A high-efficiency energy storage system and energy storage method with a cold water heat pump unit and an electric heater

Abstract

The application discloses a high-efficiency energy storage system and method with a cold water heat pump unit and electric heating, wherein the energy storage system comprises a liquid storage tank, a cold water heat pump unit, a cold / heat load and a valve unit; the liquid storage tank is provided with an auxiliary electric heater, the electric heater is heated by surplus power of renewable energy; the valve unit is used for controlling the liquid storage tank to be communicated with the cold / heat load pipeline, the liquid storage tank to be communicated with the cold water heat pump unit evaporator pipeline, the cold water heat pump unit evaporator to be communicated with external cold water or low-temperature heat source water pipeline, the cold water heat pump unit evaporator to be communicated with the cold / heat load pipeline, the cold water heat pump unit condenser to be communicated with the cold / heat load pipeline and the cold water heat pump unit condenser to be communicated with external cooling water pipeline in different modes. The application combines direct heat release of heat storage and heat pump heat release, significantly increases the capacity of heat storage, and has both heat storage and cold storage functions.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a high-efficiency energy storage system and method with a chilled water heat pump unit and electric heating. Background Technology

[0002] The proportion of renewable electricity generated globally, such as solar and wind power, is increasing. However, these sources are affected by weather, seasons, climate, and day / night cycles, making it difficult to provide continuous and stable power. Therefore, they often require the use of energy storage. While various energy storage solutions exist, including pumped-storage hydroelectric power plants, batteries, and compressed air, their costs remain high, and they are limited by site and resource constraints. Furthermore, their storage capacity is insufficient to meet the growing demand for energy storage from renewable energy sources like solar and wind power. Relying solely on supply-side energy storage is far from enough to provide a sufficiently stable power supply to society; the energy storage gap is enormous and even, to some extent, restricts the development of new energy sources.

[0003] Developing demand-side energy storage is a crucial solution. Building heating and cooling account for over 15% of total social energy consumption, and during severe weather, heating and cooling loads can exceed 50% of the grid load. Furthermore, building heating and cooling loads are inherently volatile, leading to significant fluctuations in grid load and severely impacting power security and economic operation.

[0004] If the excess electricity generated during off-peak hours (i.e., valley hours) from photovoltaic and wind power is converted into cooling and heating energy for air conditioning and stored, it avoids the curtailment of renewable energy sources, supporting the efficient operation and development of renewable energy. During periods of power shortage (peak hours), the stored energy can be used. Through demand-side energy storage and peak-shaving, people's needs for cooling and heating can be met, supporting the stable operation of the power grid.

[0005] There are many existing methods for air conditioning energy storage, including methods for storing hot water and cold water. However, traditional methods for storing hot water have low energy density because the supply water temperature for heating is generally required to be above 45℃ and the return water temperature 40℃, otherwise the comfort of heating cannot be adequately met. If the initial hot water temperature is 80℃ and the return water temperature is 40℃, the effective energy storage temperature difference is only 40℃.

[0006] Traditional cold storage primarily uses ice storage (i.e., cold energy storage) or chilled water storage. Because the refrigeration system requires a relatively low supply water temperature of 7°C, while water's freezing point is 0°C, theoretically there's only a 7°C temperature difference. In practice, to prevent pipe freezing, the water temperature is difficult to drop below 2°C, leaving only a usable temperature difference of 5°C for cold storage. Even if the supply water temperature is increased to 12°C (higher temperatures severely impact refrigeration efficiency), the usable temperature difference for cold storage is only 10°C. Therefore, traditional chilled water storage has a very low energy density. Ice has a high heat of fusion, resulting in higher energy density for ice storage. Ice storage typically uses ice balls with a polymer shell and antifreeze, leading to significant equipment investment. The ice ball shell has low heat transfer efficiency, and the ice ball and unit exchange heat secondaryly through the antifreeze, requiring a larger temperature difference for heat transfer—meaning the refrigeration temperature must be significantly lower than the freezing point. Therefore, the unit's refrigeration efficiency is lower than that of chilled water. Furthermore, ice ball storage systems cannot be used for thermal storage due to the heat resistance issues of the shell material.

[0007] Therefore, this invention combines a cold water and hot water energy storage device and a heating device with a high-efficiency cold water heat pump unit to design a high-efficiency off-peak electricity energy storage system with a high-efficiency cold water heat pump unit and electric heating. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a high-efficiency energy storage system and energy storage method that utilizes off-peak electricity, has a large heat storage capacity, and integrates a chilled water heat pump unit and electric heating.

[0009] The technical solution of this invention is: This invention discloses a high-efficiency energy storage system with a chilled water heat pump unit and electric heating, comprising a storage tank, a chilled water heat pump unit, a cooling / heating load, and a valve unit; characterized in that the storage tank is equipped with an electric heater, which is heated by surplus electricity (off-peak electricity) from renewable energy sources; the valve unit is used to control the connection between the storage tank and the cooling / heating load pipeline, the connection between the storage tank and the evaporator pipeline of the chilled water heat pump unit, the connection between the evaporator of the chilled water heat pump unit and the external chilled water or low-temperature heat source water pipeline, the connection between the evaporator of the chilled water heat pump unit and the cooling / heating load pipeline, the connection between the condenser of the chilled water heat pump unit and the cooling / heating load pipeline, and the connection between the condenser of the chilled water heat pump unit and the external cooling water pipeline in different modes.

