Solar Trough and Receiver

Abstract

A solar receiver unit comprises a generally tubular body having an internal passage for conducting a heat-transfer fluid, and an inlet chamber for receiving concentrated sunlight from a solar reflector when in use. The inlet chamber is shaped to direct reflection of concentrated sunlight at least one time in a direction that provides the reflected sunlight with an additional opportunity to heat the heat-transfer fluid.

1 . A solar trough and receiver unit comprising:
 a generally tubular receiver having an internal passage for conducting a heat-transfer fluid and an inlet chamber for receiving concentrated sunlight;   a generally parabolic trough for collecting and concentrating sunlight into the inlet chamber of the receiver to cause the heat-transfer fluid within the receiver to thereby be heated,   the inlet chamber being shaped to reflect said concentrated sunlight at least one time in a direction that provides said reflected sunlight with an additional opportunity to heat heat-transfer fluid within the receiver.   
     
     
         2 . The solar trough and receiver unit of  claim 1  wherein the inlet chamber is an integral part of the receiver. 
     
     
         3 . The solar trough and receiver unit of  claim 2  wherein the inlet chamber has a sunlight-receiving surface that is shaped to direct the majority of reflections back onto a the tube. 
     
     
         4 . The solar trough and receiver unit of  claim 1  wherein the inlet chamber has a sunlight-receiving face that is shaped to direct the majority of reflections back onto the receiving face. 
     
     
         5 . The solar trough and receiver unit of  claim 1  wherein the inlet chamber has a solar ray-receiving surface that is shaped to direct the majority of reflections back onto the tube. 
     
     
         6 . The solar trough and receiver unit of  claim 5  wherein the shape of the receiving surface causes at least a substantial portion of the concentrated solar rays from the trough to be incident on the receiver at non-perpendicular angles so that reflections from the receiving surface of concentrated sunlight from the trough are incident on the receiver at least one more time. 
     
     
         7 . The solar trough and receiver unit of  claim 3  wherein the inlet chamber includes at least at least one generally concave face impinged by the concentrated sunlight. 
     
     
         8 . The solar trough and receiver unit of  claim 3  wherein the inlet chamber includes at least a pair of generally concave faces impinged by the concentrated sunlight. 
     
     
         9 . The solar trough and receiver unit of  claim 8  wherein at least one longitudinally-extending channel is defined along the receiver by the generally concave faces. 
     
     
         10 . The solar trough and receiver unit of  claim 9  including a substantially transparent cover extending longitudinally along the length of the receiver to generally enclose the inlet chamber. 
     
     
         11 . The solar trough and receiver unit of  claim 3  including a substantially transparent cover extending longitudinally along the length of the receiver to generally enclose the inlet chamber. 
     
     
         12 . The solar trough and receiver unit of  claim 11  including a fluid within the covered inlet chamber space to substantially insulate the receiver from heat loss through the cover. 
     
     
         13 . The solar trough and receiver unit of  claim 12  wherein the fluid is a gas. 
     
     
         14 . The solar trough and receiver unit of  claim 13  wherein the gas is air. 
     
     
         15 . The solar trough and receiver unit of  claim 12  wherein the fluid is a liquid. 
     
     
         16 . The solar trough and receiver unit of  claim 11  wherein the cover is slightly concave. 
     
     
         17 . The solar trough and receiver unit of  claim 1  wherein the external receiver surfaces which are not exposed to the concentrated sunlight are generally covered with a layer of thermal insulation. 
     
     
         18 . The solar trough and receiver unit of  claim 17  wherein the layer of insulation has an outer surface coated with a high solar absorptivity coating so that the insulation absorbs sufficient solar radiation to increase the insulation's surface temperature and thereby decreases the temperature gradient across the insulation in order to minimize heat loss through the insulation layer. 
     
     
         19 . The solar trough and receiver unit of  claim 1  including a turbulator to create sufficient turbulence within the heat transfer fluid to decrease the thermal gradient within the receiver. 
     
     
         20 . The solar trough and receiver unit of  claim 19  wherein the turbulator is disposed continuously within the receiver passage. 
     
     
         21 . The solar trough and receiver unit of  claim 19  wherein a plurality of turbulator surfaces are positioned generally serially within the receiver passage. 
     
     
         22 . The solar trough and receiver unit of  claim 1  wherein the receiver lacks glass shielding around the receiver. 
     
     
         23 . The solar trough and receiver unit of  claim 1  wherein the receiver is longitudinally longer than the trough. 
     
     
         24 . The solar trough and receiver unit of  claim 1  wherein the longitudinal length of the receiver is up to approximately 50 feet. 
     
     
         25 . The solar trough and receiver unit of  claim 1  including at least one telescoping expansion joint for coupling the receiver to an adjacent receiver, the joint comprising
 a generally tubular member having an internal fluid passage and further having end regions sized to fit within each of the adjacent receivers to permit telescoping movement therewith in response to thermally induced expansions and contractions of the adjacent receivers while retaining the fluid passages of the adjacent receivers in communication, and   a seal member within the region between the unit's receiver and the generally tubular member for sealingly engaging the generally tubular member and receiver while permitting said telescoping movement.   
     
