Linear fresnel solar arrays and receievers therefor

Abstract

Described herein are solar energy collector systems, components for solar energy collector systems, and methods for installing solar energy collector systems. The components for solar energy collector systems include but are not limited to solar radiation absorbers, receivers, drives, drive systems, reflectors, and various support structures. The solar energy collection systems, solar radiation absorbers, receivers, drives, drive systems, reflectors, support structures, and/or methods may be used, for example, in LFR solar arrays. Improved solar radiation absorbers, receivers and related methods are described here.

1 . A receiver for a solar energy collection system, the receiver comprising:
 a receiver channel comprising a first sidewall, a second sidewall, and an aperture disposed between the first and second sidewalls, the first and second sidewalls and the aperture each extending along a length of the receiver channel;   a solar radiation absorber positioned in the receiver channel;   a window disposed in the aperture, so that the window and the receiver channel form a longitudinal cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window; and   one or more window support members disposed along the first sidewall and/or along the second sidewall of the receiver channel, wherein the one or more window support members is configured to allow installation of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when installed in the receiver.   
     
     
         2 . The receiver of  claim 1 , wherein the one or more window support members comprises a first window support member disposed along the first sidewall and a second window support member disposed along the second sidewall. 
     
     
         3 . The receiver of  claim 2 , wherein:
 the first window support member comprises a ledge and a step;   the second window support member comprises a slot comprising a lower slot surface, an upper slot surface spaced apart from the lower slot surface by an amount sufficient to accommodate a thickness of the window, and a slot sidewall; and   the window when installed is disposed on the ledge and on the lower slot surface and is positioned between the step and the slot sidewall, and a longitudinal edge of the window is positioned between the upper and lower slot surfaces.   
     
     
         4 . The receiver of  claim 1 , further comprising one or more tabs configured to secure the window when installed in the receiver. 
     
     
         5 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 a receiver channel comprising a first sidewall, a second sidewall, and an aperture disposed between the first and second sidewalls, the first and second sidewalls and the aperture each extending along a length of the receiver channel; 
 a solar radiation absorber positioned in the receiver channel; 
 a window disposed in the aperture so that the window and the receiver channel form a longitudinal cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window; and 
 one or more window support members disposed along the first and/or second sidewall of the receiver channel, wherein the one or more window support members is configured to allow insertion of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when installed in the receiver; and 
   first and second reflector fields positioned on opposite sides relative to a center of the elevated receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         6 . A receiver for use in a solar energy collector system, the receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel;   a solar radiation absorber positioned in the receiver channel; and   a window disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein at least one of the window and the receiver channel is configured to accommodate thermal expansion and contraction along a length of the aperture.   
     
     
         7 . The receiver of  claim 6 , wherein the window comprises two or more overlapping window sections distributed along the length of the aperture. 
     
     
         8 . A solar energy collector system comprising:
 an elevated receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel; 
 a solar radiation absorber positioned in the channel; and 
 a window disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein at least one of the window and the receiver channel is configured to accommodate thermal expansion along a length of the aperture; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         9 . A receiver for a solar energy collector system, the receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel;   a solar radiation absorber positioned in the receiver channel; and   a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein:   the junction is configured to allow the window to slide relative to the receiver channel; and   ingress of external air into the cavity through the junction between the window and the receiver channel is inhibited.   
     
     
         10 . The receiver of  claim 9 , comprising a sealing member positioned in the junction between the receiver channel and the window to inhibit ingress of external air into the cavity. 
     
     
         11 . The receiver of  claim 9 , further comprising a roof positioned over the receiver channel to form a volume between the roof and the receiver channel, wherein:
 the volume is in fluid communication with the cavity that houses the solar radiation absorber;   a thermally insulating material is disposed in the volume; and   a rate of flow of external air into the cavity through at least a portion of the insulating material in the volume is greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel.   
     
     
         12 . The receiver of  claim 9 , wherein a positive pressure of filtered air is flowed into the cavity to inhibit the ingress of external air into the cavity. 
     
     
         13 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel; 
 a solar radiation absorber positioned in the receiver channel; and 
 a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the junction is configured to allow the window to slide relative to the receiver channel and ingress of external air into the cavity through the junction between the receiver channel and the window is inhibited; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         14 . The system of  claim 13 , wherein the receiver further comprises:
 a roof positioned over the receiver channel to form a volume between the roof and the receiver channel, the volume in fluid communication with the cavity that houses the solar radiation absorber; and   a thermally insulating material disposed in the volume, wherein a rate of flow of external air into the cavity through at least a portion of the insulating material is greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel.   
     
     
         15 . A receiver for a solar energy collector system, the receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel;   a roof positioned over and extending along the length of the receiver channel, the roof having a transverse cross-section that forms a smooth curve and comprising a concave surface that faces the receiver channel;   a solar radiation absorber positioned in the receiver channel; and   a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the roof is configured to shed environmental debris away from the window.   
     
     
         16 . The receiver of  claim 15 , wherein the roof extends below the junction between the receiver channel and the window. 
     
     
         17 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 a receiver channel comprising an aperture extending along a length of the receiver channel; 
 a roof positioned over and extending along the length of the receiver channel, the roof having a transverse cross-section that forms a smooth curve and comprising a concave surface that faces the receiver channel; 
 a solar radiation absorber positioned in the receiver channel; and 
 a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the roof is configured to shed environmental debris away from the window; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         18 . The system of  claim 17 , wherein the roof extends below the junction between the window and the receiver channel. 
     
