Ice storage energy-saving method and system suitable for greenhouse in Gansu region

Abstract

The invention belongs to the technical field of greenhouses, and particularly relates to an ice storage energy-saving method and system suitable for greenhouses in Gansu province, and the method comprises the steps: dividing the greenhouses into a peak period, a flat period and a valley period according to a local electricity price policy; in the low ebb period, a refrigeration compressor is started and runs in a high-load state, cold energy is transmitted to a cold storage device through a heat exchanger, a cold storage medium in the cold storage device is subjected to water-ice phase change, and the cold energy is stored in an ice mode till the cold storage device reaches the preset cold storage capacity; the cold storage device is started to release stored cold energy in the peak period, and the greenhouse is cooled through the heat exchanger; if the cooling capacity released by the cold storage device cannot meet the refrigeration requirement, the refrigeration compressor is started for auxiliary refrigeration; the temperature and refrigeration requirements in the greenhouse are monitored in real time in the flat period, and the proportion of direct refrigeration of the refrigeration compressor and cold release of the cold storage device is dynamically adjusted. The method effectively reduces the energy consumption and electric charge expenditure in the peak period, and guarantees the suitable conditions for the peach trees to sleep in advance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of greenhouse, and particularly relates to an ice storage energy-saving method and system suitable for a greenhouse in Gansu. BACKGROUND

[0002] Greenhouses are widely used in modern agricultural planting, and provide suitable ecological environment for crop growth by regulating environmental conditions. In peach planting, low-temperature treatment is a key link to promote early dormancy, and by artificially creating a low-temperature environment, the natural dormancy period of peach trees can be shortened, thereby improving planting efficiency and economic benefits. Traditional greenhouses mostly use compression refrigeration technology to directly cool the greenhouse, and maintain a low-temperature environment by continuously operating refrigeration equipment. Ice storage technology is an energy-saving refrigeration technology, which stores cold energy by operating refrigeration equipment during off-peak hours, and releases stored cold energy to meet refrigeration demand during peak hours, which can significantly reduce direct electricity consumption during peak hours and reduce operating costs. Ice storage technology has good energy-saving effect in industrial buildings, but its application in greenhouses is less, especially in the economic analysis of the peach low-temperature demand scenario, research and practice are relatively lacking.

[0003] However, the direct refrigeration method in the prior art has many shortcomings: first, the operating cost is high, especially during the peak electricity period, the direct refrigeration equipment has high energy consumption, and the electricity bill increases significantly; second, the equipment selection is often large, in order to meet the high load demand, a large size compressor is selected, which not only increases the equipment investment cost, but also causes the compressor to have low efficiency when operating at partial load, further causing energy waste. The prior art does not make full use of peak and valley electricity prices, and fails to effectively store cold energy during off-peak hours to reduce energy consumption during peak hours. In addition, most of the current research or technical solutions lack economic analysis of the ice storage technology combined with the low-temperature demand scenario of the greenhouse, and cannot directly quantify the actual effect of the ice storage technology in reducing operating costs and optimizing equipment investment. SUMMARY

[0004] In view of the above problems of high operation cost, large equipment selection leading to low investment and operation energy efficiency, insufficient utilization of peak-valley electricity price, and lack of quantitative analysis of the economic efficiency of ice storage technology under the low temperature scenario of greenhouse, the present application provides an ice storage energy-saving method and system suitable for greenhouse in Gansu region. The present application mainly runs the compressor refrigeration and storage during the low valley period of electricity price, stores the cold energy in the form of ice, and releases the stored cold energy during the peak period of electricity price to meet the refrigeration demand, thereby effectively reducing the operation cost and ensuring the temperature in the greenhouse to be stable at about 5 DEG C, providing a suitable low temperature environment for crop dormancy, thereby fully utilizing the difference between peak and valley electricity prices, significantly reducing the operation cost of the system, improving the load rate of the compressor by concentrating the operation load of the compressor in the low valley period, and avoiding the problem of reduced efficiency of the compressor in the traditional system.

[0005] The technical means adopted by the present application are as follows: An ice storage energy-saving method suitable for greenhouse in Gansu region, comprising the following steps: According to the local electricity price policy, 24 hours a day is divided into peak period, flat period and low valley period; During the low valley period, start the refrigeration compressor and run in a high load state, transfer the cold energy to the cold storage device through the heat exchanger, make the cold storage medium in the cold storage device undergo water-ice phase change, store the cold energy in the form of ice, and store the cold energy in the form of ice until the cold storage device reaches the preset cold storage capacity; During the peak period, enable the cold storage device to release the stored cold energy, cool the greenhouse through the heat exchanger, and maintain the temperature in the greenhouse stable; if the cold energy released by the cold storage device cannot meet the refrigeration demand, start the refrigeration compressor to assist refrigeration; During the flat period, real-time monitor the temperature in the greenhouse and the refrigeration demand, dynamically adjust the proportion of direct refrigeration of the refrigeration compressor and release of the cold storage device, ensure the temperature in the greenhouse stable, and balance the operation cost and refrigeration efficiency.

[0006] Further, the preset cold storage capacity is determined by establishing a cold storage system capacity optimization model, the model analyzes the daily temperature change rule and refrigeration demand of the greenhouse during the crop dormancy period, combines the low valley period length and the rated power of the refrigeration compressor, calculates the optimal cold storage capacity, and the preset cold storage capacity is any value in the optimal cold storage capacity interval.

