A solar photovoltaic water heater

Abstract

The present invention relates to a solar photovoltaic water heater, belonging to the technical field of water heaters. The water heater comprises a photovoltaic power generation panel array and a photovoltaic electric water heater, wherein a group of AC / DC multiplexing electric heating tubes are installed in the water tank of the photovoltaic electric water heater; the power supply end of the AC / DC multiplexing electric heating tubes is respectively connected to the photovoltaic power supply and the mains power supply through the AC / DC switching relay, and is controlled by the on-off relay controlled by the controller; the controller contains a central processing chip, the central processing chip comprises corresponding signal input ports respectively connected to the photovoltaic voltage detection, the photovoltaic current detection and the upper and lower temperature sensors of the water tank, and the corresponding control end of the central processing chip is respectively connected to the on-off relay and the controlled end of the AC / DC switching relay. When the photovoltaic array is in an effective power generation state, the present invention reasonably controls the heating tubes to work under direct current; and controls the AC / DC switching relays as appropriate to make part or all of the heating tubes work under the mains to ensure the user's hot water demand.

Description

Technical Field

[0001] The invention relates to a solar water heater, in particular to a solar photovoltaic water heater, and belongs to the technical field of water heaters. Background Art

[0002] Solar water heaters are widely welcomed due to their significant advantages of energy saving and environmental protection. There are two main types of solar collectors: flat plate and vacuum tube. Their advantage is high heat conversion efficiency, but they must exchange heat with the water storage tank through a heat exchange medium. When heat exchange cannot be achieved through natural circulation, a circulating pump is required to force heat exchange. This will make the installation and construction complicated, and the connecting pipes will leak heat, which will reduce the utilization rate of solar energy. Due to the advantages of solar cell module technology development and reduced manufacturing costs, using it to directly produce hot water has gradually become economical and practical. The invention with application number 201010505019.3 as a typical example proposed the concept of photovoltaic water heaters, the essence of which is to "connect the solar cell wire with the solar cell maximum power point automatic tracker and the DC electric heating pipe in the water storage tank, so the installation can be very casual and convenient."

[0003] Many of these innovations that use photovoltaic power generation for electric heating require inversion first, such as the photovoltaic power converter for solar electric water heaters and its control method disclosed in the Chinese patent application number 201710775520.3. Since "the constantly changing low-voltage direct current emitted by the solar panel assembly is efficiently converted into a stable direct current with an effective value of 220V, and the electrical energy is continuously and equivalently converted into heat energy and stored in the heat-insulating electric water heater through MPPT control for use at any time", although the inconvenience of long pipeline construction can be avoided, the need for an inverter device not only increases the cost but also reduces the conversion efficiency due to the self-power consumption of the inverter. For this reason, the awning-type solar power generation DC power supply electric water heater disclosed in the Chinese patent application number 202010494038.4 does not need to be converted into AC power through battery storage, inverter, etc. before use, but directly uses the DC power generated by the solar panel array to "DC power supply" the electrical impedance heating device in the water tank container to heat the water in the water tank container and achieve the function of heating water.

[0004] However, in actual applications, the energy of photovoltaic power generation varies with factors such as weather, season, and region. Users have different needs for hot water, such as instant hot water, scheduled hot water, and continuous hot water. Existing technologies have failed to reasonably allocate the power of photovoltaic power and city power based on these factors, such as adaptively adjusting the load according to the photovoltaic power generation situation to make the photovoltaic output efficiency in a relatively good state, and reasonably using city power according to the demand for hot water to reduce user waiting and avoid cold water during bathing. Summary of the invention

[0005] The primary purpose of the present invention is to address the problems existing in the above-mentioned prior art and to propose a solar photovoltaic water heater which can self-regulate DC load according to the real-time capability of photovoltaic power generation so that the effective photovoltaic output is in a better range, select appropriate AC heating power according to the immediate or future demand for hot water, and realize AC and DC multiplexing of the heating tube.

