Solar Energy Collection Apparatus and Method

Abstract

An apparatus for collecting heat from a solar concentrator has an isothermal body defining an elongated cavity with a circular opening having a diameter equal to a diameter of a focus of the solar concentrator, the cavity having a reflective walls such that solar rays contacting the walls are substantially reflected. The circular opening is located at the focus of the solar concentrator and perpendicular to a principal axis of the solar concentrator, and the axis of the cavity is aligned with the principal axis of the solar concentrator. The heat generated in the isothermal body is absorbed by the heat sink. The length of the cavity is sufficient to absorb a desired proportion of the energy in the solar rays entering the cavity and is about 5 to 9 times the diameter of the opening of the cavity. Depending on material used, the isothermal body can be enclosed in a reducing atmosphere to maintain reflectivity of the cavity walls.

1 . An apparatus for collecting heat from a solar concentrator and for transferring the collected heat to a heat sink, the apparatus comprising:
 an isothermal body defining an elongated cavity with a substantially circular opening having a diameter substantially equal to a diameter of a focus of the solar collector, the cavity having reflective walls such that solar rays contacting the walls are substantially reflected;   wherein the isothermal body is adapted to be oriented such that the circular opening is located substantially at the focus of the solar collector and substantially perpendicular to a principal axis of the solar concentrator, and such that an axis of the cavity is substantially aligned with the principal axis of the solar concentrator;   wherein the isothermal body is adapted for thermal connection to the heat sink such that heat generated in the isothermal body is absorbed by the heat sink; and   wherein a length of the cavity is sufficient to absorb a desired proportion of the energy in the solar rays entering the cavity.   
     
     
         2 . The apparatus of  claim 1  wherein the proportion of the energy in the solar rays entering the cavity that is absorbed increases as the length of the cavity increases. 
     
     
         3 . The apparatus of  claim 1  wherein the length of the cavity is about 5 to 9 times the diameter of the circular opening. 
     
     
         4 . The apparatus of  claim 3  wherein the length of the cavity is between 6.5 to 7.5 times the diameter of the circular opening. 
     
     
         5 . The apparatus of  claim 1  wherein the cavity is substantially cylindrical. 
     
     
         6 . The apparatus of  claim 1  wherein the isothermal body is made from a reflective material such that the walls of the cavity are reflective. 
     
     
         7 . The apparatus of  claim 1  comprising a liner made of reflective material between the isothermal body and the cavity and operative to provide the reflective walls of the cavity. 
     
     
         8 . The apparatus of  claim 7  further comprising a low-emissivity shield covering an end of the isothermal body between the opening of the cavity and outer edges of the isothermal body. 
     
     
         9 . The apparatus of  claim 1  further comprising an enclosure enclosing the isothermal body, and a reducing atmosphere inside the enclosure operative to substantially prevent oxidation of the reflective walls of the cavity and thereby maintain reflectivity of the reflective walls. 
     
     
         10 . The apparatus of  claim 9  wherein the reflective walls comprise OFHC copper and wherein the reducing atmosphere contains hydrogen and a filler gas. 
     
     
         11 . The apparatus of  claim 9  further comprising insulation in walls of the enclosure. 
     
     
         12 . An apparatus for collecting heat from the sun and for transferring the collected heat to a heat sink, the apparatus comprising:
 a solar concentrator;   an isothermal body defining an elongated substantially cylindrical cavity with a substantially circular opening having a diameter substantially equal to a diameter of a focus of the solar collector, the cavity having reflective walls such that solar rays contacting the walls are substantially reflected;   wherein the isothermal body is oriented such that the circular opening is located substantially at the focus of the solar collector and substantially perpendicular to a principal axis of the solar concentrator, and such that an axis of the cavity is substantially aligned with the principal axis of the solar concentrator;   wherein the isothermal body is adapted for thermal connection to the heat sink such that heat generated in the isothermal body is absorbed by the heat sink; and   wherein a length of the cavity is about 5 to 9 times the diameter of the circular opening.   
     
     
         13 . The apparatus of  claim 12  further comprising a low-emissivity shield covering an end of the isothermal body between the opening of the cavity and outer edges of the isothermal body. 
     
     
         14 . The apparatus of  claim 12  further comprising an enclosure enclosing the isothermal body, and a reducing atmosphere inside the enclosure operative to substantially prevent oxidation of the reflective walls of the cavity and thereby maintain reflectivity of the reflective walls. 
     
     
         15 . The apparatus of  claim 14  wherein the reflective walls comprise OFHC copper and wherein the reducing atmosphere contains hydrogen and a filler gas. 
     
     
         16 . A method for collecting heat from a solar concentrator for transfer to a heat sink, the method comprising:
 providing an isothermal body defining an elongated cavity with a substantially circular opening having a diameter substantially equal to a diameter of a focus of the solar collector, the cavity having reflective walls such that solar rays contacting the walls are substantially reflected;   orienting the isothermal body such that the circular opening is located substantially at a focus of the solar collector and substantially perpendicular to a principal axis of the solar concentrator, and such that an axis of the cavity is substantially aligned with the principal axis of the solar concentrator;   reflecting solar rays that contact a reflective wall from a first contact point on the reflective wall to a second point on a reflective wall and to a plurality of subsequent contact points on the reflective walls until a desired proportion of the energy contained in the solar rays is absorbed by the reflective walls;   thermally connecting the heat sink to the isothermal body such that heat generated in the isothermal body by the absorbed energy of the solar rays is absorbed by the heat sink.   
     
     
         17 . The method of  claim 16  wherein the proportion of the energy in the solar rays entering the cavity that is absorbed increases as the length of the cavity increases. 
     
     
         18 . The method of  claim 16  wherein the cavity is substantially cylindrical and the length of the cavity is about 5 to 9 times the diameter of the opening of the cavity. 
     
     
         19 . The method of  claim 16  comprising enclosing the isothermal body in an enclosure and providing a reducing atmosphere inside the enclosure operative to substantially prevent oxidation of the reflective walls of the cavity and thereby maintain reflectivity of the reflective walls. 
     
     
         20 . The method of  claim 19  wherein the reflective walls comprise OFHC copper and wherein the reducing atmosphere contains hydrogen and a filler gas.