[0007] Further, the calculation process of the cold storage system capacity optimization model comprises: Obtain the electricity price corresponding to the peak period, flat period and low valley period, and the rated power of the refrigeration compressor; According to the electricity price corresponding to the peak period, flat period and low valley period, and the rated power of the refrigeration compressor, calculate the reference cost, and the calculation formula of the reference cost is: C基准 =Σ(Q×P×W) wherein, C 基准 is the benchmark cost, Q is the refrigeration demand state, which is 0 or 1, P is the electricity price corresponding to the period, and W is the rated power of the refrigeration compressor; According to the electricity price corresponding to the peak period, the flat period and the valley period, the rated power of the refrigeration compressor, the refrigeration demand satisfied by the cold storage and the demand for the refrigeration compressor to directly refrigerate, the cold storage optimization cost is calculated, and the calculation formula of the cold storage optimization cost is: C 优化 =Σ(Q 直接 ×P 直接 ×W)+Σ(Q 蓄冷 ×P 低谷 ×W) wherein, C 优化 is the cold storage optimization cost, Q 直接 is the direct refrigeration demand, P 直接 is the electricity price corresponding to the direct refrigeration period, Q 蓄冷 is the refrigeration demand satisfied by the cold storage, and P 低谷 is the valley electricity price; The benchmark cost is subtracted from the cold storage optimization cost to obtain the electricity fee saved; The electricity fee saved for different cold storage capacities is calculated, the lowest range of the electricity fee saved is found, the range is determined as the optimal cold storage capacity, and the preset cold storage capacity is any value within the optimal cold storage capacity interval.

[0008] Further, the proportion of the refrigeration compressor directly refrigerating and the cold storage device releasing refrigeration is dynamically adjusted, which comprises: The rated power of the refrigeration compressor is set as a first power, and the maximum refrigeration releasing power of the cold storage device is set as a second power, When the temperature in the greenhouse is higher than the target temperature by 2℃ or more, the power of the refrigeration compressor is adjusted to 0.7-0.9 times the first power, and the refrigeration releasing power of the cold storage device is adjusted to 0.1-0.3 times the second power; When the temperature in the greenhouse is within the range of the target temperature±2℃, the power of the refrigeration compressor is adjusted to 0.3-0.7 times the first power, and the refrigeration releasing power of the cold storage device is adjusted to 0.3-0.7 times the second power; When the temperature in the greenhouse is lower than the target temperature by 2℃ or less, the refrigeration compressor stops running, and the cold storage device stops releasing refrigeration.

[0009] Further, when the refrigeration compressor is in high load operation, the compressor load rate is maintained between 40%-90%, so that the system efficiency is maintained at 60%-100%, and low load and low efficiency operation of the compressor is avoided.

[0010] Further, the cold storage device releases cold, and the automatic control system precisely controls the cold release rate to ensure the stable dormancy environment of the crops in the greenhouse.

[0011] Further, the automatic control system precisely controls the cold release rate, and the method comprises the following steps: The automatic control system adjusts the power of the cold carrier circulating pump through the frequency converter and controls the opening degree of the cold release fluid pipeline through the electric regulating valve, calculates and adjusts the cold release flow in real time according to the deviation of the actual temperature in the greenhouse from the target temperature (5 DEG C) and the remaining capacity of the cold storage device, and effectively controls the cold release rate.

[0012] The application also comprises an ice cold storage energy-saving system suitable for the greenhouse in Gansu, which is used to realize the above-mentioned ice cold storage energy-saving method suitable for the greenhouse in Gansu, and comprises a refrigeration compressor, a cold storage device, a heat exchanger, an automatic control system and a greenhouse temperature monitoring device. The automatic control system pre-stores the local peak-valley electricity price period division rule, divides 24 hours a day into a peak period, a flat period and a valley period, and internally stores a cold storage system capacity optimization model. The greenhouse temperature monitoring device collects the temperature data in the greenhouse in real time and transmits the temperature data to the automatic control system. The automatic control system controls the operation of each component according to the electricity price period and the greenhouse temperature data, and the operation rule is as follows: In the valley period, the refrigeration compressor is controlled to operate in a high load state, the cold energy is transferred to the cold storage device through the heat exchanger, the medium in the cold storage device is subjected to water-ice phase change to store cold energy, and the process is continued until the preset cold storage capacity calculated by the cold storage system capacity optimization model is reached. In the peak period, the cold storage device is preferentially controlled to release cold energy, the greenhouse is cooled through the heat exchanger, and if the cold energy is insufficient, the refrigeration compressor is started to assist. In the flat period, the proportion of direct refrigeration of the refrigeration compressor and cold release of the cold storage device is dynamically adjusted to maintain the stable temperature in the greenhouse to meet the dormancy requirement of the crops in the greenhouse.

[0013] Further, the control logic process of the automatic control system comprises the following steps: S1. Input the real-time air temperature data, the greenhouse parameters and the electricity price period division information of the local area. S2. Calculate the air temperature change trend in the greenhouse and the corresponding refrigeration requirement according to the input data. S3. Determine the current electricity price period and execute the corresponding operation control strategy. S4. After the operation in the current period is completed, it is determined whether there is a next period, if there is, return to S2, and if there is not, calculate the total electricity fee in a day and the saved electricity fee amount compared with the traditional direct refrigeration mode, and complete a complete operation cycle.

