WO2023199341A1 - System and method for solar photovoltaic water heater - Google Patents

Abstract

The present invention provides a system and method thereof for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit. The system and method thereof of the present invention uses semiconductor devices to convert PV energy to heat energy, while simultaneously tracking the maximum power point of the PV panel array. According to system and method thereof of the present invention the semiconductor heater of the present invention can be attached to the outside surface of the water tank.

Description

SYSTEM AND METHOD FOR SOLAR PHOTOVOLTAIC WATER HEATER

Field of Invention:

[001] This invention relates to Solar Photovoltaic (PV) system, more particularly, this invention relates to Solar Photovoltaic (PV) water heater system made using plurality of semiconductor devices.

Background of Invention:

[002] Solar PV water heaters are used for heating water for both domestic applications and for commercial applications. In existing solar water heater designs, a microprocessor controls set of relays, that connect the PV module to several resistive heating elements, in a way that best matches instantaneous operating characteristics of PV module. Alternatively, pulsed DC current (PWM) can be used to control the amount of power dissipated in the heaters. Such controllers instantaneously track the maximum power point of the PV module using the Maximum Power Point Tracking (MPPT) algorithm. Usually, these water heaters also have a heating element, which is connected to the residential utility power supply. Whenever power from PV modules is not sufficient, the utility power supply is turned ON, to get the desired water temperature. A thermostat is disposed inside the storage tank for controlling the utility power to the heating element, to limit the maximum water temperature.

[003] A plurality of constructions have been disclosed through various prior systems. Some of them are listed herewith. [004] US 5,293,447, Photovoltaic Solar Water Heating System, by Fanney, et al, describes a system for heating water using solar energy comprises a PV array, a water heater comprising a variable resistive load, and a controller for varying either the load characteristics of the resistive load or the power generating characteristics of the PV array, or both, to ensure maximum power transfer efficiency.

[005] In one embodiment of the above prior art, a controller controls the connection of plural resistive elements in the water heater responsive to the sensed intensity of the incident radiation, to optimize the power output of the PV array at any given time. In another embodiment of the above prior art, the controller controls the connection of plural resistive elements responsive to the measured power output of the photovoltaic array. In another embodiment of the above prior art, the controller controls the configuration of the individual cells in the photovoltaic array responsive to the measured power output of the photovoltaic array.

[006] The Figure 1 is the reproduction of prior art schematic view of one of the embodiments of system as described by Fanney. A water heater including a plurality of discrete resistance heating elements is provided together with a controller responsive to a sensor sensing the intensity of the incident radiation, the controller varying the load provided by the resistive elements of the water heater to maximize the energy delivered by the PV array. Radiation 10 from the Sun 12 is incident on a photovoltaic array 14. A water heater 18 to which the PV array 14 is connected comprises plural resistive elements 20 in a reconfigurable circuit configuration such that the load can be varied responsive to a control signal from a controller 16 along with switching control module 22. The switching control module 22 may comprise solid state switches or relays. Water heater 18, includes storage tank 31 for water, an inlet for cold water 24 and an outlet for hot water 26. The heater 18 may also comprise a further heating element 28 to be connected to a residential utility power supply or the like for heating water when the intensity of incident solar radiation is inadequate to do so. Controller 16 provides switching signals responsive to a radiation intensity signal from a photovoltaic sensor 30. Sensor signal is amplified using amplifier 32 and resistor network 34 provides the reference signal to the controller 16.

[007] US 9,518,759 B2, Photovoltaic DC heater systems by Butler, describes Direct Current solar electric heating elements powered by an array of PV panels. Insertable immersion heating elements can be placed into any existing, gas, propane or electric hot water tank, cooking pot or hot tub. Heating elements in air can also be used for heating ovens, range cook tops and sauna heaters. The output of the PV panel is interfaced to the electric heater element via either direct connection or using a loadmatching controller which maximizes the power delivered to the heater under all sun conditions. The impedance matching power maximiser box uses PWM duty cycle control to get maximum heating efficiency. The maximum heater temperature is regulated by a thermostat.

[008] US 5,644,219, Solar Energy System, by Kurokawa, describes a solar energy system of simple construction capable of utilizing the PV source always at a high efficiency without being affected by environmental changes or yearly declination of photovoltaic cell, etc. A solar energy system provided, constructed by connecting at least two PV arrays of identical characteristics in parallel and a lead to which the electric energy of the PV array is supplied. A detecting circuit for detecting the operating point of the PV array is provided. Current limiting elements with different voltage drops in forward direction connected in series to each of the two PV arrays. The system calculates the power of the two PV arrays by detecting the terminal voltages of the two PV arrays by means of those current limiting elements and detects the operating point of the PV array from the difference of power (or differential current) between the two PV arrays. [009] US 2009/0214195 Al, PV Water Heating System, by Thomasson, describes system for heating water, and includes a first tank, solar panel, a control circuit, a second tank. There is first resistive heating element in the first tank, and a second resistive heating element in the second tank. The control circuit couples power from the solar panel to second resistive element unless the water in the second tank is at preset maximum temperature. Then the control circuit couples power to the first resistive heating element. If the water in the second tank is below a preset maximum temperature, and above a preset minimum temperature, then the control circuit couples power to both the heating elements. If the temperature of water in the second tank is below a preset minimum temperature, then the control circuit turns ON, conventional heating means in the second tank. Water is withdrawn from the second tank for use.

Objects of the present invention:

[0010] An object of the present invention is to provide a Solar PV water heater without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit.

[0011] Another object of the present invention is to use semiconductor devices to convert PV energy to heat energy, while simultaneously tracking the maximum power point of the PV panel array.

[0012] Yet another object of the invention is to attach the semiconductor heater on the outside surface of the water tank, to avoid major changes to the electric water heaters available in the market. Summary of the Invention

[0013] The present invention provides a system and method thereof for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit. The system and method thereof of the present invention uses semiconductor devices to convert PV energy to heat energy, while simultaneously tracking the maximum power point of the PV panel array. According to system and method thereof of the present invention the semiconductor heater of the present invention can be attached to the outside surface of the water tank.