[0010] Furthermore, the valve unit is used for: During the heat storage phase, the control liquid storage tank is connected to the cold / heat load pipeline, while the chilled water heat pump unit is disconnected; or the control liquid storage tank is connected to the low-temperature heat source water pipeline and the control liquid heat pump unit condenser is connected to the cold / heat load pipeline, while the control liquid storage tank is disconnected for independent heat storage. During the stage of flat-electricity heating, the heating is controlled by the chilled water heat pump unit or the heat is directly released by the liquid storage tank. During peak electricity heating, heat is released in two stages using a storage tank: —During the direct heat release stage, the cold / heat load pipelines of the storage tank are connected, and the chilled water heat pump unit is disconnected from both, so that the storage tank can directly release heat. —During the heat pump's heat release phase, control the connection between the liquid storage tank and the evaporator pipeline of the chilled water heat pump unit, and control the connection between the condenser of the chilled water heat pump unit and the cold / heat load pipeline.

[0011] Furthermore, the valve unit is also used for: During the cold storage phase, the connection between the liquid storage tank and the evaporator pipeline of the chilled water heat pump unit is controlled, as is the connection between the condenser of the chilled water heat pump unit and the external cooling water pipeline; the cold / heat load is in a disconnected state. During the power supply cooling phase, the evaporator of the chilled water heat pump unit is connected to the cold / heat load pipeline, and the condenser of the chilled water heat pump unit is connected to the external cooling water pipeline, while the liquid storage tank is disconnected. During peak power cooling phases, the liquid storage tank is connected to the cold / heat load pipelines, and the chilled water heat pump unit is disconnected.

[0012] Furthermore, the valve unit includes multiple valves and multiple valve groups; each valve is located on the liquid output pipeline and return pipeline of the liquid storage tank; the multiple valve groups are used to control the connection or disconnection between the evaporator and the liquid storage tank pipeline of the chilled water heat pump unit, the external chilled water or low-temperature heat source water pipeline, and the cold / heat load pipeline; they are also used to control the connection or disconnection between the condenser of the chilled water heat pump unit and the cold / heat load pipeline and the external cooling water pipeline.

[0013] Furthermore, the storage tank is provided with a first outlet, a second outlet, and a return outlet. The first outlet and the second outlet are respectively located at the upper and lower parts of the storage tank; the return outlet is located at the lower part of the storage tank; the valve unit includes at least four valves, namely the first valve to the fourth valve; the second outlet is divided into two branches after passing through the first valve, one branch is connected to the first delivery pump and the second valve in sequence; the other branch is connected to the third valve via a pipeline; the output end of the first delivery pump is also divided into two branches, one branch is connected to the return outlet pipeline of the storage tank via the fourth valve, and the other branch is connected to the second valve via a pipeline; the first valve to the fourth valve, the first delivery pump, and the pipeline constitute a bidirectional delivery structure.

[0014] Furthermore, the valve unit includes at least four valve groups, namely the first valve group to the fourth valve group; the first valve group is divided into four branches, one branch is connected to the first outlet of the storage tank via a pipeline, the second branch is connected to cold water (for cooling) or low-temperature heat source water (for heat pump heating), the third branch is connected to the second valve group via a pipeline, and the fourth branch is connected to the inlet of the evaporator of the cold water heat pump unit via a pipeline; the third valve group is divided into four branches, one branch is connected to the common node of the second and third valves via a pipeline; the second branch is connected to the output end of the third delivery pump via a pipeline, and together with the second branch of the first valve group, it is connected to the low-temperature heat source water system to form a circulation system; the third branch is connected to the... The fourth valve group is connected, and its fourth branch is connected to the outlet of the evaporator of the chilled water heat pump unit via a pipeline. The second valve group is divided into four branches: one branch is connected to the first valve group via a pipeline; the second branch is connected to external cooling water (during cooling); the third branch is connected to the cold / heat load (during heat pump heating) via a pipeline; and the fourth branch is connected to the outlet of the condenser of the chilled water heat pump unit via a pipeline. The fourth valve group is divided into four branches: one branch is connected to the third valve group via a pipeline; the second branch is connected to the input end of the second delivery pump via a pipeline, and together with the second branch of the second valve group, it is connected to the cooling tower; the third branch is connected to the cold / heat load via a pipeline; and the fourth branch is connected to the inlet of the condenser of the chilled water heat pump unit via a pipeline.

[0015] Furthermore, the inner liner of the liquid storage tank is provided with at least two heat insulation layers. The inner layer is a high-temperature resistant heat insulation material (such as rock wool, mineral wool, glass wool), and the outer layer is a closed-cell structure heat insulation and cold insulation material that can prevent water vapor from entering and condensing (such as rubber and plastic heat insulation foam board, polyurethane foam layer). The two heat insulation layers together constitute a heat insulation and cold insulation layer.

[0016] Furthermore, the energy storage medium in the storage tank contains corrosion inhibitors and / or antifreeze. Corrosion inhibitors can prevent corrosion and scale formation in the water system pipelines, maintain heat transfer efficiency, and extend equipment life; antifreeze can lower the freezing point of the liquid, expand the cold storage temperature range, and thus increase the cold storage capacity.

[0017] The corrosion inhibitor formulation is as follows: borax 0.01-1%, benzotriazole 0.001-0.2%, sodium benzoate 0.1-2%, and parabens 0.001-0.1%. The optimal formulation is: borax 0.1-0.5%, benzotriazole 0.002-0.01%, sodium benzoate 0.2-0.5%, and parabens 0.01-0.05%.

[0018] The antifreeze formulation is as follows: 10-40% alcohols (at least one of ethylene glycol, methanol, ethanol, and propylene glycol), 0.01-1% borax, 0.001-0.2% benzotriazole, 0.1-2% sodium benzoate, and 0.001-0.1% parabens. The optimal formulation is: 15-30% alcohols, 0.1-0.5% borax, 0.002-0.01% benzotriazole, 0.2-0.5% sodium benzoate, and 0.01-0.05% parabens.