[0014] Further, the greenhouse monitoring points are arranged at the periphery and the central position of the greenhouse.

[0015] Compared with the prior art, the present application has the following advantages: 1. The present application realizes the staggered operation of cold storage in the valley period and preferential cold release in the peak period by precisely matching the peak-valley electricity price period division and the stable low-temperature environment required for crop dormancy, effectively reduces the energy consumption and electricity bill in the peak period, and at the same time guarantees the suitable conditions for peach tree to enter dormancy in advance.

[0016] 2. The present application realizes the improvement of compressor operation efficiency by combining the high-load operation control of the refrigeration compressor and the capacity optimization model of the cold storage system, avoids the energy waste caused by the low-load and low-efficiency operation of the compressor in traditional direct refrigeration, and reasonably controls the initial equipment investment cost.

[0017] 3. The present application realizes the dynamic response to the large diurnal temperature difference and seasonal temperature fluctuation by the synergistic work of the automatic control system and the greenhouse temperature monitoring device, stably controls the temperature in the greenhouse within the target range, and greatly reduces the operation cost compared with the traditional direct refrigeration mode.

[0018] Based on the above reasons, the present application can be widely popularized in the field of greenhouse and the like. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 It is a process flow diagram of the ice storage energy-saving method suitable for greenhouse in Gansu region of the present application.

[0021] Figure 2 It is an energy-saving principle and implementation flowchart of the ice storage air conditioning system of the present application.

[0022] Figure 3 It is a temperature change in a day and a temperature trend from October to November in Gansu region.

[0023] Figure 4 It is a control logic flowchart of the ice storage system in the embodiment of the present application.

[0024] Figure 5 It is a load rate law of the ice storage air conditioner and the conventional air conditioner in the embodiment of the present application.

[0025] Figure 6 It is an air conditioning system combined with the ice storage technology in the embodiment of the present application.

[0026] Figure 7 The figure shows the relationship between the cold storage capacity and the electricity cost saving in the embodiment of the present application.

[0027] Figure 8 The figure shows the relationship between the cold storage capacity and the incremental capital cost and payback period in the embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiment of the present application will be described clearly and completely in combination with the drawings in the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, not all. Based on the embodiment in the present application, all other embodiments obtained by the personnel in the field without creative labor should belong to the protection scope of the present application.

[0029] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] As shown in Figure 1 The present application provides an ice storage energy-saving method suitable for greenhouse in Gansu region. The steps are as follows: S1. According to the local electricity price policy, divide 24 hours a day into peak period (7:00-9:00 and 18:00-23:00), flat period (0:00-2:00, 4:00-6:00, 10:00-11:00 and 15:00-17:00) and valley period (2:00-3:00 and 11:00-14:00).

[0031] S2. In the valley period, start the refrigeration compressor and run in high load state, transfer cold quantity to the cold storage device through the heat exchanger, make the cold storage medium in the cold storage device undergo water-ice phase change, store cold quantity in the form of ice, until the cold storage device reaches the preset cold storage capacity.

[0032] S3. In the peak period, the cold storage device is activated to release stored cold, and the greenhouse is cooled through the heat exchanger to maintain the temperature stability. If the cold released by the cold storage device cannot meet the cooling demand, the refrigeration compressor is started to assist cooling.

[0033] S4. In the flat period, the temperature in the greenhouse and the cooling demand are monitored in real time, and the proportion of direct cooling by the refrigeration compressor and the cold release by the cold storage device is dynamically adjusted to ensure the temperature stability in the greenhouse, taking into account the operation cost and cooling efficiency.

[0034] Specifically, the system operates the compressor to cool in the valley period, and stores the cold in the cold storage device. In the peak period, the cold stored in the cold storage device is used preferentially to avoid the long-time operation of the compressor in the peak period, thereby significantly reducing the energy consumption and electricity cost in the peak period. In the flat period, the system dynamically adjusts the proportion of direct cooling and cold release according to the actual load demand to ensure accurate control of the temperature in the greenhouse. This peak-shaving operation mode fully utilizes the difference between peak and valley electricity prices, and significantly reduces the operation cost of the system. At the same time, by concentrating the operation load of the compressor in the valley period, the load rate of the compressor is improved, and the problem of reduced efficiency of the compressor in low-load operation in the traditional system is avoided.

[0035] Further, the preset cold storage capacity is determined by establishing a cold storage system capacity optimization model. The model analyzes the daily temperature variation law and cooling demand of the greenhouse during the crop dormancy period, and calculates the optimal cold storage capacity based on the length of the valley period and the rated power of the refrigeration compressor. The preset cold storage capacity is set to any value within the interval.

[0036] The calculation process of the cold storage system capacity optimization model is as follows: First, the electricity prices corresponding to the peak period, the flat period and the valley period, and the rated power of the refrigeration compressor are obtained. Based on the electricity prices corresponding to the peak period, the flat period and the valley period, and the rated power of the refrigeration compressor, the benchmark cost is calculated, and the calculation formula of the benchmark cost is: C 基准 =Σ(Q×P×W) wherein C 基准 is the benchmark cost, Q is the cooling demand state, which is 0 or 1, P is the electricity price of the corresponding period, and W is the rated power of the refrigeration compressor.