[0014] According to one of the embodiments of the present invention, a system for solar photovoltaic water heater comprises a Hot water heater (118), at least one Photovoltaic array (114), at least one fuse, and at least one Conformal coating. The Hot water heater (118) comprises a storage tank (130) to store the water for heating, at least one cold water inlet pipe (124) configured as a source of the cold water to the storage tank (130) of the Hot water heater (118), at least one hot water outlet pipe (126) configured as an outlet of the hot water from the storage tank (130) of the Hot water heater (118), a heating element (128) connected to a utility power supply and operative when the intensity of solar radiation is inadequate, a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters attached on the outside surface of the storage tank (130) with good thermal contact, at least one fastener configured to place and attach the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130), a thermal cut off device TC attached to the storage tank (130) on its outside surface, and a ground connectivity (132) to the storage tank (130) configured to provide safety to the user against any leakage current. The at least one Photovoltaic array (114) have a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells. The at least one Photovoltaic array (114) is configured to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The at least one fuse is connected between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +Vpv terminal of Photovoltaic array (114). The at least one Conformal coating is confirmed to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature.

[0015] According to one of the embodiments of the present invention, a method for solar photovoltaic water heater comprising steps of constructing a Hot water heater (118). The method includes configuring at least one Photovoltaic array (114) having a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells, to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method includes connecting at least one fuse between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +Vpv terminal of Photovoltaic array (114). The method includes setting at least one Conformal coating confirming to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature.

[0016] The method of constructing a Hot water heater (118) includes configuring a storage tank (130) to store the water for heating. The method includes configuring at least one cold water inlet pipe (124), as a source of the cold water to the storage tank (130) of the Hot water heater (118). The method includes configuring at least one hot water outlet pipe (126), as an outlet of the hot water from the storage tank (130) of the Hot water heater (118). The method includes connecting a heating element (128), to a utility power supply to make it operative when the intensity of solar radiation is inadequate. The method includes attaching and activating a thermal cut off device TC to the storage tank (130) on its outside surface. The method includes constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method includes attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) with good thermal contact. The method includes fasting by at least one fastener, the placed and attached plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130). The method includes providing a ground connectivity (132) to the storage tank (130) to provide safety to the user against any leakage current.

Brief description of the drawings:

[0017] The embodiments can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, the emphasis instead being placed upon illustrating the principles of the embodiments. Moreover, the figures, like reference numerals designate corresponding parts throughout the different views.

[0018] Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

[0019] The above and other objects, features, and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 is the reproduction of prior art schematic view of one of the embodiments of system as described by Fanney. Figure 2 shows the schematic view of the Solar Photovoltaic Water Heater using Semiconductor Devices according to one of the embodiments of the present invention.

Figure 3 (a) shows the top view of the thermal cutoff device TC according to one of the embodiments of the present invention.

Figure 3 (b) shows the front view of the thermal cutoff device TC according to one of the embodiments of the present invention.

Figure 4 shows the perspective view of thermal cutoff device TC according to one of the embodiments of the present invention.

Figure 5 shows the circuit diagram of the solar PV semiconductor heaters in accordance with the present invention according to one of the embodiments of the present invention.

Figure 6 shows typical layer assignment of a standard single sided metal core/clad PCB according to one of the embodiments of the present invention.

Figure 7 (a) shows the top perspective view of the SMA package of Zener Diode according to one of the embodiments of the present invention.

Figure 7 (b) shows the bottom perspective view of the SMA package of Zener Diode according to one of the embodiments of the present invention.

Figure 8 (a) shows Pad layout for Zener diode having SMA type package. All dimensions are in mm according to one of the embodiments of the present invention.

Figure 8 (b) shows Pad layout for resistor with size 2512 (or metric 6432). All dimensions are in mm according to one of the embodiments of the present invention.

Figure 9 (a) shows top view of assembled MCPCB with one Zener diode and one resistor according to one of the embodiments of the present invention (Solder alloy, Solder mask layer and Silk screen layer are not shown). Figure 9 (b) shows side view of assembled PCB with one Zener diode and one resistor according to one of the embodiments of the present invention (Solder alloy, Solder mask layer and Silk screen layer are not shown).

Figure 10 (a) shows the top view of the assembled Zener heater MCPCB, ZH1 according to one of the embodiments of the present invention.

Figure 10 (b) shows the end view of the assembled Zener heater MCPCB, ZH1 according to one of the embodiments of the present invention.

Figure 11 shows assembled MCPCB mounted on the metallic wall of water storage tank using heat conductive adhesive. The arrows show direction of flow of heat energy according to one of the embodiments of the present invention.

Figure 12 (a) shows perspective view of the water storage tank with MCPCBs mounted on the water tank and protective coating applied over the MCPCBs according to one of the embodiments of the present invention.

Figure 12 (b) shows the bottom view of the water storage tank with MCPCBs mounted and protective coating applied over the MCPCBs according to one of the embodiments of the present invention.

Figure 13 shows the bottom view of the water heater along with the outer enclosure and thermal insulation according to one of the embodiments of the present invention.

Figure 14 shows typical derating curve for one watt Zener diode according to one of the embodiments of the present invention.

Figure 15 (a) shows comparison of 100% MPPT graph with Zener Heater tracking graph according to one of the embodiments of the present invention.

Figure 15 (b) shows comparison of 90% MPPT graph with Zener Heater tracking graph according to one of the embodiments of the present invention.

Figure 16 shows the circular clamp as a fastener wound around the outside surface of the storage tank (130) for holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) according to one of the embodiments of the present invention.

Detailed description of the Invention

[0020] The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

[0021] The present invention is a system and method for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit. The system and method thereof of the present invention uses semiconductor devices to convert PV energy to heat energy, while simultaneously tracking the maximum power point of the PV panel array. According to system and method thereof of the present invention the semiconductor heater of the present invention can be attached to the outside surface of the water tank, to avoid major changes to the electric water heaters available in the market.

[0022] In the following description, for the purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of systems.

[0023] The various embodiments of the present invention provide a system and method for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit.

[0024] Furthermore, connections between components and/or modules within the figures are not intended to be limited to direct connections. Rather, these components and modules may be modified, re-formatted or otherwise changed by intermediary components and modules.

[0025] The systems/device and methods described herein are explained using examples with specific details for better understanding. However, the disclosed embodiments can be worked on by a person skilled in the art without the use of these specific details.

