CN118147674A - Photo-thermal and electrolyzed water coupled hydrogen production system and method - Google Patents

Abstract

The invention relates to the technical field of photovoltaics, and discloses a photo-thermal and electrolyzed water coupled hydrogen production system and a method. The invention solves the problems of complex system design, high cost and the like in the prior art.

Description

Photo-thermal and electrolyzed water coupled hydrogen production system and method

Technical Field

The invention relates to the technical field of photovoltaics, in particular to a hydrogen production system and method by coupling light and heat with electrolyzed water.

Background

Because the photovoltaic power generation changes along with the change of seasons, weather and different times of day, the volatility of the photovoltaic power generation is very large, so that the grid-connected utilization rate is low and the electricity discarding rate is high. The Proton Exchange Membrane (PEM) water electrolysis hydrogen production with the characteristics of wide working current density range and strong adaptability to power supply fluctuation is a few applications which can be compatible with the characteristic of photovoltaic fluctuation, and an ideal green energy utilization path can be formed theoretically. There are some designs of the photovoltaic-coupled proton exchange membrane water electrolysis hydrogen production system in this aspect, but there are still more problems, so that design redundancy is caused and hydrogen production efficiency is low. In particular, the following aspects are core problems:

(1) In order to achieve the purpose of photovoltaic peak shaving, an energy storage power station, a fuel cell, a storage battery and the like are additionally arranged for buffering or feedback adjustment of photovoltaic fluctuation, so that the cost is high;

(2) Most of the design and peak shaving metrics are based on Photovoltaic (PV) characteristics, and do not fully take into account the operating characteristics of the cells with the highest investment cost ratio in the system. For example, the temperature characteristics of the electrolyzer, the frequent face of cold starts under diurnal alternation of off-grid photovoltaic direct systems can have a major impact on the electrolyzer life (A. Weiβ; journal of The Electrochemical Society,166 (8) F487-F497 (2019)) and the continued operation of the electrolyzer at high current densities can impair the electrolyzer's long life (Christoph Rakousky; electrochimica Acta,278, 324-331).

In theory, the adaptable temperature of the PEM electrolyzer can reach 0-90 ℃, and the adaptable current density can reach 0-3A/cm ² or even wider. The minimum turn-on voltage of the electrolyzer is temperature dependent, and as electrolyzer power increases, the electrolyzer's heat demand may change from endothermic to exothermic. However, most of the current designs of the photovoltaic direct-connected PEM electrolyzer only consider power supply, or respectively design a heat supply management module and a power supply management module (as shown in fig. 1), and similar systems are complex in design and high in cost.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a photo-thermal and electrolyzed water coupled hydrogen production system and a method thereof, which solve the problems of complex system design, high cost and the like in the prior art.

The invention solves the problems by adopting the following technical scheme:

The photo-thermal and electrolyzed water coupled hydrogen production system comprises a PV-PVT module, a heat storage module and a electrolyzed water hydrogen production system which are sequentially communicated through pipelines, and also comprises a DC/DC module, wherein the PV-PVT module, the DC/DC module and the electrolyzed water hydrogen production system are sequentially and electrically connected, and the PV-PVT module comprises a PV component and a PVT component.

As a preferable technical scheme, the water electrolysis hydrogen production system comprises an electrolytic tank, a PV-PVT module, a heat storage module and an electrolytic tank which are sequentially communicated through pipelines, and the PV-PVT module, the DC/DC module and the electrolytic tank are sequentially electrically connected.

As a preferred technical solution, the PVT assembly is provided with a heat collector.

As a preferred technical solution, the PVT assembly is provided with a waterway.

As a preferred technical solution, the PVT assembly is provided with a photovoltaic assembly and a wire.

As a preferred technical scheme, the heat storage module is provided with a heat transfer medium, and the heat transfer medium is water or glycol water solution.

As a preferable technical scheme, the heat storage module is provided with a phase change material with a phase change temperature of 40-80 ℃.