[0019] One aspect of this invention is an energy storage method for a high-efficiency energy storage system with a chilled water heat pump unit and electric heating, comprising a heat storage / heat release control method, specifically: Thermal storage stage: The surplus electricity from renewable energy sources is used to heat the energy storage medium in the storage tank; or during the thermal storage stage, the storage tank is directly supplied with heat to the cold / heat load by adjusting various valves and valve groups; or while the storage tank is storing heat, the chilled water heat pump unit is controlled to supply heat independently, that is, the chilled water heat pump unit evaporator is connected to the low-temperature heat source water system pipeline, and the heat from the low-temperature heat source water is absorbed through the chilled water heat pump unit evaporator; and the chilled water heat pump unit condenser is connected to the cold / heat load pipeline to form a hot water circulation. During the electric heating phase: heating is provided by chilled water heat pump units or by directly releasing heat from storage tanks; During peak electricity heating, heat is released in two stages using a storage tank: —Direct heat release stage: The evaporator and condenser of the chilled water heat pump unit are isolated from the storage tank and the cold / heat load and do not operate; the storage tank is connected to the cold / heat load pipeline to release heat; after the temperature drops, the water returns to the bottom of the storage tank, and the first delivery pump is a circulating power; since the density of water increases as the temperature drops, the water temperature in the storage tank shows a temperature gradient of high at the top and low at the bottom, until the water temperature at the top of the storage tank is lower than the first target temperature, this stage of heat release ends, and the heat pump heat release stage is started; —Heat Pump Heat Release Stage: After the direct heat release stage ends, the connection between the evaporator and the liquid storage tank of the chilled water heat pump unit is controlled, as is the connection between the condenser and the cold / heat load pipelines of the chilled water heat pump unit. Hot water in the upper part of the liquid storage tank reaches the evaporator of the chilled water heat pump unit, releases heat, and its temperature drops before returning to the liquid storage tank. At the same time, the chilled water heat pump unit starts working, using the heat obtained from the evaporator to reach a higher temperature in the condenser of the chilled water heat pump unit through a reverse Carnot cycle. Hot water from the condenser of the chilled water heat pump unit reaches the cold / heat load, releases heat, and then returns to the condenser of the chilled water heat pump unit, forming a heating cycle. The second transfer pump is the driving force for the cycle. Finally, the water temperature in the liquid storage tank can be reduced to -10℃~5℃, and the heat release ends.

[0020] Furthermore, it also includes cold storage / cooling control methods, specifically: Cooling storage stage: The chilled water heat pump unit's condenser is isolated from the cold / heat load and connected to the cooling tower piping to dissipate heat for the chilled water heat pump unit's cooling operation; and the chilled water heat pump unit's evaporator is connected to the liquid storage tank piping. Water at the top of the liquid storage tank, close to room temperature, reaches the chilled water heat pump unit's evaporator, releases heat, and returns to the liquid storage tank after its temperature drops; the water in the liquid storage tank exhibits a temperature gradient from top to bottom. The cooling storage stage ends when the water temperature at the top of the liquid storage tank is lower than the second target temperature; or the chilled water heat pump unit's evaporator is simultaneously connected to the chilled water system, storing cold water while simultaneously supplying cooling to the load.

[0021] During the power supply cooling phase: The chilled water heat pump unit is isolated from the liquid storage tank, and the evaporator of the chilled water heat pump unit is connected to the cold / heat load pipeline. A third transfer pump forms a chilled water circulation to supply cooling for the cold / heat load. The condenser of the chilled water heat pump unit is also connected to the cooling tower pipeline, and a second transfer pump forms a cooling water circulation to dissipate heat for the chilled water heat pump unit in cooling mode. In this phase, the liquid storage tank is disconnected from the cooling system, and the chilled water heat pump unit operates as a load cooling unit.

[0022] Peak power cooling phase: The chilled water heat pump unit is isolated from the storage tank and the cooling / heating load. The chilled water in the storage tank reaches the cooling / heating load for cooling. Once the chilled water temperature rises to a certain level, it returns to the storage tank. The water temperature in the storage tank exhibits a temperature gradient, higher at the top and lower at the bottom, until the water temperature at the bottom of the storage tank exceeds the third target temperature, at which point this cooling phase ends. In this phase, the chilled water heat pump unit is disconnected from the cooling system, and the storage tank provides cooling for the load. If the storage tank's cooling capacity is exhausted, the system switches to the off-peak power cooling phase, where the chilled water heat pump unit operates as a load cooling unit.

[0023] The beneficial effects of the present invention are as follows: The storage tank and heating device for storing cold water and hot water of the present invention are combined with a high-efficiency cold water heat pump unit to form a high-efficiency off-peak electricity energy storage system, which has both heat storage and cold storage functions, and can also be adjusted by valves and valve groups to operate independently of the energy storage system.

[0024] By combining direct heat release from thermal storage with heat pump heat release, the thermal storage capacity is significantly increased. Specifically, in the direct heat release stage, the amount of heat released from thermal storage can reach the existing hot water thermal storage capacity, such as a water temperature of 80-45℃ with a usable temperature difference of 35℃. In the heat pump heat release stage, the amount of heat released from thermal storage is equivalent to the existing hot water thermal storage capacity, such as a water temperature of 45-5℃ with a usable temperature difference of 40℃. That is, the total heat release temperature difference range reaches 75℃, and the thermal storage capacity is increased by more than 100%. By using antifreeze for heat storage, the heat pump can utilize a temperature difference of 55°C during the heat release phase from 45°C to -10°C, resulting in a total heat release temperature difference range of 85°C and an increase in total heat storage capacity of 2.5 times. By employing antifreeze for cold storage, and through direct heat exchange between the antifreeze and the chilled water heat pump unit, chilled water (antifreeze) at -10℃ can be produced, with a minimum and maximum of -20℃. At a standard supply chilled water temperature of 7℃, the cold storage temperature difference can reach 17℃ (maximum 27℃), far exceeding the 5℃ difference of typical 2℃ cold water (clean water). Even when the supply chilled water temperature is increased to 12℃, the cold storage temperature difference is only 10℃. Therefore, this invention achieves a -10℃ cold storage temperature difference of 22℃ (with a maximum cold storage temperature difference of 32℃ at -20℃) when the supply chilled water temperature is increased to 12℃.

