Phase change heat storage device based on low-cost high-density mixed paraffin heat storage material and heat pump electricity storage system

Abstract

The invention discloses a phase change heat storage device based on a low-cost high-density mixed paraffin heat storage material and a heat pump electricity storage system.The phase change heat storage device comprises fins, a coil pipe and a phase change material, the coil pipe is of a single-loop structure, and the fins are annularly, evenly and densely distributed on the outer wall of the coil pipe; gaps between the outer wall of the coil pipe and the fins are filled with the phase-change materials. According to the heat pump electricity storage system, low-grade waste heat is improved into high-temperature heat through the high-temperature heat pump, then the heat is obtained through pressurized water, then the heat enters a coil pipe of the phase change heat storage device, the heat is transmitted into a mixed paraffin layer attached to fins, and the heat storage process is achieved; and the heat energy is taken out by the pressurized water and supplied to an organic Rankine cycle for power generation. According to the invention, low-cost, high-density and long-term stable heat storage is realized, so that electricity-heat-electricity storage and conversion are realized, and a guarantee is provided for large-scale application of a heat pump electricity storage system.

Description

Technical Field

[0001] The present invention relates to the field of heat storage technology, and in particular to a phase change heat storage device and a heat pump power storage system based on a low-cost and high-density mixed paraffin heat storage material. Background Art

[0002] At present, the proportion of renewable energy generation continues to increase, but due to its intermittent and volatile characteristics, the problem of power consumption is becoming increasingly prominent. At the same time, the mismatch between source and load also puts higher requirements on the peak and frequency regulation of the power grid. Energy storage technology, especially heat and electricity storage technology, has become the key to solving these problems.

[0003] At present, pumped storage is the most widely used energy storage technology in the world, with a cumulative installed capacity of about 86%. Pumped storage has the advantages of high efficiency, long life, large capacity, and low cost per kilowatt-hour, but it also faces challenges such as long construction period, high investment cost, large environmental impact, and strict requirements on geographical and geological conditions. The cumulative installed capacity of lithium-ion batteries accounts for about 11%, and they are known for their high energy storage efficiency, short construction period, high energy density and fast response speed, but they have problems such as high cost per kilowatt-hour, short life and safety hazards. Other new energy storage technologies, including sodium-sulfur batteries, flow batteries, compressed air energy storage, liquid air energy storage and molten salt heat storage, are still in the research and development and demonstration stage, and have not yet been applied on a large scale in commercial applications, nor can they meet the needs of high-density, low-cost and long-term energy storage at the same time.

[0004] As an emerging energy storage technology, heat pump power storage is centered on the conversion of "electricity-heat-electricity". With the help of the intermediate process of heat storage, it has the advantages of no geographical restrictions, safe and reliable, and long-term energy storage. Existing heat storage technologies are mainly divided into sensible heat storage technology, latent heat (phase change) heat storage technology, and thermochemical heat storage technology. Sensible heat storage technology is the most mature, with simple operation, low cost, long service life, high thermal conductivity, but its heat storage capacity is small and the temperature is not constant during heat release, which limits its future application prospects. The energy storage density of thermochemical reaction heat storage is higher than that of sensible heat storage and phase change heat storage, but the application technology and process are too complex and there are many uncertainties, such as harsh reaction conditions, difficult to achieve, short life of energy storage system, high corrosion of energy storage materials to equipment, large one-time investment and low efficiency. In comparison, phase change heat storage has the advantages of high heat storage density per unit volume, and has large energy absorption and release within the phase change temperature range, and a narrow storage and release temperature range, which is conducive to temperature stability during the heat charging and heat release process. However, the existing phase change heat storage technology has an imbalance between the operating temperature range and material cost. Most phase change materials have a low operating temperature range (less than 100°C) and are highly substitutable, thus having a low cost. As the operating temperature increases, the cost will also increase. Summary of the invention

[0005] The object of the present invention is to provide a phase change heat storage device and a heat pump energy storage system based on a low-cost and high-density mixed paraffin heat storage material, so as to effectively solve the problems of low heat storage density, high cost and instability of the heat pump energy storage system, thereby achieving long-term high-efficiency and low-cost high-density heat storage.

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions: In the first aspect, the present invention provides a phase change heat storage device based on a low-cost and high-density mixed paraffin heat storage material, including: fins, coiled pipes and phase change materials; The coiled pipe has a single-loop structure, the fins and the coiled pipe are integrally welded, and the fins are densely distributed in a ring shape on the outer wall of the coiled pipe; The phase change material fills the gap between the outer wall of the coiled pipe and the fins.

