Generation of steam from solar energy

Abstract

A cavity-type solar energy receiver for generating high pressure steam, which includes panels of tubes defining a cavity within an outer enclosure. Concentrated solar energy provided by a heliostat enters the cavity opening in the enclosure and evaporates water within some of the tube panels. The evaporating tubes receive hot water from a steam drum by natural circulation and return a mixture of steam and hot water to the steam drum. Additional tube panels are positioned to receive reflected solar energy, which is used to preheat feed water and to superheat steam.

1 . A solar energy receiver for generating high pressure steam with concentrated solar energy comprising:
 (a) a steam drum for receiving heated boiler feed water and discharging high pressure steam;   (b) at least one panel of evaporator tubes, said evaporator tubes for receiving hot water by natural circulation from said steam drum and returning steam and hot water into said steam drum; and   (c) at least one panel of superheater tubes, said superheater tubes for receiving steam from said steam drum and discharging superheated steam;   wherein said steam drum is mounted adjacent to an enclosure containing said tube panels of (b) and (c), said tube panels defining a cavity surrounding an opening in said enclosure for admitting concentrated solar energy.   
     
     
         2 . A solar energy receiver of  claim 1  further comprising at least one panel of economizer tubes, said economizer tubes for receiving boiler feed water and discharging said heated boiler feed water into said steam drum; 
     
     
         3 . A solar energy receiver of  claim 1  wherein said at least one panel of said evaporator tubes is positioned in said enclosure opposite said opening to receive concentrated solar energy directly. 
     
     
         4 . A solar energy receiver of  claim 3  further comprising additional panels of evaporator tubes adjacent said at least one panel of evaporator tubes of  claim 2 , said additional panels of evaporator tubes being positioned on the side walls of said cavity to receive reflected solar energy. 
     
     
         5 . A solar energy receiver of  claim 2  wherein panels of economizer tubes are positioned on the side walls and/or floor of said cavity adjacent said opening for admitting concentrated solar energy. 
     
     
         6 . A solar energy receiver of  claim 1  wherein said at least one panel of superheater tubes is positioned at the roof of said cavity. 
     
     
         7 . A solar energy receiver of  claim 1  further comprising a second set of tube panels corresponding to tube panels (b) and (c) within a second enclosure positioned in a mirror image of said at least one tube panels of  claim 1 , said steam drum being positioned between said first and second tube sets of tube panels. 
     
     
         8 . A solar energy receiver of  claim 1  wherein at least one of said panel of tubes is disposed to present a continuous heat transfer surface exposed to solar energy, each of said tubes being joined to adjacent tubes by metal bars welded to each tube, thereby creating a continuous heat transfer surface. 
     
     
         9 . A solar energy receiver of  claim 1  further comprising insulation positioned between each of said tube panels and said enclosure. 
     
     
         10 . A solar energy receiver of  claim 1  wherein said at least one panel of evaporator tubes is in fluid communication with said steam drum via inlet and outlet manifolds. 
     
     
         11 . A solar energy receiver of  claim 10  wherein said outlet manifold is in fluid communication with said steam drum through multiple pipes, said multiple pipes having a bend for accommodating thermal expansion and contraction. 
     
     
         12 . A solar energy receiver of  claim 10  wherein said inlet manifold is in fluid communication with said steam drum via multiple down corner pipes between said steam drum and said inlet manifold. 
     
     
         13 . A solar energy receiver of  claim 11  wherein said bends have an angle of about 90°. 
     
     
         14 . A solar energy receiver of  claim 10  wherein the evaporator tubes enter said inlet manifold and exit into said outlet manifold through horizontal connections. 
     
     
         15 . A solar energy receiver of  claim 1  wherein a reflective coating is located on each of said tube panels of (b)(c), and (d). 
     
     
         16 . A solar energy receiver of  claim 15  wherein said reflective coating is a silicone-based material resisting temperatures up to about 1100° F. 
     
     
         17 . A solar energy receiver of  claim 16  wherein said reflective coating reflects up to 50% of incident light. 
     
     
         18 . A solar energy of  claim 16  wherein said reflective coating is a mixture of black and white coatings. 
     
     
         19 . A solar energy receiver of  claim 18  wherein said reflective coating reflects about 20% of incident light. 
     