[0037] Secondly, based on the electricity prices corresponding to the peak period, the flat period and the valley period, the rated power of the refrigeration compressor, the cooling demand satisfied by the cold storage and the cooling demand required by the compressor, the cold storage optimization cost is calculated, and the calculation formula of the cold storage optimization cost is: C 优化 =Σ(Q 直接 ×P 直接 ×W)+Σ(Q 蓄冷 ×P 低谷XW) wherein C 优化 is the cold storage optimization cost, Q 直接 is the direct cooling demand, P 直接 is the electricity price corresponding to the direct cooling period, Q 蓄冷 is the cooling demand satisfied by cold storage, P 低谷 is the off-peak electricity price.

[0038] Subsequently, the benchmark cost is subtracted from the cold storage optimization cost to obtain the electricity bill savings.

[0039] Finally, the electricity bill savings for different cold storage capacities are calculated, the lowest range of electricity bill savings is found, the range is determined as the optimal cold storage capacity, and the preset cold storage capacity is any value within the optimal cold storage capacity range.

[0040] The cold storage system capacity optimization model determines the optimal cold storage capacity by analyzing the daily temperature variation and cooling demand in the greenhouse. Research shows that a reasonable cold storage capacity not only meets the daytime cooling demand, but also enables the compressor to operate stably at high load, fully utilizing the efficiency advantage of the equipment. During system operation, the compressor operates at high load to cool during the off-peak period, storing cold energy in the ice storage tank; during the peak period, the rate of cold energy release from the cold storage device is precisely controlled according to the greenhouse temperature variation and cooling demand, thereby achieving efficient control of the greenhouse temperature. By fully utilizing the difference between peak and off-peak electricity prices and optimizing the operation strategy, the system achieves significant energy saving and economic benefits.

[0041] Further, when the refrigeration compressor operates at high load, the compressor load rate is maintained between 40% and 90%, keeping the system efficiency at 60%-100%, avoiding low-load and low-efficiency operation of the compressor. Below 40%, the compressor frequently starts and stops, with a sharp efficiency; between 40% and 90%, it is in the high-efficiency operation range of the compressor; and above 90%, it is close to full load, requiring a margin for equipment life and safety considerations. Here, "efficiency" actually refers to the system performance output level, and within the reasonable load rate range, the system can maintain good refrigeration performance COP.

[0042] Further, when the cold storage device releases cold, the release rate is precisely controlled by the automatic control system to ensure a stable dormancy environment for crops in the greenhouse.

[0043] wherein the release rate is precisely controlled by the automatic control system, including: An automatic control system is adopted to adjust the power of the cold carrier circulating pump (20%-100%) through a frequency converter and control the opening of the cold release fluid pipeline (0-100%) through an electric regulating valve, according to the deviation of the measured temperature in the greenhouse from the target temperature 5℃ and the remaining capacity of the cold storage device, to calculate and adjust the cold release flow in real time, effectively controlling the release rate.

[0044] Specifically, the proportion of direct refrigeration by the refrigeration compressor and cold release by the cold storage device is dynamically adjusted, including: The rated power of the refrigeration compressor is set as a first power P1, and the maximum cold release power of the cold storage device is set as a second power P2. The refrigeration compressor uses frequency conversion control to adjust the operating power according to the environmental temperature deviation. The cold storage device adjusts the cold release power by adjusting the flow of the cold release fluid (glycol solution) through the valve. The control system calculates the required total refrigeration power according to the temperature deviation in the greenhouse and the remaining capacity of the cold storage device and distributes it to the two refrigeration sources.

[0045] When the temperature in the greenhouse is higher than the target temperature by 2℃ or more, the power of the refrigeration compressor is adjusted to 0.7 to 0.9 times the first power, and the cold release power of the cold storage device is adjusted to 0.1 to 0.3 times the second power.

[0046] When the temperature in the greenhouse is within ±2℃ of the target temperature, the power of the refrigeration compressor is adjusted to 0.3 to 0.7 times the first power, and the cold release power of the cold storage device is adjusted to 0.3 to 0.7 times the second power.

[0047] When the temperature in the greenhouse is lower than the target temperature by 2℃ or more, the refrigeration compressor stops running, and the cold storage device stops releasing cold.

[0048] An ice storage energy-saving system suitable for greenhouse in Gansu region is used to realize the ice storage energy-saving method suitable for greenhouse in Gansu region, which includes a refrigeration compressor, a cold storage device, a heat exchanger, an automatic control system, and a greenhouse temperature monitoring device. The automatic control system pre-stores the local peak-valley electricity price period division rule, divides 24 hours a day into peak period, flat period and valley period, and has a built-in cold storage system capacity optimization model. The greenhouse temperature monitoring device collects real-time greenhouse temperature data and transmits it to the automatic control system. The automatic control system controls the operation of each component according to the electricity price period and the greenhouse temperature data. During the valley period, the refrigeration compressor is controlled to run at high load, and the cold energy is transferred to the cold storage device through the heat exchanger, causing the medium in the cold storage device to undergo water-ice phase change to store cold energy, until the preset cold storage capacity calculated by the cold storage system capacity optimization model is reached. During the peak period, the cold storage device is preferentially controlled to release cold energy, which is used to cool the greenhouse through the heat exchanger. If the cold energy is insufficient, the refrigeration compressor is started. During the flat period, the proportion of direct refrigeration by the refrigeration compressor and cold release by the cold storage device is dynamically adjusted to maintain the temperature in the greenhouse stable to meet the needs of the crops in the greenhouse.