As a preferred embodiment, the electrolyzer is an alkaline electrolyzer, a solid oxide electrolyzer, an anion exchange membrane electrolyzer or a PEM electrolyzer.

The hydrogen production method by coupling light and heat with electrolyzed water adopts the hydrogen production system by coupling light and heat with electrolyzed water, and realizes heat supply and/or electricity supply of the electrolyzer by adjusting the quantity ratio or the generation power ratio of PV components and PVT components in the PV-PVT module.

As a preferred solution, the heat transfer means are:

pure water is used as a medium, and a heat storage medium of the heat storage module, a heat transfer medium of the PVT component and raw water of the electrolytic tank form a thermal cycle of the hydrogen production system with photo-thermal and electrolytic water coupling.

Compared with the prior art, the invention has the following beneficial effects:

(1) The invention regulates the supply of heat and electricity based on the temperature characteristic of PVT, omits a great number of designs related to heat management and power management, and greatly reduces the system cost;

(2) The invention effectively reduces the occurrence rate of cold start-stop and overload running states by regulating the supply of heat and electricity, and is beneficial to delay the performance attenuation of the electrolytic tank.

Drawings

FIG. 1 is a schematic diagram of a prior art power and heat supply independently controlled light Fu Zhi with PEM electrolyzed water hydrogen production system;

FIG. 2 is a schematic diagram of a photo-thermal and electrolyzed water coupled hydrogen production system according to the present invention;

FIG. 3 is a graph comparing power versus temperature for an electrolyzer and photovoltaic at a particular voltage;

FIG. 4 is a flow chart of a method for configuring PV-PVT modules of an off-grid water electrolysis hydrogen production system;

FIG. 5 is a schematic diagram of a photo-thermal and electrolyzed water coupled hydrogen production system according to the present invention;

fig. 6 is a schematic structural diagram of a PVT sheet.

The reference numerals in the drawings and their corresponding names: 1. PV-PVT module 2, heat storage module 3, DC/DC module 4, electrolytic water hydrogen production system 11, PV subassembly, 12, PVT subassembly, 41, electrolysis cell, 121, heat collector, 122, water route, 123, photovoltaic subassembly and wire.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.

Example 1

As shown in fig. 1 to 6, in order to solve the problems in the prior art, the invention is inspired by the relation between the photovoltaic module and the temperature, namely the power generation of the photovoltaic module is reduced when the temperature is increased, the invention creatively realizes the optimization of heat and electricity supply of the electrolytic tank through reasonable proportioning (quantity proportioning or power generation proportioning) of the solar PV panel and the PVT panel, weakens the generated energy when the irradiation peak value and converts the generated energy into heat for storage, and is used for preheating before the electrolytic tank is started; the occurrence frequency of the electrolytic tank in the condition of super power or cold start can be effectively avoided. The proposal realizes the optimal peak regulation of photovoltaic heat supply and power supply within the acceptable range of the electrolytic tank, and greatly simplifies the design and application cost of the whole system (shown in figure 2).

The invention provides an off-grid hydrogen production system design scheme of a photovoltaic/photo-thermal coupling water electrolysis system for optimizing photovoltaic supply while properly introducing a small amount of PVT components to provide heat supply in a PV component based on the temperature characteristics of a photovoltaic-photo-thermal Plate (PVT), and compared with the currently disclosed technology, the off-grid hydrogen production system design scheme is simpler in design and lower in application cost.

The invention provides the following scheme:

The proposal of the scheme is mainly based on the correlation of the power generated by the PVT assembly and the temperature in a certain temperature range and the correlation of the power of the PEM electrolytic tank and the temperature, and the proposal of the system design scheme realizes the dynamic collaborative management of the power supply and the heat supply of the electrolytic tank by the simplest and low-cost PVT assembly matching mode.

The PV-PVT module refers to a module comprising a PV assembly and a PVT assembly simultaneously, and can output heat energy and electric energy simultaneously.