[0026] Throughout this application, with respect to all reasonable derivatives of such terms, and unless otherwise specified (and/or unless the particular context clearly dictates otherwise), each usage of:

“a” or “an” is meant to read as “at least one.”

“the” is meant to be read as “the at least one.”

References in the present invention to “one embodiment” or “an embodiment” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[0027] Embodiments of the present invention include various steps, which will be described below. The steps may be performed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general- purpose or special purpose processor programmed with the instructions to perform the steps. Alternatively, steps may be performed by a combination of hardware, software, firmware and/or by human operators.

[0028] If the specification states a component or feature "may¹ can", "could", or "might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0029] As used in the description herein and throughout the claims that follow, the meaning of "a, an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0030] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this invention will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).

[0031] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claim. [0032] The present invention provides a system and method thereof for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit. The system and method thereof of the present invention uses semiconductor devices to convert PV energy to heat energy, while simultaneously tracking the maximum power point of the PV panel array. According to system and method thereof of the present invention the semiconductor heater of the present invention can be attached to the outside surface of the water tank.

[0033] This invention relates to Solar Photovoltaic (PV) system, more particularly, this invention relates to Solar Photovoltaic (PV) water heater system made using plurality of semiconductor devices connected in series and parallel combinations. These semiconductor devices are soldered on PCBs and the assembled PCBs are mounted on the external surface of the water tank. Heat dissipated by the semiconductor devices raises the temperature of water inside storage tank. In addition, semiconductor devices closely track the instantaneous maximum power point of PV panels. There is no separate electronic controller required in between the PV panels and the semiconductor heaters. Hence all the power generated by PV panels goes to the semiconductor devices thus providing maximum power transfer efficiency. Since the heaters are mounted on the external surface of the water tank, this system can be installed in existing electric water heaters with small modifications.

[0034] According to one of the embodiments of the present invention, a system for solar photovoltaic water heater comprises a Hot water heater (118), at least one Photovoltaic array (114), at least one fuse, and at least one Conformal coating. The Hot water heater (118) comprises a storage tank (130) to store the water for heating, at least one cold water inlet pipe (124) configured as a source of the cold water to the storage tank (130) of the Hot water heater (118), at least one hot water outlet pipe (126) configured as an outlet of the hot water from the storage tank (130) of the Hot water heater (118), a heating element (128) connected to a utility power supply and operative when the intensity of solar radiation is inadequate, a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters attached on the outside surface of the storage tank (130) with good thermal contact, at least one fastener configured to place and attach the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130), a thermal cut off device TC attached to the storage tank (130) on its outside surface, and a ground connectivity (132) to the storage tank (130) configured to provide safety to the user against any leakage current. The at least one Photovoltaic array (114) have a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells. The at least one Photovoltaic array (114) is configured to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The at least one fuse is connected between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +Vpv terminal of Photovoltaic array (114). The at least one Conformal coating is confirmed to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature.

[0035] According to one of the embodiments of the system of present invention, each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters comprises an array of a plurality of Zener diodes, at least two current limiting resistors, and at least one diode. The array of a plurality of Zener diodes have a plurality of Zener Diodes connected in series. The two current limiting resistors are connected in series at the cathode end of the array of a plurality of Zener diodes. The at least one diode is connected in series with the two current limiting resistors connected in series at the cathode end of the array of a plurality of Zener diodes. [0036] According to one of the embodiments of the system of present invention, a positive terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters is connected to first terminal of the Fuse and a negative terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters is connected to first terminal TC I of thermal cutoff device TC. The second terminal of the Fuse is connected to the +Vpv terminal of the Photovoltaic array (114). The second terminal TC_2 of thermal cutoff device TC is connected to the -Vpv terminal of the Photovoltaic array (114).

[0037] According to one of the embodiments of the system of present invention, the thermal cut off device TC is a fixed temperature type cutoff device comprising two terminals TC I and TC_2 as normally connected (NC) contacts. The first terminal TC I is connected to all negative terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and the second terminal TC_2 is connected to the - Vpv terminal of the Photovoltaic array (114). The thermal cut off device TC configured to senses the temperature of a surface on which it is mounted, the outside surface of the storage tank (130), and electrically disconnect the two terminals TC I and TC2 when the device cutoff temperature is reached, cutting off the Photovoltaic power supply to the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters.

[0038] According to one of the embodiments of the system of present invention, the Metal Clad Printed Circuit Boards (MCPCB) comprises a Metal Core/clad Layer, a dielectric layer, a copper layer, a Solder Mask Layer, and a Silk screen layer. The Metal Core/clad Layer is made of Aluminium or Copper and have thickness of about 1 to 3 mm as a bottom most layer. The dielectric layer as a next upper layer to the Metal Core/clad Layer is configured to decide an insulation resistance and a voltage rating of the MCPCB. The copper layer as a next upper layer to the dielectric layer is configured to etch the interconnecting tracks and SMD mounting pads. The Metal Core/clad Layer of the Metal Clad Printed Circuit Boards (MCPCB) is configured to take away the heat from the component soldered to the copper layer and dissipate it. A dielectric material of the dielectric layer of the Metal Clad Printed Circuit Boards (MCPCB) has better thermal conductivity as compared with standard glass epoxy or FR4 PCB.

[0039] According to one of the embodiments of the system of present invention, the at least one fastener can be heat conductive adhesive, thermal compound, thermal conductive adhesive, thermal paste or any type of circular clamps/tie such as but not limited to cable tie wound around the outside surface of the storage tank (130), holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) or any suitable combination of both. The various fixing methods for heater PCBs on the outer surface of the water storage tank are discussed below.

1) Using Heat conductive adhesive: The heat conductive adhesive fixes the PCBs to the tank permanently. Hence, if any PCB fails, the whole water tank needs replacement.

2) Heat conducting paste (thermal compound): In this method, a thin layer of heat conducting paste is applied to the back side of heater PCBs. Then these PCBs are stuck to the outer surface of the water tank. Using plurality of cable ties or circular clamps, these PCBs are held in the position. In this method, if any heater PCB fails, it can be easily replaced.

3) PCB fabrication on the storage tank: It may be possible to fabricate the PCBs on the water tank surface itself. In this case, the aluminium core is not required for the PCB. It gets replaced with the metal used to make the water storage tank. In this case also, if one of the heater PCB fails, the whole tank has to be replaced.