     
         20 . A solar energy receiver of  claim 9  wherein said insulation is ceramic fiber in back of said superheater tube panels and mineral wool in back of said evaporator and economizer tube panels. 
     
     
         21 . A cavity-type solar energy receiver for generating high pressure steam from concentrated solar energy comprising:
 (a) a steam drum for receiving heated boiler feed water and discharging high pressure steam;   (b) two cavities having openings for receiving concentrated solar energy and facing in opposite directions, said cavities located on opposite sides of said steam drum. said cavities defined by panels of tubes forming the sides of said cavities, said panels of tubes for receiving solar energy and generating high pressure steam therefrom;   (c) at least one panel of evaporator tubes in each of said cavities for receiving hot water by natural circulation from said steam drum and for returning steam and hot water into said steam drum; and   (d) at least one panel of superheater tubes in each of said cavities for receiving steam from said drum and discharging superheated steam.   
     
     
         22 . A cavity-type solar energy receiver of  claim 21  further comprising at least one panel of economizer tubes in each of said cavities for preheating boiler feed water and discharging said heated boiler feed water into said steam drum; 
     
     
         23 . A cavity-type solar energy receiver of  claim 21  wherein said at least one panel of evaporator tubes in each of said cavities is located opposite said openings for receiving concentrated solar energy directly. 
     
     
         24 . A cavity-type solar energy receiver of  claim 22  further comprising additional panels of evaporator tubes located adjacent said at least one panel of evaporator tubes of  claim 21 , said additional panels of evaporator tubes being positioned on the side walls of said cavity to receive reflected energy. 
     
     
         25 . A cavity-type solar energy receiver of  claim 22  wherein said panels of economizer tubes for each of said cavities are located on the side walls of said cavities adjacent the openings for admitting concentrated solar energy. 
     
     
         26 . A cavity-type solar energy receiver of  claim 21  wherein said at least one panel of superheater tubes are located at the top of each of said cavities. 
     
     
         27 . A cavity-type solar energy receiver of  claim 21  wherein at least one of said panels of tubes is disposed to present a continuous heat transfer surface exposed to solar energy, each of said tubes being joined to adjacent tubes by metal bars welded to each tube, thereby creating a continuous heat transfer surface. 
     
     
         28 . A cavity-type solar energy receiver of  claim 21  further comprising insulation positioned between each of said cavities and an enclosure surrounding both of said cavities and said steam drum. 
     
     
         29 . A cavity-type solar energy receiver of  claim 21  wherein said at least one panel of evaporator tubes in each cavity is in fluid communication with said steam drum via inlet and outlet manifolds. 
     
     
         30 . A cavity-type solar energy receiver of  claim 29  wherein said outlet manifold is in fluid communication with said steam drum through multiple pipes, said multiple pipes having bends for accommodating thermal expansion and contraction. 
     
     
         31 . A cavity-type solar energy receiver of  claim 29  wherein said inlet manifold is in fluid communication with said steam drum via multiple downcomer pipes between said steam drum and said inlet manifold. 
     
     
         32 . A cavity-type solar energy receiver of  claim 30  wherein said bends have an angle of about 90°. 
     
     
         33 . A cavity-type solar energy receiver of  claim 29  wherein the evaporator tubes enter said inlet manifold and exit into said outlet manifold through horizontal connections. 
     
     
         34 . A cavity-type solar energy receiver of  claim 21  wherein a reflective coating is located on each of said tube panels in (b), (c), and (d). 
     
     
         35 . A cavity-type solar energy of receiver of  claim 34  wherein said reflective coating is a silicone-based material resisting temperatures up to about 1100° F. 
     
     
         36 . A cavity-type solar energy receiver of  claim 35  wherein said reflective coating reflects up to 50% of incident light. 
     
     
         37 . A cavity-type solar energy receiver of  claim 35  wherein said reflective coating is a mixture of black and white coatings. 
     
     
         38 . A cavity-type solar energy receiver of  claim 37  wherein said reflective coating reflects about 20% of incident light. 
     
     
         39 . A cavity-type solar energy receiver of  claim 28  wherein said insulation is ceramic fiber in back of said superheater tube panels and mineral wool in back of said evaporator and economizer tube panels.