltaic cells utilized in the present invention can be selected from any of the different types of available photovoltaic cells, including, but not limited to amorphous silicon, crystalline silicon, thin film, nanocrystal, cadmium telluride, carbon nanotube, and gallium arsenide germanium. Double-sided photovoltaic cells, as well as multi p-n junction photovoltaic cells can also be utilized.
In some embodiments of the present invention, elongated photovoltaic modules can comprise an elongated conductive inner core electrode encased by layers of photovoltaic materials and a transparent conductive outer electrode. Elongated photovoltaic modules having inner core electrodes can have a circular cross-section resulting in cylinder-shaped bodies. Other cross-section shapes are possible such as triangles, squares, and semi-circles to name a few.
Elongated photovoltaic modules can also be constructed using any of the methods taught in the art for constructing elongated solar cells. For example, U.S. Pat. No. 7,196,262 and No. 8,742,252 describe elongated solar cells that can be used as elongated photovoltaic modules in the present invention. U.S. Pat. No. 8,067,688 to Gronet et al. discloses a solar cell assembly comprised of elongated solar cells. The elongated solar cells of the '688 patent are arranged parallel to each other in a planar array and not in the three-dimensional arrangement of the present invention.
In other embodiments of the present invention, elongated photovoltaic modules can comprise an elongated body covered by a thin flexible photovoltaic sheet. Thin flexible photovoltaic sheets can first be produced in roll form and subsequently cut to the desired size and then secured around an elongated body to produce an elongated photovoltaic module.
In some embodiments, elongated photovoltaic modules are provided with an electrical/structural support module base at their basal end, and the central trunk is provided with a plurality of socket connectors. Module bases can provide both a means of physically securing the elongated photovoltaic modules to the central trunk and a means of electrically connecting the elongated photovoltaic modules to the central electric circuit via the socket connectors. The central electric circuit can comprise a network of other elongated photovoltaic modules connected in series, in parallel, or a combination of series and parallel to provide the desired electric output. Bypass diodes can be included in the circuit to account for any photovoltaic cells not exposed to sunlight (shaded) at any given time throughout the day. Other components and capabilities such as, but not limited to, chargers, inverters, maximum power point tracking, blocking diodes, and batteries can be included with the three-dimensional elongated photovoltaic cell assemblies of the present invention in the construction of photovoltaic energy systems.
In some embodiments of the present invention, elongated photovoltaic modules function as luminescent elongated solar concentrators and comprise a luminescent elongated body with at least one photovoltaic cell provided on at least one end of the luminescent elongated body. Sunlight absorbed by the luminescent elongated body can be converted to fluorescence and guided to the photovoltaic cell(s) to produce electricity.
Visual indicators such as light emitting diodes (LEDs) can be integrated into the assemblies of the present invention as a means for indicating the functioning state of the elongated photovoltaic modules. Visual indicators can be useful for identifying a defective elongated photovoltaic module not producing electricity in the specified range that needed to be replaced or repaired. Alternatively, visual indicators can indicate when the elongated photovoltaic modules were producing electricity within their specified limits.
Photovoltaic assemblies of the present invention can also be installed within protective enclosures. An enclosure can comprise a container of transparent material with a reflective interior surface. Reflective surfaces can also be placed in the proximity of the assemblies as means of increasing the amount of solar irradiance reaching the assemblies.
Additionally, three-dimensional elongated photovoltaic cell assemblies of the present invention can be designed to be more visually appealing than the traditional flat designs of the prior art. For example, the assemblies can be designed to resemble trees and as such can be less obtrusive and easier to architecturally integrate than flat assemblies.
By referencing preferred embodiments the present invention is described in greater detail in the detailed description and illustrated in the appended drawings. The drawings are not necessarily to scale and are intended to better illustrate different aspects of the embodiments of the invention. The specific details and embodiments are provided for illustrative purposes and are not intended to limit the scope of the invention.
A cross-section detailed view of the distal end of elongated photovoltaic module 120 of
Connectors 140 in the present embodiment depicted in
The intensity of solar radiation received by a photovoltaic cell is dependent on the angle of incidence or angle between the photovoltaic cell's surface normal and the sun's rays. In the present invention the three-dimensional configuration of the elongated photovoltaic modules, in conjunction with the photovoltaic cells being provided on multiple sides of the elongated photovoltaic modules, result in the photovoltaic cells facing the sun at a plurality of angles and thus having a plurality of angles of incidence at any given time of day. This is in contrast to flat two-dimensional photovoltaic assemblies of the prior art where the photovoltaic cells have essentially one solar angle of incidence at any given time. Using computer-generated models of three-dimensional elongated photovoltaic cell assembly 100 of
Solar Radiation Intensity (SRI)=COS(A)×100%,
where A is the average assembly solar angle of incidence for a given solar angle.
The solar irradiance profiles of assemblies 701 and 702 were obtained by first determining average assembly solar angles of incidence for solar time from 7.5 hour to 16.5 hour for an assembly location of 30 degrees north latitude on the equinox. Assembly solar radiation intensity (SRI) values were then calculated using computer-generated models as previously described for the average assembly solar angles of incidence. Additionally, since as the sun moves across the sky throughout the day there is a shading effect of the elongated photovoltaic modules due to the three-dimensional arrangement of the modules, the degree of module shading or conversely the percentage of photovoltaic area non-shaded was also determined for the assemblies for solar time from 7.5 hour to 16.5 hour. For vertical three-dimensional elongated photovoltaic cell assemblies such as assemblies 701 and 702, the amount of module shading is greatest at solar noon (12 hour) when the sun is at its highest point in the sky. Assembly Solar Irradiance (or the amount of solar radiation in KW that can be captured by an assembly) was then calculated by using the following equation:
Assembly Solar Irradiance=IG×SRI×NS×PVA,
where IG was the global solar intensity (KW/m2), SRI was the solar radiation intensity (%), NS was the degree of photovoltaic area non-shaded (%), and PVA was the total photovoltaic area (m2) of the assembly. Assembly Solar Irradiance can provide a direct indicator of the power output that could be achieved by the assemblies.
Plots of the Assembly Solar Irradiance (KW) between solar time 7.5 hour and 16.5 hour for three-dimensional elongated photovoltaic cell assemblies 701 and 702 and for a flat assembly with the same footprint are shown in
Various embodiments of elongated photovoltaic modules that can be utilized with the present invention are illustrated in
Assemblies can further comprise means of physically and electrically connecting an assembly's central trunk to the central trunk of a second assembly. An additional embodiment of the present invention illustrates how multiple three-dimensional elongated photovoltaic cell assemblies can be interconnected into larger more complex three-dimensional elongated photovoltaic cell assemblies.
It is to be understood that while the invention has been described in conjunction with specific embodiments thereof, the description and examples are intended to illustrate and not limit the scope of the invention. The data presented are not intended to provide absolute performance values for the assemblies of the present invention and are only intended for comparative purposes. Other embodiments, modifications, and advantages within the scope of the invention will be apparent to those skilled in the art.
