Night off-peak electricity heat storage and supply system and method based on phase change heat storage material

Abstract

The invention provides a night off-peak electricity heat storage and supply system and method based on a phase change heat storage material, and the system comprises an electric heating device which is used for converting electric energy into heat energy in an off-peak electricity period; the phase change heat storage unit is connected with the electric heating device and is used for storing heat energy; the heat exchange assembly is connected with the phase change heat storage unit and a user heating system to realize heat transfer; the user heating system is used for providing heating heat for the user side; the intelligent control system is connected with the electric heating device, the phase change heat storage unit, the heat exchange assembly and the user heating system and used for generating and executing a heat storage and release strategy; the system automation level and the energy utilization efficiency are improved, and the whole system has the advantages of being economical, capable of saving energy, stable in operation and capable of achieving peak load shifting.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of renewable energy and building energy saving, and particularly relates to a night valley electricity heat storage and supply system and method based on phase change heat storage materials. BACKGROUND

[0002] In northern winter heating, electric heating as an important form of clean heating, the proportion is increasing year by year, but the traditional electric boiler "turn on and heat" operation mode has obvious defects: affected by the peak valley electricity price policy (the electricity fee is usually 3-5 times of the valley electricity price in the peak period, such as 8:00 in the morning-22:00 in the evening for peak time, 22:00 in the evening-6:00 the next day for valley time), the user heating cost is high, and some residents and enterprises are difficult to bear.

[0003] In order to reduce the cost, the heat storage type electric heating technology is gradually popularized, and the current mainstream scheme has obvious limitations, and there is a gap between the conventional heating theory and the engineering demand: (1) Inherent defects of traditional heat storage technology 1. Water heat storage technology: relying on the heat storage of water (specific heat capacity 4.2kJ / (kg•℃)), a large heat storage water tank (such as 100m 3 The above tank) needs to be built, which occupies a large area, and the heat storage density is only about 20Wh / kg (much lower than the "compactness" requirement of the heating system). At the same time, affected by natural convection, the 24-hour heat loss rate is more than 10% (not meeting the recommended value of "heat loss rate of heat storage system ≤8%" in "Urban Heating Pipe Network Design Specification"), and the heating temperature fluctuates by ±3℃ with the decrease of water temperature, affecting the user comfort.

[0004] 2. Solid sensible heat storage technology: using magnesium bricks, concrete and other materials as heat storage medium, the heat storage density is slightly higher than water (about 30-40Wh / kg), but the temperature fluctuation during heat storage and release can reach 15-20℃, resulting in high and low user room temperature; and the heat exchange efficiency is only 60-70% (because the thermal conductivity of solid medium is low, and the contact with the heat exchange pipeline is insufficient), which causes serious energy waste and does not meet the "high efficient energy use" principle of conventional heating.

[0005] (2) Defects of existing phase change heat storage heating scheme 1. Phase change heat storage material (PCM) has the characteristics of "absorbing / releasing a large amount of latent heat at a constant temperature" (heat storage density can reach 70-150Wh / kg), which becomes the key to break through the bottleneck of traditional heat storage technology, but the existing scheme does not fully meet the actual engineering demand, and the main problems include: 2. Phase change material and heat supply demand mismatch: phase change temperature is too high (such as more than 100℃) or too low (such as less than 50℃), resulting in unreasonable heat exchange temperature difference with user heating terminal (50-55℃ for floor heating, 65-70℃ for fan coil), violating the conventional heat transfer theory of "heat transfer temperature difference adaptation", and the heat exchange efficiency is low.

[0006] 3. Lack of intelligent scheduling coordinated with time-of-use electricity price: no precise heat storage strategy based on valley electricity period is established, and there is still the case of starting electric heating during non-valley electricity period, which fails to fully utilize the price difference to reduce cost and does not comply with the power grid optimization principle of "demand side response".

[0007] 4. Unreasonable heat exchange structure design: the contact area between the phase change material and the heat exchange pipeline is insufficient, resulting in slow heat storage and release rate (response time more than 30 minutes), which cannot quickly respond to the change of user heat demand, violating the conventional control theory of "dynamic adaptation of heating system".

[0008] (Three) necessity of technology development With the maturity of smart grid and Internet of Things technology, real-time acquisition of time-of-use electricity price signal and accurate prediction of meteorological data (error ≤2℃) become possible, providing technical support for the collaborative system of "valley electricity heat storage + phase change technology + intelligent regulation and control". Developing a phase change heat storage and supply system that is adapted to valley electricity scenario, has high heat storage density, constant temperature heating and intelligent control has become the core path to solve the contradiction between "economy - comfort - efficiency" of electric heating, and conforms to the conventional trend of building heating towards "low carbonization, intelligentization and compactness". SUMMARY

[0009] The purpose of the present application is to provide a night valley electricity heat storage and supply system and method based on phase change heat storage material, which solves the problems in the prior art.

