Abstract:
A solar heater with a primary circuit course in a panel for heating two separate inter connected storage reservoirs.

Description:
This application is a Continuation in Part of Application Ser. No. 11/921,930, filed May 16, 2008, claiming priority based on International Application No. PCT/PT2005/000014, filed Sep. 14, 2005, which claims priority based on Portugal Application No. 103300, filed Jun. 30, 2005, the disclosure of each is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     There has always been a great interest in the use of solar power for heating water. 
     The systems of prior art, however, have a low yield and users therefore complain that they have to consume a large amount of back-up electric power. 
     In order to resolve the problems existing in prior art, the applicant has devised a high-yielding system which basically results from the association between panels, as well as a utilization of a high stratification reservoir (wherein the cold water that enters does not mix with the hot water that exits, and wherein only after the first 150 liters are sufficiently hot are the other 150 liters heated). 
     Thus, a much higher yield is achieved, which provides much hotter water with the same solar radiation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description which follows is based on the drawings attached hereto, which are of a non-restrictive nature and represent: 
       In  FIG. 1 , a panel belonging to prior art; 
       In  FIG. 2 , a panel according to the invention; 
       In  FIG. 3 , a perspective view and cross-section of the panel represented in  FIG. 2 . 
     
    
    
     PRIOR ART 
     Hereunder is a brief explanation of the mode of operation of the systems of prior art, which function by thermosyphon, comparing them with the system of the invention (functioning by thermosyphon of panels connected in series). 
     The primary circuit which functions by thermosyphon can have a volume, with this type of equipment, of around fifteen liters and it works simply by gravity force and by the alteration of the water density due to temperature variations (functioning by thermosyphon). 
     Thus, if there is solar radiation, the water in the primary circuit is constantly travelling from panels ( 5 ) and ( 6 ) to reservoirs ( 3 ) and ( 4 ), where heat will be transferred from the water in the primary circuit to the water for consumption by means of heat exchangers ( 9 ) and ( 10 ), and afterwards from reservoir to panels ( 5 ) and ( 6 ) to be heated again. 
     The said panels are constituted by tubes where the water from the primary circuit circulates, by the sheet in the circuit which absorbs the heat and joins the tubes in order to direct the heat to them, and also by an insulating material and a piece of glass. 
     In the others systems of prior art, the water course in the primary circuit is the following:
         a) The less warm water which exits reservoir (C) goes down an external tube in the panels, outside of the heating zone (A), which causes loss of yield. The system of our invention does not have this external tube.   b) In the other system which function by thermosyphon the panels are arranged parallel to one other, i.e. upon each passage, the thermofluid either passes through panel B or through panel B and never through the two in the same cycle.   c) When the water enters the panels, and supposing that each panel is two meters high and one meter wide, it will travel four meters inside the heating zone (see  FIG. 1 ), whatever its path inside the tubes, and two meters outside subject to cooling.   d) When the water returns to the reservoir, it transfers all its heat to just one reservoir (C), meaning that on days when there is little solar radiation, it is difficult to raise the temperature of the 300 liters of water, thus preventing it from being used. However, in the system of the invention the first 150 liters of water are heated in the panels, and only after they reach a very hot temperature are the other 150 liters heated.   e) Since the solar heater systems of prior art have just one reservoir, the cold water that enters mixes directly with the hot water that exits, thereby producing right from the outset a very unfavourable mix. In the system of the present invention, by making use of the fact that the panels connected in series function by thermosyphon, it is possible to obtain a drainage speed suitable for transferring all the initial heat to the first reservoir.       