[0007] Preferably, the outermost sides at the inlet and outlet of the coiled pipe are long external threads, and a sealing structure is provided on the long external threads, and the sealing structure is a hexagonal nut, a stainless steel washer and a high-temperature resistant rubber washer arranged in sequence.

[0008] Preferably, there are two groups of the sealing structures, which are symmetrically distributed on the long external threads.

[0009] Preferably, the fins, the coiled pipes and the hexagonal nuts are all made of stainless steel.

[0010] Preferably, the phase change material is mixed paraffin, the phase change temperature is 110 - 120 °C, and the heat storage density is 250 kJ / kg.

[0011] In the second aspect, the present invention provides a heat pump energy storage system based on a low-cost and high-density mixed paraffin heat storage material, including: a high-temperature heat pump cycle, a phase change heat storage device and an organic Rankine cycle; The high-temperature heat pump cycle is used to absorb heat from a low-grade heat source, convert the low-grade heat into high-temperature heat through a compressor, exchange heat through a condenser, and send it to a phase change heat exchanger to store the heat in the phase change heat exchanger, realizing electro-thermal conversion; The phase change heat storage device is the above-mentioned phase change heat storage device based on a low-cost and high-density mixed paraffin heat storage material; The organic Rankine cycle is used to convert the thermal energy stored in the phase change heat storage device into electrical energy, realizing thermal-electric conversion.

[0012] Preferably, the high-temperature heat pump cycle includes a first evaporator, a compressor, a first condenser and a throttle valve. The cold-side working fluid inlet of the first evaporator is connected to the outlet of the throttle valve, the inlet of the throttle valve is connected to the hot-side working fluid outlet of the first condenser, the hot-side inlet of the first condenser is connected to the outlet of the compressor, and the inlet of the compressor is connected to the cold-side working fluid outlet of the first evaporator; The organic Rankine cycle includes an expander, a second condenser, a working fluid pump, and a second evaporator. The cold-side working fluid inlet of the second evaporator is connected to the outlet of the working fluid pump. The inlet of the working fluid pump is connected to the hot-side working fluid outlet of the second condenser. The hot-side working fluid inlet of the second condenser is connected to the outlet of the expander. The inlet of the expander is connected to the cold-side working fluid outlet of the second evaporator; The cold-side outlet of the first condenser is connected to the left pipe orifice of the phase change heat exchanger. The right pipe orifice of the phase change heat exchanger is connected to the cold-side inlet of the first condenser. The hot-side outlet of the second evaporator is connected to the right pipe orifice of the phase change heat exchanger. The left pipe orifice of the phase change heat exchanger is connected to the hot-side inlet of the second evaporator.

[0013] Preferably, a first valve is provided on the connecting pipe between the cold-side outlet of the first condenser and the left pipe orifice of the phase change heat exchanger. A fourth valve is provided on the connecting pipe between the right pipe orifice of the phase change heat exchanger and the cold-side inlet of the first condenser. A third valve is provided on the connecting pipe between the hot-side outlet of the second evaporator and the right pipe orifice of the phase change heat exchanger. A second valve is provided on the connecting pipe between the left pipe orifice of the phase change heat exchanger and the hot-side inlet of the second evaporator.

[0014] Preferably, during charging, the first valve and the fourth valve of the heat pump energy storage system are opened, and the second valve and the third valve are closed; During discharging, the first valve and the fourth valve of the heat pump energy storage system are closed, and the second valve and the third valve are opened.

[0015] Preferably, the low-grade heat source includes solar thermal energy, geothermal energy, and industrial waste heat. The electric power includes valley electricity, green electricity (such as wind power, photovoltaic power, and hydropower).

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention uses a phase change heat storage device as the core heat storage component and a phase change material mixed with paraffin as the heat storage material. The former has a simple structure, a large heat exchange area, and a long heat exchange time. The latter has a high heat storage density and a low price. The combined effect of the two realizes the low-cost, high-density, and long-term stable storage of electric energy, effectively solving the problems of new energy consumption and power grid peak shaving and frequency modulation. The mixed paraffin proposed by the present invention can operate in the medium temperature range, ensuring the phase change latent heat while having a low price, which has great advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic internal structure diagram of a phase change heat storage device based on a low-cost and high-density mixed paraffin heat storage material provided by an embodiment of the present invention; Figure 2It is a schematic external structure view in the A direction of a phase change heat storage device based on a low-cost and high-density mixed paraffin heat storage material provided by an embodiment of the present invention; Figure 3 It is a schematic layout view of a heat pump electricity storage system based on a low-cost and high-density mixed paraffin heat storage material provided by an embodiment of the present invention.