The comparison of the various fixing methods for heater PCBs on the outer surface of the water storage tank is depicted in Table 1 below. Table 1

[0040] Figure 16 shows the circular clamp as a fastener wound around the outside surface of the storage tank (130) for holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) according to one of the embodiments of the present invention.

[0041] According to one of the embodiments of the system of present invention, the maximum power point tracking is immune to the operating temperature of the Zener diodes.

[0042] According to one of the embodiments of the system of present invention, the at least one Photovoltaic array (114) comprises preferably at least seven Photovoltaic panels each comprising a plurality of photovoltaic cells.

[0043] According to one of the embodiments of the system of present invention, upon receiving power, the heat generated at the junction of Zener diode travels through the lead to the solder-able terminal of the device and then gets transferred to the Copper pad on the MCPCB, from Copper pad the heat flows through the dielectric layer to the metal core/clad layer of MCPCB, heat conductive adhesive conducts this heat to the metallic wall of the water heater tank, the water heater tank in turn transfer the heat to the water inside the tank, heating up the water inside the water heater tank. Thus, the water inside the tank gets heated up, from the heat dissipated by the semiconductor devices and resistors.

[0044] According to one of the embodiments of the present invention, a method for solar photovoltaic water heater comprising steps of constructing a Hot water heater (118). The method includes configuring at least one Photovoltaic array (114) having a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells, to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method includes connecting at least one fuse between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +Vpv terminal of Photovoltaic array (114). The method includes setting at least one Conformal coating confirming to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature.

[0045] The method of constructing a Hot water heater (118) includes configuring a storage tank (130) to store the water for heating. The method includes configuring at least one cold water inlet pipe (124), as a source of the cold water to the storage tank (130) of the Hot water heater (118). The method includes configuring at least one hot water outlet pipe (126), as an outlet of the hot water from the storage tank (130) of the Hot water heater (118). The method includes connecting a heating element (128), to a utility power supply to make it operative when the intensity of solar radiation is inadequate. The method includes attaching and activating a thermal cut off device TC to the storage tank (130) on its outside surface. The method includes constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method includes attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130). The method includes fasting by at least one fastener, the placed and attached plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) with good thermal contact. The method includes providing a ground connectivity (132) to the storage tank (130) to provide safety to the user against any leakage current.

[0046] According to one of the embodiments of the method of present invention, the method step of constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters includes constructing, by connecting a plurality of Zener diodes in series, an array of the plurality of Zener diodes. The method step includes connecting, at least two current limiting resistors in series at the cathode end of the array of a plurality of Zener diodes. The method step includes connecting at least one diode in series with the two current limiting resistors connected in series at the cathode end of the array of a plurality of Zener diodes.

[0047] According to one of the embodiments of the method of present invention, the method step of attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) includes connecting, to a first terminal of the Fuse, a positive terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method step includes connecting, to a first terminal TC I of thermal cutoff device TC, a negative terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method step includes connecting, to a +Vpv terminal of the Photovoltaic array (114), a second terminal of the Fuse. The method step includes connecting to a -Vpv terminal of the Photovoltaic array (114), a second terminal TC_2 of thermal cutoff device TC.

[0048] According to one of the embodiments of the method of present invention, the two terminals TC I an TC_2 of the thermal cut off device TC are normally connected (NC) contacts having the first terminal TC I connected to all negative terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and the second terminal TC_2 connected to the -Vpv terminal of the Photovoltaic array (H4). [0049] According to one of the embodiments of the present invention, the method step of attaching and activating a thermal cut off device TC to the storage tank (130) on its outside surface includes configuring thermal cut off device TC to senses the temperature of a surface on which it is mounted, the outside surface of the storage tank (130) and electrically disconnect the two terminals TC I and TC2 when the device cutoff temperature is reached, cutting off the Photovoltaic power supply to the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters.

[0050] According to one of the embodiments of the present invention, the method step of constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters includes constructing, a Metal Core/clad Layer made of Aluminum or Copper, having thickness of about 1 to 3 mm as a bottom most layer. The method step includes constructing, a dielectric layer as a next upper layer to the Metal Core/clad Layer, configured to decide an insulation resistance and a voltage rating of the MCPCB. The method step includes constructing, a copper layer as a next upper layer to the dielectric layer, configured to etch the interconnecting tracks and SMD mounting pads. The method step includes constructing, a Solder Mask Layer; and constructing, a Silk screen layer.

[0051] According to one of the embodiments of the present invention, the method step of fasting by at least one fastener, the placed and attached plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) wherein the at least one fastener can be heat conductive adhesive, thermal compound, thermal conductive adhesive, thermal pest or any type of circular clamps/tie such as but not limited to cable tie wound around the outside surface of the storage tank (130), holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) or any suitable combination of both. Figure 16 shows the circular clamp as a fastener wound around the outside surface of the storage tank (130) for holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) according to one of the embodiments of the present invention.

[0052] According to one of the embodiments of the method of present invention a maximum power point tracking is immune to the operating temperature of the Zener diodes.

[0053] According to one of the embodiments of the method of present invention the at least one Photovoltaic array (114) comprises preferably at least seven Photovoltaic panels each comprising a plurality of photovoltaic cells.

[0054] According to one of the embodiments of the method of present invention upon receiving power, the heat generated at the junction of Zener diode travels through the lead to the solder-able terminal of the device and then gets transferred to the Copper pad on the MCPCB. From the Copper pad the heat flows through the dielectric layer to the metal core/clad layer of MCPCB. The heat conductive adhesive conducts this heat to the metallic wall of the water heater tank. The water heater tank in turn transfers the heat to the water inside the tank, heating up the water inside the water heater tank. Thus, the water inside the tank gets heated up, from the heat dissipated by the semiconductor devices and resistors.

[0055] The Figure 1 illustrates reproduction of schematic view of one of the embodiments of prior art, Photovoltaic Solar Water heating system (1) by Fanney.