[0010] In order to achieve the above purpose, the technical scheme adopted by the present application is: In a first aspect, the present application provides a night valley electricity heat storage and supply system based on phase change heat storage material, comprising: An electric heating device for converting electric energy into heat energy during valley electricity period; A phase change heat storage unit connected with the electric heating device for storing heat energy; A heat exchange assembly connecting the phase change heat storage unit and the user heating system to realize heat transfer; A user heating system for providing heating heat to the user end; An intelligent control system connected with the electric heating device, phase change heat storage unit, heat exchange assembly and user heating system for generating and executing heat storage and release strategy.

[0011] Preferably, the electric heating device is an electric heating tube or an electrode boiler.

[0012] Preferably, the phase change heat storage unit comprises a heat storage shell, an inner cavity of the heat storage shell being filled with a phase change material; a heat exchange pipeline is arranged in the inner cavity of the heat storage shell and is pre-embedded in the phase change material, a heat exchange medium port of the heat exchange pipeline being connected to the electric heating device, and a heat supply medium port of the heat exchange pipeline being connected to the heat exchange assembly.

[0013] Preferably, the heat exchange pipeline is a spiral pipe or a finned tube.

[0014] Preferably, the heat exchange assembly comprises a plate heat exchanger, a primary side port of the plate heat exchanger being connected to the phase change heat storage unit, and a secondary side port of the plate heat exchanger being connected to the user heating system.

[0015] Preferably, a circulating pump is arranged on a connecting pipeline between the heat exchange assembly and the user heating system.

[0016] Preferably, an electric regulating valve is arranged on the connecting pipeline between the heat exchange assembly and the user heating system.

[0017] Preferably, the intelligent control system comprises: a data acquisition unit configured to acquire valley electricity time period signals, temperature data, weather forecasts and equipment operation parameters; a strategy generation module configured to generate heat storage time, heat release rate and equipment control instructions based on a time sequence control algorithm; an execution control module configured to control the running states of the electric heating device, the circulating pump and the electric regulating valve.

[0018] Preferably, the user heating system is a floor heating system or a fan coil system.

[0019] In a second aspect, the present application provides a night valley electricity heat storage and supply method based on a phase change heat storage material, comprising the following steps: acquiring valley electricity time periods, weather data and user temperature settings; starting the electric heating device in the valley electricity time period to store heat in the phase change heat storage unit; starting a heat release process according to user heat demand in a non-valley electricity time period to supply heat to the user heating system through the heat exchange assembly; real-time monitoring of system states and feedback of optimized heat storage and release strategies.

[0020] Compared with the prior art, the present application has the following beneficial effects: The application provides a night valley electricity heat storage and supply system based on a phase change heat storage material, through introduction of a phase change heat storage unit and integration with an electric heating device, a heat exchange assembly and a user heating system, under unified scheduling of an intelligent control system, efficient heat storage can be conducted during a night valley electricity period, and the electricity cost of a user is significantly reduced; the phase change heat storage material has high energy storage density and constant temperature heat release characteristics, can effectively store a large amount of heat energy and stably release the heat energy during a power consumption peak period, relieves the peak valley difference pressure of a power grid, and guarantees heat supply continuity and indoor temperature stability; the intelligent control system improves the system automation level and energy utilization efficiency by real-time monitoring and strategy optimization, dynamically adjusts the heat storage and release process, and has the outstanding advantages of economic energy saving, stable operation and peak load shifting. DETAILED DESCRIPTION

[0021] In the following description, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the application. However, persons having ordinary skill in the art will appreciate that the application can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the application.

[0022] It should be understood that the term "comprises" when used in this specification and the appended claims specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0023] It should also be understood that the term "and / or" when used in this specification and the appended claims, such as in the phrases "A and / or B" and "A and / or B and / or C", means any combination of one or more of the associated listed items, and includes at least one of each of the associated listed items.

[0024] As used in this specification and the appended claims, the term "if' can, in some instances, be interpreted as meaning "when," or "once," or "in response to a determination," or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [a described condition or event] is detected" can, in some instances, be interpreted to mean "once it is determined," or "in response to determining," or "once [the described condition or event] is detected," or "in response to detecting [the described condition or event]," depending on the context.

[0025] In addition, in the description of the application and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0026] Reference to "one embodiment" or "some embodiments" or "one implementation" or "some implementations" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" or "in some embodiments" or "in other embodiments" or "in still other embodiments" or other similar phrases in the specification are not necessarily all referring to the same embodiment.