[0049] Further, the control logic process of the automatic control system includes: S1. Input local real-time air temperature data, greenhouse parameters and electricity price period division information; S2. Calculate the greenhouse air temperature change trend and corresponding cooling demand every hour according to the input data; S3. Determine the current electricity price period and execute the corresponding operation control strategy; S4. After completing the operation in the current period, determine whether there is a next period, if there is, return to S2, if not, calculate the total electricity cost in a day and the saved electricity cost compared with the traditional direct cooling method, and complete a complete operation cycle.

[0050] Further, the greenhouse monitoring points are arranged at the four corners and the central position of the greenhouse. The temperature monitoring points arranged at the four corners of the greenhouse are used to control the starting time of the hot air circulation cooling, and the monitoring points at the central position are used to control the stopping time of the hot air circulation cooling. That is, when the average temperature at the four corners of the greenhouse is 2°C higher than the set temperature, the fan is started to circulate hot air, and when the temperature at the central position is 2°C lower than the set temperature, the hot air circulation is stopped. The average temperature inside the greenhouse is ensured to be within ±2°C of the set temperature.

[0051] The economic analysis results show that, compared with the traditional direct cooling method, the system can reduce the operation cost by more than 40%. While significantly reducing the operation cost, due to the reduction of the excessive configuration demand of the compressor by the operation optimization strategy, the capacity can be appropriately reduced, thereby effectively reducing the initial equipment investment. At the same time, the system adopts advanced automatic control technology, which can intelligently adjust the operation mode according to the outdoor temperature change, the actual load demand of the greenhouse and the electricity price period, further reducing the demand for manual operation, improving the automation and reliability of the system operation. The technical scheme not only provides an economically feasible low-temperature solution for peach tree planting in greenhouse in Gansu region, but also significantly reduces the operating cost of the grower, while ensuring the growth environment of the peach tree, and has good popularization value.

[0052] The technical scheme of the present application shows excellent adaptability and reliability in practical application. The system runs stably, is convenient to maintain, and can meet the cooling demand of greenhouses of different scales. By optimizing the system design and operation strategy, the system realizes the unity of energy saving and economy, and provides reliable technical support for energy saving reconstruction of greenhouses. The implementation of the scheme will effectively promote the development of agricultural modernization and provide important technical support for the sustainable development of facility agriculture.

[0053] Embodiment The present embodiment provides an ice storage energy saving method for greenhouse in Gansu region, which designs a set of efficient ice storage energy saving method for the low temperature demand of peach tree dormancy in greenhouse, combined with the climate characteristics and peak-valley electricity price policy in Gansu region.

[0054] In this embodiment, the cold storage system capacity optimization model is based on the actual meteorological data and time-of-use electricity price policy in Gansu Province, and the optimal cold storage capacity configuration is determined by economic analysis method. The detailed calculation process of the model is as follows: 1. Meteorological data analysis of Gansu Province: According to the meteorological data of Gansu Province from October to November, the daily maximum temperature gradually decreases from 19℃ to 13℃, and the daily minimum temperature decreases from 6℃ to -2℃ in October; the daily maximum temperature decreases from 13℃ to 4℃, and the daily minimum temperature decreases from -2℃ to -10℃ in November. Gansu Province has typical continental climate characteristics, with large diurnal temperature difference, and the minimum temperature usually occurs at 4:00 in the morning, and the maximum temperature occurs at 15:00 in the afternoon.

[0055] During the dormancy period of peach trees, the refrigeration system needs to be started when the temperature in the greenhouse is above 5℃. According to the temperature change rule of Gansu Province and the greenhouse insulation characteristics, the refrigeration demand is mainly concentrated in the daytime when the temperature is high.

[0056] 2. Time-of-use electricity price cost calculation: Gansu Province implements time-of-use electricity price policy: Peak period (7:00-9:00, 18:00-23:00): P 高峰 =0.6564 yuan / kWh Flat period (0:00-2:00, 4:00-6:00, 10:00-11:00, 15:00-17:00): P 平段 =0.4389 yuan / kWh Low valley period (2:00-3:00, 11:00-14:00): P 低谷 =0.2215 yuan / kWh 3. Base cost calculation: Taking a 50kW compressor as an example, the total electricity cost when not using cold storage is calculated by formula C 基准 =Σ(Q×P×W), where C 基准 is the base cost (yuan), Q is the refrigeration demand state (dimensionless), the refrigeration demand state is 0 or 1, P is the electricity price corresponding to the period (yuan / kWh), and W is the rated power of the refrigeration compressor (kW).

[0057] 4. Cold storage optimization cost calculation: The cold storage system stores cold energy in the low valley period, and preferentially releases the stored cold energy in the peak period, and the insufficient part is directly refrigerated by the compressor. The optimization cost is calculated by formula C 优化 =Σ(Q 直接 ×P 直接 ×W)+Σ(Q 蓄冷 ×P 低谷 ×W), where C优化 Cost for cold storage optimization (yuan), Q 直接 Direct cooling demand (dimensionless), P 直接 Electricity price corresponding to direct cooling period (yuan / kWh), Q 蓄冷 Cooling demand satisfied by cold storage (dimensionless), P 低谷 Low valley electricity price 0.2215 (yuan / kWh).

