Broadband reflectors, concentrated solar power systems, and methods of using the same
Broadband reflectors include a UV-reflective multilayer optical film and a VIS/IR-reflective layer. In various embodiments, the VIS/IR reflective layer may be a reflective metal layer or a multilayer optical film. Concentrated solar power systems and methods of harnessing solar energy using the broadband reflectors and optionally comprising a celestial tracking mechanism are also disclosed.
1. A broadband reflector comprising:
a UV-reflective multilayer optical film having a first major surface and comprising a UV-reflective optical layer stack, wherein the UV-reflective optical layer stack comprises first optical layers and second optical layers, wherein at least a portion of the first optical layers and at least a portion of the second optical layers are in intimate contact and have different refractive indexes, wherein the first optical layers comprise a first polymer and the second optical layers comprise a second polymer, and wherein neither the first polymer nor the second polymer absorb UV light in a wavelength range from 350 nanometers to 400 nanometers; and
a VIS/IR-reflective metal layer disposed on at least a portion of the first major surface.
2. The broadband reflector of claim 1 , further comprising an adhesive layer disposed on the metal layer opposite the UV-reflective multilayer optical film.
3. The broadband reflector of claim 1 , wherein the VIS/IR-reflective metal layer comprises at least one of silver, copper, stainless steel, or aluminum.
4. The broadband reflector of claim 1 , wherein at least one of the following conditions is met:
the broadband reflector has an average light reflectivity of 90 percent over a wavelength range of 300 to 400 nanometers; or
the broadband reflector has an average light reflectivity of at least 95 percent over a wavelength range of 350 to 2494 nanometers.
5. A concentrated solar power system comprising:
at least one broadband reflector according to claim 1 capable of being aligned to direct solar radiation onto a hollow receiver; and
a heat transfer fluid partially disposed within the hollow receiver.
6. The concentrated solar power system of claim 5 , further comprising an electrical generator in fluid communication with the hollow receiver.
7. The concentrated solar power system of claim 5 , further comprising a celestial tracking mechanism for the at least one broadband reflector.
8. The concentrated solar power system of claim 7 ,
wherein the celestial tracking mechanism comprises a louver pivotally mounted adjacent the hollow receiver, wherein the louver comprises the at least one broadband reflector.
9. A method of harnessing solar energy, the method comprising reflecting solar radiation using at least one broadband reflector according to claim 1 onto a hollow receiver containing a heat transfer fluid to provide a heated heat transfer fluid.
10. A method of using the broadband reflector of claim 1 , the method comprising:
adhering the broadband reflector to an existing solar reflector adapted for use in a concentrated solar power system.
11. The broadband reflector of claim 1 , wherein the UV-reflective multilayer optical film further comprises a tie layer that comprises the first major surface of the UV-reflective multilayer optical film.
12. The broadband reflector of claim 1 , wherein the UV-reflective multilayer optical film further comprises a second major surface opposite the first major surface, and wherein the UV-reflective multilayer optical film further comprises an abrasion resistant layer that forms the second major surface of the UV-reflective multilayer optical film.
13. The broadband reflector of claim 1 , wherein the UV-reflective multilayer optical film also reflects visible light.
14. A broadband reflector comprising:
a UV-reflective multilayer optical film having a first major surface and comprising a UV-reflective optical layer stack, wherein the UV-reflective optical layer stack comprises first optical layers and second optical layers, wherein at least a portion of the first optical layers and at least a portion of the second optical layers are in intimate contact and have different refractive indexes; and
a VIS/IR-reflective metal layer disposed on at least a portion of the first major surface, wherein:
(i) the first optical layers comprise a syndiotactic polystyrene and the second optical layers comprise a polydiorganosiloxane polyoxamide block copolymer; or
(ii) the first optical layers comprise a syndiotactic polystyrene and the second optical layers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride; or
(iii) the first optical layers comprise a polymethyl methacrylate and the second optical layers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride; or
(iv) the first optical layers comprise a copolymer of ethylene and a cyclic olefin and the second optical layers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride; or
(iv) the first optical layers comprise a copolymer of ethylene and vinyl acetate and the second optical layers comprise a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride.
15. The broadband reflector of claim 14 , wherein at least one of the following conditions is met:
the broadband reflector has an average light reflectivity of 90 percent over a wavelength range of 300 to 400 nanometers; or
the broadband reflector has an average light reflectivity of at least 95 percent over a wavelength range of 350 to 2494 nanometers.
16. The broadband reflector of claim 14 , wherein the UV-reflective multilayer optical film further comprises a second major surface opposite the first major surface, and wherein the UV-reflective multilayer optical film further comprises an abrasion resistant layer that forms the second major surface of the UV-reflective multilayer optical film.
17. The broadband reflector of claim 14 , wherein the UV-reflective multilayer optical film also reflects visible light.
18. A concentrated solar power system comprising:
at least one broadband reflector according to claim 14 capable of being aligned to direct solar radiation onto a hollow receiver; and
a heat transfer fluid partially disposed within the hollow receiver.
19. The broadband reflector of claim 14 , further comprising an adhesive layer disposed on the metal layer opposite the UV-reflective multilayer optical film.
20. The broadband reflector of claim 14 , wherein the VIS/IR-reflective metal layer comprises at least one of silver, copper, stainless steel, or aluminum.