Optics for solar concentrators
Optics are provided for use in solar concentrators, the optics having a light guide, a redirecting layer including a plurality of lenses, and a plurality of reflector elements. Sunlight is received by the redirecting lenses, which focus the sunlight onto reflective surfaces of the reflector elements. The reflective surface of each reflector element redirects the light into the light guide, which guides the light toward a solar energy collector, such as a photovoltaic cell. The light from the light guide may be directed onto the solar energy collector by a light conditioning element.
1. An optic for use with a solar energy collector in a solar concentrator, the optic comprising:
a light guide of light transmissive material, the light guide comprising
a first surface;
a second surface opposite the first surface;
a light coupling area for emitting light from the light guide; and
a peripheral edge;
a redirecting layer comprising a plurality of lenses, the redirecting layer being optically attached to the first surface of the light guide;
a plurality of reflector elements made of light transmissive material of lower refractive index than the material of the light guide, the reflector elements optically connected to a portion of the second surface of the light guide having a downward slope equal to or less than the average downward slope of the second surface between the peripheral edge and the light coupling area, each reflector element being associated with a lens of the redirecting layer and having a reflective surface for receiving light focused thereon by the associated lens, the reflective surface reflecting the received light into the light guide for transmission therein toward the solar energy collector; wherein the light being transmitted within the light guide can undergo total internal reflection at the interface between the second surface of the light guide and the optically connected surface of the reflector element; and
a light conditioning element for receiving light from the light coupling area of the light guide and collecting the received light onto the solar energy collector.
2. The optic of claim 1 where the light guide is made from a material selected from the group of glass, polycarbonate, injection molded poly(methyl methacrylate) (PMMA), injection molded polymethyl methacrylimide (PMMI), cyclo olefin polymers (COP), cyclo olefin copolymers (COC), and silicone.
3. The optic of claim 1 where the first surface is a planar surface.
4. The optic of claim 1 where the plurality of lenses of the redirecting layer is plano-convex lenses that are adjacent to one another.
5. The optic of claim 1 where the redirecting layer is integrated or over molded with the first surface of the light guide.
6. The optic of claim 1 where the reflector elements further comprise an inter-step portion to transmit reflected light to the light guide and wherein the reflector elements comprise flat, parabolic analytical or free-form reflective surfaces to reflect light towards the inter-step portions.
7. The optic of claim 6 wherein the reflector elements further comprise a first section to reflect light from the associated lens of the redirecting layer and a second section, to reflect light to the interstep portion from the first portion.
8. The optic of claim 6 further comprising a low refractive index film between a reflector element and the light guide whereby light exiting the reflector element via the inter-step portion of the reflector element undergoes total internal reflection at the interface of the low refractive index film and the reflector element.
9. The optic of claim 1 wherein light is totally internally reflected by the first surface of the light guide and a step portion of the second surface of the light guide.
10. The optic of claim 1 wherein the first surface of the light guide is sloped relative to the light emitting surface of the redirecting layer and the redirecting layer is wedged-shape in cross-section so that the combined thickness of the redirecting layer and light guide is substantially constant.
11. The optic of claim 1 further comprising an optical coupling layer between the redirecting layer and the light guide, wherein the optical coupling layer is made from a heat-deformable, optically transmissive material and the redirecting layer and the light guide are fused together into a monolithic optic.
12. The optic of claim 1 wherein the second surface of the light guide comprises a plurality of protrusions extending from a substantially flat portion whereby light from the reflector element passes into the light guide through an optical aperture formed by the protrusion and the reflector element.
13. The optic of claim 1 wherein the redirecting layer comprises a plurality of concavo-convex lenses; and the second surface of the light guide is stepped.
14. The optic of claim 13 wherein the reflector elements comprise a plurality of primary reflector elements interspersed between a plurality of secondary reflector elements, the secondary reflector elements totally internally reflect light into the light guide and the primary reflector elements reflect substantially collimated light from the concave portions of the associated lenses to light guide.
15. A solar concentrator device comprising:
an optic of claim 1 ;
a solar energy collector coupled to the light coupling area of the optic.
16. The solar concentrator device of claim 15 wherein the optic has a rotational symmetry about a central axis passing through the solar energy collector.
17. The solar concentrator device of claim 15 wherein the optic device is planar cuboid has a linear solar energy collector and a plane of symmetry about the solar energy collector.