[0058] 5. Capacity optimization analysis: Economic analysis is performed by traversing different cold storage capacities S (in hours, corresponding to S hours x 50 kW of storage capacity): S = 2-3 hours (100-150 kWh): can replace part of the peak period cooling demand S = 4-5 hours (200-250 kWh): can replace most of the peak period and part of the flat period cooling demand S = 6 hours (300 kWh): can replace all peak period and most of the flat period cooling demand Electricity savings ΔC = C 基准 -C 优化 Mainly comes from the transfer of peak electricity price and flat period electricity price to low valley electricity price.

[0059] 6. Optimal capacity determination: Through economic analysis, 4-6 hours of cold storage capacity (200-300 kWh) is the recommended configuration interval. In this interval, the peak-valley electricity price difference (P 高峰 is 2.96 times P 低谷 ), effectively addressing the climate characteristics of large diurnal temperature difference in Gansu, and achieving a good balance between equipment investment and energy saving benefits.

[0060] This optimization model provides a scientific capacity configuration basis for greenhouse cold storage systems.

[0061] Figure 2 The energy saving principle and implementation flowchart of the cold storage air conditioning system. The energy saving principle and implementation flowchart of the ice storage air conditioning system mainly includes five key links: taking electricity price difference as the basis for energy saving, using water-ice phase change process as the core of energy storage, adopting low valley cold storage and high peak cold release operation strategy, combining load rate optimization to ensure high efficiency of the system, and finally realizing the energy saving goal of reducing operation cost and improving equipment utilization efficiency. This system effectively realizes the time transfer of energy use and maximizes economic benefits by reasonably utilizing the peak-valley electricity price difference and cold storage technology.

[0062] The energy-saving principle and implementation process of ice storage air conditioning system are developed in multiple aspects. On the basis of energy saving, the peak-valley electricity price difference is utilized, with the peak electricity price being nearly 3 times the valley electricity price, providing a premise for energy saving. The core of energy saving lies in the physical process of water-ice phase change, which can store energy using the latent heat of water, with a storage efficiency of 60%, realizing efficient conversion and storage of low-valley electricity to cold energy. The energy-saving strategy is implemented through the operation mode, with ice making and energy storage during the valley period, cooling supply during the peak period, and on-demand selection during the flat period, so as to achieve time peak-shifting and save electricity costs. In terms of energy-saving optimization, the load rate is controlled at 40%-90%, the system efficiency is improved from 60% to 100%, and the storage capacity can be reasonably matched according to the demand to ensure the system operates in the efficient zone. The energy-saving results are remarkable, which can reduce the peak electricity consumption, improve the equipment utilization rate, shorten the investment recovery period, and ultimately achieve the dual optimization of economic benefits and energy efficiency.

[0063] Figure 3 The left side shows the temperature variation curve of a typical day in Gansu, with a large diurnal temperature difference. The temperature gradually decreases from early morning to morning, with the minimum temperature occurring around 6:00 in the morning. Then, with the sunrise, the temperature gradually rises, reaching the maximum value at 15:00 in the afternoon, and then decreases to the nighttime low temperature level. The right side shows the variation curve of the maximum and minimum temperature in Gansu from October to November 2023. As can be seen from the right graph, the external temperature gradually decreases over time, with the maximum temperature decreasing from about 19°C in early October to about 13°C in late November, and the minimum temperature decreasing from about 6°C in early October to about 10°C in late November. Through the ice storage system, the internal temperature of the greenhouse can be stably controlled at about 5°C after the harvest in October, ensuring the peach trees enter a stable dormant state. The system stores cold energy during the valley electricity price period and releases cold energy during the peak electricity price period to cope with the diurnal temperature difference and seasonal temperature drop, avoiding the interference of external temperature fluctuations on the dormancy environment of peach trees in the greenhouse. This operation mode not only significantly reduces the electricity load during the peak electricity price period, but also effectively improves the economic benefits of the system.

[0064] As Figure 4As shown, the ice storage system control logic flow first starts from initialization, inputting air temperature data and system parameters, and then calculating hourly air temperature and cooling demand. The system will determine the type of the current period, which is divided into three cases: valley period (2:00-3:00, 11:00-14:00), peak period (7:00-9:00, 18:00-23:00) and flat period (0:00-2:00, 4:00-6:00, 10:00-11:00, 15:00-17:00). In the valley period, the system checks whether the storage capacity is full, and if not, it runs the refrigeration system and stores cold; in the peak period, the system checks whether the storage capacity is sufficient, and if so, it prioritizes the use of stored cold, and if not, it directly cools; in the flat period, the system directly cools to meet the current demand. After completing the control of the current period, the system determines whether there is a next period, and if so, it continues to execute the control strategy of the next period, and if not, it calculates the total electricity cost and the saved electricity cost, and finally ends the entire control flow. This control strategy makes full use of the price difference, stores cold during the valley period, and releases cold during the peak period, thereby achieving the goal of saving electricity costs.

[0065] Figure 5 As shown, when the storage capacity is 100 kWh, the compressor load rate of the conventional air conditioning system is high (yellow column) during the day when the cooling demand is high, and low at night when the cooling demand is low. After combining the storage technology (blue column), the air conditioning system stores cold during the night valley period and releases cold during the day peak period, thereby significantly reducing the load rate during the peak period and shifting most of the load to the low valley period. By taking advantage of the peak-valley electricity price difference, the air conditioning system combined with the storage technology effectively reduces the electricity demand during the peak period.