[0025] Furthermore, the liquid storage tank of the present invention adopts a double-layer heat preservation and cold preservation structure, which has a higher heat preservation effect; the inner heat preservation material, such as rock wool, mineral wool or glass wool, is more heat-resistant, avoiding the problem of easy aging of rubber and plastic insulation materials when the heat storage temperature is high; the outer rubber and plastic insulation material has a closed-cell structure, which avoids the decrease in heat preservation performance of rock wool, mineral wool or glass wool insulation materials after water absorption due to water vapor condensation and penetration during cold preservation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the external low-temperature heat source water in the heat storage stage of this invention. Figure 3 This is a schematic diagram of the direct exothermic stage in an embodiment of the present invention; Figure 4 This is a schematic diagram of the heat pump heat release stage in an embodiment of the present invention; Figure 5 This is a schematic diagram of the cold storage stage in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the electric cooling stage in an embodiment of the present invention; Figure 7 This is a schematic diagram of the peak power cooling stage according to an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1The diagram illustrates a high-efficiency energy storage system with a chilled water heat pump unit and electric heating, comprising a storage tank, a chilled water heat pump unit, a cooling / heating load, and a valve unit. The system is characterized in that the storage tank is equipped with an electric heater, which can be located inside or outside the storage tank, and the electric heater uses surplus electricity from renewable energy sources for heating and heat storage. The valve unit is used to control the connection between the storage tank and the cooling / heating load pipelines, the connection between the storage tank and the evaporator pipeline of the chilled water heat pump unit, the connection between the evaporator of the chilled water heat pump unit and the external chilled water or low-temperature heat source water pipeline, the connection between the evaporator of the chilled water heat pump unit and the cooling / heating load pipelines, the connection between the condenser of the chilled water heat pump unit and the cooling / heating load pipelines, and the connection between the condenser of the chilled water heat pump unit and the external cooling water pipeline in different modes.

[0029] In this embodiment, the storage tank can store various liquids such as water and aqueous solutions. It uses stainless steel or carbon steel with an anti-corrosion coating as the inner liner. The inner liner is surrounded by two insulation layers. The inner layer is made of high-temperature resistant insulation materials such as rock wool, mineral wool, or glass wool, which have high heat resistance and insulation capabilities. The outer layer is a closed-cell rubber-plastic insulation material that prevents water vapor from condensing. Together, these two insulation layers form a heat-insulating and cold-insulating layer. The outer shell of the storage tank is made of aluminum or armored panels made of coated or plated steel plates.

[0030] In this embodiment, the energy storage medium in the storage tank is preferably inexpensive and safe softened water. Corrosion inhibitors are added to prevent corrosion of the storage tank, pipes and pipe components, cold / hot load terminal equipment (such as fan coil units), and water-contacting parts, and to prevent the aqueous solution from spoiling. Trace amounts of corrosion inhibitors such as borax, sodium benzoate, and benzotriazole are preferably added to delay corrosion. Specifically, the corrosion inhibitor formulation is: 0.01-1% borax, 0.001-0.2% benzotriazole, 0.1-2% sodium benzoate, and 0.001-0.1% parabens. The optimal formulation is: 0.1-0.5% borax, 0.002-0.01% benzotriazole, 0.2-0.5% sodium benzoate, and 0.01-0.05% parabens.

[0031] In this embodiment, to increase the temperature difference of the storage liquid, the energy storage medium in the storage tank preferably contains antifreeze and corrosion inhibitors. The antifreeze formulation is as follows: 10-40% alcohols (ethylene glycol, methanol, ethanol, propylene glycol, or mixtures thereof), 0.01-1% borax, 0.001-0.2% benzotriazole, 0.1-2% sodium benzoate, and 0.001-0.1% parabens. The optimal formulation is 15-30% alcohols, 0.1-0.5% borax, 0.002-0.01% benzotriazole, 0.2-0.5% sodium benzoate, and 0.01-0.05% parabens.

[0032] In this embodiment, the chilled water heat pump unit can be a magnetic levitation centrifugal water-cooled chilled water heat pump unit, a centrifugal water-cooled chilled water heat pump unit, a screw water-cooled chilled water heat pump unit, a scroll water-cooled chilled water heat pump unit, or a piston water-cooled heat pump unit. It is characterized by using water cooling and water as a low-temperature heat source, and has both cooling and heat pump heating functions.

[0033] In this embodiment, the liquid storage tank is provided with a first liquid outlet, a second liquid outlet, and a return liquid outlet. The first liquid outlet and the second liquid outlet are respectively located at the upper and lower parts of the liquid storage tank; the return liquid outlet is located at the lower part of the liquid storage tank, and below the second liquid outlet. The first liquid outlet also serves as the return liquid outlet during cold storage. The valve unit includes four valves (i.e., the first valve, the second valve, the third valve, and the fourth valve) and four valve groups (i.e., the first valve group, the second valve group, the third valve group, and the fourth valve group); wherein the four valves are located on the output pipeline of the second liquid outlet and the input pipeline of the return liquid outlet.