     
         19 . A receiver for a solar energy collector system, the receiver comprising:
 a solar radiation absorber comprising a plurality of parallel absorber tubes each extending along a length of the receiver; and   a plurality of spacers, each spacer positioned between two adjacent ones of the parallel absorber tubes, wherein transverse space provided by each spacer accommodates thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes.   
     
     
         20 . The receiver of  claim 19 , wherein one of the spacers positioned between two adjacent ones of the parallel absorber tubes that are located near a transverse center of the receiver channel is larger than another of the spacers that is positioned between two adjacent ones of the parallel absorber tubes that are located near an outer longitudinal edge of the absorber. 
     
     
         21 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and 
 a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture; 
 a plurality of spacers, each spacer positioned between two adjacent ones of the parallel absorber tubes, wherein transverse space provided by each spacer accommodates thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         22 . A receiver for a solar energy collector system, the receiver comprising:
 a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver; and   one or more rollers extending transversely across the receiver, wherein:   the plurality of parallel absorber tubes is supported by at least one of the one or more rollers;   at least one of the one or more rollers comprises a central shaft disposed within a hollow cylinder comprising two cylinder ends; and   the hollow cylinder is supported at each of the two cylinder ends by a bushing coupled to the central shaft.   
     
     
         23 . The receiver of  claim 22 , wherein a diameter of the central shaft is at most about one half a diameter of the hollow cylinder. 
     
     
         24 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and 
 a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture, the plurality of parallel absorber tubes supported by one or more rollers positioned transversely across the receiver channel, wherein at least one of the one or more rollers comprises a central shaft disposed within a hollow cylinder comprising two cylinder ends, and the hollow cylinder is supported at each of the two cylinder ends by a bushing coupled to the central shaft; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes; and 
 the reflectors are driven to at least partially track diurnal motion of the sun. 
   
     
     
         25 . The system of  claim 24 , wherein a diameter of the central shaft is at most about one half of a diameter of the hollow cylinder. 
     
     
         26 . A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising a plurality of absorber tubes, wherein each of the absorber tubes is coupled via a tube structure to a header manifold, and the header manifold and/or at least one of the tube structures that couples each of the absorber tubes to the header manifold is configured to accommodate differential thermal expansion of the absorber tubes. 
     
     
         27 . The solar radiation absorber of  claim 26 , wherein the header manifold comprises an input/output manifold, and the input/output manifold comprises an inlet section that can move independently from the output section. 
     
     
         28 . The solar radiation absorber of  claim 26 , wherein at least one of the tube structures that connecting each absorber tubes to the header manifold comprises two non-coplanar bends. 
     
     
         29 . The solar radiation absorber of  claim 26 , wherein at least a portion of the header manifold is configured to move to accommodate thermal expansion and contraction in the tubes. 
     
     
         30 . The solar radiation absorber of  claim 26 , further comprising a flow control element inserted into or disposed on at least one of the absorber tubes. 
     
     
         31 . A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising:
 a plurality of absorber tubes; and   a flow control element applied to at least one absorber tube to maintain a relatively constant fluid flow between the absorber tubes.   
     
     
         32 . The solar radiation absorber of  claim 31 , wherein the flow control element accounts for about 30% to about 70% of the pressure drop in the at least one absorber tube. 
     
     
         33 . A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising a plurality of absorber tubes, wherein:
 the plurality of absorbing tubes comprises one or more inlet tubes for supplying heat exchange fluid to the absorber and one or more outlet tubes for releasing heat exchange fluid from the absorber; and   the plurality of absorber tubes is configured so that the one or more outlet tubes is positioned closer to an interior of the absorber relative to the one or more inlet tubes.   
     
     
         34 . A solar energy collector system comprising:
 an elevated receiver, the receiver comprising:
 an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and 
 a solar radiation absorber comprising a plurality of spaced-apart parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture; and 
   first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:
 each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel; 
 the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes; 
 the reflectors are driven to at least partially track diurnal motion of the sun; and 
 spacings between adjacent ones of the spaced-apart parallel absorber tubes are selected to reduce leakage of reflected solar radiation past the absorber tubes. 
   
     
     
         35 . The solar energy collector system of  claim 34 , wherein spacings between adjacent ones of the spaced apart parallel absorber tubes are determined using a set of tangents extending from an inner edge of at least one of the reflectors. 
     
     
         36 . A method of setting spacings between adjacent ones of spaced apart parallel absorber tubes in an elevated receiver of a solar energy collector system, the method comprising:
 arranging the absorber tubes lengthwise and side-by-side on a horizontal plane that is elevated with respect to a reflector in the solar energy collector system; and   aligning an outer circumferential edge of each absorber tube with a tangent line extending from an inner edge of the reflector to space the absorber tubes apart on the horizontal plane.   
     
     
         37 . A receiver for a solar energy collector system, the receiver comprising:
 an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel;   a solar radiation absorber positioned in a cavity formed between the first and second sidewalls and above the aperture; and   a frame for supporting the solar radiation absorber and the receiver channel,   wherein at least one of a junction between the frame and a mounting structure coupled to the solar radiation absorber and a junction between the frame and the receiver channel is configured to inhibit thermal conduction between the cavity and the frame.   
     
     
         38 . The receiver of  claim 37 , comprising a thermal separation member pin a junction between the frame and the mounting structure and/or in a junction between the frame and the receiver channel. 
     
     
         39 . A receiver for a solar energy collector system, the receiver comprising a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver, wherein the plurality of parallel absorber tubes is supported by a set of coaxial rollers extending transversely across the receiver. 
     
     
         40 . The receiver of  claim 39 , wherein the set of coaxial rollers comprises an individual roller for each absorber tube.