[0006] A further main purpose of the present invention is to provide a solar photovoltaic water heater that takes into account both photovoltaic power utilization and user hot water needs.

[0007] In order to achieve the above primary purpose, the basic technical scheme of the solar photovoltaic water heater of the present invention is as follows: it includes a photovoltaic power generation panel array and a photovoltaic electric water heater, wherein a group of AC and DC multiplexing electric heating tubes are installed in the water tank of the photovoltaic electric water heater; the power supply end of the AC and DC multiplexing electric heating tubes are respectively connected to the photovoltaic power supply and the mains power supply through the AC and DC switching relays, and are controlled by the on-off relay controlled by the controller;

[0008] The controller includes a central processing chip, which includes corresponding signal input ports respectively connected to photovoltaic voltage detection, photovoltaic current detection and upper and lower temperature sensors of the water tank, and corresponding control terminals of the central processing chip are respectively connected to the controlled terminals of the on-off relay and the AC / DC switching relay;

[0009] The central processing chip contains:

[0010] Upper water temperature lower limit judgment unit - used to judge whether the upper water temperature of the water tank after photovoltaic heating is lower than a predetermined value according to the received water temperature signal, if not, the lower water temperature lower limit judgment unit is activated; if yes, the control is switched to AC heating, and then the upper water temperature upper limit judgment unit is activated;

[0011] Upper water temperature upper limit judgment unit - used to judge whether the upper water temperature of the water tank after AC heating is higher than the set value according to the received water temperature signal. If so, the control switches to photovoltaic heating, and then the upper water temperature lower limit judgment unit is enabled; otherwise, the upper water temperature lower limit judgment unit is enabled;

[0012] The lower water temperature lower limit judgment unit is used to judge whether the water temperature at the lower part of the water tank is lower than the preset value according to the received water temperature signal. If not, the control switches to photovoltaic heating and then activates the upper water temperature lower limit judgment unit; if yes, activates the preset time water temperature drop judgment unit;

[0013] The water temperature drop judgment unit for a predetermined time period is used to judge whether the water temperature in the lower part of the water tank continues to drop according to the water temperature signals received successively for a predetermined time period. If so, the AC heating power is increased step by step, and then a cycle judgment is performed until the power is increased to the maximum level. If not, the lower water temperature upper limit judgment unit is activated after maintaining the current heating mode;

[0014] The lower water temperature upper limit judgment unit is used to judge whether the water temperature at the bottom of the water tank is higher than the preset value according to the received water temperature signal. If so, it switches to photovoltaic heating and then activates the upper water temperature lower limit judgment unit; otherwise, it activates the water temperature drop judgment unit for a preset time.

[0015] Such cycle control can reasonably control the on-off relay to make some or all of the heating tubes work under DC power when the photovoltaic array is in an effective power generation state, so as to provide DC heating power that is compatible with the photovoltaic power generation capacity; when it is known that the photovoltaic power generation capacity cannot meet the user's immediate or scheduled hot water needs, by controlling the AC and DC switching relays, some or all of the heating tubes can work under AC power to ensure the user's hot water needs.

[0016] In order to achieve further purposes, the central processing chip of the controller also contains

[0017] Control management start unit - used to start photovoltaic load regulation and management, start and close the voltage judgment unit;

[0018] The shutdown voltage judgment unit is used to judge whether the detected photovoltaic voltage is greater than the predetermined shutdown voltage. If the judgment result is yes, the startup voltage judgment unit is enabled; if the judgment result is no, the load high to low judgment unit is enabled;

[0019] The start-up voltage judgment unit is used to judge whether the detected photovoltaic voltage is greater than the predetermined start-up voltage. If the judgment result is yes, the DC load from low to high judgment unit is enabled; if the judgment result is no, the current state is maintained and the shutdown voltage judgment unit is enabled;

