Patent Publication Number: US-8536495-B2

Title: Device for regulated water heating using the energy gained by photovoltaic cells

Description:
RELATED APPLICATION 
     This application claims benefit of priority of Slovak Republic Patent Application No. PUV 83-2010, filed Jun. 30, 2010; and of Slovak Republic Patent Application No. PUV 142-2010, filed Oct. 1, 2010, each under 35 USC 119(a). All of the above-identified related applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns the use of the direct current power gained by photovoltaic cells for heating of water in a boiler, which is provided by thermal protection and by a control system. 
     STATE OF THE ART 
     Photovoltaic cells use a sunlight energy to produce the direct current, which can be stored in an accumulator, or which can be transformed by inverter to the alternating current for the main power supply. 
     The photovoltaic cells are not typically used to heat water due to the direct current characteristics of the power supply, which are not compatible with circuit devices such as switches or thermostats, which are intended for alternating current power supply. Previously it was not possible to use the photovoltaic cells, so the direct current, for water heating in compliance with relevant safety requirements for safe operation of boilers. 
     The aim of the invention is to disclose a new type of the device enables safe water heating by using the energy gained by the photovoltaic panels. 
     SUMMARY OF THE INVENTION 
     The above mentioned disadvantages are considerably eliminated by use of the device for regulated water heating using the energy gained by photovoltaic cells it, where it consists of terminals, where to the terminal is brought a protective earth, which is then brought to a thermostat, whereas to the terminal is brought a line conductor of the alternating current, which is then brought to a normally closed contact of a thermal fuse and then the line conductor is brought to a normally closed contact of a thermostat and then the line conductor is brought to a terminal of a coil of the contactor, whereas to the terminal is brought a neutral conductor, which is then brought to a normally closed contact of the thermal fuse and then the neutral conductor is connected to a terminal of the coil of the contactor, whereas to the terminal is brought a conductor of the positive phase of the direct current, which is then brought to a terminal of a switch of the contactor and then the conductor of the positive phase is brought from a terminal of a switch of the contactor to an inlet terminal of a heating coil of the direct current circuit, whereas to the terminal is brought a conductor of the negative phase of the direct current, which is then brought to a second inlet terminal of the heating coil of the direct current circuit. 
     In an advantageous embodiment the line conductor behind the contact of the thermal fuse is split and brought both to the thermostat and to the additional thermostat, whereas the line conductor is brought from the additional thermostat to an inlet terminal of a heating coil of the alternating current circuit, whereas the neutral conductor behind the contact of the thermal fuse is split and brought both to the terminal of the coil of the contactor and to a second inlet terminal of the heating coil of the alternating current circuit, whereas the protective earth is brought to an additional thermostat. 
     In another advantageous embodiment between the terminals of the coil of the contactor a signalization is connected. 
     In another advantageous embodiment between the inlet terminals of the heating coil of the alternating current circuit a signalization is connected. 
     In another advantageous embodiment between the inlet terminals of the heating coil of the direct current circuit a signalization is connected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will be further explained by use of a drawing, where  FIG. 1  is a schematic view of the device for regulated water heating according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     Photovoltaic cells are the main source of the direct current. An output of the photovoltaic cells is, e.g., 250 W per panel, i.e., four panels have an output 1 kWh. The photovoltaic cells are connected by conductors to the boiler via a terminal X 4  and a terminal X 5 . A conductor L+ is brought from the terminal X 4  to the terminal  1  of a switch of a contactor ST and then the conductor L+ is brought from the terminal  6  of the switch of the contactor ST to an inlet terminal of a heating coil R 2 . A conductor L− is brought directly from the terminal X 5  to a second inlet of the heating coil R 2 . The output of the heating coil R 2  has to be equal to the maximum output of the used photovoltaic cells. The contactor ST has to be designed for switching the direct current to ensure the safety of its operations. 
     The alternating current is connected to the boiler via a terminal X 2  and via a terminal X 3 , where a line conductor L is connected to the terminal X 2  and a neutral conductor N is connected to the terminal X 3 . A protective earth PE is connected to the terminal X 1  and then to a thermostat T 1  and to a thermostat T 2 . 
     The line conductor L is brought from the terminal X 2  to a normally closed contact Y 1  of a thermal fuse TP. The line conductor L behind the contact Y 1  of the thermal fuse TP is split and directed both to the thermostat T 1  and to the thermostat T 2 . The line conductor L is directed from the thermostat T 1  to an inlet terminal of a heating coil R 1  and the line conductor L is brought from the thermostat T 2  to a terminal A 1  of a coil of the contactor ST. 
     The neutral conductor N is brought from the terminal X 3  to a normally closed contact Y 2  of the thermal fuse TP. The neutral conductor N, behind the contact Y 2  of the thermal fuse TP, is split and directed both to the terminal A 2  of the coil of the contactor ST and to a second inlet terminal of the heating coil R 1 . 
     If the source of the alternating current is connected to the terminals X 2 , X 3 , the contacts  1 ,  6  of the contactor ST are switched on and the direct current heats the heating coil R 2 . 
     If a pre-set temperature of a water is reached, the thermostat T 2  breaks the supply of the alternating current to the coil of the contactor ST, which causes opening of the contact of the contactor ST, which causes breaking of the supply of the direct current to the heating coil R 2 . In the case of failure of the thermostat T 2 , there is arranged the thermal fuse TP before the thermostat T 2 , which is able to break the supply of the alternating current into the coil of the contactor ST after reaching the set temperature. By this means full control of water heating carried out by the heating coil R 2 , so by the direct current, is guaranteed. 
     In case of lack of sunlight energy and consequently to that, in case of lack of the direct current, water heating is carried out by heating coil R 1  supplied by alternating current. If a pre-set temperature of water is reached, the thermostat T 1  breaks the supply of the alternating current to the heating coil R 1 . Heating is terminated. 
     The signalization of functionality of the contactor ST is provided by signalization S 1 , which is connected between the terminals A 1  and A 2  of the coil of the contactor ST. 
     A heating signalization of the heating coil R 1  is provided by signalization S 3 , which is connected between the inlet terminals of the heating coil R 1 . 
     A heating signalization of the heating coil R 2  is provided by signalization S 2 , which is connected between the inlet terminals of the heating coil R 2 . 
     The device solves the problem of safeness of water heating by direct current reached by the photovoltaic cells. It enables a new utilization of the photovoltaic cells. Simple installation allows use of the above mentioned device in each house both for domestic and industrial purposes, with a minimal impact to the construction of the building. At the time of lack of sunlight intensity, water heating is provided by gas or other heating source or by use the heating coil R 1  supplied by alternating current for that heating. When the sunlight intensity is high, the photovoltaic cells can be use alone. However, the source of the direct current has to be properly dimensioned in dependence on the volume of the boiler. An output 1 kWh of the source of the direct current gained by photovoltaic cells, can be used to heat a water of the volume of 100 L. The estimated minimal durability of the photovoltaic cells is 25 years, whereas the system is able to return the acquisition costs by saving the energy consumption in a period of 2 to 5 years. This makes it an effective investment. 
     The device for regulated water heating uses energy gained by photovoltaic cells, is able to produce safe and environmental friendly energy just by using a sunlight energy.