[0056] Referring to figures 2 - 15, a system for Solar Photovoltaic (PV) water heater made using plurality of semiconductor devices without the controller box, in order to improve the water heating efficiency by eliminating the associated power loss in the controller circuit is shown in accordance with the present invention. [0057] In Figure 2, schematic view of Solar Photovoltaic Water Heater using Semiconductor Devices (100) in accordance with the present invention is shown. Radiation from Sun is incident on the Photovoltaic array (114). The Photovoltaic array (114) generates electrical power responsive to incident solar energy. The photovoltaic array (114) includes plurality of photovoltaic cells. Hot water heater (118) is a generally conventional storage tank heater, having cold water inlet pipe (124), hot water outlet pipe (126), heating element (128) to be connected to a utility power supply and operative when the intensity of solar radiation is inadequate. A plurality of Metal Clad Printed Circuit Boards (MCPCB), preferably Four Metal Clad Printed Circuit Boards (MCPCB), ZH1, ZH2, ZH3 and ZH4 are attached on the outside surface of the storage tank (130). A thermal cut off device TC is also attached to the storage tank (130) on its outside surface. For user safety, the storage tank (130) is connected to ground (132). Earthing provides safety to the user against any leakage current.

[0058] Figure 3 (a) shows the top view of the thermal cutoff device TC. Figure 3 (b) shows the front view of the thermal cutoff device TC. Figure 4 shows the perspective view of thermal cutoff device TC. TC has two terminals, TC I and TC_2, these are normally connected (NC) contacts. TC senses the temperature of the surface on which it is mounted. It is a fixed temperature type cutoff device. When the device cutoff temperature is reached, it electrically disconnects the two terminals TC I and TC2, thus cutting off the PV power supply to the heaters ZH1, ZH2, ZH3 and ZH4.

[0059] Figure 5 shows the circuit diagram of semiconductor heaters. Four MCPCB heaters ZH1, ZH2, ZH3 and ZH4 are connected to the output of PV array. Each MCPCB heater consists of an array of Zener diodes ZA1, ZA2, ZA3 and ZA4 respectively. Each array having plurality of Zener Diodes connected in series. For each Zener array, two current limiting resistors (Rl l, R12), (R21, R22), (R31, R32) 1 and (R41, R42) are connected. Plurality of resistors are used instead of a single resistor in order to handle higher power dissipation for the selected package of resistors. Diodes DI, D2, D3 and D4 are connected in series with each heater circuit. These diodes provide protection against accidental reverse polarity connection to the PV panel terminals. All four positive terminals of the heaters +ZH1, +ZH2, +ZH3 and +ZH4 are connected to first terminal of a Fuse. The second terminal of Fuse is connected to the +Vpv terminal of the PV array. Fuse provides protection against short circuit. Similarly, all negative terminals of heaters -ZH1, -ZH2, -ZH3 and -ZH4 are connected to first terminal TC I of thermal cutoff device TC. The second terminal TC_2 is connected to the -Vpv terminal of the PV array. The PV array consists of seven PV panels PV1, PV2, PV3, PV4, PV5, PV6 and PV7 connected in series.

[0060] Figure 6 shows typical layer assignment of single sided metal core/clad PCB. The bottom most layer is the Metal Core/clad Layer. It is either made of Aluminum or Copper, having thickness of about 1 to 3 mm. Next upper layer is the dielectric layer, which decides the insulation resistance and the voltage rating of the MCPCB. The copper layer is used to etch the interconnecting tracks and SMD mounting pads. Above copper layer there is Solder Mask Layer and Silk screen layer.

[0061] The function of metal core/clad is to take away the heat from the component soldered to the copper layer and dissipate it. In the MCPCB the dielectric material used has better thermal conductivity as compared with standard glass epoxy or FR4 PCB. Also, the thickness of dielectric material is kept as small as possible for getting improved thermal conductivity. The metal core/clad layer is thickest of all layers and provides rigidity.

[0062] Typical thickness for aluminum/copper Metal Core/clad Layer is 1.0mm to 3.2mm. Typical thickness of dielectric layer is between 0.075mm to 0.2mm. The copper thickness can be anywhere between 35pm to 350pm (1 - 10 oz. /ft2). Solder mask coating covers the entire board to protect the circuit.

[0063] Aluminum and Copper, has much better thermal conductivity than that of FR4. Generally, the thermal conductivity of FR4 is around 0.25W/m K, but the thermal conductivity of Aluminum MCPCB is minimum IW/m K, the thermal conductivity of Copper MCPCB is minimum 3W/m K. With high thermal conductivity, the metal core/clad circuit board will dissipate the heat generated by electronic components quicker and ensures lower junction temperature in comparison with FR4.

[0064] Figure 7 (a) shows the top perspective view of the SMA package of Zener Diodes used in the array and Diodes DI, D2, D3 and D4. Figure 7 (b) shows the bottom perspective view of the SMA package.

[0065] Figure 8 (a) shows the copper pad layout for SMA package which has been selected for all Zener Diodes and also for the diodes DI, D2, D3 and D4. Figure 8 (b) shows the copper pad layout for resistor of size 2512 (or metric 6432). The MCPCB is designed for mounting SMD components only. With the use of SMD components, there is no need to drill holes in the PCB. This provides very good isolation for the devices against any leakage voltage present on the metallic water tank.

[0066] Figure 9 (a) shows the top view of a Zener Diode and a resistor 2512 (metric 6432) soldered on the MCPCB. Figure 9 (b) shows the side view.

[0067] Figure 10 (a) shows the top view of the assembled Zener heater MCPCB, ZH1. Top terminal +ZH1 is the positive terminal of the heater. Then diode DI in SMA package, resistors Rl l, R12 in 2512 package and Zener array ZA1 consisting of 21 Zener diodes in SMA package are mounted in a straight line on the MCPCB. All the devices are connected in series. The bottom terminal -ZH1 is the negative terminal of the heater. Figure 10 (b) shows the end view of ZH1. In the same manner remaining three MCPCBs i.e. ZH2, ZH3 and ZH4 are assembled.

[0068] Figure 11 shows assembled MCPCB mounted on the metallic wall of water storage tank using heat conductive adhesive. One of the brands available in market is “Arctic Silver Thermal Adhesive” having conductivity of 7.5 W/m.K. Heat generated at the junction of Zener diode travels through the lead to the solder-able terminal of the device. This heat then gets transferred to the Copper pad on the PCB. From Copper pad the heat flows through the dielectric layer to the metal core/clad layer of MCPCB. The direction of arrow show the path travelled by the heat energy. Heat conductive adhesive conducts this heat to the metallic wall of the water heater tank. Which in turn transfer the heat to the water inside the tank. Thus, the water inside the tank gets heated up, from the heat dissipated by the semiconductor devices and resistors.