[0027] Embodiment 1 The embodiment provides a night valley electricity heat storage and supply system based on a phase change heat storage material, which comprises an electric heating device, a phase change heat storage unit, a heat exchange assembly, a user heating system and an intelligent control system, and wherein: The electric heating device is used for providing a heat source for the phase change heat storage unit. The outlet of the phase change heat storage unit is connected to the heat supply end of the user heating system through the heat exchange assembly. The intelligent control system is connected with other modules through a circuit, and realizes heat storage and release strategy optimization and whole system collaborative regulation and control.

[0028] The electric heating device adopts a high-temperature-resistant electric heating pipe or an electrode boiler, the rated power of which is adapted to the heat storage demand of the system, and the electric heating device is started only during preset valley electricity time periods, and forms an energy utilization mode of "valley electricity energy storage - non-valley electricity energy use" with the phase change heat storage unit.

[0029] Embodiment 2 Based on the embodiment 1, the embodiment provides a night valley electricity heat storage and supply system based on a phase change heat storage material, and the phase change heat storage unit comprises: A heat storage shell body is made of a corrosion-resistant and high-pressure-bearing stainless steel material, the volume of a single shell body is 1-5 m 3 , and a plurality of shell bodies are supported to be modularly combined; A phase change material adopts an inorganic hydrated salt and an organic ester compound phase change material, the phase change temperature is 60-95 DEG C, the phase change latent heat is greater than or equal to 200 kJ / kg, the cyclic service life is greater than or equal to 5000 times, and there is no supercooling and phase separation phenomenon; An embedded heat exchange pipeline adopts a spiral coil pipe or a finned tube structure, is made of 316L stainless steel, and has a total heat exchange area which is 40% higher than that of a traditional straight pipe, is deeply buried in the phase change material, and forms independent circulation loops with the electric heating device and the user heating system.

[0030] Embodiment 3 Based on the embodiment 1, the embodiment provides a night valley electricity heat storage and supply system based on phase change heat storage material, the heat exchange assembly comprises a circulating pump (including a heat storage circulating pump, a heat release circulating pump), an electric regulating valve and a plate heat exchanger, wherein: The plate heat exchanger has a heat transfer coefficient greater than or equal to a typical value of 3000 W / (m 2 ℃), which is used to realize heat exchange between the phase change heat storage unit and the user heating system, and avoid corrosion of the heat storage unit by water quality on the user side.

[0031] The plate heat exchanger and the user heating system are provided with a circulating pump.

[0032] The intelligent control system comprises: A data acquisition unit acquires a valley electricity period signal (including electricity price period division), a phase change heat storage unit temperature (precision ±0.5℃), a user indoor temperature, outdoor meteorological data (including temperature, wind speed forecast), and heat exchange assembly operating parameters (pump frequency, valve opening degree); A strategy generation module: built-in time sequence control algorithm, taking the minimum running cost + stable heating temperature + optimal heat storage efficiency as the objective function, outputting heat storage time, heat release rate and electric heating device start-stop instructions; An execution control module: regulating and controlling the power of the electric heating device, the start-stop / frequency of the circulating pump and the opening degree of the electric regulating valve, to realize automatic switching of the heat storage, heat preservation and heat release modes.

[0033] The user heating system is adapted to the terminal forms of floor heating and fan coil, is connected with the phase change heat storage unit through the heat exchange assembly, and the user indoor temperature fluctuation range is controlled within ±1℃.

[0034] The heat storage density of the heating system protected by the application is more than 60% higher than that of the traditional water heat storage method, the operation cost is more than 50% lower than that of the traditional electric boiler direct heating, and the heating stability (temperature fluctuation) is more than 80% higher than that of the solid sensible heat storage system.