[0020] Load from high to low judgment unit - used to judge whether the current DC load is in the highest power mode. If the judgment result is yes, the DC load is reduced by one level and the control management start unit is enabled; if the judgment result is no, it is judged whether the current DC load is in the second highest power mode, and then the previous cycle is repeated until the DC load is reduced to the lowest level and the control management start unit is enabled;

[0021] Load from low to high judgment unit - used to judge whether the current DC load is lower than the lowest power mode. If the judgment result is yes, the DC load is increased by one level and the control management start unit is enabled; if the judgment result is no, it is judged whether the current DC load is the second lowest power mode, and then the previous cycle is repeated until the DC load is increased to the highest level and the control management start unit is enabled.

[0022] It can be seen that after adopting the present invention, on the one hand, the photovoltaic power generation energy can be reasonably utilized while meeting the user's immediate or scheduled hot water needs; on the other hand, the photovoltaic direct current and the city power alternating current reuse the same set of heating tubes, and the photovoltaic water heater has a simple structure, saves space and has low cost.

[0023] A further improvement of the present invention is that the photovoltaic power generation panel array is formed by at least two photovoltaic panels connected in series.

[0024] A further improvement of the present invention is that the photovoltaic voltage detection plug-in terminal connected across the positive and negative cables of the photovoltaic panel array aggregation cable isolates and samples the DC voltage through a photoelectric isolation device and connects it to the voltage detection processing circuit, and then sends it to the voltage signal input terminal of the central processing chip; the Hall effect current sensor chip connected in series in the photovoltaic panel array aggregation cable isolates and samples the DC current and connects it to the current detection processing circuit, and then sends it to the current signal input terminal of the central processing chip.

[0025] A further improvement of the present invention is that the heating control end of the central processing chip is respectively connected to the controlled end of the on-off relay of the corresponding AC and DC multiplexed electric heating tube and the switching control end of the AC and DC switching relay through the driving chip.

[0026] The present invention is further improved in that: the communication terminal of the central processing chip is connected to the communication circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the system structure of the first embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the system structure of the second embodiment of the present invention.

[0029] Figure 3 yes Figure 1 Controller circuit diagram of an embodiment.

[0030] Figure 4 yes Figure 1 Logic block diagram of AC / DC switching control in an embodiment.

[0031] Figure 5 yes Figure 1 Block diagram of controller circuit of an embodiment.

[0032] Figure 6 yes Figure 1 The embodiment is a control logic block diagram that takes into account both photovoltaic power utilization and user needs. DETAILED DESCRIPTION Example

[0033] The solar photovoltaic water heater according to the embodiment of the present invention is as follows Figure 1 and Figure 2 As shown, it includes a photovoltaic panel array 1 laid on the top of a building or a residential balcony or wall, and a photovoltaic electric water heater 2 installed in the user's building area. There are two photovoltaic panels, each with a rated output voltage of DC40V and a load capacity of 450W, which are connected in series to form a DC80V / 900W photovoltaic panel array.

[0034] The water tank capacity of the photovoltaic electric water heater 2 is 80L, in which a group of AC / DC multiplex electric heating tubes EH1, EH2, and EH3 are installed, which are distributed in the upper, middle, and lower parts. The power supply ends of each AC / DC multiplex electric heating tube EH1, EH2, and EH3 are respectively connected to the photovoltaic power supply and the mains power supply through the corresponding AC / DC switching relays KA11, KA21, and KA31, and are controlled by the on-off relays KA12, KA22, and KA32 controlled by the controller. Figure 1 and Figure 2 The main difference between the two embodiments is that the water tank is horizontal or vertical, and the EH1, EH2, and EH3 heating tubes are integrated or separated. The combined levels of photovoltaic DC heating power and AC heating power of each electric heating tube are shown in the table below.