[0034] Specifically, the second outlet splits into two branches after passing through the first valve. One branch connects sequentially to the transfer pump P1, the second valve, and the third valve group pipeline; the other branch connects to the third valve group pipeline via the third valve. Additionally, the output of the transfer pump P1 also splits into two branches: one branch connects to the return port pipeline of the storage tank via the fourth valve, and the other branch connects to the third valve group pipeline via the second valve. The first outlet of the storage tank is connected to the first valve group pipeline. In short, the first valve, second valve, third valve, fourth valve, transfer pump P1, and pipelines constitute a bidirectional transfer structure.

[0035] The first valve group is divided into four branches. One branch connects to the first outlet of the storage tank via a pipeline. The second branch connects to external cold water or low-temperature heat source water. The third branch connects to the second valve group via a pipeline. The fourth branch connects to the inlet of the evaporator of the chilled water heat pump unit via a pipeline. The third valve group is also divided into four branches. One branch connects to the common node of the second and third valves via a pipeline. The second branch connects to the output end of the transfer pump P3 via a pipeline, and together with the second branch of the first valve group, connects to the cold water or low-temperature heat source water system to form a water circulation. The third branch connects to the fourth valve group via a pipeline. The fourth branch connects to the outlet of the evaporator of the chilled water heat pump unit via a pipeline.

[0036] The second valve group is divided into four branches. One branch connects to the first valve group via piping. The second branch connects to external cooling water. The third branch connects to the cooling / heating load via piping. The fourth branch connects to the outlet of the chilled water heat pump unit's condenser via piping. The fourth valve group is also divided into four branches. One branch connects to the third valve group via piping. The second branch connects to the input of the transfer pump P2 via piping, and together with the second branch of the second valve group, connects to the cooling tower. The third branch connects to the cooling / heating load via piping. The fourth branch connects to the inlet of the chilled water heat pump unit's condenser via piping.

[0037] In this embodiment, the combination of the first valve, the second valve, the third valve, the fourth valve, and the delivery pump P1 can reverse the flow direction of the liquid, allowing it to flow out from the bottom of the storage tank and into the top, or vice versa, thus adapting to the switching between heat storage and cold storage.

[0038] In this embodiment, the first valve group and the third valve group can be combinations of one-way valves, two-way valves, three-way valves, and four-way valves. Their function is to enable or disable the connection between the evaporator water side of the chilled water heat pump unit and the energy storage system; or to enable or disable the connection between the evaporator water side of the chilled water heat pump unit and chilled water or low-temperature heat source water (i.e., to supply chilled water when disconnected from the energy storage system and used for independent cooling).

[0039] In this embodiment, the second and fourth valve groups can be combinations of check valves, two-way valves, three-way valves, and four-way valves, such as a combination of four check valves, or a combination of a two-way valve and a three-way valve. Their function is to allow the connection or disconnection between the condenser water side of the chilled water heat pump unit and the water side of this energy storage system; it can also allow the connection or disconnection between the condenser water side of the chilled water heat pump unit and the cooling water (i.e., disconnected from this energy storage system, using cooling water for heat dissipation when cooling independently).

[0040] The working principle of the energy storage / heat release system in this embodiment includes: 1. Thermal storage stage (off-peak electricity hours): Surplus electricity is used to heat the energy storage medium (water or aqueous solution) in the storage tank. Under non-pressurized conditions, it is typically heated to 80℃, with a maximum temperature of 95℃. It is understandable that, during the heat storage stage, the following three methods for direct heat release can also be used, by adjusting various valves and valve groups to supply heat to the heat load while storing heat.

[0041] like Figure 2 As shown: If other low-temperature heat source water is available, the chilled water heat pump unit can operate independently to provide heating while the liquid storage tank stores heat. The specific method is as follows: Adjust the first and second valves to close; adjust the first and third valve groups to connect the chilled water heat pump unit's evaporator to the low-temperature heat source water system pipeline; the transfer pump P3 provides the circulation power for the low-temperature heat source water; and the chilled water heat pump unit's evaporator absorbs heat from the low-temperature heat source water. Adjust the second and fourth valve groups to connect the chilled water heat pump unit's condenser to the cold / heat load pipeline, thus forming a hot water circulation. This heat pump method has a higher heating efficiency than direct heating using off-peak electricity and utilizes inexpensive off-peak electricity to drive the heat pump and store heat.

[0042] 2. Electric Heating Stage: This stage uses a chilled water heat pump unit for heating or direct heat release from a storage tank. See the methods for the heat storage stage for specific adjustments. The low-temperature heat source water can come from various sources, such as industrial waste heat, air-source heating (e.g., heat source towers), low-temperature waste heat recovered from building ventilation, and waste heat from building sewage discharge. This heat pump method is far more efficient than electric heating. However, if there is no low-temperature heat source water, electric heating can be used directly, or the heat from the storage tank can be utilized (provided the storage tank has sufficient heat storage capacity).

[0043] 3. Direct heat release stage (peak electricity period): such as Figure 3 As shown: The first and second valves are closed, and the evaporator and condenser of the chilled water heat pump unit are isolated from the storage tank and the cold / heat load, and are not operating. Hot water in the upper part of the storage tank is output through the second outlet, passing through the first and second valve groups to reach the heat load and release heat. When the temperature drops to approximately 40℃, it returns to the bottom of the storage tank through the fourth and third valve groups, the third valve, the transfer pump P1, and the fourth valve, with the transfer pump P1 providing circulating power. Because the density of water increases as the temperature decreases, the water temperature in the storage tank will maintain a relatively stable temperature gradient, higher at the top and lower at the bottom, until the water temperature in the upper part of the storage tank drops below 45℃. At this point, the heat release phase ends, and the heat pump heat release phase begins.