[0018] Among them, 1 is a phase change heat storage device; 1-1 is a fin; 1-2 is a coil; 1-3 is a hexagon nut; 1-4 is a stainless steel washer; 1-5 is a high-temperature resistant rubber washer; 1-6 is a long external thread; 1-7 is a mixed paraffin; 2 is a first valve; 3 is a second valve; 4 is a third valve; 5 is a fourth valve; 6 is a compressor; 7 is a first condenser; 8 is a throttle valve; 9 is a first evaporator; 10 is an expander; 11 is a second condenser; 12 is a working fluid pump; 13 is a second evaporator. Specific embodiments

[0019] Next, the specific embodiments of the present invention will be further described in detail in conjunction with the drawings and embodiments. The embodiments described below with reference to the drawings are illustrative and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0020] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "end", "bottom", "side", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, so it should not be construed as limiting the present invention.

[0021] In the present invention, unless otherwise clearly defined and limited, terms such as "connection" and "installation" should be understood in a broad sense. For example, it can be a fixed connection, a direct connection, or a connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Secondly, the "one embodiment" or "embodiment" referred to in the present invention means a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments.

[0023] Next, the specific embodiments of the present invention will be further described in detail in conjunction with the drawings. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0024] The first embodiment of the present invention provides a phase change heat storage device based on a low-cost and high-density mixed paraffin heat storage material, and its structure is asFigure 1 and Figure 2 As shown in Figure 2 , it specifically includes: fin 1-1, coiled pipe 1-2, hexagonal nut 1-3, stainless steel washer 1-4, high-temperature resistant rubber washer 1-5, long external thread 1-6, and composite paraffin 1-7.

[0025] Specifically, the coiled pipe 1-2 has a single-loop structure, with pressurized water entering and leaving singlely, saving equipment costs while increasing the heat exchange area; The fin 1-1 and the coiled pipe 1-2 are integrally welded. The fins 1-1 are densely distributed in a ring shape on the outer wall of the coiled pipe 1-2, thereby prolonging the heat exchange time between the pressurized water and the composite paraffin; The outermost sides at the inlet and outlet of the coiled pipe 1-2 are long external threads 1-6, and the hexagonal nut 1-3, stainless steel washer 1-4, and high-temperature resistant rubber washer 1-5 are fixed on the long external thread 1-6.

[0026] It should be noted that there are two sets of the hexagonal nut 1-3, stainless steel washer 1-4, and high-temperature resistant rubber washer 1-5, which are symmetrically distributed on the long external thread 1-6.

[0027] The phase change material fills the gap between the outer wall of the coiled pipe 1-2 and the fins 1-1 to achieve better heat exchange.

[0028] In the embodiment of the present invention, the fins 1-1, coiled pipe 1-2, and hexagonal nut 1-3 are all made of stainless steel.

[0029] In the embodiment of the present invention, the phase change material is composite paraffin 1-7, whose phase change temperature is 110 - 120 °C and the heat storage density is 250 kJ / kg.

[0030] The second embodiment of the present invention provides a heat pump electricity storage system based on a low-cost and high-density composite paraffin heat storage material. Refer to Figure 3 , which includes: low-grade heat source, high-temperature heat pump cycle, phase change heat storage device, and organic Rankine cycle.

[0031] In the embodiment of the present invention, the high-temperature heat pump cycle is used to absorb heat from the low-grade heat source, and then convert the low-grade heat into high-temperature heat through a compressor. After heat exchange in the condenser, it is sent to the phase change heat exchanger to store the heat in the phase change heat exchanger, realizing the conversion of electricity to heat.

[0032] In the embodiment of the present invention, the phase change heat exchanger is the phase change heat exchanger provided in the above first embodiment.

[0033] In the embodiment of the present invention, the organic Rankine cycle is used to convert the thermal energy stored in the phase change heat storage device into electrical energy to achieve the conversion of heat to electricity.

[0034] Refer to Figure 3, in one embodiment, the high-temperature heat pump cycle includes a first evaporator 9, a compressor 6, a first condenser 7, and a throttle valve 8. The cold-side (working fluid) inlet of the first evaporator 9 is connected to the outlet of the throttle valve 8, the inlet of the throttle valve 8 is connected to the hot-side (working fluid) outlet of the first condenser 7, the hot-side inlet of the first condenser 7 is connected to the outlet of the compressor 6, and the inlet of the compressor 6 is connected to the cold-side (working fluid) outlet of the first evaporator 9.