[0066] The working principle of the air conditioning system combined with the storage technology is shown in Figure 6 As shown, hot air is sent to the heat exchanger 2 of the storage system and the air conditioning evaporator for cooling through the regulating valve 1 and the regulating valve 2. The storage device in the storage system is used to cool the heat exchanger 2, and the air conditioning evaporator is a component of the compression refrigeration system, which is cooled by refrigerant. The compression refrigeration system includes a compressor, a condenser, an expansion valve and an air conditioning evaporator. The refrigerant in the compression refrigeration system can flow to the heat exchanger 1 in the storage system through the three-way valve, and then supply cold to the storage device through the heat exchanger 1, and the storage device supplies cold to the heat exchanger 2 after storage.

[0067] During off-peak electricity price periods, when cooling demand is low, a portion of the cooling capacity of the compressor is transferred to the cold storage device via a heat exchanger, storing the cold energy in the cold storage medium. Conversely, during peak electricity price periods, when cooling demand is high, the system operates in parallel with the compressor and the cold storage device, working together to cool the hot air, thereby reducing the compressor's operating load during peak hours. In this way, the system stores energy during off-peak hours and releases cooling energy to meet demand during peak hours, fully utilizing the peak-valley electricity price difference and significantly reducing operating electricity costs.

[0068] In this embodiment, a screw compressor is selected as the refrigeration compressor. After the refrigerant flow direction is changed by the three-way valve, the refrigerant flows to... Figure 6 Heat exchanger 1 in the system automatically starts the compressor. The heat exchanger is a shell-and-tube type, and is heat exchanger 1 in the compression refrigeration system (e.g., heat exchanger 1). Figure 6 It is installed near the refrigeration compression system. An ice tank is selected as the cold storage device. Clean water is selected.

[0069] Figure 7 This study demonstrates the relationship between the cold storage capacity (kWh) of a cold storage system and electricity cost savings. As the cold storage capacity increases, the electricity cost savings from utilizing peak-valley electricity price differences gradually increase, but the growth trend gradually flattens. In the initial stage (0-20 kWh), the increase in cold storage capacity brings significant electricity cost savings, with the savings rapidly rising from 0 yuan to approximately 3335 yuan, indicating that even a small amount of cold storage capacity can effectively reduce electricity costs during peak electricity price periods. In the growth stage (20-100 kWh), further increases in cold storage capacity continue to bring electricity cost savings, but the rate of increase gradually decreases. For example, when the cold storage capacity is 60 kWh, the electricity cost savings are approximately 4887 yuan, while when the cold storage capacity reaches 100 kWh, the electricity cost savings are approximately 6095 yuan. In the saturation stage (100-140 kWh), the growth in electricity cost savings tends to flatten, eventually reaching approximately 6335 yuan. This indicates that at higher cold storage capacities, the marginal benefit of further increasing the cold storage capacity gradually weakens. Properly allocating cold storage capacity is key to achieving electricity cost savings. By storing cold energy during off-peak hours and releasing it during peak hours, cold storage systems can effectively reduce peak-hour electricity load and fully utilize the peak-valley price difference to maximize economic benefits.

[0070] Figure 8The relationship between the cold storage capacity and the incremental capital cost and the payback period is shown. With the increase of the cold storage capacity, the incremental capital cost shows a nonlinear growth trend, which grows faster in the initial stage (0-40 kWh) and then gradually tends to be flat (100-140 kWh), indicating that the marginal increase of the cost decreases at high cold storage capacity. The payback period is shorter at low cold storage capacity stage (0-20 kWh), gradually extends with the increase of the cold storage capacity, and tends to be stable at high cold storage capacity stage, reflecting the marginal decreasing law of the economic benefit of the system. Overall, by reasonably configuring the cold storage capacity (such as 60-100 kWh), the capital cost can be controlled while the payback period is shortened, the peak-valley electricity price difference is fully utilized, and the economic benefit is maximized.

[0071] In summary, the greenhouse ice storage energy-saving system provided by the present application uses a 50kW compressor as the main refrigeration equipment, which shows significant technical advantages and economic benefits. By combining the optimization operation strategy of peak-valley electricity price, the system can reduce the operation cost by about 25.65%-30.19%. In the best cold storage capacity interval (120-140kWh), more than 6300 yuan of electricity fee can be saved per year. At the same time, thanks to the optimization of the operation mode, the initial equipment investment cost is effectively controlled.

[0072] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An ice storage energy-saving method suitable for a greenhouse in Gansu Province, characterized in that, Includes the following steps: According to local electricity pricing policies, a 24-hour day is divided into peak hours, average hours, and off-peak hours. During the low period, the refrigeration compressor is started and runs under high load. The cold energy is transferred to the cold storage device through the heat exchanger, causing the cold storage medium in the cold storage device to undergo a water-ice phase change and store the cold energy in the form of ice until the cold storage device reaches the preset cold storage capacity. During the peak period, the cold storage device is activated to release the stored cold energy, and the greenhouse is cooled through the heat exchanger to maintain a stable temperature inside the greenhouse; if the cold energy released by the cold storage device cannot meet the cooling demand, the refrigeration compressor is then activated to assist in cooling. During the stable period, the temperature and cooling demand inside the greenhouse are monitored in real time, and the ratio of direct cooling by the refrigeration compressor to the release of cold by the cold storage device is dynamically adjusted to ensure stable temperature inside the greenhouse while balancing operating costs and cooling efficiency.