[0035]

[0036] Controller such as Figure 3 (See Figure 5 ), which contains a central processing chip IC5 (N76E003AT20) as a central processing chip. The photovoltaic voltage detection plug-in terminals PVDC+ and PVDC-P2, which are connected across the positive and negative cables of the photovoltaic panel array aggregation cable, isolate and sample the DC voltage through the optoelectronic isolation device U9 and its peripheral circuits, and then connect to the input end of the voltage reference chip U10.2. After passing through the voltage detection processing circuit composed of U10.2 and its peripheral devices, it is sent to the voltage signal input terminal 6 of the central processing chip IC5. The Hall effect current sensor chip U16, which is connected in series in the aggregation cable, isolates and samples the DC current and connects it to the signal input terminal of the current reference chip U15.1. After passing through the current detection processing circuit composed of U15.1 and its peripheral devices, it is sent to the current signal input terminal 11 of the central processing chip IC5.

[0037] In addition, the signal outputs of the upper and lower temperature sensors PT1 and PT22-6 of the water tank are connected to the temperature signal input ports 1 and 5 of the central processing chip IC5 respectively, and the heating control terminals 13-18 of the central processing chip IC5 are connected to the controlled terminals of the on-off relays KA12, KA22, and KA32 of the three AC and DC multiplexed electric heating tubes EH1, EH2, and EH3 respectively through the driver chip IC4, and the switching control terminals of the AC and DC switching relays KA11, KA21, and KA31, so as to control whether the AC and DC multiplexed electric heating tubes EH1, EH2, and EH3 are powered and whether DC or AC power is provided. The communication terminal of the central processing chip IC5 can be used for data collection and centralized management through the RS-485 communication circuit containing IC2 through the communication ports 2 and 3, and can be used for providing data related to energy saving and emission reduction of photovoltaic water heaters. L1, TR1, U1 and their peripheral components constitute the power supply circuit, providing the +5V and +12V DC voltages required by the water tank controller.

[0038] like Figure 4 As shown, the central processing chip implements AC / DC switching control in the following steps:

[0039] Upper water temperature lower limit judgment step - after starting up and entering the instant heating mode, judge whether the upper water temperature "Tup" of the water tank after photovoltaic heating is lower than the preset value "Tset-5℃" according to the received water temperature signal. If not, enter the lower water temperature lower limit judgment step; if so, control switches to EH1, EH2, EH3 AC heating, and then enter the upper water temperature upper limit judgment step;

[0040] Upper water temperature upper limit judgment step - judge whether the upper water temperature "Tup" of the water tank after AC heating is higher than the set value "Tset" according to the received water temperature signal. If so, control is switched to EH1, EH2, EH3 photovoltaic heating, and then recirculates to enter the upper water temperature lower limit judgment step; if not, enter the upper water temperature lower limit judgment step;

[0041] The lower water temperature lower limit judgment step: judge whether the lower water temperature "Tlower" of the water tank is lower than the preset value "Tset-5°C" according to the received water temperature signal. If not, control is switched to EH1, EH2, EH3 photovoltaic heating, and then recirculates to enter the upper water temperature lower limit judgment step; if yes, enter the preset time water temperature drop judgment step;

[0042] The step of judging the water temperature drop in a predetermined time period: judging whether the water temperature "T lower" in the lower part of the water tank continues to drop within the time period Δt according to the water temperature signals successively received within the predetermined time period Δt, if so, the AC heating power is increased step by step, and then a cyclic judgment is performed, thereby increasing step by step from AC1 level to AC7 level; if not, the current heating mode is maintained and the step of judging the upper limit of the lower water temperature is entered;

[0043] The lower water temperature upper limit judgment step - judge whether the lower water temperature "Tlower" of the water tank is higher than the preset value "Tset" according to the received water temperature signal. If so, switch to EH1, EH2, EH3 photovoltaic heating, and then recycle to enter the upper water temperature lower limit judgment step; otherwise, enter the preset time water temperature drop judgment step.

