Solar chimney for daytime and nighttime use

Abstract

A solar chimney includes a solar collector which heats air in the chimney, producing updrafts which can be harnessed to perform useful work. The solar collector may be located inside or outside the chimney. The device may include a reservoir for storing a heat transfer fluid, thus enabling the device to be used during both day and night. The solar chimney may be equipped with both internal and external solar collectors, operating in parallel. The solar chimney may also be equipped with multiple external solar collectors, connected in parallel to a reservoir. The solar chimney of the invention provides a convenient and practical way to convert solar energy into electrical power.

1 . A solar chimney, comprising:
 a) an enclosure defining a path for flow of a fluid to be heated, the enclosure containing a heat exchanger,   b) a solar collector located outside the enclosure,   c) a reservoir for storing a heat transfer fluid, and   d) means for directing heat transfer fluid between the reservoir, the solar collector, and the heat exchanger,   wherein, in a first position of the directing means, appropriate for use during daytime, heat transfer fluid can flow from the reservoir, then into the solar collector, then into the heat exchanger, and then back to the reservoir, and   wherein, in a second position of the directing means, appropriate for use during nighttime, heat transfer fluid can flow from the reservoir, into the heat exchanger, and then back to the reservoir.   
     
     
         2 . The solar chimney of  claim 1 , wherein the reservoir includes a movable partition which thermally and mechanically divides the reservoir into compartments. 
     
     
         3 . The solar chimney of  claim 2 , wherein the directing means is configured such that heat transfer fluid is withdrawn from a first compartment of the reservoir, and such that heat transfer fluid is returned, from the heat exchanger, into a different compartment of the reservoir. 
     
     
         4 . The solar chimney of  claim 1 , wherein the solar collector comprises a target substrate located within a housing, the housing including means for allowing solar radiation to enter the housing and to impinge upon the target substrate, the target substrate being in thermal contact with a portion of the directing means so as to transfer heat to fluid being conveyed by the directing means. 
     
     
         5 . The solar chimney of  claim 4 , wherein the target substrate is located within an inner casing disposed within the housing. 
     
     
         6 . The solar chimney of  claim 5 , wherein there is an intermediate casing surrounding the inner casing and located within the housing. 
     
     
         7 . The solar chimney of  claim 6 , wherein the inner casing has a heat absorptive inner surface, wherein the intermediate casing has a heat absorptive inner surface, and wherein the housing has a reflective inner surface. 
     
     
         8 . The solar chimney of  claim 1 , wherein the reservoir includes at least two movable partitions, the partitions comprising means for thermally and mechanically dividing the reservoir into compartments. 
     
     
         9 . The solar chimney of  claim 2 , wherein the partition is mounted to rollers which are movable within a track guide formed in a wall of the reservoir. 
     
     
         10 . The solar chimney of  claim 1 , wherein the directing means include conduits for directing heat transfer fluid from the reservoir and into either of the solar collector or the heat exchanger, valves for opening and closing some of said conduits, and a pump for conveying heat transfer fluid through the conduits. 
     
     
         11 . The solar chimney of  claim 1 , wherein there are a plurality of solar collectors located outside the enclosure, and wherein all of said solar collectors are connected to said reservoir. 
     
     
         12 . A solar chimney, comprising:
 a) an enclosure defining a path for flow of a fluid to be heated, the enclosure containing a heat exchanger,   b) a plurality of solar collectors located outside the enclosure,   c) a reservoir for storing a heat transfer fluid, and   d) means for directing heat transfer fluid between the reservoir, the solar collectors, and the heat exchanger,   wherein, in a first position of the directing means, appropriate for use during daytime, heat transfer fluid can flow from the reservoir, then into at least one of the solar collectors, then into the heat exchanger, and then back to the reservoir, and   wherein, in a second position of the directing means, appropriate for use during nighttime, heat transfer fluid can flow from the reservoir, into the heat exchanger, and then back to the reservoir.   
     
     
         13 . The solar chimney of  claim 12 , wherein the reservoir includes a movable partition which thermally and mechanically divides the reservoir into compartments. 
     
     
         14 . The solar chimney of  claim 12 , wherein the directing means is configured such that heat transfer fluid is withdrawn from a first compartment of the reservoir, and such that heat transfer fluid is returned, from the heat exchanger, into a different compartment of the reservoir. 
     
     
         15 . A method of operating a solar chimney system, the system including a chimney having a heat exchanger disposed therein, a solar collector, and a reservoir, the heat exchanger, solar collector, and reservoir being interconnected by a plurality of conduits and valves, the method comprising:
 a) directing a heat transfer fluid, during daytime, from the reservoir, into the solar collector, and into the heat exchanger, and returning the heat transfer fluid to the reservoir after the fluid has released some heat to the heat exchanger, thereby causing air in the chimney to become heated and to move by convection,   b) directing the heat transfer fluid, during nighttime, from the reservoir to the heat exchanger, and returning the heat transfer fluid to the reservoir after the fluid has released some heat to the heat exchanger, thereby causing air in the chimney to become heated and to move by convection,   c) using moving air in the chimney to perform useful work.   
     
     
         16 . The method of  claim 15 , wherein the reservoir has a plurality of compartments defined by at least one movable partition disposed within the reservoir, and wherein fluid is withdrawn from one of said compartments, and wherein fluid is returned to another of said compartments. 
     
     
         17 . The method of  claim 15 , wherein step (b) is preceded by the step of closing a valve in a conduit connecting the reservoir to the solar collector, and opening a valve in a conduit connecting the reservoir to the heat exchanger. 
     
     
         18 . The method of  claim 15 , wherein steps (a) and (b) are performed in repeated alternating fashion, wherein the solar chimney system is operated substantially continuously, during day and night. 
     
     
         19 . The method of  claim 15 , wherein the reservoir has at least three compartments defined by at least two partitions, and wherein the heat transfer fluid is withdrawn from a plurality of said compartments. 
     
     
         20 . The method of  claim 16 , further comprising moving a position of at least one partition before switching from daytime operation to nighttime operation and vice versa.