The present invention relates to domestic hot water systems which utilize solar radiation as a source of heat and specifically to such apparatus using solar radiation in the form of heat to supply the motive force and controlling instrumentality for transfer and control of a heat absorbing fluid so as to maximize heat gain and preclude heat loss. The power and control factor, which is the subject of this invention, is provided by the predetermined vaporization of a fluid in phase transition which in turn generates fluid pressure acting upon a heat transporting fluid.
Essentially only two methods have been used to pump a fluid heat absorbing medium such as water into and from a solar collector. The first uses the technique of a thermosiphon whereby hot water rises by virtue of gravity out of the collector to be stored in a tank placed higher than the collector. This system is obviously subject to freeze damage and must place major design restrictions on the installation. Additionally, if the water is protected by antifreeze and a heat exchanger is used the water in the collector suffers substancial heat loss in the cold and must first reabsorb this loss before becoming operational again. This consideration greatly reduces the efficiency of the entire system. The second method is to employ an electric pump to circulate the water through the collector. Freeze protection is provided by either draining the collector or by using antifreeze; both these methods create substancial heat losses. Control in a pump system is provided by conventional electronic means employing relays, themostats, and valves. Such control is a major cost element in such operations and by virtue of its complexity creates maintenance concerns. While the thermosiphon system is simple, it is subject to freeze damage and imposes design considerations not easily accepted. It is also somewhat inefficient because of night cooling. The second system using the pump is higher in cost and complexity in addition to requiring outside energy to function properly. These systems comprise the present level of art as found in works such as Farrington Daniels' Direct Use Of The Sun's Energy (1964), W. M. Foster's Homeowner's Guide to Solar Heating and Cooling (1976), and J. C. McVeigh's Sun Power (1977).
The present invention eliminates or lessens the undesirable features of both these conventional hot water systems. Primarily, the present invention provides a single mechanism that both transfers a fluid heat absorbing medium such as water into a simple flat plate solar collector and provides a control means by virtue of this same mechanism that controls this transfer in such a manner as to maximize the heat gain. Further, this natural analog system conserves heat by removal of all fluid from the collect when cooling occurs and thus provides freeze protection. This simple mechanism acts as both pump and electronic controls of the pump system and is simple as the thermosiphon's operation, yet has neither the cost nor restraints of either operation.
Essentially the present invention comprises a vapor pressure pump utilizing the same solar radiation energy used to heat the water transport medium, the strength of the radiation acts as the control for the system by analog means. When solar radiation is present to heat the water transport medium, other elements of the same radiation are being trapped in a second fluid tight flat plate collector which contains a flexible vapor bag containing a fluid which substancially vaporizes at a predetermined temperature and pressure. Air surrounding the vapor bag is placed under pressure by the vaporization and in turn transmits this pressure to an enclosed storage tank that in turn discharges water into a first solar collector designed to heat a water medium. The water begins to absorb the solar heat trapped within the collector. When solar radiation is eliminated from the pressure generating collector by either natural or contrived means such as a fluid shade, the vapor condenses and creates a negative pressure which withdraws the heated water from its collector and places it in a holding tank for storage. Thus a form of active heating is created that does not require external power or a separate network of control.
Accordingly, it is an object of the present invention to provide a domestic hot water heating system using solar energy for heat gain and transportation of heat bearing fluids by means of solar generated fluid pressures.
Another object of the invention is to create a control means that optimizes the collection and retention of solar created heat by means of solar generated fluid pressures.
Other objects, advantages and novel features of the invention will become apparent from the following detailed description.