Laminated solar concentrating photovoltaic device
View Patent ↗A solar concentrator photovoltaic (CPV) device in which concentrator elements (optics, PV cells and wiring) are laminated to form a composite, substantially planar structure. The concentrator optics are implemented by a solid (e.g. glass) optical element that defines a focal point at which solar light received by the optical element is concentrated. Using vacuum lamination techniques, a printed circuit structure attached by way of an adhesive layer onto a surface of the optical element. The printed circuit structure includes one or more non-conductive layers and conductors that are disposed on the non-conductive layers. The PV cell is connected to printed circuit structure, and is positioned at the focal point of the optical element. Optional front and/or back protective layers are also attached prior to the lamination process. A CPV array includes multiple devices formed on an optical tile using a string-like flexible printed circuit structure.
1. A concentrating photovoltaic device comprising:
a solid, light-transparent optical element having a first side including a convex surface, a second side including a substantially flat aperture surface and a depression in a central portion of the flat aperture surface, wherein the depression is smaller than the convex surface;
a primary mirror disposed on the convex surface such that the primary mirror substantially takes a shape of the convex surface, and a secondary mirror disposed on the depression such that the secondary mirror substantially takes a shape of the depression, the primary and secondary mirrors defining a focal point at which light received by the optical element is concentrated, the primary mirror being formed such that the primary mirror takes a shape of the convex surface;
a photovoltaic cell disposed at the focal point; and
a backsheet fixedly mounted over the convex surface of the optical element, the backsheet including a flexible printed circuit structure and a first adhesive layer disposed between the flexible printed circuit structure and the convex surface,
wherein the flexible printed circuit structure includes one or more non-conductive layers and first and second conductors disposed on the non-conductive layers,
wherein portions of the flexible printed circuit structure conform to follow a contour of the primary mirror, and
wherein the photovoltaic cell includes first and second terminals respectively electrically connected to the first and second conductors of the flexible printed circuit structure.
2. The concentrating photovoltaic device according to claim 1 , wherein the flexible printed circuit structure includes a central portion disposed over a center of the convex surface of the optical element and one or more peripheral portions extending from the central portion over the convex surface.
3. The concentrating photovoltaic device according to claim 2 , wherein a first thickness of the first adhesive layer adjacent to the center of the convex surface is less than a second thickness adjacent to a peripheral edge of the convex surface.
4. The concentrating photovoltaic device according to claim 2 , wherein a first thickness of the backsheet adjacent to the center of the convex surface is less than a second thickness adjacent to a peripheral edge of the convex surface.
5. The concentrating photovoltaic device according to claim 2 , further comprising an optically transparent material disposed on the center of the convex surface between the central portion of the flexible printed circuit structure and an adjacent surface of the optical element.
6. The concentrating photovoltaic device according to claim 5 , wherein the optically transparent material defines a cavity located at the center of the convex surface, and wherein the concentrating photovoltaic device further comprising a heat slug disposed in the cavity and electrically connected between at least one of the first and second terminals of the PV device and at least one of the first and second conductors of the flexible printed circuit structure.
7. The concentrating photovoltaic device according to claim 2 , wherein the one or more peripheral portions of the flexible printed circuit structure comprise a plurality of radial arms extending from the central portion, wherein each adjacent pair of radial arms are separated by an associated slit.
8. The concentrating photovoltaic device according to claim 1 ,
wherein the one or more non-conductive layers of the flexible printed circuit structure comprise a flexible polyimide film, and
wherein the first and second conductors of the flexible printed circuit structure comprise one of copper or Fe—Ni alloy disposed on the flexible polyimide film.
9. The concentrating photovoltaic device according to claim 8 ,
wherein the second conductor is disposed between the first conductor and the optical element, and
wherein a mass per unit area of the second conductor is greater than a mass per unit area of the first conductor.
10. The concentrating photovoltaic device according to claim 1 , wherein the first adhesive layer comprises ethylene vinyl acetate copolymers.
11. The concentrating photovoltaic device according to claim 1 , wherein the backsheet further comprises a protective shell layer disposed on a backside surface of the flexible printed circuit structure, and a second adhesive layer disposed between the backside surface of the flexible printed circuit structure and the protective shell layer.
12. The concentrating photovoltaic device according to claim 11 , wherein the protective shell layer comprises a relatively high melting point plastic material with respect to a melting point of the second adhesive layer, and the second adhesive layer comprises ethylene vinyl acetate copolymers.
13. The concentrating photovoltaic device according to claim 1 , further comprising a transparent coversheet disposed over the aperture surface and the secondary mirror, and a third adhesive layer disposed between the transparent coversheet and the aperture surface.
14. The concentrating photovoltaic device according to claim 13 , wherein transparent coversheet comprises tempered glass and the third adhesive layer comprises ethylene vinyl acetate copolymers.
15. The concentrating photovoltaic device according to claim 14 , wherein transparent coversheet comprises one of an antireflective coating and an element for rejecting radiation having one or more predetermined wavelengths.
16. A laminated concentrating solar collector array comprising:
a solid, light-transparent optical tile having opposing first and second surfaces, wherein the first surface includes a plurality of convex portions, the second surface includes a plurality of substantially flat aperture portions and a plurality of depressions, the depressions being smaller than the convex portions;
a plurality of optical elements formed on the optical tile, each optical element including a primary mirror disposed on an associated one of the plurality of convex portions and a secondary mirror disposed on an associated one of the plurality of depressions, each optical element defining a focal region at which light received by the optical element is concentrated by the primary and secondary mirrors of said each optical element;
a plurality of photovoltaic cells, each photovoltaic cell being disposed at the focal point of an associated optical element; and
a backsheet fixedly mounted over the first surface of the optical tile, the backsheet including a flexible printed circuit array and a first adhesive layer disposed between the printed circuit array and the first surface,
wherein the flexible printed circuit array includes one or more non-conductive layers and first and second conductors disposed on the non-conductive layers,
wherein portions of the flexible printed circuit array conform to follow a contour of each primary mirror of the plurality of optical elements, and
wherein each PV cell includes first and second terminals respectively electrically connected to the first and second conductors of the flexible printed circuit array.
17. The laminated concentrating solar collector array according to claim 16 , wherein the flexible printed circuit array comprises:
a plurality of printed circuit structures, each printed circuit structure including a central portion having an associated photovoltaic cell mounted thereon; and
a plurality of extensible structures connected between adjacent pairs of said printed circuit structures.
18. A method for producing a concentrating photovoltaic device comprising:
forming a solid, light-transparent optical element having opposing first and second surfaces, wherein the first surface includes a convex surface, the second surface includes a substantially flat aperture surface and a curved surface and the curved surface is smaller than the convex surface;
disposing a primary mirror on the convex surface and a secondary mirror on the curved surface such that the primary mirror and secondary mirror define a focal point at which light received by the optical element is concentrated;
forming a flexible printed circuit structure including one or more non-conductive layers and first and second conductors disposed on the non-conductive layers;
mounting a photovoltaic cell onto the flexible printed circuit structure such that a terminal of the PV cell is electrically connected to at least one of the first or second conductors of the flexible printed circuit structure; and
laminating the flexible printed circuit structure onto the optical element such that portions of the flexible printed circuit structure conform to follow a contour of the primary mirror, and the photovoltaic cell is disposed at the focal point.