[0035] See Figure 3 , in one embodiment, the organic Rankine cycle includes an expander 10, a second condenser 11, a working fluid pump 12, and a second evaporator 13. The cold-side (working fluid) inlet of the second evaporator 13 is connected to the outlet of the working fluid pump 12, the inlet of the working fluid pump 12 is connected to the hot-side (working fluid) outlet of the second condenser 11, the hot-side (working fluid) inlet of the second condenser 11 is connected to the outlet of the expander 10, and the inlet of the expander 10 is connected to the cold-side (working fluid) outlet of the second evaporator 13.

[0036] The cold-side (pressurized water) outlet of the first condenser 7 is connected to the left pipe orifice of the phase change heat exchanger 1, the right pipe orifice of the phase change heat exchanger 1 is connected to the cold-side inlet of the first condenser 7, the hot-side outlet of the second evaporator 13 is connected to the right pipe orifice of the phase change heat exchanger 1, and the left pipe orifice of the phase change heat exchanger 1 is connected to the hot-side inlet of the second evaporator 13.

[0037] Further, a first valve 2 is provided on the connecting pipe between the cold-side (pressurized water) outlet of the first condenser 7 and the left pipe orifice of the phase change heat exchanger 1, and a fourth valve 5 is provided on the connecting pipe between the right pipe orifice of the phase change heat exchanger 1 and the cold-side inlet of the first condenser 7. A third valve 4 is provided on the connecting pipe between the hot-side (pressurized water) outlet of the second evaporator 13 and the right pipe orifice of the phase change heat exchanger 1, and a second valve 3 is provided on the connecting pipe between the left pipe orifice of the phase change heat exchanger 1 and the hot-side (pressurized water) inlet of the second evaporator 13.

[0038] The working process of the above heat pump energy storage system includes: opening the first valve 2 and the fourth valve 5, closing the second valve 3 and the third valve 4, and the phase change heat storage device 1 is in the heat storage process; during heat storage, the low-temperature pressurized water flows through the first condenser 7 to obtain high-temperature heat and stores it in the phase change heat storage device 1; closing the first valve 2 and the fourth valve 5, opening the second valve 3 and the third valve 4, and the phase change heat storage device 1 is in the heat release process; during heat release, the low-temperature pressurized water transfers the high-temperature heat in the phase change heat storage device 1 to the organic Rankine cycle.

[0039] The specific implementation process is as follows: As Figure 3As shown, open the first valve 2 and the fourth valve 5, and close the second valve 3 and the third valve 4. At this time, it is the charging process. The low-temperature working fluid flows through the first evaporator 9, absorbs heat from the low-grade heat source, and then the compressor 6 driven by electricity boosts the low-temperature working fluid to a high-temperature working fluid. Then it flows through the first condenser 7 to exchange heat with the low-temperature pressurized water. The heated pressurized water enters the phase change heat exchanger 1 and exchanges heat with the phase change material (mixed paraffin) to achieve high-temperature heat storage. After releasing heat, the pressurized water flows out of the phase change heat exchanger 1 and then enters the first condenser 7 again to absorb heat. This cycle repeats. After the working fluid releases heat, it flows through the throttle valve 8 and then enters the first evaporator 9 again to absorb heat.

[0040] As Figure 3 As shown, open the second valve 3 and the third valve 4, and close the first valve 2 and the fourth valve 5. At this time, it is the discharging process. The low-temperature pressurized water enters the phase change heat exchanger 1 and absorbs heat from the phase change material (mixed paraffin). Then it flows through the second evaporator 13 to exchange heat with the low-temperature working fluid. After releasing heat, the pressurized water enters the phase change heat exchanger 1 again to cycle and extract heat. The heated working fluid generates electricity externally through the expander 10. After discharging, the working fluid enters the second condenser 11 to be cooled by the cooling water. The cooled working fluid flows through the working fluid pump 12 and then is pumped into the second evaporator 13 to absorb heat again. This cycle repeats.

[0041] It should be noted that the low-grade heat source includes solar thermal, geothermal, and industrial waste heat (industrial waste gas, wastewater, etc.), and the electricity includes valley electricity, green electricity (wind power, photovoltaic power, hydropower, etc.).