[0069] Thermal resistance from Junction to terminal 0jt is available in the data sheet of the Zener diode. This parameter is used for calculating the rise in junction temperature. These calculations are given in the design section.

[0070] Figure 12 (a) shows perspective view of the water storage tank with MCPCBs mounted on the water tank and protective coating applied over the MCPCBs. Figure 12 (b) shows the bottom view of the water storage tank with MCPCBs mounted and protective coating applied over the MCPCBs. One type of protective coating is “Conformal coating”. Conformal coating confirms to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature. [0071] Figure 13 shows the bottom view of the water heater (118) along with the outer cover (140) and thermal insulation (142). The thermal insulation is usually glass wool or mineral wool.

[0072] Heater Design: A detailed design of Solar Photovoltaic Water Heater using Semiconductor Devices in accordance with the present invention is given below.

[0073] PV Panel selection: Array of Solar Photovoltaic panel 114, as shown in Figure 2 consists of seven panels PV1 to PV7, connected in series. When panels are connected in series, higher Vpv voltage is obtained at lower currents. For lower currents thinner wires can be used, which will reduce the losses in the wires and reduce the cost of the system.

Specifications of Single PV Panel:

1) Voltage at maximum power = V_mp = 17.5 V

2) Peak Power Rating = 10 Wp

3) Panel current at maximum power = 0.57 A

4) Open circuit voltage = V_oc = 21.2 V

Specifications of PV Array with seven panels:

5) Voltage at maximum power = V_pv = 122.5 V DC

6) Peak PV Power Rating = 70 Wp

7) Array current at maximum power = 0.57 A

8) Maximum Open Circuit voltage = V_oc (max) = 148.4 V

[0074] Above calculations show that with series connected 7 PV panels, Vpv is about 120 V. This voltage is standard voltage in many countries. It is fairly safe to work with 120 V. Due to higher voltage, the panel currents are lower. Hence, we can use thinner wire to reduce cost as well as to reduce power loss in cables. Hence 7 panels is a preferred embodiment. However, there are no restrictions on the number of panels to be used. The system can be designed using a single panel or plurality of panels connected in series or series/ parallel combination as required.

[0075] The maximum open circuit voltage should be used for selecting the dielectric strength of insulating layer in PCB as well as other components.

[0076] Zener Diode Selection: There are three reasons for selecting Zener diodes as semiconductor heating device. Those are: i) To generate heat energy by dissipating power in the junction. ii) To track the maximum power point for the photovoltaic panels. iii) To get stable Zener voltage over wide temperature range, by selecting device with minimal or zero thermal coefficient.

Above 5 V, a Zener diode has a positive temperature coefficient, i.e. Zener voltage increases with temperature. Below 5 V, it has a negative temperature coefficient, ie Zener voltage decreases as temperature rises. Therefore at around 5 volts Zener diodes have almost zero temperature coefficient. Hence, by selecting Zener voltage around 5 volts, it is possible to eliminate the variation in voltage due to temperature variation. Therefore here in this example 5.1 V Zener has been selected. Hence, the maximum power point tracking is immune to the operating temperature of the Zener diodes.

Diode Specifications:

9) Forward Voltage of Diode = Vj = 0.7 V

10) Nominal voltage of Zener = V_z = 5.1 V

11) Zener Power Rating = P_z = 1 W

Table 2: Zener Diode SMD packages and respective thermal parameters.

[0077] Zener Package and Derating: Table 2 shows Zener diode SMD packages available and their thermal parameters. Here SMA package is selected because of easy availability and good thermal characteristics.

[0078] Figure 14 shows typical derating curve with respect to the ambient temperature for selected SMA package. Usually, the thermostat maximum water temperature setting is 60 °C. Hence, at 60 °C ambient temperature, the device dissipation is 0.9 W. Zener Array calculations:

12) Zener power rating at 60 °C = P_z = 0.9 W

13) Zener Current I_zmax = P_Z/V_Z = 0.9/5.1 = 0.176 A

14) No of MCPCBs = 4

15) Power dissipation per MCPCB = 70 Wp/4 = 17.5 Wp

16) Current in each MCPCB = 17.5 Wp/122.5 V = 0.143 A

17) Actual Zener Voltage at 0.143 A is = 5.39 V (By testing)

18) Current limiting resistance used = R = (R11+R12) = 59 Q

19) Standard 1 W Resistors used are R1 1 = 39 Q, R12 = 20 Q

20) No of Zener Diodes in array = {(V_pv -V_d) - (R * 0.143)}/V_z

={(122.5-0.7)- (59*0.143)}/5.39

= 113.37/5.39 = 21

Zener Diode Junction Temperature calculations:

21) Maximum Tank Water Temperature = 60 °C

22) Thermal resistance Junction to terminal = 0j_t =30 K/W

23) Thermal Resistance of MCPCB =1 K/W

24) Total Thermal resistance = 31 K/W

25) Temperature Difference (Junction to Water) = 0.9 * 31 = 27.9 °C

26) Junction Temperature of Zener Diode = 60 + 27.9 = 87.9 °C

[0079] From the above calculations the maximum junction temperature of Zener Diode comes to 87.9 °C. From Table 2, the maximum allowed junction temperature is 150 °C. Hence, the design has sufficient margin, and the operating point is in safe thermal region.

[0080] Figure 15 (a) shows the comparison of standard MPPT curve of PV panels and the curve traced by the Zener Heater in accordance with the present invention. These plots indicate the variation in the heater power output when the Vpv voltage varies from 107.5 V to 122.5 V. This voltage variation occurs due to variation in the sunlight intensity. a) MPPT curve: This curve is obtained by connecting a variable load resistor to the output of the PV array. For different sunlight conditions, the load resistor is varied to get maximum power. Then the graph of power output is plotted against V_pv. b) Zener Heater Curve: The power dissipated by the heaters is obtained by measuring V_pv and the panel current for different sunlight intensities. Then graph of heater power dissipated against V_pv is plotted.

[0081] From the graph of Figure 15 (a) it is seen that the Zener Heater closely tracks the MPPT curve in the higher power range. At lower power range it diverges so some extent.