[0035] Embodiment 4 The embodiment provides a night valley electricity heat storage and supply method based on phase change heat storage material, comprising the following steps: S1: The intelligent control system acquires a valley electricity period (such as 22:00-6:00 the next day) through an electricity price signal receiving module, synchronously acquires outdoor meteorological forecast (temperature change in the next 24 hours), user indoor reference temperature (such as 18-22℃) and phase change heat storage unit initial temperature; S2: The strategy generation module combines historical heating data and real-time parameters to calculate the required heat storage amount and output heat storage mode start instruction; S3: Regeneration mode (valley electricity period): The intelligent control system starts the electric heating device and the regeneration circulating pump. The high-temperature heat-conducting medium (heat-conducting oil or water) circulates between the electric heating device and the embedded heat exchange pipeline of the phase change heat storage unit. The phase change material absorbs heat and gradually melts until it reaches the preset temperature (such as the phase change temperature + 5°C) or the valley electricity period ends. The system automatically switches to the heat preservation mode. S4: Heat preservation mode: The phase change heat storage unit maintains temperature stability through the shell heat preservation layer (using nano aerogel material, heat loss ≤5% / 24h). The intelligent control system monitors the phase change material temperature in real time. If it is lower than the phase change temperature - 3°C, auxiliary heat preservation measures (such as low-power electric heating compensation) are started. S5: Heat release mode (non-valley electricity period): When the user indoor temperature is lower than the lower limit of the reference temperature (such as 18°C), the intelligent control system starts the heat release circulating pump and the plate heat exchanger. The user side low-temperature return water flows into the embedded heat exchange pipeline, absorbs the latent heat released by the solidification of the phase change material, and is heated to the preset temperature (such as 70-80°C) before being delivered to the user heating system. At the same time, the heat release rate is dynamically adjusted according to the outdoor temperature change (such as every 5°C decrease in outdoor temperature, the heat release rate increases by 15%). S6: Feedback optimization: The actual heat storage efficiency, heat release temperature stability, and user room temperature data are fed back to the strategy generation module for iterative optimization of the next day's heat storage duration and heat release control parameters.

[0036] Example 5 Take "5000m 2 Office building (fan coil heating, room temperature set to 20°C)" as an example, the system workflow is divided into five stages, strictly following the conventional theories of "energy conservation", "heat transfer temperature difference adaptation", "feedback optimization", etc.: 1. Data collection and strategy generation stage (1 hour before valley electricity period, 19:00-20:00) The intelligent control system obtains the valley electricity period of the day through the power grid interface: 22:00-6:00 the next day (8 hours); Obtain the outdoor temperature forecast of the next day through the weather API: 5°C→-10°C (minimum temperature at 7:00 the next day, change rate 1.5°C / h), solar radiation intensity 500W / m 2 (midday); Collect the initial temperature of the phase change heat storage unit: 55°C (lower than the phase change temperature 75°C, uncharged state), the current indoor temperature of the user: 18°C (lower than the set value 20°C); The strategy generation module calculates: Building heat load 100kW (based on the steady-state heat transfer formula in the "Code for Design of Heating, Ventilation and Air Conditioning of Civil Buildings", considering heat transfer from the building envelope, heat dissipation from occupants, and heat gain from solar radiation), required heat storage Q = 100kW × 10h (heating from 8:00 to 18:00 the next day) = 1000kWh; total system energy utilization rate = 98% (electric heating efficiency) × (1-5%) (heat storage loss) ≈ 93.1%, actual required heat storage = 1000kWh / 93.1% ≈ 1074kWh; heat storage capacity of a single phase change heat storage unit = 250kJ / kg × 3 m³ 3 ×1200kg / m 3 =250kWh, so 5 units need to be started (total heat storage capacity 1250kWh), and the heat storage power is set to 135kW (to ensure completion in 8 hours).

[0037] 2. Thermal storage mode phase (off-peak electricity hours, 22:00 - 6:00 the next day) At 22:00, the intelligent control system issued the following command: start the electric heating device (power 135kW) and the thermal storage circulation pump (frequency 50Hz, flow rate 30 m³ / h). 3 / h), open the heat storage circuit valve and close the heat release circuit valve; The electric heating device heats the heat transfer oil to 95°C. The high-temperature heat transfer oil enters the phase change heat storage unit through the spiral coil and exchanges heat with the phase change material. The temperature of the phase change material gradually rises from 55°C (sensible heat stage). At 0:30 the next day, the material temperature reached 72℃ (close to the phase transition temperature, with a difference of 3℃), and the power dropped to 55% (transition stage). At 1:00 AM the next day, the material temperature reached 75°C, entering the phase change stage (melting). The temperature remained constant, the power increased to 80%, and it continued to absorb latent heat (which is consistent with the "constant temperature heat storage" characteristic of phase change materials). At 5:30 the next day, the phase change material completely melted and the temperature rose to 80°C (the set upper limit). The intelligent control system detected "heat storage saturation", shut down the electric heating device and the heat storage circulation pump, the heat storage mode ended, and the system entered the heat preservation mode.

[0038] 3. Heat preservation mode phase (initial period outside off-peak electricity hours, 6:00-8:00 the next day) The phase change thermal storage unit maintains the temperature through a nano-aerogel insulation layer, and the sensor monitors the temperature change in real time (data is collected once every 5 minutes). The following day at 7:00 AM, the outdoor temperature dropped to -10℃, and the electric heat tracing device (500W / m²) was activated. 2The material temperature is stabilized at 78℃ (within the allowable range); if the heating is not activated, the temperature will drop to 72℃, and the electric heating device needs to be activated at low power (20kW) to compensate for heat loss (in accordance with the conventional theory of "heat loss control").

