Double-walled solar heater apparatus and method for use

Abstract

The solar heater apparatus disclosed comprises an inner container and an outer container each having an opening forming a mouth. The inner container is contained within the outer container and has on its outside surface a solar-selective coating optimized to absorb a large fraction of the incident solar radiation while reradiating little of the absorbed energy. The two containers are joined creating one unified apparatus with a reservoir, an opening and a void between the two containers. The void is evacuated to reduce the heat loss due to thermal conduction from the inner container and the contents of the reservoir. In operation, the reservoir is filled with material and exposed to the sun. The solar radiation from the sun penetrates the outer container and is absorbed by the solar-selective coating and, by conduction, passes thermal energy through the inner container into the apparatus reservoir heating the reservoir contents.

1 . A solar heater apparatus for heating material comprising:
 an outer container, transparent to solar radiation, having a mouth;   an inner container having a mouth and an outer surface having a solar selective coating to absorb solar radiation; and   said inner container contained within said outer container and both containers joined at their mouths creating an apparatus opening, an apparatus reservoir, and a void between said outer and inner container.   
   
   
       2 . The apparatus in  claim 1  wherein said solar selective coating comprises a coating capable of near simultaneously converting to heat at least about 85% of said solar radiation while reradiating less than about 15% of said heat while said coating is at a temperature of less than about 100° C. 
   
   
       3 . The apparatus in  claim 1  wherein said solar selective coating comprises at least one cermet layer. 
   
   
       4 . The apparatus in  claim 1  wherein said outer container and said inner container form a self-supporting apparatus whereby said apparatus can be placed on a surface and exposed to solar radiation to transfer heat to said apparatus reservoir. 
   
   
       5 . The apparatus in  claim 1  wherein said outer container and said inner container are flask shaped whereby said apparatus can be placed on a surface and exposed to solar radiation to transfer heat to said apparatus reservoir. 
   
   
       6 . The apparatus in  claim 1  further comprising:
 a plug shaped to fit in said apparatus opening;   said plus comprising a transparent hollow evacuated cylinder having a bottom portion, an inside surface and a solar selective coating on said inside surface of said bottom portion; and   said outer container and said inner container are pot shaped whereby said apparatus can be placed on a surface and exposed to solar radiation to transfer heat to said apparatus reservoir.   
   
   
       7 . The apparatus in  claim 4  wherein said apparatus is capable of near simultaneously converting to heat at least about 85% of said solar radiation while reradiating less than about 15% of said heat while said coating is at a temperature of less than about 100° C. 
   
   
       8 . The apparatus in  claim 4  wherein said solar selective coating comprises at least one cermet layer. 
   
   
       9 . The apparatus in  claim 4  wherein said reservoir is capable of holding water and said solar selective coating comprises at least one cermet layer capable of transferring heat to raise the temperature of said water to a temperature at or above a temperature sufficient to disinfect water. 
   
   
       10 . The apparatus in  claim 4  wherein said reservoir is capable of holding a material and said solar selective coating comprises at least one cermet layer capable of transferring heat to raise the temperature of said material to a temperature above an ambient temperature. 
   
   
       11 . The apparatus in  claim 4  wherein said reservoir is capable of holding an edible material and said solar selective coating comprises at least one cermet layer capable of transferring heat to raise the temperature of said edible material. 
   
   
       12 . The apparatus in  claim 4  further comprising a solar reflective surface wherein said inner container is placed in proximity to said reflective surface whereby said solar radiation incident to said apparatus is increased. 
   
   
       13 . A method of heating material comprising the steps of:
 providing a solar heater apparatus comprising:
 an outer container, transparent to solar radiation, having a mouth; 
 an inner container having a mouth and an outer surface having a solar collective coating to absorb solar radiation; 
 said inner container contained within said outer container and both containers joined at their mouths creating an apparatus opening, a apparatus reservoir, and a void between said outer and inner container; and 
   inserting a material into said apparatus reservoir;   exposing said apparatus to solar radiation heating said material; and   removing said material from said apparatus reservoir.   
   
   
       14 . The method of  claim 13  wherein said solar selective coating comprises a coating capable of near simultaneously converting to heat at least about 85% of said solar radiation while reradiating less than about 15% of said heat while said coating is at a temperature of less than about 100° C. 
   
   
       15 . The method of  claim 13  wherein said solar selective coating comprises at least one cermet layer. 
   
   
       16 . The method of  claim 13  wherein said apparatus is self-supporting. 
   
   
       17 . The method of  claim 16  wherein said apparatus is capable of near simultaneously converting to heat at least about 85% of said solar radiation while reradiating less than about 15% of said heat while said coating is at a temperature of less than about 100° C. 
   
   
       18 . The method of  claim 16  wherein said solar selective coating comprises at least one cermet layer. 
   
   
       19 . The method of  claim 17  wherein said material comprises water and said solar radiation raises the temperature of said water to a temperature at or above a temperature sufficient to disinfect water. 
   
   
       20 . The method of  claim 17  wherein said solar radiation raises the temperature of said material to a temperature above an ambient temperature.