Multi-layer thin film solar collector

Abstract

A solar collector is provided that is formed from relatively thin polymer sheets. Three or more sheets are welded together to integrally define a storage tank, a plurality of layers of fluid flow channels (e.g. risers), and other desired features within the collector. The storage tank is located at a first end of the collector and a heat exchanger is provided within the storage tank. The heat exchanger is arranged to transfer heat from the storage tank to a target fluid (such as water) that is to be heated or preheated by the collector. The collector is arranged so that when it is installed, the collector may be positioned with the storage tank located generally above the fluid flow channels. The storage tank and the fluid flow channels are arranged such that when the collector is installed and filled with a working fluid, a thermosiphon effect will cause the collection of hot water within the storage tank.

1 . A solar collector, comprising:
 a front sheet formed from a polymer film;   a middle sheet formed from a polymer film; and   a back sheet formed from a polymer film, wherein the front, middle, and back sheets are welded together, with the middle sheet being between the front and back sheets, to define a storage tank, a manifold and a front layer of fluid flow channels and a back layer of fluid flow channels, wherein a plurality of longitudinal welds define the fluid flow channels, wherein some of the longitudinal welds are only between the front sheet and the middle sheet to form the front layer of channels and other of the longitudinal welds are only between the middle sheet and the back sheet to form the back layer of channels, wherein each layer of fluid flow channels comprises a plurality of fluid flow channels that extend substantially longitudinally between the manifold and the storage tank, wherein each of the fluid flow channels opens directly into the storage tank, the storage tank being located at a first end of the collector and the manifold being located at a second end of the collector, and wherein the front layer of fluid flow channels provides a hot thermosiphonic flow path therethrough in a first direction and the back layer of fluid flow channels provides a cold flow path therethrough in a second direction, wherein the first and second directions are opposite directions.   
     
     
         2 . The solar collector as recited in  claim 1 , wherein the middle sheet is shorter than the front and back sheets such that the storage tank is formed between the front and back sheets. 
     
     
         3 . The solar collector as recited in  claim 1 , wherein the manifold allows fluid flow between the two layers of fluid flow channels. 
     
     
         4 . The solar collector as recited in  claim 3 , wherein the manifold is formed by a mesh strip attached to a bottom end of the middle sheet. 
     
     
         5 . The solar collector as recited in  claim 3 , wherein the manifold is formed by providing a plurality of holes at a bottom end of the middle sheet. 
     
     
         6 . The solar collector as recited in  claim 1 , wherein the front and back sheets are further welded to define elongated tie down channels on top and bottom ends of the solar collector, the tie down channels being arranged to receive a tie down mechanism and not being in fluid communication with either the storage tank or the fluid flow channels, wherein the elongated tie down channels each have a longitudinal axis that extends substantially perpendicular to the fluid flow channels in a plane defined the fluid flow channels. 
     
     
         7 . The solar collector as recited in  claim 1 , further comprising a heat exchanger disposed in the storage tank, the heat exchanger having an inlet and an outlet at the storage tank. 
     
     
         8 . A solar collector, comprising:
 a front sheet formed from a polymer film;   a middle sheet formed from a polymer film; and   a back sheet formed from a polymer film, wherein the front, middle, and back sheets are welded together by a plurality of longitudinal welds, with the middle sheet being between the front and back sheets, wherein some of the longitudinal welds are only between the front sheet and the middle sheet to form the front layer of channels between the front and middle sheets and other of the longitudinal welds are only between the middle sheet and the back sheet to form the back layer of channels between the middle and back sheets, wherein each layer of fluid flow channels comprises a plurality of fluid flow channels that extend substantially longitudinally along the solar collector, and wherein the first layer of fluid flow channels provides a flow path therethrough in a first direction and the second layer of fluid flow channels provides a flow path therethrough in a second direction, wherein the first and second directions are opposite directions.   
     
     
         9 . The solar collector as recited in  claim 8 , further comprising a manifold at a bottom end of the collector, the manifold allowing fluid flow between the first layer and second layer of fluid flow channels. 
     
     
         10 . The solar collector as recited in  claim 9 , further comprising a storage tank at a top end of the collector, wherein the fluid flow channels extend longitudinally between the manifold and the storage tank, wherein each of the fluid flow channels opens directly into the storage tank. 
     
     
         11 . The solar collector as recited in  claim 10 , further comprising a heat exchanger disposed in the storage tank, the heat exchanger having an inlet and an outlet at the storage tank. 
     
     
         12 . The solar collector as recited in  claim 10 , wherein the middle sheet is shorter than the front and back sheets to define the storage bank at the top end of the collector, the storage tank being formed between the front and back sheets. 
     
     
         13 . The solar collector as recited in  claim 8 , further comprising a fill port that may be used to facilitate filling the fluid flow channels and the storage tank portions of the solar collector with a working fluid. 
     
     
         14 . A solar collector system comprising:
 a front sheet formed from a polymer film;   a middle sheet formed from a polymer film; and   a back sheet formed from a polymer film, the back sheet having a substantially same length as the front sheet and the middle sheet being shorter than the front and back sheets wherein the front, middle and back sheets are welded together by a plurality of longitudinal welds to define first and second layers of substantially parallel fluid flow channels that extend longitudinally along the collector, the longitudinal welds on the middle sheet alternate between a weld to the front sheet and a weld to the back sheet, wherein the first layer is between the front sheet and the middle sheet and the second layer is between the middle sheet and the back sheet, and wherein the first layer of fluid flow channels provides a hot thermosiphonic flow path therethrough in a first direction and the second layer of fluid flow channels provides a cold flow path therethrough in a second direction, wherein the first and second directions are opposite directions.   
     
     
         15 . The solar collector as recited in  claim 14 , further comprising a storage tank at a first end of the collector, the fluid flow channels being in fluid communication with the tank and arranged to open into the tank. 
     
     
         16 . The solar collector as recited in  claim 15 , wherein the storage tank is between the front sheet and the back sheet at the first end of the collector to which the middle sheet does not extend. 
     
     
         17 . The solar collector as recited in  claim 14 , further comprising a manifold at a second end of the collector, the manifold allowing fluid flow between the first and second layers. 
     
     
         18 . The solar collector as recited in  claim 14 , wherein the middle sheet extends neither to the top nor bottom end of the collector. 
     
     
         19 . The solar collector as recited in  claim 14 , further comprising a heat exchanger disposed in the storage tank, the heat exchanger having inlet and outlet ports. 
     
     
         20 . The solar collector as recited in  claim 14 , further comprising a glazing layer over the front sheet.