[0039] 4. Heat release mode phase (heating period outside of off-peak electricity hours, 8:00-18:00 the following day) The following day at 8:00 AM, office staff arrived at their posts, and the room temperature dropped to 19°C (1°C below the set value). The system then activated the heat dissipation circulation pump (40Hz, 25 m³ / h). 2 / h), plate heat exchanger (heat exchange area 2 m²) 2 Open the venting valve; The 78°C heat transfer oil in the phase change heat storage unit enters the primary side of the plate heat exchanger and exchanges heat with the user's heating return water (45°C) on the secondary side. The secondary side water temperature rises to 65°C and is sent into the room through the fan coil unit. At 12:00 the following day, the outdoor temperature rose to 5℃, solar radiation heat gain increased, and the room temperature rose to 21℃ (1℃ higher than the set value). The system reduced the circulation pump frequency to 30Hz (18 m). 3 / h), adjust the valve opening to 60% (reduce the heat release rate, in line with the theory of "dynamically adapting to heat demand"); At 17:00 the next day, the outdoor temperature dropped to -2℃, solar radiation weakened, and the room temperature dropped to 19.5℃. The system increased the circulation pump frequency to 45Hz and opened all valves to ensure stable room temperature. At 18:00 the next day, the office building closed for the day, and the indoor temperature of the users was maintained at 20℃. The system shut down the heat release circulation pump and valves, and the heat release mode ended. The phase change heat storage unit had a remaining temperature of 65℃ (not fully released, reserved for preheating the next morning).

[0040] 5. Feedback and optimization phase (18:00-20:00 daily) The daily heat storage efficiency (93.5%), heat release temperature stability (fluctuation ±0.8℃), and user room temperature data are fed back to the strategy generation module. Because the solar radiation heat gain on that day was higher than predicted, the actual heat load was lower than expected (90kW). The heat storage power was adjusted to 120kW the next day, and 4 heat storage units were started to avoid excessive heat storage (in line with the conventional control theory of "iterative optimization").

[0041] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials, characterized in that, include: Electric heating devices are used to convert electrical energy into heat energy during off-peak electricity hours. A phase change thermal energy storage unit is connected to the electric heating device and is used to store thermal energy; A heat exchange component connects the phase change heat storage unit to the user's heating system to achieve heat transfer; User heating systems are used to provide heating heat to users. The intelligent control system is connected to the electric heating device, phase change heat storage unit, heat exchange components and user heating system, and is used to generate and execute heat storage and release strategies.

2. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, The electric heating device is an electric heating tube or an electrode boiler.

3. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, The phase change heat storage unit includes a heat storage shell, the inner cavity of which is filled with a phase change material; a heat exchange pipeline is arranged in the inner cavity of the heat storage shell and is embedded in the phase change material; the heat exchange medium port of the heat exchange pipeline is connected to an electric heating device, and the heat supply medium port of the heat exchange pipeline is connected to a heat exchange assembly.

4. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 3, characterized in that, The heat exchange pipeline is a spiral tube or a finned tube.

5. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, The heat exchange assembly includes a plate heat exchanger, the primary port of which is connected to a phase change heat storage unit, and the secondary port of which is connected to the user's heating system.

6. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, A circulation pump is installed on the connecting pipe between the heat exchange component and the user's heating system.

7. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, An electrically adjustable valve is installed on the connecting pipe between the heat exchange component and the user's heating system.

8. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, The intelligent control system includes: The data acquisition unit is used to collect signals, temperature data, weather forecasts, and equipment operating parameters during off-peak electricity hours. The strategy generation module generates heat storage duration, heat release rate, and equipment control commands based on a timing control algorithm. The execution control module is used to control the operating status of the electric heating device, circulating pump, and electric regulating valve.

9. A nighttime off-peak electricity thermal storage heating system based on phase change thermal storage materials according to claim 1, characterized in that, The user's heating system is either underfloor heating or a fan coil system.

10. A method for nighttime off-peak electricity storage and heating based on phase change thermal storage materials, characterized in that, Includes the following steps: Acquire off-peak electricity hours, meteorological data, and user temperature settings; During off-peak electricity hours, the electric heating device is activated to store heat in the phase change heat storage unit; During off-peak hours, the heat release process is initiated based on the user's heat demand, and heat is supplied to the user's heating system through heat exchange components; Real-time monitoring of system status and feedback to optimize heat storage and release strategies.