Bivalent water heating system

Abstract

A bivalent water-heating system includes a water-storage tank having at least one wall defining an interior storage cavity configured for storing water to be heated. The storage cavity includes an upper-cavity and lower-cavity portions. A non-solar heating unit is situated at least partially in the upper-cavity portion and includes a combustion chamber defined by at least one wall through which heat produced by the combustion of fuel is transferred to stored water located within the upper-cavity portion. Water stored in the lower-cavity portion is heated by a solar heating subsystem that circulates a heat-transferring fluid between a solar collector that converts solar radiation to heat energy and a heat exchanger situated within the lower-cavity portion such that heat-transferring fluid (i) absorbs heat at the solar collector, (ii) is routed to the heat exchanger where the heat-transferring fluid transfers heat to water stored in the lower-cavity portion, and (iii) is returned from the heat exchanger to the solar collector to absorb additional heat.

1 . A bivalent water-heating system comprising:
 a water-storage tank with an interior storage cavity configured for storing a quantity of water to be heated, the storage cavity including upper-cavity and lower-cavity portions that are in mutual fluid communication;   a non-solar heating unit situated at least partially within the upper-cavity portion and including at least one heat-conductive wall through which heat produced by the non-solar heating unit is transferred to water stored within the upper-cavity portion;   a solar heating subsystem including, in a circulatory fluid pathway, a solar collector that converts solar radiation to heat energy, a heat exchanger situated within the lower-cavity portion, and fluid conduits rendering the solar collector and heat exchanger in mutual fluid communication; and   a circulator that is selectively activated to circulate a heat-transferring fluid through the fluid pathway in response to the presence of a predetermined temperature differential between a first temperature at the solar collector and a lower second temperature indicative of the temperature of water stored in the lower cavity portion such that, when the circulator is activated, the circulating heat-transferring fluid (i) absorbs heat at the solar collector, (ii) is delivered to the heat exchanger where the heat-transferring fluid transfers heat to water stored in the lower-cavity portion, and (iii) is returned from the heat exchanger to the solar collector to absorb additional heat.   
   
   
       2 . The bivalent water-heating system of  claim 1  wherein the non-solar heating unit comprises a combustion chamber situated at least partially within the upper-cavity portion and within which a combustible fuel is selectively burned, the combustion chamber being defined by at least one heat-conductive wall through which heat produced by the combustion of the combustible fuel is transferred to stored water located within the upper-cavity portion 
   
   
       3 . The bivalent water-heating system of  claim 2  wherein at least a majority of the vertical extent of the combustion chamber is situated above at least a majority of the vertical extent of the heat exchanger. 
   
   
       4 . The bivalent water-heating system of  claim 2  wherein the combustion chamber is configured for the combustion of at least one of oil, propane, and natural gas. 
   
   
       5 . The bivalent water-heating system of  claim 2  wherein, as viewed along a vertical axis, the highest portion of the heat exchanger situated within the storage cavity is separated from the lowest portion of the combustion chamber situated within the storage cavity by a predetermined vertical-separation distance such that, at least when the heat exchanger is inactive for an extended period of time, a measurable temperature gradient is maintained between a portion of stored water located in the lower-cavity portion and a portion of stored water located in the upper-cavity portion. 
   
   
       6 . The bivalent water-heating system of  claim 5  wherein the heat exchanger is formed as a tubular helix. 
   
   
       7 . The bivalent water-heating system of  claim 6  wherein the heat exchanger is fabricated from at least one of (i) copper, (ii) cast iron, and (iii) brass. 
   
   
       8 . The bivalent water-heating system of  claim 5  wherein the combustion chamber is configured for the combustion of at least one of oil, propane, and natural gas. 
   
   
       9 . The bivalent water-heating system of  claim 8  wherein the heat exchanger is formed as a tubular helix. 
   
   
       10 . The bivalent water-heating system of  claim 9  wherein the heat exchanger is fabricated from at least one of (i) copper, (ii) cast iron, and (iii) brass. 
   
   
       11 . A bivalent water-heating system comprising:
 a water-storage tank having an upper end, a lower end and at least one wall defining an interior storage cavity configured for storing a predetermined quantity of water, the storage cavity including an upper-cavity portion and a lower-cavity portion situated below the upper-cavity portion;   a non-solar heating unit including a combustion chamber situated at least partially within the upper-cavity portion and within which a combustible fuel is selectively burned, the combustion chamber being defined by at least one heat-conductive wall through which heat produced by the combustion of the combustible fuel is transferred to stored water located within the upper-cavity portion; and   a solar heating subsystem including (i) a heat exchanger situated within the lower-cavity portion of the tank, (ii) a solar collector remotely located from the heat exchanger and including an absorber that converts solar radiation to heat energy, (iii) an heat-transferring-fluid input conduit, and (iv) a heat-transferring fluid output conduit;   wherein the heat exchanger, the solar collector, the input conduit and the output conduit are incorporated in a circulatory fluid pathway such that, when the heat exchanger is immersed in stored water located within the lower-cavity portion, heat-transferring fluid that is caused to flow through the fluid pathway (i) absorbs heat from the absorber, (ii) flows through the input conduit to the heat exchanger, where the heat-transferring fluid transfers heat to the stored water, and (iii) is returned from the heat exchanger to the solar collector through the output conduit.   
   
   
       12 . The bivalent water-heating system of  claim 11  wherein the combustion chamber is configured for the combustion of at least one of oil, propane, and natural gas. 
   
   
       13 . The bivalent water-heating system of  claim 11  wherein, as viewed along a vertical axis, the highest portion of the heat exchanger situated within the storage cavity is separated from the lowest portion of the combustion chamber situated within the storage cavity by a predetermined vertical-separation distance such that, at least when the heat exchanger is inactive for an extended period of time, a measurable temperature gradient is maintained between a portion of stored water located in the lower-cavity portion and a portion of stored water located in the upper-cavity portion. 
   
   
       14 . The bivalent water-heating system of  claim 13  further comprising a circulator that is selectively activated to circulate the heat-transferring fluid through the fluid pathway in response to the presence of a predetermined temperature differential between a first temperature at the solar collector and a lower second temperature indicative of the temperature of water stored in the lower cavity portion. 
   
   
       15 . The bivalent water-heating system of  claim 11  wherein at least a majority of the vertical extent of the combustion chamber is situated above at least a majority of the vertical extent of the heat exchanger. 
   
   
       16 . The bivalent water-heating system of  claim 11  further comprising a circulator that is selectively activated to circulate the heat-transferring fluid through the fluid pathway in response to the presence of a predetermined temperature differential between a first temperature at the solar collector and a lower second temperature indicative of the temperature of water stored in the lower cavity portion. 
   
   
       17 . The bivalent water-heating system of  claim 16  wherein the combustion chamber is configured for the combustion of at least one of oil, propane, and natural gas. 
   
   
       18 . The bivalent water-heating system of  claim 17  wherein at least a majority of the vertical extent of the combustion chamber is situated above at least a majority of the vertical extent of the heat exchanger. 
   
   
       19 . The bivalent water-heating system of  claim 17  wherein, as viewed along a vertical axis, the highest portion of the heat exchanger situated within the storage cavity is separated from the lowest portion of the combustion chamber situated within the storage cavity by a predetermined vertical-separation distance such that, at least when the heat exchanger is inactive for an extended period of time, a measurable temperature gradient is maintained between a portion of stored water located in the lower-cavity portion and a portion of stored water located in the upper-cavity portion.