Broadband reflectors, concentrated solar power systems, and methods of using the same

Abstract

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.

What is claimed is: 
     
         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, and wherein the UV-reflective optical layer stack is reflective to UV-light;   a VIS/IR-reflective multilayer optical film comprising a VIS/IR-reflective optical layer stack, wherein the VIS/IR-reflective optical layer stack comprises third optical layers and fourth optical layers, wherein at least a portion of the third optical layers and at least a portion of the fourth optical layers are in intimate contact and have different refractive indexes, and wherein the VIS/IR-reflective multilayer optical film is reflective to VIS/IR-light; and   a UV-absorbing layer disposed between the first major surface of the UV-reflective multilayer optical film and the VIS/IR-reflective multilayer optical film, wherein the UV-absorbing layer comprises a polymer and a UV-absorber.   
     
     
         2 . The broadband reflector of  claim 1 , wherein the third optical layers and fourth optical layers respectively comprise a polyethylene terephthalate and a THV, a polyethylene terephthalate and an OTP, a PEN and a THV, a PEN and an OTP, a PEN and a PMMA, a polyethylene terephthalate and a coPMMA, a PEN and a coPMMA layer pairs, a coPEN and a PMMA layer pairs, a coPEN and an OTP, a coPEN and a THV, a sPS and an OTP, a sPS and a THV, a PMMA and a THV, a COC and a THV, or an EVA and a THV. 
     
     
         3 . The broadband reflector of  claim 1 , further comprising an adhesive layer disposed on the VIS/IR-reflective multilayer optical film opposite the UV-absorbing layer. 
     
     
         4 . The broadband reflector  claim 1 , wherein the first optical layers and second optical layers respectively comprise a polyethylene terephthalate and a coPMMA, a sPS and an OTP, a sPS and a THV, a PMMA and a THV, a COC and a THV, or an EVA and a THV. 
     
     
         5 . The broadband reflector  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. 
     
     
         6 . The broadband reflector of  claim 5 , wherein the tie layer comprises an inorganic tie layer. 
     
     
         7 . The broadband reflector of  claim 1 , wherein the broadband reflector has an average light reflectivity of at least 90 percent over a wavelength range of from 300 to 2494 nanometers. 
     
     
         8 . 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. 
     
     
         9 . The broadband reflector of  claim 8 , wherein the abrasion resistant layer comprises:
 an antisoiling component selected from the group consisting of fluoropolymers, silicone polymers, titanium dioxide particles, polyhedral oligomeric silsesquioxanes, and combinations thereof.   
     
     
         10 . A concentrated solar power system comprising:
 at least one broadband reflector of  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.   
     
     
         11 . The concentrated solar power system of  claim 10 , further comprising an electrical generator in fluid communication with the hollow receiver. 
     
     
         12 . The concentrated solar power system of  claim 10 , further comprising a celestial tracking mechanism for the at least one broadband reflector. 
     
     
         13 . The concentrated solar power system of  claim 12 , wherein the celestial tracking mechanism comprises a louver pivotally mounted adjacent the hollow receiver, wherein the louver comprises the at least one broadband reflector. 
     
     
         14 . A method of harnessing solar energy, the method comprising reflecting solar radiation using at least one broadband reflector of  claim 1  onto a hollow receiver containing a heat transfer fluid to provide a heated heat transfer fluid. 
     
     
         15 . The method of  claim 14 , further comprising thermally heating at least a portion of a building with heat given off from the heated heat transfer fluid. 
     
     
         16 . The method of  claim 14 , further comprising generating electrical power using the heated heat transfer fluid. 
     
     
         17 . 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.   
     
     
         18 . A solar collection device comprising at least one solar cell and a broadband reflector according to  claim 1  positioned in proximity to the at least one solar cell.