[0082] The MPPT plot in Figure 15 (a) is actually under ideal conditions. However, in actual design, MPPT controller is used. This is usually PWM type controller and has power loss in the switching device. Figure 15 (b) shows the comparison of 0.9 x MPPT with Zener Heater graph. The multiplying factor of 0.9 is assumed to be the efficiency of the MPPT controller. From this comparison it is seen that at higher power range, the Zener Heater performs better than the MPPT controller. At lower power range also, the gap has been reduced.

[0083] It is to be noted that the above results are obtained by using 5.1 V Zener. Slightly different value of Zener Voltage for example 4.7 V could be chosen to fine tune the plots of Zener Heater and reduce the gap with respect to MPPT curve. Further, a mix of two different Zener Voltages say 5.1 V and 4.7 V can also be used for fine tuning the MPPT curve. [0084] Tracking mechanism of Zener Heater. The maximum power point tracking mechanism of Zener Heater is due to slight variation in the Zener voltage in response to variation in the Zener Current. In the above calculations, the nominal Zener voltage of 5.1 V is used. However, with variation in Zener Current, there is a small variation in the Zener Voltage. Following readings were obtained from the actual experiments: a) Zener Voltage V_zi = 5.10 V @Zener Current of I_zi = 3.3 mA. b) Zener Voltage V_Z2 = 5.39 V @Zener Current of I_Z2 = 143 mA.

The variation in Zener Voltage provides the desired maximum power point tracking of PV panels as shown in graphs of Figure 15 (a) and Figure 15 (b).

PV Energy and Rise in Water Temperature:

27) Clear Sunlight in a day = 6 hrs. (Assumed)

28) PV Energy Supplied to water = 70 Wp * 6 hrs. = 420 Wh

29) No of Calories in 1 Wh = 860 Calories

30) Energy in kCal = 420 * 860 = 361.2 kCal

31) Water Tank Capacity = 25 Liters

32) Initial Water Temperature = 26 °C (Assumed)

33) Rise in temperature = 361.2/25 = 14.5 °C

34) Final Water temperature = 26 + 14.5 = 40.5 °C

[0085] Figure 16 shows the circular clamp as a fastener wound around the outside surface of the storage tank (130) for holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) according to one of the embodiments of the present invention.

[0086] For different storage capacities of water heaters, guidelines for selection of Solar Panel power rating are depicted in the Table 3 given below. Also, the estimated temperature rise for each case has been calculated. For the exemplary calculations the initial water temperature is considered to be 25 °C and it is also considered that 6 hours of clear sunshine is available per day. Based on this assumption, the energy collected by the panels per day has been derived.

Table 3

* initial water temperature 25 °C ^ANo of panels in PV array = 7

[0087] The present invention as implemented through various embodiments is economically viable and can be adopted by the businesses easily as it provides the higher graded security in economical plans.

[0088] Further, while one or more operations have been described as being performed by or otherwise related to certain modules, devices or entities, the operations may be performed by or otherwise related to any module, device or entity.

[0089] Further, the operations need not be performed in the disclosed order, although in some examples, an order may be preferred. Also, not all functions need to be performed to achieve the desired advantages of the disclosed system and method, and therefore not all functions are required.

[0090] While select examples of the disclosed system and method have been described, alterations and permutations of these examples will be apparent to those of ordinary skill in the art. Other changes, substitutions, and alterations are also possible without departing from the disclosed system and method in its broader aspects.

[0091] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.

