Direct flow solar collector

Abstract

A direct flow solar collector and solar hot water system are presented wherein high pressure connections are eliminated to lower installation costs while freeze and stagnation protection is provided by a cooling loop and a continuous circulation protocol. A novel fin design and a modular concept deliver manufacturing, shipping and assembly efficiencies while providing flexibility for customizing the collector configuration.

What is claimed is: 
     
         1 . A solar collector, comprising:
 a manifold having an input port, an output port and a plurality of orifices;   a corresponding plurality of solar tubes connected to the manifold through the orifices, the plurality of solar tubes assembled in a planar array and positioned for exposure to solar radiation;   at least one liquid channel from the input port to the output port, said liquid channel having at least one continuous flow path there through;   a means for transferring heat absorbed from solar radiation in each solar tube to a solar liquid flowing through the at least one continuous flow path;   a means for circulating the solar liquid through the means for transferring heat; and   is a means for cooling the solar liquid to maintain its temperature at or below a preferred temperature;   whereby heat from solar radiation is transported for work purposes through the solar liquid by the means for transferring heat and by the means for circulating and the solar liquid is prevented from overheating by the means for cooling.   
     
     
         2 . The solar collector of  claim 1 , wherein the means for transferring heat comprises a fin inserted into each solar tube and extending the length of the tube, said fin having an integrated U-shaped channel extending from an input end to an output end, the input end of a first U-shaped channel in a first solar tube of the planar array forming a fluid connection to the input port, the output end of the first U-shaped channel of the first solar tube forming a fluid connection in preferred configuration to the input end of a last U-shaped channel in a last solar tube, the output end of the last U-shaped channel in the last solar tube forming a fluid connection to the output port, whereby at least one liquid channel is formed for a continuous flow path through each solar tube, the flow of solar liquid therein receiving heat by conduction from the fin. 
     
     
         3 . The solar collector of  claim 2 , wherein the preferred configuration is a serial linkage joining a preferred number of solar tubes and a parallel linkage joining a preferred number of serial linkages. 
     
     
         4 . The solar collector of  claim 3 , wherein the preferred number of solar tubes in a serial linkage is ten and the preferred number of serial linkages in a parallel linkage is four. 
     
     
         5 . The solar collector of  claim 2 , wherein the integrated U-shaped channel is formed as a part of an extrusion of the fin in a construction eliminating air gaps in a heat conduction path while simplifying assembly steps. 
     
     
         6 . The solar collector of  claim 5 , wherein the fin extrusion is comprised of aluminum or an alloy thereof. 
     
     
         7 . The solar collector of  claim 6 , wherein the fin is formed into a U-shape by bending a single extrusion length. 
     
     
         8 . The solar collector of  claim 7 , wherein the fin is resiliently biased to make contact with the wall of the solar tube and essentially eliminate thereby any insulating air space there between. 
     
     
         9 . The solar collector of  claim 1 , wherein the means for cooling comprises a cooling loop and a controller, the controller programmed to redirect circulation of the solar liquid through the cooling loop when the solar liquid is above a first preferred temperature. 
     
     
         10 . The solar collector of  claim 9 , wherein the first preferred temperature is in the range of 55-60° C. 
     
     
         11 . The solar collector of  claim 1 , wherein the means for circulating the solar liquid comprises a low-pressure pump in a low-pressure loop. 
     
     
         12 . The solar collector of  claim 11 , wherein the low-pressure loop comprises flexible tubing for at least a part of the continuous flow path. 
     
     
         13 . The solar collector of  claim 12 , further comprising a means for preventing freezing of the solar liquid. 
     
     
         14 . The solar collector of  claim 13 , wherein the means for preventing freezing comprises maintenance of low pressure circulation below a second preferred temperature and an insulation wrap of the flexible tubing combined with a resilient insulation plug situated in the interstitial space of each solar tube. 
     
     
         15 . The solar collector of  claim 1 , further comprising a means for preventing freezing of the solar liquid. 
     
     
         16 . The solar collector of  claim 15 , wherein the means for preventing freezing comprises a low pressure circulation of the solar liquid below a second preferred temperature. 
     
     
         17 . The solar collector of  claim 14 , wherein the second preferred temperature is in the range of 2-5° C. 
     
     
         18 . The solar collector of  claim 16 , wherein the second preferred temperature is in the range of 2-5° C. 
     
     
         19 . The solar collector of  claim 1 , wherein the plurality of solar tubes is arrayed bi-laterally from opposing sides of the manifold. 
     
     
         20 . The solar collector of  claim 1 , wherein the plurality of solar tubes is arrayed unilaterally from one side of the manifold. 
     