[0044] 4. Heat pump heat release phase (peak electricity period): such as Figure 4 As shown: After the direct heat release stage ends, adjust the first and third valve groups to connect the chilled water heat pump unit's evaporator to the storage tank pipeline; adjust the second and fourth valve groups to connect the chilled water heat pump unit's condenser to the cold / heat load pipeline. At this time, the first and second valve groups are isolated from each other; the third and fourth valve groups are isolated from each other; the first and second valves are closed. Hot water from the upper part of the storage tank reaches the chilled water heat pump unit's evaporator through the first valve group, releasing heat and lowering its temperature. It then flows along the third valve group, the third valve, the transfer pump P1, and the fourth valve, returning to the storage tank through the storage tank's return port. Simultaneously, the chilled water heat pump unit begins operation, using a higher energy efficiency ratio to transfer the heat obtained from the evaporator through a reverse Carnot cycle, reaching a higher temperature in the chilled water heat pump unit's condenser. Hot water from the chilled water heat pump unit's condenser reaches the cold / heat load through the second valve group, releasing heat, and then returns to the chilled water heat pump unit's condenser through the fourth valve group and the transfer pump P2, forming a heating cycle, with the transfer pump P2 serving as the cycle power source. At this point, during peak electricity consumption, the off-peak electricity storage can be fully utilized with minimal power consumption. Based on the typical performance of vapor compression heat pumps, the energy efficiency ratio is over 3 times. Finally, the water temperature in the storage tank can be reduced to 5℃ (for simple water storage); it can even reach -10℃ (for antifreeze storage), at which point heat release ends.

[0045] It can be said that the energy storage system of this embodiment has the following advantages over the prior art in terms of heat storage / heat release technology: (1) In the direct heat release stage, the heat storage and heat release can reach the existing hot water heat storage capacity, such as water temperature 80-45℃, and a temperature difference of 35℃ can be utilized; (2) In the heat pump heat release stage, the heat storage and heat release is equivalent to the existing hot water heat storage capacity, such as water temperature 45-5℃, and a temperature difference of 40℃ can be utilized, that is, the total heat release temperature difference range reaches 75℃, and the heat storage capacity is increased by more than 1 times; if antifreeze is used for heat storage, the heat pump heat release stage is 45---minus 10℃, and a temperature difference of 55℃ can be utilized, that is, the total heat release temperature difference range reaches 85℃, and the total heat storage capacity is increased by 2.5 times.

[0046] The working principle of the energy storage system for cold storage / cooling supply in this embodiment includes: 1. Cold storage stage like Figure 5 As shown: During off-peak electricity hours, the second and fourth valve groups are adjusted to isolate the chilled water heat pump unit's condenser from the cold / heat load and from the first and third valve groups; the chilled water heat pump unit's condenser is connected to the cooling tower pipeline, and the delivery pump P2 is the cooling water pump, which dissipates heat for the chilled water heat pump unit in cooling mode.

[0047] Adjusting the first and third valve groups connects the chilled water heat pump unit to the liquid storage tank pipeline, forming a circulation path. The first and second valves are closed. Water at near room temperature in the upper part of the liquid storage tank reaches the evaporator of the chilled water heat pump unit through the first valve group, releasing heat and lowering its temperature to approximately 4°C. It then returns to the bottom of the liquid storage tank through the third valve group, the third valve, the transfer pump P1, and the fourth valve. The transfer pump P1 provides the power for the chilled water circulation.

[0048] —If the cooling load is not large, water-based cooling with added corrosion inhibitors can be used. Because the density of water increases as the temperature decreases, reaching its maximum at 4°C, the water temperature in the storage tank will maintain a relatively stable temperature gradient, higher at the top and lower at the bottom. The cooling phase ends once the water temperature at the top of the tank drops below 4°C. This method offers high refrigeration efficiency.

[0049] —If the cooling load is large, antifreeze is used for cold storage. The antifreeze directly exchanges heat with the chilled water heat pump unit, producing chilled water (antifreeze) at -10℃, with a minimum temperature of -20℃. The cold storage phase ends once the antifreeze in the storage tank reaches the set temperature. This method offers a large cold storage capacity.

[0050] If necessary, during the cold storage stage, the evaporator of the chilled water heat pump unit can be connected to the chilled water system simultaneously by adjusting the first and third valve groups, so as to store cold water while supplying chilled water to the cold / heat load.

[0051] 2. Cooling supply phase with stable power supply like Figure 6As shown: Adjust the first valve group and the third valve group to isolate the chilled water heat pump unit from the liquid storage tank; connect the evaporator of the chilled water heat pump unit to the cold / heat load pipeline, and form a chilled water circulation through the transfer pump P3 to supply cooling for the cold / heat load.

[0052] Adjust the second and fourth valve groups to connect the condenser of the chilled water heat pump unit to the cooling tower pipeline, and form a cooling water circulation through the transfer pump P2 to dissipate heat for the chilled water heat pump unit in cooling mode.

[0053] 3. Peak power cooling phase like Figure 7 As shown: Open the first and second valves, close the third and fourth valves, and adjust the first, second, third, and fourth valve groups to isolate the chilled water heat pump unit from the storage tank and the cooling / heating load. The chilled water in the storage tank reaches the cooling / heating load through the first valve, transfer pump P1, the second valve, the third valve group, and the fourth valve group. When the chilled water temperature rises to 15℃, it returns to the upper part of the storage tank via the second and first valve groups. Because the density of water increases as temperature decreases, the water temperature in the storage tank will maintain a relatively stable temperature gradient, higher at the top and lower at the bottom, until the water temperature at the bottom of the storage tank exceeds 10℃ (if the cooling load does not require a high cooling temperature, a higher temperature can be set, such as 12℃, to increase the cooling capacity), at which point this stage of cooling supply ends.