Claims

stem for solar photovoltaic water heater, the system comprises: a Hot water heater (118), the Hot water heater (118) comprises a storage tank (130), the storage tank to store the water for heating; at least one cold water inlet pipe (124), the at least one cold water inlet pipe (124) configured as a source of the cold water to the storage tank (130) of the Hot water heater (118); at least one hot water outlet pipe (126), the at least one hot water outlet pipe (126) configured as a outlet of the hot water from the storage tank (130) of the Hot water heater (118); a heating element (128), the heating element (128) connected to a utility power supply and operative when the intensity of solar radiation is inadequate; a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters attached on the outside surface of the storage tank (130) with good thermal contact; at least one fastener, the at least one fastener configured to place and attach the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130); a thermal cut off device TC, the thermal cut off device TC attached to the storage tank (130) on its outside surface; and a ground connectivity (132), the ground connectivity (132) to the storage tank (130) configured to provide safety to the user against any leakage current; at least one Photovoltaic array (114) having a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells, the at least one Photovoltaic array (114) configured to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters; at least one fuse, the at least one fuse connected between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +V_pv terminal of Photovoltaic array (114); and at least one Conformal coating, the Conformal coating confirmed to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature. The system as claimed in claim 1 wherein each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters comprises an array of a plurality of Zener diodes, the array of a plurality of Zener diodes have a plurality of Zener Diodes connected in series; at least two current limiting resistors, the two current limiting resistors connected in series at the cathode end of the array of a plurality of Zener diodes; at least one diode, the at least one diode connected in series with the two current limiting resistors connected in series at the cathode end of the array of a plurality of Zener diodes. The system as claimed in claim 1 wherein positive terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters is connected to first terminal of the Fuse; negative terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters is connected to first terminal TC I of thermal cutoff device TC; the second terminal of the Fuse is connected to the +V_pv terminal of the Photovoltaic array (114); the second terminal TC_2 of thermal cutoff device TC is connected to the -V_pv terminal of the Photovoltaic array (114). The system as claimed in claim 1 wherein the thermal cut off device TC is a fixed temperature type cutoff device comprising two terminals TC I and TC_2 as normally connected (NC) contacts, the first terminal TC I connected to all negative terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and the second terminal TC_2 connected to the -V_pv terminal of the Photovoltaic array (114). The system as claimed in claim 1 wherein the thermal cut off device TC comprises two terminals TC I and TC_2 as normally connected (NC) contacts, the thermal cut off device TC configured to senses the temperature of a surface on which it is mounted, the outside surface of the storage tank (130); electrically disconnect the two terminals TC I and TC2 when the device cutoff temperature is reached, cutting off the Photovoltaic power supply to the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The system as claimed in claim 1 wherein Metal Clad Printed Circuit Boards (MCPCB) comprises a Metal Core/clad Layer, Metal Core/clad Layer made of Aluminum or Copper, having thickness of about 1 to 3 mm as a bottom most layer; a dielectric layer, the dielectric layer as a next upper layer to the Metal Core/clad Layer, configured to decide an insulation resistance and a voltage rating of the MCPCB; a copper layer, the copper layer as a next upper layer to the dielectric layer, configured to etch the interconnecting tracks and SMD mounting pads; a Solder Mask Layer; and a Silk screen layer. The system as claimed in claim 1 wherein the Metal Core/clad Layer of the Metal Clad Printed Circuit Boards (MCPCB) is configured to take away the heat from the component soldered to the copper layer and dissipate it. The system as claimed in claim 1 wherein a dielectric material of the dielectric layer of the Metal Clad Printed Circuit Boards (MCPCB) has better thermal conductivity as compared with standard glass epoxy or FR4 PCB. The system as claimed in claim 1 wherein the at least one fastener can be heat conductive adhesive, thermal compound, thermal conductive adhesive, thermal pest or any type of circular clamps/tie such as but not limited to cable tie wound around the outside surface of the storage tank (130), holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) or any suitable combination of both. The system as claimed in claim 1 wherein a maximum power point tracking is immune to the operating temperature of the Zener diodes. The system as claimed in claim 1 wherein the at least one Photovoltaic array (114) comprises preferably at least seven Photovoltaic panels each comprising a plurality of photovoltaic cells. The system as claimed in claim 1 wherein upon receiving power, the heat generated at the junction of Zener diode travels through the lead to the solderable terminal of the device and then gets transferred to the Copper pad on the MCPCB, from Copper pad the heat flows through the dielectric layer to the metal core/clad layer of MCPCB, heat conductive adhesive conducts this heat to the metallic wall of the water heater tank, the water heater tank in turn transfer the heat to the water inside the tank, heating up the water inside the water heater tank. A method for solar photovoltaic water heater, the method comprising steps of: a constructing a Hot water heater (118), the step of constructing Hot water heater (118) comprise steps of: configuring a storage tank (130) to store the water for heating; configuring at least one cold water inlet pipe (124), as a source of the cold water to the storage tank (130) of the Hot water heater (118); configuring at least one hot water outlet pipe (126), as an outlet of the hot water from the storage tank (130) of the Hot water heater (118); connecting a heating element (128), to a utility power supply to make it operative when the intensity of solar radiation is inadequate; attaching and activating a thermal cut off device TC to the storage tank (130) on its outside surface; constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters; attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) with good thermal contact; fasting by at least one fastener, the placed and attached plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130); and providing a ground connectivity (132) to the storage tank (130) to provide safety to the user against any leakage current; configuring at least one Photovoltaic array (114) having a plurality of Photovoltaic panels each comprising a plurality of photovoltaic cells, the at least one Photovoltaic array (114) to power through the thermal cut off device TC, the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters; connecting at least one fuse between all positive terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and a +V_pv terminal of Photovoltaic array (114); and setting at least one Conformal coating confirming to the contours of the PCB to protect the components and the MCPCBs, against moisture, dust, chemicals and high temperature. The method as claimed in claim 13 wherein step of constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters includes: constructing, by connecting a plurality of Zener diodes in series, an array of the plurality of Zener diodes; connecting, at least two current limiting resistors in series at the cathode end of the array of a plurality of Zener diodes; connecting at least one diode in series with the two current limiting resistors connected in series at the cathode end of the array of a plurality of Zener diodes. The method as claimed in claim 13 wherein step of attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) includes: connecting, to a first terminal of the Fuse, a positive terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters; connecting, to a first terminal TC I of thermal cutoff device TC, a negative terminal of each of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters; connecting, to a +V_pv terminal of the Photovoltaic array (114), a second terminal of the Fuse; connecting to a -V_pv terminal of the Photovoltaic array (114), a second terminal TC_2 of thermal cutoff device TC. The method as claimed in claim 13 wherein the two terminals TC I and TC_2 of the thermal cut off device TC are normally connected (NC) contacts having the first terminal TC I connected to all negative terminals of the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters and the second terminal TC_2 connected to the -V_pv terminal of the Photovoltaic array (H4). The method as claimed in claim 13 wherein the step of attaching and activating a thermal cut off device TC to the storage tank (130) on its outside surface includes configuring thermal cut off device TC to senses the temperature of a surface on which it is mounted, the outside surface of the storage tank (130); electrically disconnect the two terminals TC I and TC2 when the device cutoff temperature is reached, cutting off the Photovoltaic power supply to the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters. The method as claimed in claim 13 wherein step of constructing a plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters includes constructing, a Metal Core/clad Layer made of Aluminum or Copper, having thickness of about 1 to 3 mm as a bottom most layer; constructing, a dielectric layer as a next upper layer to the Metal Core/clad Layer, configured to decide an insulation resistance and a voltage rating of the MCPCB; constructing, a copper layer as a next upper layer to the dielectric layer, configured to etch the interconnecting tracks and SMD mounting pads; constructing, a Solder Mask Layer; and constructing, a Silk screen layer. The method step of fasting by at least one fastener, the placed and attached plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) as claimed in claim 13 wherein the at least one fastener can be heat conductive adhesive, thermal compound, thermal conductive adhesive, thermal pest or any type of circular clamps/tie such as but not limited to cable tie wound around the outside surface of the storage tank (130), holding and attaching the plurality of Metal Clad Printed Circuit Boards (MCPCB) heaters on the outside surface of the storage tank (130) or any suitable combination of both. The method as claimed in claim 13 wherein a maximum power point tracking is immune to the operating temperature of the Zener diodes. The method as claimed in claim 13 wherein the at least one Photovoltaic array (114) comprises preferably at least seven Photovoltaic panels each comprising a plurality of photovoltaic cells. The method as claimed in claim 1 wherein upon receiving power, the heat generated at the junction of Zener diode travels through the lead to the solderable terminal of the device and then gets transferred to the Copper pad on the MCPCB, from Copper pad the heat flows through the dielectric layer to the metal core/clad layer of MCPCB, heat conductive adhesive conducts this heat to the metallic wall of the water heater tank, the water heater tank in turn transfer the heat to the water inside the tank, heating up the water inside the water heater tank.