Solar receiver with varied reflectivity

1 . A solar receiver, comprising:

a porous structure;

wherein the porous structure comprises at least one channel,

wherein the porous structure includes a uniform or varying porosity distribution,

wherein the at least one channel comprises a first pair of opposing surfaces and a second pair of opposing surfaces,

wherein the at least one channel has a length and an opening height,

wherein the length is larger than the opening height,

wherein the first pair of opposing surfaces comprise a specular reflective region,

wherein the second pair of opposing surfaces comprise a diffuse reflective region,

wherein a reflectivity of at least one of the specular reflective region or the diffuse reflective region varies along a length of the at least one channel

wherein the at least one channel has a polygonal cross-section,

wherein the first pair of opposing surfaces are a first and second side of the at least one channel, and

wherein the second pair of opposing surfaces are a third and fourth side of the at least one channel.

2 . The solar receiver of claim 1 , wherein the porous structure has at least one of the following: a monolithic or assembled honeycomb shape, a stacked shape plate, a corrugated structure, or a foam structure.

3 . The solar receiver of claim 1 , wherein the specular reflective region has higher reflectivity compared to the total reflectivity of the diffuse reflective region.

4 . The solar receiver of claim 1 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is opposite to the surface comprising the diffuse reflective region.

5 . The solar receiver of claim 1 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is adjacent to the surface comprising the diffuse reflective region.

6 . The solar receiver of claim 1 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is the same surface comprising the diffuse reflective region.

7 . A solar receiver, comprising:

a plurality of channels forming a porous structure, each channel extending from a solar radiation collection side to a heat transfer side, each channel including a uniform or varying porosity distribution,

wherein each channel comprises a first pair of opposing surfaces and a second pair of opposing surfaces,

wherein the first pair of opposing surfaces comprise a specular reflective region,

wherein the second pair of opposing surfaces comprise a diffuse reflective region,

wherein a reflectivity of at least one of the specular reflective region or the diffuse reflective region varies along the length of each channel,

wherein each channel has a length and an opening height,

wherein the length is larger than the opening height,

wherein each channel has a polygonal cross-section,

wherein the first pair of opposing surfaces are a first and second side each channel, and

wherein the second pair of opposing surfaces are a third and fourth side each channel.

8 . The solar receiver of claim 7 , wherein the specular reflective region has higher reflectivity compared to the total reflectivity of the diffuse reflective region.

9 . The solar receiver of claim 7 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is opposite to the surface comprising the diffuse reflective region.

10 . The solar receiver of claim 7 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is adjacent to the surface comprising the diffuse reflective region.

11 . The solar receiver of claim 7 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is the same surface comprising the diffuse reflective region.

12 . A method of fabricating a solar receiver comprising:

applying a desired reflectivity distribution of specular reflective regions and diffusive reflective regions to surfaces of planar pieces of a porous material; and

assembling the planar pieces into a porous structure, wherein the porous structure has a uniform or varying porosity,

wherein the porous structure comprises at least one channel,

wherein the porous structure includes a uniform or varying porosity distribution,

wherein the at least one channel comprises a first pair of opposing surfaces and a second pair of opposing surfaces,

wherein the at least one channel has a length and an opening height,

wherein the length is larger than the opening height,

wherein the first pair of opposing surfaces comprise a specular reflective region,

wherein the second pair of opposing surfaces comprise a diffuse reflective region,

wherein applying the desired reflectivity distribution comprises applying different reflectivity characteristics at different positions along a length of the planar pieces prior to assembly,

wherein the at least one channel has a polygonal cross-section,

wherein the first pair of opposing surfaces are a first and second side of the at least one channel, and

wherein the second pair of opposing surfaces are a third and fourth side of the at least one channel.

13 . The method of claim 12 , wherein planar pieces form a porous structure having a monolithic or assembled honeycomb shape, a stacked shape plate, a corrugated structure, or a foam structure.

14 . The method of claim 12 , wherein the reflectivity distribution is applied utilizing one of physical sputtering, physical polishing, chemical polishing, coating application, or chemical vapor distillation.

15 . The method of claim 12 , wherein the reflectivity distribution is applied to the surfaces of assembled planar pieces.

16 . The method of claim 12 , wherein applied the specular reflective region has higher reflectivity compared to the total reflectivity of the applied diffuse reflective region.

17 . The method of claim 12 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is opposite to the surface comprising the diffuse reflective region.

18 . The method of claim 12 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is adjacent to the surface comprising the diffuse reflective region.

19 . The method of claim 12 , wherein the surface comprising the specular reflective region is a surface of a channel of the porous structure that is the same surface comprising the diffuse reflective region.