[0044] In order to take into account both photovoltaic power utilization and user needs, the central controller also calls Figure 6 The subroutine of the logic shown performs the following steps:

[0045] Control management start-up steps - start photovoltaic load control management and enter the shutdown voltage judgment step;

[0046] Shutdown voltage judgment step: judge whether the detected photovoltaic voltage "U" is greater than the predetermined shutdown voltage "Ushutdown", if the judgment result is yes, enter the start voltage judgment step; if the judgment result is no, enter the load from high to low judgment step;

[0047] Turn-on voltage judgment step: judge whether the detected photovoltaic voltage "U" is greater than the predetermined turn-on voltage "Uon", if the judgment result is yes, enter the load from low to high judgment step; if the judgment result is no, keep the current state and enter the turn-off voltage judgment step;

[0048] Load from high to low judgment step - judge whether the current DC load is the highest power mode DC1 level. If the judgment result is yes, reduce the DC load by one level and enter the control management start step; if the judgment result is no, judge whether the current DC load is the second highest power mode DC2 level, and then cycle again until the DC load is reduced to the lowest DC7 level and enter the control management start step;

[0049] Load judgment step from low to high - judge whether the current DC load is lower than the lowest power mode DC7 level. If the judgment result is yes, increase the DC load by one level DC6 and enter the control management startup step; if the judgment result is no, judge whether the current DC load is the second lowest power mode, and then cycle again until the DC load increases to the highest level DC1 and enters the control management startup step.

[0050] The test shows that the photovoltaic water heating system and method of this embodiment has the following outstanding advantages compared with the prior art:

[0051] 1. When the photovoltaic is in the power generation state and does not require AC heating. Switch part or all of the heating tubes to DC through relay KA11 / KA21 / KA31, and select the serial number of the heating tubes to be connected according to the load current capacity of the photovoltaic panel under the current light intensity through relay KA12 / KA22 / KA32, so that the output efficiency of the photovoltaic system is in a relatively high range. Real-time regulation of DC loads is carried out during the later operation. According to the heating tube parameter settings in the above table, the photovoltaic load can have 7 power ranges that can be adjusted, namely: 200W / 300W / 400W / 500W / 600W / 700W / 900W.

[0052] 2. When the photovoltaic water heater can make the water tank reach the set temperature by relying solely on photovoltaic power generation energy, all photovoltaic DC heating tube loads will be disconnected after the water tank temperature reaches the set temperature.

[0053] 3. When the photovoltaic power generation cannot meet the demand for hot water in the immediate and scheduled time periods, select a single or all heating tubes to switch to the mains through relay KA11 / KA21 / KA31, and select the power of AC heating through relay KA12 / KA22 / KA32. According to the heating tube parameter settings in the table above, the AC heating power has 7 adjustable power ranges, namely: 1512W / 2268W / 3025W / 3780W / 4537W / 5293W / 6805W.

[0054] 4. According to the actual hot water demand and the current photovoltaic power generation capacity, the three heating tubes can work under direct current and alternating current respectively, so as to achieve the purpose of satisfying the user's hot water demand and maximizing the use of photovoltaic energy.