[0054] In summary, the storage tank and heating device for storing cold and hot water of this invention, combined with a high-efficiency chilled water heat pump unit, form a high-efficiency off-peak electricity energy storage system. On the one hand, by combining direct heat release from the stored heat with heat pump heat release, the heat storage capacity is significantly increased; on the other hand, it has both heat storage and cold storage functions, and the chilled water heat pump unit can form a high-efficiency energy storage system with the storage tank, and can also operate independently of the energy storage system through valves and valve groups. Furthermore, the storage tank of this invention adopts a double-layer insulation and cold insulation structure, which has a higher insulation effect; the inner insulation material, such as rock wool, mineral wool, or glass wool, is more heat-resistant, avoiding the problem of easy aging of rubber and plastic insulation materials when the heat storage temperature is high; the outer rubber and plastic insulation material has a closed-cell structure, preventing water vapor condensation and penetration during cold insulation, which would cause the insulation performance of the rock wool, mineral wool, or glass wool insulation material to decrease after absorbing water. This invention uses water and antifreeze with added corrosion inhibitors, which can not only lower the freezing point of the liquid and expand the cold storage temperature range, thereby increasing the cold storage capacity, but also reduce corrosion and scaling in the water system pipelines of this device and the cold / heat load terminals, maintain high heat transfer efficiency, which is conducive to energy saving, extends the service life of the equipment and the service life of the energy storage medium, and reduces operating costs.

Claims

1. A high-efficiency energy storage system with a chilled water heat pump unit and electric heating, comprising a liquid storage tank, a chilled water heat pump unit, and a valve unit; characterized in that, The storage tank is equipped with an electric heater, which uses surplus electricity from renewable energy sources for heating; The valve unit includes multiple valves and multiple valve groups; each valve is located on the liquid output pipeline and return pipeline of the liquid storage tank; the multiple valve groups are used to control the connection or disconnection between the evaporator and the liquid storage tank pipeline of the chilled water heat pump unit, the external chilled water or low-temperature heat source water pipeline, and the cold / heat load pipeline; they are also used to control the connection or disconnection between the condenser and the cold / heat load pipeline of the chilled water heat pump unit and the external cooling water pipeline; The valve unit is used to switch the on / off state of each pipeline in different modes: (1) During the heat storage stage, the valve unit is used to control the liquid storage tank to disconnect from the cold / heat load pipeline and to be connected to the chilled water heat pump unit; or to control the chilled water heat pump unit evaporator to be connected to the low temperature heat source water pipeline, and to control the water heat pump unit condenser to be connected to the cold / heat load pipeline, while the liquid storage tank is disconnected and stores heat independently; during the flat power supply stage, the chilled water heat pump unit is controlled to work and supply heat or the liquid storage tank is used to directly release heat; during the peak power supply stage, heat is released in two stages: direct heat release from the liquid storage tank and heat pump heat release: during the direct heat release stage of the liquid storage tank, the liquid storage tank is controlled to be connected to the cold / heat load pipeline, while the chilled water heat pump unit is disconnected from both, so that the liquid storage tank can directly release heat; during the heat pump heat release stage, the liquid storage tank is controlled to be connected to the chilled water heat pump unit evaporator pipeline, and the chilled water heat pump unit condenser is controlled to be connected to the cold / heat load pipeline; (2) During the cold storage stage, the valve unit is used to control the connection between the liquid storage tank and the evaporator pipeline of the cold water heat pump unit, and to control the connection between the condenser of the cold water heat pump unit and the external cooling water pipeline; the cold / heat load is in the disconnected state; during the normal power supply cooling stage, the evaporator of the cold water heat pump unit is connected to the cold / heat load pipeline, and the condenser of the cold water heat pump unit is connected to the external cooling water pipeline, and the liquid storage tank is in the disconnected state; during the peak power supply cooling stage, the liquid storage tank is connected to the cold / heat load pipeline, and the cold water heat pump unit is in the disconnected state.

2. The high-efficiency energy storage system with chilled water heat pump unit and electric heating according to claim 1, characterized in that, The storage tank is provided with a first outlet, a second outlet, and a return outlet. The first outlet and the second outlet are respectively located at the upper and lower parts of the storage tank. The return outlet is located at the lower part of the storage tank. The valve unit includes at least four valves, namely the first valve to the fourth valve. The second outlet is divided into two branches after passing through the first valve. One branch is connected to the first delivery pump and the second valve in sequence. The other branch is connected to the third valve via a pipeline. The output end of the first delivery pump is also divided into two branches. One branch is connected to the return outlet pipeline of the storage tank via the fourth valve. The other branch is connected to the second valve via a pipeline. The first valve to the fourth valve, the first delivery pump, and the pipeline constitute a bidirectional delivery structure.

3. The high-efficiency energy storage system with chilled water heat pump unit and electric heating according to claim 2, characterized in that, The valve unit includes at least four valve groups, namely the first valve group to the fourth valve group; the first valve group is divided into four branches, one branch is connected to the first outlet of the storage tank via a pipeline, the second branch is connected to cold water or low-temperature heat source water, the third branch is connected to the second valve group via a pipeline, and the fourth branch is connected to the inlet of the evaporator of the cold water heat pump unit via a pipeline; the third valve group is divided into four branches, one branch is connected to the common node of the second valve and the third valve via a pipeline; the second branch is connected to the output end of the third delivery pump via a pipeline, and together with the second branch of the first valve group, it is connected to the low-temperature heat source water system to form a circulation system; The third branch line connects to the fourth valve group via a pipeline, and the fourth branch line connects to the outlet of the evaporator of the chilled water heat pump unit via a pipeline; the second valve group is divided into four branches, one branch line connects to the first valve group via a pipeline, the second branch line connects to external cooling water, the third branch line connects to the cold / heat load via a pipeline, and the fourth branch line connects to the outlet of the condenser of the chilled water heat pump unit via a pipeline. The fourth valve group is divided into four branches. One branch is connected to the third valve group via a pipeline. The second branch is connected to the input end of the second delivery pump via a pipeline and is connected to the cooling tower together with the second branch of the second valve group. The third branch is connected to the cold / heat load via a pipeline, and the fourth branch is connected to the inlet of the condenser of the chilled water heat pump unit via a pipeline.