The configuration method of the PV-PVT module is shown in FIG. 4. Firstly, monomer parameters of relevant modules such as an electrolytic tank, a PV assembly, a PVT assembly and the like are obtained; then configuring a PV assembly, DC/DC (direct current chopper) module based on local climate parameters, PV assembly parameters, electrolyzer power, etc. according to electrolyzer requirements; in addition, the quantity of PVT components is configured according to climate parameters, heat storage module efficiency, PVT component heat collection parameters and the like, and the scale of the heat storage module is configured; finally, a PV-PVT module is constructed.

The design of the PV-PVT coupled electrolyzed water hydrogen production system is shown in FIG. 5. Heat supply route: the PVT assembly 12, while participating in power generation, also collects and transfers heat through a heat collector 121 (preferably copper tubing) under the photovoltaic panel and transfers heat to the heat storage module 2 through a waterway 122, the heat storage module 2 being controlled by the control system of the water electrolysis system to transfer heat to the feed water of the electrolyzed water hydrogen production system 4 (preferably PEM electrolyzed water hydrogen production system) when needed. The PVT assembly 12 has a photovoltaic assembly and leads 123 thereon. Circuit supply route: the electric energy generated by the PV assembly 11 and the PVT assembly 12 in the PV-PVT module 1 is converted by the DC/DC3 and then is connected with the electrolytic water hydrogen production system 4 to be used as an electrolytic power supply.

The complete operation state control and monitoring system is built by adding sensors as comprehensively as possible in the system, and comprises temperature control parameters (raw water inlet temperature, outlet temperature, PVT temperature, heat storage temperature in a water tank and the like), liquid level control parameters (hydrogen side separator liquid level, oxygen side separator liquid level and the like), water supply control parameters (water supplementing pump start-stop control, heat exchanger water flow, conductivity, circulating raw water flow and the like), pressure control parameters (electrolyzer inlet pressure, hydrogen side pressure, oxygen side pressure, oxyhydrogen side pressure difference and the like), power supply control parameters (PV, PVT real-time output current or power, electrolyzer current, electrolyzer voltage and the like), and gas production performance parameters (hydrogen in oxygen, hydrogen in hydrogen and the like). Under normal conditions, the heat exchange cycle can be opened and closed at regular time before sunrise and after sunset every day, the opening and closing of the electrolytic water hydrogen production system can completely carry out fluctuation hydrogen production along with irradiation change, and the fluctuation hydrogen production under unattended operation can be realized through monitoring of liquid level, temperature, power and the like and control of opening and closing of a valve and a power supply.

Example 2

As further optimization of embodiment 1, as shown in fig. 1 to 6, this embodiment further includes the following technical features on the basis of embodiment 1:

Fig. 2 shows a photovoltaic/photo-thermal coupling electrolytic water hydrogen production system provided by the invention, which mainly comprises a PV-PVT module 1, a heat storage module 2, a DC/DC module 3 and an electrolytic water hydrogen production system 4.

The working process principle is as follows:

1. power supply of the water electrolysis hydrogen production system: the electric energy generated by the PV-PVT module 1 is connected to an electrolytic tank 41 of the water electrolysis hydrogen production system 4 as an electrolysis power supply after being converted by DC/DC 3;

2. Heating of the hydrogen production system by water electrolysis: the PVT component 12 in the PV-PVT module 1 collects heat while participating in power generation, transfers the heat to the heat storage module 2 through a waterway, and then supplies heat for raw water of the electrolytic tank 41 through the heat storage module 2;

3. Heat supply and power supply dynamic cooperative management principle of electrolytic water hydrogen production system: as shown in fig. 6, the photovoltaic temperature fluctuation of the surface of the PVT assembly 12 is greater due to the addition of the heat collecting device 121 on the back as compared to the PV assembly 11. When the irradiation intensity continuously rises, the temperature of the medium in the heat collecting pipeline rises, and the heat can be influenced by four ways:

(1) The heat is transferred to the photovoltaic devices in the PVT, and the relation between the power curve and the temperature of the PVT in the figure 3 shows that the generated power of the PVT assembly is reduced, so that the total PV-PVT generated power is stable, the PV-PVT output power is prevented from greatly fluctuating, the fluctuation range of the input power supply of the electrolytic cell is reduced, and the occurrence probability of the electrolytic cell exceeding the rated power operation is reduced;

(2) Heat is transferred to the heat storage module 2 (also including when the electrolyzer is radiating at high power) through the pipeline, and the temperature higher than the medium in the heat storage module 2 is stored for the heat compensation of the electrolyzer in a specific period of time;

(3) The heat storage module transfers heat to the feed water and the electrolyzer, as can be seen from the power curve versus temperature for the PEM electrolyzer of fig. 3, the electrolyzer voltage is lower at the same power (or current density) over the rated range; on the other hand, the probability of the PEM electrolyzer being in an overload operation state is further reduced;

(4) When the irradiation intensity is very low in overcast and rainy days or before the startup of the PEM electrolytic tank, the raw water temperature is low, and the heat stored by the heat storage module 2 through the path (2) in the high-radiation intensity period can be continuously released to improve the raw water temperature, so that the startup voltage (or current) threshold value of the electrolytic tank can be reduced, the average hydrogen production time per day can be improved, the hydrogen production capacity under the same power can be improved, and meanwhile, the service life reduction caused by frequent cold startup and rapid temperature change of the PEM electrolytic tank can be effectively avoided.

Based on the correlation of the power generated by the PVT component and the temperature in a certain temperature range and the correlation of the power of the PEM electrolytic tank and the temperature, the design realizes the heat supply and power supply dynamic collaborative management of the water electrolysis hydrogen production system by a PV-PVT component matching method.

Embodiment one: sunny days with good irradiation conditions

In the morning, the photovoltaic voltage is lower than the starting voltage, the temperature of the electrolytic tank approaches to the ambient temperature, the electrolytic tank starts to be preheated at regular time, and the heat stored in the heat storage module 2 in the previous day is transferred to the electrolytic tank 41 through the raw material water circulation, so that the temperature reaches the starting temperature. After the irradiation value is higher than the starting voltage, the electrolytic tank is automatically started to operate, so that the daily cold start of the electrolytic tank can be avoided, and the rapid decay of the service life of the electrolytic tank caused by frequent low-temperature start is prevented.

During the middle of the day when solar radiation is at peak, the heat collection of the PVT sheet is at peak and the temperature or stored heat in the PVT sheet, the circulating medium and the heat storage module all rise. At this time, as shown in fig. 3, on the one hand, due to the negative correlation between the photovoltaic power generation amount and the temperature, the power generation amount of PVT may continuously decrease with the increase of the temperature, and the total output power may tend to be stable; on the other hand, due to the negative dependence of the cell voltage or power on temperature at a certain current density, the hydrogen production of the cell increases at the same power as the temperature delivered to cell 41 increases; meanwhile, when the temperature of the electrolytic tank is higher than the temperature of cooling water (the heat storage temperature in the heat storage module), the electrolytic tank 41 can exchange heat to the heat storage module, and the temperature of the electrolytic tank 41 can be well controlled in a certain range so as to prevent over-temperature operation. Therefore, when the radiation intensity is high, the PVT still keeps higher hydrogen production efficiency through the two functions of reducing the generated energy after temperature rise and increasing the temperature of the electrolytic tank by heat collection, and meanwhile, the occurrence of an ultra-power or ultra-temperature running state can be effectively restrained, and the service life attenuation of the electrolytic tank is effectively relieved.