     DETAILED DESCRIPTION OF THE INVENTION 
     As may be observed, the solar system of the invention for heating domestic water comprises solar panels functioning by thermosyphon in series, which have a primary circuit containing a fluid that passes between heat exchangers ( 9  and  10 ) mounted on reservoirs ( 3  and  4 ) containing piped water to be heated and tubes ( 15 ,  25 ,  20  and  24 ) and ( 16 ,  26 ,  21  and  27 ) of the panels ( 6  and  5 ). The said fluid of the primary circuit circulates by thermosyphon effect, the fluid of the primary circuit that comes from heat exchanger ( 10 ) entering directly into panel ( 6 ) through tube ( 15 ) and being heated immediately even though it is flowing downwards. 
     In the system of the invention, the course of the primary circuit is completely different as the thermofluid (water and antifreeze) has to travel ten meters inside the panels and is therefore always subject to heating. 
     The main question is to determine how the water can travel downwards after it exits the reservoir, bearing in mind that when entering the panels it will be heated and will want to travel upwards. 
     This is achieved by the fact that thermosyphon effect in the panels ( 6  and  5 ) is possible due to the total closure ( 1 - 1 ′) of the upper tube ( 24 ), which forces the fluid to travel ( 18 ) down tube ( 15 ), even while it is being heated, circulating to tube ( 25 ) and flowing up tubes ( 20 ) to tube ( 24 ), from which it passes to the adjacent panel ( 5 ), and due to the partial closure ( 2 - 2 ′) of tube ( 27 ), which forces the fluid to travel ( 18 ) down tube ( 16 ), circulating to tube ( 26 ) and flowing up tube ( 21 ) to tube ( 27 ), the end of which is connected to heat exchanger ( 9 ) of reservoir ( 3 ). 
     The downwards path of the fluid of the primary circuit in vertical tubes ( 15  and  16 ) is guaranteed by the suction caused by the fluid flowing up tubes ( 20  and  21 ), due to the fact that these tubes are greater in number than the single tube ( 15  and  16 ) in each of the panels. 
     Thus, for each panel of ten tubes, in nine tubes the water that wants to travel upwards will have sufficient power for there to be suction in tube ( 15 ) where the water, even though it is being heated, will be forced to travel downwards. 
     Since there is no connection between panels ( 5 ) and ( 6 ) in the lower part, the water enters the second panel ( 5 ) from above ( 17 ) and in the same way, in the first panel ( 6 ), the water is forced to travel down the first tube ( 16 ). 
     Therefore, the course of this primary circuit is meters long inside the heating zone, which is considerably greater than the four meters of the other systems. 
     This naturally means that the water in this primary circuit is significantly warmer. 
     The partial closure ( 2 - 2 ′) has a bleeding function as it permits the passage of air in order to allow the fluid to circulate and the panels to be filled, i.e. if the primary circuit is filled through tube ( 7 ), the water will reach tube ( 25 ) and start to fill tubes ( 20 ), going down tube ( 16 ) and then filling tube ( 26 ), and when this happens the air remaining inside tubes ( 16 ,  20  and  24 ) will exit through the said partial closure ( 2 - 2 ′), thus avoiding air pockets which would prevent the thermosyphon from functioning, and if the primary circuit is filled through the other tube ( 8 ), the water will fill tubes ( 21 ,  16  and  26 ) and when it reaches tube ( 25 ), the air in tubes ( 20  and  24 ) will only be able to exit through the space reserved for the passage of air by means of the said closure ( 2 - 2 ′), whereby it may be concluded that if the closure ( 2 - 2 ′) were total, the thermosyphon would not function. 
     This passage of air and the passage of an insignificant amount of fluid of the primary circuit means that nearly all of the said fluid goes down tube ( 16 ), having for this purpose a small air passage which acts as a bleeder for the system. 
     When entering the reservoirs, this circuit will have two heat exchangers ( 9 ) and ( 10 ) in the respective reservoirs ( 3 ) and ( 4 ). Thus, the thermofluid (water with antifreeze) which exits the panels and then enters the left-hand reservoir ( 3 ) will start by heating the water therein, and when the water passes to the second heat exchanger ( 10 ) (which is inside the right-hand reservoir ( 4 )), it will already be much lower in temperature (minimum temperature of the first reservoir). That is to say, for example, if the water reaches the first heat exchanger ( 9 ) at 80°, the temperature in the first reservoir can rapidly be lowered to 50° in the upper part and 30° in the lower part. 
     Thus, the temperature which goes to the second heat exchanger ( 10 ) will be approximately 30° and will not significantly heat up the second reservoir. 
     As the temperature rises in the first reservoir which the water from the primary circuit reaches ( 3 ), the transfer of heat from the second reservoir ( 4 ) increases. 
     Thus, if we have water in the first reservoir in the upper part at 70° and in the lower part at 50°, the water from the primary circuit which goes to the second heat exchanger is already at a temperature of around 50° and the water in the other reservoir starts to heat up to temperatures suitable for consumption. 
     This effect is achieved precisely by the fact that the two panels function by thermosyphon and in series, which guarantees that the temperature is much higher per cycle and that the speed of the cycle is the most suitable for rapidly transferring the heat to the first reservoir that it encounters. 
     The water for consumption which passes from the highest part of the reservoir on the right-hand side ( 4 ) to the left-hand side ( 3 ) is also forced to go down to the bottom ( 12 ) of the reservoir on the left-hand side ( 3 ) for the same purpose, i.e. to delay as much as possible the “contact” between the piped water that enters ( 11 ) (which, throughout its course, is progressively heated) and the water that exits ( 13 ). 
     The cold piped water which enters on the right-hand side ( 11 ), i.e. in the reservoir containing water that is less hot ( 4 ), will not mix directly with the hot water that exits ( 13 ) the reservoir containing hotter water, thus preventing sudden decreases in the temperature of the water for consumption. 
     As may be understood from the above, the course ( 22 ) of the fluid in the primary circuit in the heat exchangers ( 9  e  10 ), in conjunction with the course ( 19 ) of the piped water to be heated in the reservoirs ( 3  e  4 ), allows the said reservoirs ( 3  e  4 ) to have a high degree of stratification and function with different temperatures, in view of the fact that the greater the difference in temperature between the primary fluid which reaches heat exchanger ( 9 ) from panel ( 5 ) and the piped water in reservoir ( 3 ), the greater will be the transfer of heat acquired in the panels ( 5  e  6 ) to the piped water in the said reservoir ( 3 ). 
     The cold piped water which enters reservoir ( 4 ) on the right-hand side through tube ( 11 ) does not mix directly with the hot water which exits the top of reservoir ( 3 ) on the left-hand side through tube ( 13 ), which allows the water to be progressively heated in the reservoir on the right-hand side ( 4 ), passing through tube ( 12 ) to the lower part of the reservoir on the left-hand side ( 3 ) so that it is heated even further in reservoir ( 3 ). 
     The tubes ( 7  e  8 ) for filling the primary circuit extend a few centimeters inside the respective heat exchangers ( 10  and  9 ), with the objective of always having some air in the primary circuit in order to allow space for the increased volume of the fluid which occurs at high temperatures, since the said circuit has to be plugged ( 23 ) so that the fluid will not evaporate when it reaches high temperatures.