4. The high-efficiency energy storage system with chilled water heat pump unit and electric heating according to claim 1, characterized in that, The inner liner of the liquid storage tank is provided with at least two heat insulation layers. The inner layer is a high-temperature resistant heat insulation material, and the outer layer is a closed-cell structure heat insulation and cold insulation material that can prevent water vapor from entering and condensing. The two heat insulation layers together constitute a heat insulation, heat insulation and cold insulation layer.

5. The high-efficiency energy storage system with chilled water heat pump unit and electric heating according to claim 1, characterized in that, The energy storage medium in the storage tank is supplemented with corrosion inhibitors and / or antifreeze agents; the corrosion inhibitor formula is: 0.01-1% borax, 0.001-0.2% benzotriazole, 0.1-2% sodium benzoate, and 0.001-0.1% para-hydroxybenzoate; the antifreeze formula is: 10-40% alcohols, 0.01-1% borax, 0.001-0.2% benzotriazole, 0.1-2% sodium benzoate, and 0.001-0.1% para-hydroxybenzoate.

6. An energy storage method utilizing the high-efficiency energy storage system with chilled water heat pump unit and electric heating as described in claim 1, characterized in that, This includes control methods for heat storage / release, specifically: Thermal storage stage: The surplus electricity from renewable energy sources is used to heat the energy storage medium in the storage tank; or during the thermal storage stage, by adjusting various valves and valve groups, the storage tank can directly supply heat to the cold / heat load while storing heat; or while storing heat in the storage tank, the chilled water heat pump unit is controlled to supply heat independently, that is, the evaporator of the chilled water heat pump unit is connected to the low-temperature heat source water system pipeline, and the heat from the low-temperature heat source water is absorbed through the evaporator of the chilled water heat pump unit; and the condenser of the chilled water heat pump unit is connected to the cold / heat load pipeline to form a hot water circulation. During the electric heating phase: heating is provided by chilled water heat pump units or by directly releasing heat from storage tanks; Peak power heating phase: This phase utilizes both direct heat release from the storage tank and heat pump heat release. Direct heat release phase: The evaporator and condenser of the chilled water heat pump unit are isolated from the storage tank and the cold / heat load, and do not operate. The storage tank is connected to the cold / heat load pipeline to release heat. After the temperature drops, the heat returns to the bottom of the storage tank, and the first delivery pump is used for circulation. Because the density of water increases with decreasing temperature, the water temperature in the storage tank exhibits a temperature gradient from top to bottom until the water temperature at the top of the storage tank falls below the first target temperature. At this point, the heat release phase ends, and the heat pump heat release phase begins. Heat pump heat release phase: After the direct heat release phase ends, the evaporator and condenser of the chilled water heat pump unit are controlled to... The evaporator is connected to the storage tank pipeline, and the control system connects the chilled water heat pump unit condenser to the cold / heat load pipeline. Hot water in the upper part of the storage tank reaches the chilled water heat pump unit evaporator, releases heat, and its temperature drops before returning to the storage tank. At the same time, the chilled water heat pump unit starts working, using the heat obtained from the evaporator through a reverse Carnot cycle to reach a higher temperature in the chilled water heat pump unit condenser. Hot water from the chilled water heat pump unit condenser reaches the cold / heat load, releases heat, and then returns to the chilled water heat pump unit condenser, forming a heating cycle. The second transfer pump is the driving force for the cycle. Finally, the water temperature in the storage tank can be reduced to -10℃ to 5℃, and the heat release ends.

7. The energy storage method of the high-efficiency energy storage system with chilled water heat pump unit and electric heating according to claim 6, characterized in that, This also includes cold storage / cooling control methods, specifically: Cold storage stage: The chilled water heat pump unit's condenser is isolated from the cold / heat load and connected to the cooling tower piping to dissipate heat during cooling operation; The chilled water heat pump unit's evaporator is connected to the liquid storage tank piping, allowing near-room-temperature water at the top of the tank to reach the evaporator, release heat, and return to the tank after its temperature drops; The water in the tank exhibits a temperature gradient, higher at the top and lower at the bottom. The cold storage stage ends when the water temperature at the top of the tank falls below the second target temperature; Alternatively, the chilled water heat pump unit's evaporator can be simultaneously connected to the chilled water system, storing cold water while simultaneously supplying cooling to the load; Electricity-powered cooling stage: The chilled water... The heat pump unit is isolated from the liquid storage tank, and the evaporator of the chilled water heat pump unit is connected to the cold / heat load pipeline. A third transfer pump forms a chilled water circulation to supply cooling for the cold / heat load. The condenser of the chilled water heat pump unit is also connected to the cooling tower pipeline. A second transfer pump forms a cooling water circulation to dissipate heat for the chilled water heat pump unit during cooling operation. Peak power cooling stage: The chilled water heat pump unit is isolated from the liquid storage tank and the cold / heat load. The chilled water in the storage tank reaches the cold / heat load for cooling. When the chilled water temperature rises to a certain temperature, it returns to the liquid storage tank. The water temperature in the liquid storage tank shows a temperature gradient from top to bottom until the water temperature at the bottom of the liquid storage tank exceeds the third target temperature, at which point this stage of cooling ends.

Images