Embodiment two: overcast and rainy days with weak irradiation condition

In the morning, the photovoltaic voltage is lower than the starting voltage, the temperature of the electrolytic tank approaches to the ambient temperature, the electrolytic tank starts to be preheated at regular time, and the heat stored in the heat storage module 2 is circularly transferred to the electrolytic tank 41 through the raw material water so as to reach the starting temperature. After the irradiation value is higher than the starting voltage, the electrolytic tank is automatically started to operate, so that the daily cold start of the electrolytic tank can be avoided, and the rapid decay of the service life of the electrolytic tank caused by frequent low-temperature start is prevented. During daytime operation, when the electrolysis cell 41 radiates more heat to the environment than itself generates heat at low power, the heat storage module 2 will automatically transfer the heat stored on sunny days to the electrolysis cell 41 through water circulation. Since the higher the temperature of the electrolyzer is in the normal operating temperature range, the lower the overpotential is, the lower the operable voltage threshold of the electrolyzer is; therefore, continuous heat supplement under low load can also improve the average daily running time of the electrolytic tank and improve the hydrogen production.

The continuous implementation effect corresponding to the second embodiment: using Deyang City of Sichuan as experimental implementation place, 2023, 10, 23 and 24, 9, where irradiation conditions were close, were selected: 00-17: data at 30 are compared. The two days are cloudy days, the electrolytic tank is in a low-power running state (current density is less than 1A/cm < 2 >), the 17-day PVT heating circuit is in an off state, and the 23-day heating circuit is in an on state.

As shown in table 1, the comparative experimental data carried out on irradiation of similar days 23 and 24 show that when the thermal cycle loop provided by PVT is opened, the raw material level of the electrolytic cell is raised by 16.7 ℃ and the temperature fluctuation is reduced by more than 50%; the hydrogen production capacity is improved by 3.0 percent. The above experimental data fully demonstrates the significant effect of this design. In fact, with the increase of irradiation intensity, the power of the electrolytic cell is increased, and the effect of the thermal circulation loop on the hydrogen production capacity is more obvious.

TABLE 1 comparison Table of PVT heating effects on overcast days

In the PVT configuration method, the PVT configuration can be performed according to the maximum power-on requirement Q1; the maximum demand configuration can be regulated and controlled according to the whole day temperature of the electrolytic tank; it can also be configured according to annual irradiation characteristics.

In the invention, the capacity of the heat storage module can be configured based on the different requirements; the heat transfer medium in the heat storage module comprises but is not limited to water or glycol aqueous solution, and the phase change energy storage material can be placed in the module at the same time, and the phase change energy storage material comprises but is not limited to paraffin, sunflower acid and other phase change materials with the temperature change of about 40-80 ℃. The heat transfer is as follows: the heat storage medium of the heat storage module 2, the heat transfer medium of the PVT assembly 12 and the raw water of the electrolyzer 41 constitute the thermal cycle of the system. The specific connection form is one or more of the following forms:

(1) The heat storage medium of the heat storage module 2 is directly communicated with the pipeline of the PVT assembly 12 or the heat transfer medium is indirectly connected through a heat exchanger (the heat exchanger is selectively added in the pipeline);

(2) The heat storage medium of the heat storage module 2 and the raw water of the electrolytic tank 41 are directly communicated through a pipeline or indirectly connected through a heat exchanger.

The method for regulating and controlling the total power generation of the PV-PVT module by introducing PVT based on the correlation of the power generation power of PVT and the temperature characteristic of the electrolytic tank is applicable to alkaline electrolytic tanks, high-temperature solid oxide electrolytic devices, anion exchange membrane electrolytic tanks and PEM electrolytic tanks in a water electrolysis hydrogen production system, and the PVT quantity can be configured according to the working temperature and the power requirement of the specific electrolytic tank.

In the invention, the temperature application range of the PEM electrolytic tank is wide, and the temperature regulation requirement of PVT on raw water can be reduced as much as possible, so that the actual ratio of PV in the ratio of PV and PVT is as high as possible, and the power generation efficiency is improved. Considering that the temperature of the PVT sheet will be higher when the irradiation intensity is higher, the power generation of PVT will drop sharply, and the contribution of PVT power generation to the total input power is extremely low, so the number of PVs can be between (a-B) to a without exceeding the maximum rated power of the PEM electrolyzer, and is not limited to (a-B).