     
         21 . A solar hot water system, comprising:
 a solar collector having a manifold with an input port, an output port and a plurality of orifices; a corresponding plurality of solar tubes connected to the manifold through the orifices, the plurality of solar tubes assembled in a planar array and positioned for exposure to solar radiation; at least one liquid channel from the input port to the output port, said liquid channel having at least one continuous flow path there through; and a means for transferring heat absorbed from solar radiation in each solar tube to a solar liquid flowing through the at least one continuous flow path;   a storage vessel for hot water in fluid communication with the input port and the output port of the manifold;   a means for circulating the solar liquid through the means for transferring heat to the storage vessel; and   a means for cooling the solar liquid to maintain its temperature at or below a preferred temperature;   whereby heat from solar radiation is used to heat the water in the storage vessel by the means for transferring heat and by the means for circulating, and the solar liquid is prevented from overheating by the means for cooling.   
     
     
         22 . The solar hot water system of  claim 21 , wherein the solar liquid is the water in the storage vessel and the means for circulating comprises circulation through the storage vessel, the water of the storage vessel having a stratification of heat therein defining a hot section and a cold section, the input port of the manifold in fluid connection to the cold section of the storage vessel and the output port of the manifold in fluid connection to the hot section. 
     
     
         23 . The solar hot water system of  claim 21 , wherein the means for transferring heat comprises a fin inserted into each solar tube and extending the length of the tube, said fin having an integrated U-shaped channel extending from an input end to an output end, the input end of a first U-shaped channel in a first solar tube of the planar array forming a fluid connection to the input port, the output end of the first U-shaped channel of the first solar tube forming a fluid connection in preferred configuration to the input end of a last U-shaped channel in a last solar tube, the output end of the last U-shaped channel in the last solar tube forming a fluid connection to the output port, whereby at least one liquid channel is formed for a continuous flow path through each solar tube, the flow of solar liquid therein receiving heat by conduction from the fin. 
     
     
         24 . The solar hot water system of  claim 23 , wherein the preferred configuration is a serial linkage joining a preferred number of solar tubes and a parallel linkage joining a preferred number of serial linkages. 
     
     
         25 . The solar hot water system of  claim 24 , wherein the preferred number of solar tubes in a serial linkage is ten and the preferred number of serial linkages in a parallel linkage is four. 
     
     
         26 . The solar hot water system of  claim 23 , wherein the integrated U-shaped channel is formed as a part of an extrusion of the fin in a construction eliminating air gaps in a heat conduction path while simplifying assembly steps. 
     
     
         27 . The solar hot water system of  claim 22 , wherein the means for cooling comprises a cooling loop and a controller, the cooling loop in fluid communication with the hot section, the controller programmed to switch on circulation through the cooling loop when the water of the storage vessel is above a first preferred temperature. 
     
     
         28 . The solar hot water system of  claim 27 , wherein the first preferred temperature is in the range of 55-60° C. 
     
     
         29 . The solar hot water system of  claim 21 , wherein the means for circulating the solar liquid comprises a low-pressure pump in a low-pressure loop. 
     
     
         30 . The solar hot water system of  claim 29 , further comprising a means for preventing freezing of the solar liquid. 
     
     
         31 . The solar hot water system of  claim 30 , wherein the means for preventing freezing comprises a low pressure circulation of the solar liquid below a second preferred temperature. 
     
     
         32 . The solar hot water system of  claim 31 , wherein the second preferred temperature is in the range of 2-5° C. 
     
     
         33 . The solar hot water system of  claim 21 , wherein heated water for application purposes is provided by circulation through a heat exchanger immersed in the storage vessel. 
     
     
         34 . A method of configuring a solar collector to achieve operating efficiency, comprising:
 providing a solar collector having a manifold with an input port, an output port and a plurality of orifices; a corresponding plurality of solar tubes connected to the manifold through the orifices, the plurality of solar tubes assembled in a planar array and positioned for exposure to solar radiation; at least one liquid channel from the input port to the output port, said liquid channel having at least one continuous flow path there through; and a fin inserted into each solar tube and extending the length of the tube, said fin having an integrated U-shaped channel extending from an input end to an output end, the input end of a first U-shaped channel in a first solar tube of the planar array forming a fluid connection to the input port, the output end of the first U-shaped channel in the first solar tube forming a fluid connection in a preferred configuration to the input end of a last U-shaped channel in a last solar tube, the output end of the last U-shaped channel in the last solar tube forming a fluid connection to the output port, whereby at least one liquid channel is formed for a continuous flow path through each solar tube, the flow of solar liquid therein receiving heat by conduction from the fin;   implementing the preferred configuration by joining a preferred number of solar tubes in a serial linkage, said serial linkage balancing heat transfer efficiency with non-turbulent hydraulic flow; and   implementing the preferred configuration by joining a preferred number of serial linkages in a parallel linkage, said parallel linkage balancing heat transfer efficiency with hydraulic pressure;   whereby the cost per BTU is optimized by balancing pressure and flow characteristics.   
     
     
         35 . The method of  claim 34 , wherein the preferred number of solar tubes in a serial linkage is ten and the preferred number of serial linkages in a parallel linkage is four.