Patent ID: 8220453

Claim:
A solar water heating system including: a water tank to hold water to be heated, a heat transfer fluid circuit including an heat exchanger associated with said water tank to heat water therein, a solar collection means in communication with said heat exchanger, an inlet connection to carry heat transfer fluid by thermosyphoning from said solar collection means to said heat exchanger where said water will be heated; and an outlet connection to carry heat transfer fluid from said heat exchanger to said solar collection means where said heat transfer fluid will be heated, said heat transfer fluid circuit including a reversibly evaporable heat transfer fluid (HTF), in a liquid state, which will absorb heat from said solar collection means and which will transfer said heat to said water in said water tank by means of said heat exchanger; an isolation valve operated to close to interrupt said thermosyphoning to cause said liquid heat transfer fluid in said solar collection means to become stagnant and open to allow said thermosyphoning to continue or resume in response to a temperature or pressure sensor; and a liquid diversion path including a receptacle arranged to receive liquid phase heat transfer fluid (HTF) from the heat transfer fluid circuit when stagnant heat transfer fluid in the said solar collection means vaporizes; whereby when a predetermined temperature of the heat transfer fluid is reached or exceeded, said isolation valve closes and flow of said heat transfer fluid, in a liquid state, becomes stagnant, a portion of heat transfer fluid changes to a gaseous state in said solar collection means and is retained in said solar collection means by said isolation valve, and heat transfer fluid in a liquid state will be forced out of said solar collection means into said liquid diversion path.