In the invention, the water electrolysis hydrogen production system comprises a PLC control system and a hydrogen production system communicatively connected with the PLC control system: the electromagnetic valve is opened and closed; a liquid level sensor; a temperature sensor; a water pump; a flow meter; a heat sink; a heater; hydrogen explosion detector; a gas-water separator; pressure sensors, etc. The system can monitor the running state of each device in real time through the sensor and the flowmeter in the use process, and then the terminal processor timely controls the electromagnetic valve, the water pump and the like according to the setting to correct the abnormal state so that the electrolytic tank is in the optimal electrolytic environment, and an unattended electrolytic water hydrogen production system is built. Specifically, the terminal processor monitors the safety of the hydrogen production process by the hydrogen explosion detector; detecting the abnormal liquid level of the gas-water separator through a liquid level sensor and performing operations such as water supplementing and the like; and the heat exchange is controlled by a timing or constant temperature switch.

As described above, the present invention can be preferably implemented.

All of the features disclosed in all of the embodiments of this specification, or all of the steps in any method or process disclosed implicitly, except for the mutually exclusive features and/or steps, may be combined and/or expanded and substituted in any way.

The foregoing description of the preferred embodiment of the invention is not intended to limit the invention in any way, but rather to cover all modifications, equivalents, improvements and alternatives falling within the spirit and principles of the invention.

Claims (10)

1. The photo-thermal and electrolyzed water coupled hydrogen production system is characterized by comprising a PV-PVT module (1), a heat storage module (2) and a electrolyzed water hydrogen production system (4) which are communicated sequentially through pipelines, and further comprising a DC/DC module (3), wherein the PV-PVT module (1), the DC/DC module (3) and the electrolyzed water hydrogen production system (4) are sequentially and electrically connected, and the PV-PVT module (1) comprises a PV component (11) and a PVT component (12).

2. The photo-thermal and electrolyzed water coupled hydrogen production system as claimed in claim 1, wherein the electrolyzed water hydrogen production system (4) comprises an electrolyzer (41), the PV-PVT module (1), the heat storage module (2) and the electrolyzer (41) are sequentially communicated through pipelines, and the PV-PVT module (1), the DC/DC module (3) and the electrolyzer (41) are sequentially electrically connected.

3. A photo-thermal and electrolyzed water coupled hydrogen production system as in claim 1 wherein the PVT assembly (12) is provided with a heat collection device (121).

4. A photo-thermal and electrolyzed water coupled hydrogen production system as defined in claim 1 wherein the PVT assembly (12) is provided with a waterway (122).

5. The photo-thermal and electrolyzed water coupled hydrogen production system as described in claim 1 wherein the PVT assembly (12) is provided with a photovoltaic assembly and a wire (123).

6. A system for producing hydrogen by coupling light and heat with electrolyzed water as in claim 1 wherein the heat storage module (2) has a heat transfer medium, the heat transfer medium being water or an aqueous glycol solution.

7. A system for producing hydrogen by coupling light and heat with electrolyzed water as in claim 6 wherein the heat storage module (2) has a phase change material with a phase change temperature of 40-80 ℃.

8. A photo-thermal and electrolyzed water coupled hydrogen production system according to any of claims 2 to 7 wherein the electrolyzer (41) is an alkaline electrolyzer, a solid oxide electrolyzer, an anion exchange membrane electrolyzer or a PEM electrolyzer.

9. A method for producing hydrogen by coupling photo-thermal and electrolyzed water, characterized in that the photo-thermal and electrolyzed water-coupled hydrogen production system as described in any one of claims 2 to 9 is adopted, and the heat supply and/or the electricity supply of the electrolyzer is realized by adjusting the quantity ratio or the generated power ratio of the PV component (11) and the PVT component (12) in the PV-PVT module (1).

10. The method for producing hydrogen by coupling light and heat with electrolyzed water according to claim 9, wherein the heat transfer is performed by:

Pure water is used as a medium, and a heat storage medium of the heat storage module (2), a heat transfer medium of the PVT component (12) and raw water of the electrolytic tank (41) form a thermal cycle of the hydrogen production system with photo-thermal and electrolytic water coupling.