Retrofittable tankless passive solar water heater

Abstract

A tankless solar water heater for heating domestic pressurized water having a flexible insulated heat exchanger housing that contracts to accommodate volume reduction when the solar heating fluid cools. A check valve releases gas and solar heating fluid if interior pressure exceeds ambient pressure by more than one pound per square inch, without admitting air into the container or the heat exchanger when volume of the solar heating fluid reduces due to cooling.

What is claimed is: 
     
         1 . A tankless solar water heater for heating domestic pressurized water, comprising:
 an insulated container, open at an upper end, for solar heating and insulating a solar heating fluid;   a flexible insulated heat exchanger housing having heat exchange ports and a check valve port, sealingly attached over said upper end, wherein said check valve port is located at an uppermost location of said heat exchanger housing;   a check valve sealingly mounted in said check valve port;   heat exchanger tubing at least partially contained within said heat exchanger housing, sealingly extending through said heat exchange ports to exchange heat between said solar heating fluid and said domestic pressurized water circulating through said heat exchanger tubing when said solar heating fluid fills said insulated container and said heat exchanger housing;   wherein said check valve releases air, and said solar heating fluid and any gas therefrom, in said container and said heat exchanger housing, when interior pressure in said container and said heat exchanger housing is greater than approximately 1 pound per square inch above ambient pressure, without admitting air into said container or said heat exchanger housing when said interior pressure is less than said ambient pressure due to volume reduction of said solar heating fluid from cooling;   wherein said heat exchanger housing contracts to accommodate said volume reduction of said solar heating fluid from cooling; and   wherein said container and said flexible heat exchanger are sufficiently insulated to reduce cooling of said solar heating fluid in said heat exchanger housing to 1 degree Fahrenheit per hour at 130 degrees Fahrenheit.   
     
     
         2 . A tankless solar water heater according to  claim 1 , wherein said insulated container comprises an outer rigid transparent tube and an inner opaque tube, with an insulating vacuum in the space between said tubes. 
     
     
         3 . A tankless solar water heater according to  claim 1 , wherein said solar heating fluid comprises water. 
     
     
         4 . A tankless solar water heater according to  claim 1 , wherein said heat exchanger tubing is entirely contained within said heat exchanger housing. 
     
     
         5 . A tankless solar water heater according to  claim 1 , wherein said check valve releases said solar heating fluid and any gas therefrom if interior pressure in said container and said heat exchanger housing exceed ambient pressure by more than one pound per square inch, to minimize air and gas from said solar heating fluid in said container and said heat exchanger housing, and to maintain said interior pressure of said solar heating fluid in said container and said heat exchanger housing at a maximum pressure of one pound per square inch above ambient pressure. 
     
     
         6 . A tankless solar water heater according to  claim 1 , wherein said check valve vents said solar heating fluid and gas therefrom in case of boiling. 
     
     
         7 . A tankless solar water heater for heating domestic pressurized water, comprising:
 a plurality of insulated solar heating tubes, each having an upper end, for solar heating and insulating a solar heating fluid contained therein;   a flexible insulated heat exchanger housing having heat exchange ports and a check valve port, sealingly attached over each of said upper ends, wherein said check valve port is located at an uppermost portion of each of said heat exchanger housings;   a check valve sealingly mounted in each of said check valve ports; and   heat exchanger tubing mounted at least partially within each of said heat exchanger housings, each sealingly extending through said heat exchanger ports;   said heat exchanger tubing in each of said heat exchanger housings being connected in series with heat exchanger tubing in another of said heat exchanger housings;   whereby when solar heating fluid fills said insulated tubes and said heat exchanger housings, heat is exchanged between said solar heating fluid and said domestic pressurized water circulating through said heat exchanger tubing;   whereby said flexible heat exchanger housings contract to accommodate volume reduction when said solar heating fluid cools;   whereby said check valves release said solar heating fluid and any gas therefrom if interior pressure in said tubes and said heat exchanger housing exceed ambient pressure by more than one pound per square inch, without admitting air into said tubes or said heat exchanger when volume of said solar heating fluid reduces due to cooling, to minimize air and gas from said solar heating fluid in said tubes and said heat exchanger housings, to maintain said interior pressure of said solar heating fluid in said tubes and said heat exchanger housings at a maximum pressure of one pound per square inch above ambient pressure, and to vent said solar heating fluid and gas therefrom in case of boiling; and   wherein said tubes and said flexible heat exchangers are sufficiently insulated to reduce cooling of said solar heating fluid in said heat exchanger housing to 1 degree Fahrenheit per hour at 130 degrees Fahrenheit.   
     
     
         8 . A tankless solar hot water heater according to  claim 3 , wherein said heat exchanger tubing comprises approximately 10 feet of ½ inch copper tubing in at least two loops, each approximately 20 inches long and approximately 3 inches wide. 
     
     
         9 . A tankless solar water heater according to  claim 3 , wherein each of said solar heating tubes comprises a transparent outer tube and an opaque inner tube, with a vacuum between said inner tube and said outer tube. 
     
     
         10 . A tankless solar water heater for heating domestic pressurized water, comprising:
 an insulated solar heating means, having an upper end, for solar heating and insulating a solar heating fluid contained therein;   a flexible insulated heat exchanger housing means having heat exchange ports and a check valve port sealingly attached said upper end, wherein said check valve port is located at an uppermost location of said heat exchanger housing, for insulating said solar heating fluid contained therein and for contracting to accommodate volume reduction when said solar heating fluid cools;   heat exchanger means mounted within said heat exchanger housing means, sealingly extending through said heat exchanger ports, for exchanging heat between solar heating fluid in said heat exchanger means and domestic pressurized water circulating through said heat exchanger means when said solar heating fluid fills said insulated tubes and said heat exchanger means;   a check valve means sealingly mounted in said check valve port for releasing air and said solar heating fluid and any gas therefrom if interior pressure in said solar heating means and said heat exchanger housing means exceeds ambient pressure by more than one pound per square inch, without admitting air into said solar heating means or said heat exchanger means when volume of said solar heating fluid reduces due to cooling, whereby air and gas from said solar heating fluid in said solar heating means and said heat exchanger housing means is minimized, whereby said interior pressure of said solar heating fluid in said solar heating means and said heat exchanger housing means is maintained at a maximum pressure of one pound per square inch above ambient pressure, and whereby any gas from boiling of said solar heating fluid is vented in case of boiling; and   wherein said solar heating means and said heat exchanger housing means are sufficiently insulated to reduce cooling of said solar heating fluid in said heat exchanger housing means to 1 degree Fahrenheit per hour at 130 degrees Fahrenheit.