[0042] Enlightened by the ideal embodiments of the present invention described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A phase change heat storage device based on low-cost and high-density mixed paraffin heat storage material, characterized in that: include: fins, coils, and phase change materials; The coil is a single-circuit structure, the fins and the coil are welded into an integral structure, and the fins are densely distributed in a ring shape on the outer wall of the coil; The phase change material fills the gap between the outer wall of the coil and the fin.

2. A phase change heat storage device based on low-cost and high-density mixed paraffin heat storage material according to claim 1, characterized in that: The outermost side of the coil inlet and outlet is a long external thread, and a sealing structure is arranged on the long external thread. The sealing structure is a hexagonal nut, a stainless steel washer and a high-temperature resistant rubber washer arranged in sequence.

3. A phase change heat storage device based on low-cost and high-density mixed paraffin heat storage material according to claim 2, characterized in that: The sealing structure has two groups, which are symmetrically distributed on the long external thread.

4. A phase change heat storage device based on low-cost and high-density mixed paraffin heat storage material according to claim 3, characterized in that: The fins, coils and hexagonal nuts are all made of stainless steel.

5. A phase change heat storage device based on low-cost and high-density mixed paraffin heat storage material according to claim 1, characterized in that: The phase change material is mixed paraffin, the phase change temperature is 110-120° C., and the heat storage density is 250 kJ / kg.

6. A heat pump power storage system based on low-cost, high-density mixed paraffin heat storage material, characterized in that: include: High temperature heat pump cycles, phase change thermal storage and organic Rankine cycles; The high-temperature heat pump cycle is used to absorb heat from a low-grade heat source, convert the low-grade heat into high-temperature heat through a compressor, exchange heat through a condenser, and send the heat into a phase-change heat exchanger to store the heat in the phase-change heat exchanger to achieve electrical-thermal conversion; The phase change heat storage device is a phase change heat storage device based on a low-cost, high-density mixed paraffin heat storage material as claimed in any one of claims 1 to 5; The organic Rankine cycle is used to convert the thermal energy stored in the phase change heat storage device into electrical energy, thereby realizing heat-electricity conversion.

7. A heat pump power storage system based on low-cost and high-density mixed paraffin heat storage material according to claim 6, characterized in that: The high-temperature heat pump cycle comprises a first evaporator, a compressor, a first condenser and a throttle valve, wherein the cold-side working medium inlet of the first evaporator is connected to the throttle valve outlet, the throttle valve inlet is connected to the hot-side working medium outlet of the first condenser, the hot-side inlet of the first condenser is connected to the compressor outlet, and the compressor inlet is connected to the cold-side working medium outlet of the first evaporator; The organic Rankine cycle comprises an expander, a second condenser, a working fluid pump and a second evaporator, the cold side working fluid inlet of the second evaporator is connected to the outlet of the working fluid pump, the working fluid pump inlet is connected to the hot side working fluid outlet of the second condenser, the hot side working fluid inlet of the second condenser is connected to the outlet of the expander, and the inlet of the expander is connected to the cold side working fluid outlet of the second evaporator; The cold side outlet of the first condenser is connected to the left pipe mouth of the phase change heat exchanger, the right pipe mouth of the phase change heat exchanger is connected to the cold side inlet of the first condenser, the hot side outlet of the second evaporator is connected to the right pipe mouth of the phase change heat exchanger, and the left pipe mouth of the phase change heat exchanger is connected to the hot side inlet of the second evaporator.

8. A heat pump power storage system based on low-cost and high-density mixed paraffin heat storage material according to claim 7, characterized in that: A valve No. 1 is provided on the connecting pipe between the cold side outlet of the first condenser and the left pipe outlet of the phase change heat exchanger, a valve No. 4 is provided on the connecting pipe between the right pipe outlet of the phase change heat exchanger and the cold side inlet of the first condenser, a valve No. 3 is provided on the connecting pipe between the hot side outlet of the second evaporator and the right pipe outlet of the phase change heat exchanger, and a valve No. 2 is provided on the connecting pipe between the left pipe outlet of the phase change heat exchanger and the hot side inlet of the second evaporator.

9. A heat pump power storage system based on low-cost and high-density mixed paraffin heat storage material according to claim 8, characterized in that: When charging, open valve No. 1 and valve No. 4 of the heat pump power storage system, and close valve No. 2 and valve No. 3; When discharging, the No. 1 valve and the No. 4 valve of the heat pump power storage system are closed, and the No. 2 valve and the No. 3 valve are opened.

10. A heat pump power storage system based on low-cost and high-density mixed paraffin heat storage material according to claim 6, characterized in that: The low-grade heat sources include solar heat, geothermal heat and industrial waste heat.

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