[0055] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A solar photovoltaic water heater, comprising a photovoltaic power generation panel array and a photovoltaic electric water heater, wherein a group of AC / DC multiplexing electric heating tubes are installed in a water tank of the photovoltaic electric water heater; the power supply end of the AC / DC multiplexing electric heating tubes is respectively connected to a photovoltaic power supply and a city power supply through an AC / DC switching relay, and is controlled by an on-off relay controlled by a controller; The controller includes a central processing chip, which includes corresponding signal input ports respectively connected to photovoltaic voltage detection, photovoltaic current detection and upper and lower temperature sensors of the water tank, and corresponding control terminals of the central processing chip are respectively connected to the controlled terminals of the on-off relay and the AC / DC switching relay; The central processing chip contains: Upper water temperature lower limit judgment unit - used to judge whether the upper water temperature of the water tank after photovoltaic heating is lower than a predetermined value according to the received water temperature signal, if not, the lower water temperature lower limit judgment unit is activated; if yes, the control is switched to AC heating, and then the upper water temperature upper limit judgment unit is activated; Upper water temperature upper limit judgment unit - used to judge whether the upper water temperature of the water tank after AC heating is higher than the set value according to the received water temperature signal. If so, the control switches to photovoltaic heating, and then the upper water temperature lower limit judgment unit is enabled; otherwise, the upper water temperature lower limit judgment unit is enabled; The lower water temperature lower limit judgment unit is used to judge whether the water temperature at the lower part of the water tank is lower than the preset value according to the received water temperature signal. If not, the control switches to photovoltaic heating and then activates the upper water temperature lower limit judgment unit; if yes, activates the preset time water temperature drop judgment unit; The water temperature drop judgment unit for a predetermined time period is used to judge whether the water temperature in the lower part of the water tank continues to drop according to the water temperature signals received successively for a predetermined time period. If so, the AC heating power is increased step by step, and then a cycle judgment is performed until the power is increased to the maximum level. If not, the lower water temperature upper limit judgment unit is activated after maintaining the current heating mode; The lower water temperature upper limit judgment unit is used to judge whether the water temperature at the bottom of the water tank is higher than the preset value according to the received water temperature signal. If so, it switches to photovoltaic heating and then activates the upper water temperature lower limit judgment unit; otherwise, it activates the water temperature drop judgment unit for a preset time.

2. The solar photovoltaic water heater according to claim 1, characterized in that The central processing chip of the controller also contains: Control management start unit - used to start photovoltaic load regulation and management, start and close the voltage judgment unit; Shutdown voltage judgment unit - used to judge whether the detected photovoltaic voltage is greater than the predetermined shutdown voltage. If the judgment result is yes, the start voltage judgment unit is enabled; if the judgment result is no, the unit DC load from high to low judgment unit is enabled; The start-up voltage judgment unit is used to judge whether the detected photovoltaic voltage is greater than the predetermined start-up voltage. If the judgment result is yes, the DC load from low to high judgment unit is enabled; if the judgment result is no, the current state is maintained and the shutdown voltage judgment unit is enabled; Load from high to low judgment unit - used to judge whether the current DC load is in the highest power mode. If the judgment result is yes, the DC load is reduced by one level and the control management start unit is enabled; if the judgment result is no, it is judged whether the current DC load is in the second highest power mode, and then the previous cycle is repeated until the DC load is reduced to the lowest level and the control management start unit is enabled; Load from low to high judgment unit - used to judge whether the current DC load is lower than the lowest power mode. If the judgment result is yes, the DC load is increased by one level and the control management start unit is enabled; if the judgment result is no, it is judged whether the current DC load is the second lowest power mode, and then the previous cycle is repeated until the DC load is increased to the highest level and the control management start unit is enabled.

3. The solar photovoltaic water heater according to claim 1 or 2, characterized in that: The photovoltaic panel array is formed by at least two photovoltaic panels connected in series.

4. The solar photovoltaic water heater according to claim 3, characterized in that: The photovoltaic voltage detection plug-in terminal connected across the positive and negative cables of the photovoltaic panel array aggregation cable isolates and samples the DC voltage through the photoelectric isolation device and connects it to the voltage detection processing circuit, and then sends it to the voltage signal input terminal of the central processing chip; the Hall effect current sensor chip connected in series in the photovoltaic panel array aggregation cable isolates and samples the DC current and connects it to the current detection processing circuit, and then sends it to the current signal input terminal of the central processing chip.

5. The solar photovoltaic water heater according to claim 4, characterized in that: The heating control end of the central processing chip is respectively connected to the controlled end of the on-off relay of the corresponding AC / DC multiplexing electric heating tube and the switching control end of the AC / DC switching relay through the driving chip.

6. The solar photovoltaic water heater according to claim 5, characterized in that: The communication terminal of the central processing chip is connected to the communication circuit.

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