     
         26 . The solar trough and receiver unit of  claim 1  including at least one telescoping expansion joint for coupling the receiver to an adjacent receiver, the joint comprising
 a tubular member having an internal fluid passage and terminating in a pair of generally longitudinally-spaced end regions,   the receiver having at least one end region sized to fit within an end region of the tubular member, the tubular member permitting telescoping movement therewith in response to thermally induced expansions and contractions of the adjacent receivers while retaining the fluid passages of the adjacent receivers in communication through the generally tubular member, and   a seal member within the region between the receiver and tubular member for sealingly engaging the tubular member and receiver while permitting said telescoping movement.   
     
     
         27 . The solar trough and receiver unit of  claim 1  further including a first length of flexible tubing for coupling the fluid passage of the receiver to a source of heat-transfer fluid at an upstream end region of the receiver, and a second length of flexible tubing at a downstream end region of the receiver for conducting the heat-transfer fluid from the fluid passage of the receiver. 
     
     
         28 . The solar trough and receiver unit of  claim 27  wherein the source of heat-transfer fluid is an adjacent receiver. 
     
     
         29 . The solar trough and receiver unit of  claim 1  wherein the receiver includes a plurality of internal heat-exchanging fins extending into the fluid passageway and structured to conduct heat from the inlet chamber into the heat-exchange fluid. 
     
     
         30 . The solar trough and receiver unit of  claim 28  wherein the fins extend substantially the longitudinal length of the receiver. 
     
     
         31 . The solar trough and receiver unit of  claim 1  wherein the trough includes
 a back shell,   a front reflective layer, and   an interjacent foam core  18  binding the back shell and the reflector together.   
     
     
         32 . The solar trough and receiver unit of  claim 31  wherein the foam core is a closed cell foam having substantially the same thermal coefficient of expansion as the back shell and sufficiently high modulus of elasticity to accommodate the differential strain between the foam and the reflector. 
     
     
         33 . The solar trough and receiver unit of  claim 32  wherein the foam is a polyurethane foam. 
     
     
         34 . The solar trough and receiver unit of  claim 33  wherein the foam has a density of approximately 1 to 5 lbs/ft 3 . 
     
     
         35 . The solar trough and receiver unit of  claim 1  including a support structure positioned on the trough to support the receiver near the region of maximally concentrated sunlight reflected from the trough. 
     
     
         36 . The solar trough and receiver unit of  claim 35  wherein the trough has a pair of longitudinally-extending edge regions separated by the width of the trough, and the support structure is a bridge spanning the width of the trough. 
     
     
         37 . The solar trough and receiver unit of  claim 36  wherein the bridge is coupled to the trough at the trough's outer longitudinally-extending edge regions. 
     
     
         38 . The solar trough and receiver unit of  claim 37  wherein the trough has a pair of longitudinally-spaced end regions, and the bridge is coupled to the receiver at one of the receiver's end regions. 
     
     
         39 . The trough and receiver unit of  claim 36  wherein the trough has a pair of longitudinally-spaced end regions, and the bridge is coupled to the receiver at one of the receiver's end regions. 
     
     
         40 . The solar trough and receiver unit of  claim 39  wherein a second trough is adjacent the trough at their respective end regions, and the bridge is coupled to the adjacent end regions on at least one side of the adjacent troughs to secure the adjacent troughs together. 
     
     
         41 . The solar trough and receiver unit of  claim 40  wherein the receiver extends longitudinally along the pair of troughs. 
     
     
         42 . The solar trough and receiver unit of  claim 41  wherein the receiver is supported by the pair of troughs. 
     
     
         43 . The solar trough and receiver unit of  claim 36  wherein one of the bridge and the receiver includes mounting tabs protruding from its outer surface and
 the other of the bridge and receiver has tab-receiving slots for supporting the receiver, the tabs and slots being sized and shaped to prevent rotation about the receiver's longitudinal axis of the inlet chamber with respect to the trough.   
     
     
         44 . The solar trough and receiver unit of  claim 43  wherein the tabs and slots are sized and shaped to allow expansion of the receiver along that axis. 
     
     
         45 . The solar trough and receiver unit of  claim 43  wherein the inlet chamber of the receiver has an aperture through which concentrated sunlight from the trough enters the inlet chamber, and
 the tabs and slots are positioned to keep the receiver's inlet chamber's aperture generally aligned with the area of maximum concentration of the incoming sunlight.   
     
     
         46 . The solar trough and receiver unit of  claim 36  including means supported by the bridge for delivering cleaning liquid against the reflector for periodic washing of the reflector surface. 
     
     
         47 . The solar trough and receiver unit of  claim 46  including a generally tubular cleaning fluid member extending adjacent to at least one of the longitudinally-extending edge regions of the trough for conducting cleaning fluid, and
 at least one outlet from the cleaning fluid member for directing at least some of the conducted cleaning fluid against the trough in a direction generally transverse to the longitudinal.   
     
     
         48 . A solar receiver unit comprising:
 a generally tubular body having an internal passage for conducting a heat-transfer fluid, and an inlet chamber for receiving concentrated sunlight from a solar reflector when in use;   the inlet chamber being shaped to reflect said concentrated sunlight at least one time in a direction that provides said reflected sunlight with an additional opportunity to heat the heat-transfer fluid.   
     
     
         49 . The solar receiver of  claim 48  wherein the chamber is an integral part of the tube.