2. The ice storage energy-saving method suitable for the greenhouse in Gansu region according to claim 1, characterized in that, The preset cold storage capacity is determined by establishing a cold storage system capacity optimization model. The model analyzes the daily temperature change patterns and refrigeration needs of the greenhouse during crop dormancy, and calculates the optimal cold storage capacity by combining the duration of the low period and the rated power of the refrigeration compressor. The preset cold storage capacity is any value within the optimal cold storage capacity range.

3. The ice storage energy-saving method suitable for the greenhouse in Gansu according to claim 2, characterized in that, The calculation process of the cold storage system capacity optimization model includes: Obtain the local electricity prices for peak, off-peak, and low-peak periods, as well as the rated power of the refrigeration compressor; Based on the electricity prices corresponding to peak, off-peak, and low-peak periods, and the rated power of the refrigeration compressor, the baseline cost is calculated. The formula for calculating the baseline cost is as follows: C 基准 =Σ(Q×P×W) wherein C 基准 is the base cost, Q is the refrigeration demand state, which takes 0 or 1, P is the electricity price of the corresponding period, and W is the rated power of the refrigeration compressor. Based on the electricity prices corresponding to peak, flat, and low periods, the rated power of the refrigeration compressor, the refrigeration demand satisfied by the cold storage, and the demand for direct refrigeration by the compressor, the optimized cost of cold storage is calculated. The formula for calculating the optimized cost of cold storage is as follows: C 优化 =Σ(Q 直接 ×P 直接 ×W)+Σ(Q 蓄冷 ×P 低谷 ×W) wherein C 优化 is the cost of the cold storage optimization, Q 直接 is the direct cooling demand, P 直接 is the electricity price corresponding to the direct cooling period, Q 蓄冷 is the cooling demand satisfied by the cold storage, P 低谷 is the low valley electricity price; Subtracting the baseline cost from the optimized cold storage cost yields the electricity savings. Calculate the electricity savings for different cold storage capacities, find the lowest range of electricity savings, and determine the range as the optimal cold storage capacity. The preset cold storage capacity is any value within the optimal cold storage capacity range.

4. The ice storage energy-saving method suitable for the greenhouse in Gansu according to claim 1, characterized in that, The dynamic adjustment of the ratio of direct refrigeration by the refrigeration compressor to the cold release by the cold storage device includes: The rated power of the refrigeration compressor is set as the first power, and the maximum cold release power of the cold storage device is set as the second power. When the temperature inside the greenhouse is more than 2°C higher than the target temperature, the power of the refrigeration compressor is adjusted to 0.7 to 0.9 times the first power, and the cold storage device's cold release power is adjusted to 0.1 to 0.3 times the second power. When the temperature inside the greenhouse is within ±2℃ of the target temperature, the power of the refrigeration compressor is adjusted to 0.3 to 0.7 times the first power, and the cold storage device's cold release power is adjusted to 0.3 to 0.7 times the second power. When the temperature inside the greenhouse is 2°C below the target temperature, the refrigeration compressor stops running and the cold storage device stops releasing cold.

5. The ice storage energy-saving method suitable for the greenhouse in Gansu region according to claim 1, characterized in that, When the refrigeration compressor is running under high load, the compressor load rate is maintained between 40% and 90%, so that the system efficiency is kept between 60% and 100%, and the compressor is prevented from running inefficiently under low load.

6. The ice storage energy-saving method suitable for the greenhouse in Gansu region according to claim 1, characterized in that, When the cold storage device releases cold, the release rate is precisely controlled by an automatic control system to ensure a stable dormancy environment for crops inside the greenhouse.

7. The ice storage cooling and energy-saving method for greenhouses in Gansu Province according to claim 6, characterized in that, The precise control of the cooling rate through an automatic control system includes: An automatic control system is adopted, which uses a frequency converter to adjust the power of the refrigerant circulation pump and an electric regulating valve to control the opening of the cold release fluid pipeline. Based on the deviation of the measured temperature in the greenhouse from the target temperature by 5°C and the remaining capacity of the cold storage device, the cold release flow rate is calculated and adjusted in real time to achieve effective control of the cold release rate.

8. An ice storage cooling and energy-saving system suitable for greenhouses in Gansu Province, used to implement the ice storage cooling and energy-saving method for greenhouses in Gansu Province as described in any one of claims 1-7, characterized in that, include: Refrigeration compressor, cold storage device, heat exchanger, automatic control system and greenhouse temperature monitoring device; The automatic control system pre-stores the local peak-valley electricity price time period division rules, dividing a 24-hour day into peak period, flat period and low period, and has a built-in cold storage system capacity optimization model; The greenhouse temperature monitoring device collects temperature data inside the greenhouse in real time and transmits it to the automatic control system. The automatic control system controls the operation of each component based on electricity price periods and greenhouse temperature data. The operating rules are as follows: During off-peak periods, the refrigeration compressor is controlled to operate under high load, and the cold energy is transferred to the cold storage device through the heat exchanger, causing the medium in the cold storage device to undergo a water-ice phase change to store the cold energy, until the preset cold storage capacity calculated by the cold storage system capacity optimization model is reached. During peak periods, priority is given to controlling the release of cold energy from the cold storage device to cool the greenhouse through the heat exchanger. If the cold energy is insufficient, the refrigeration compressor is started as an auxiliary device. During the dormancy period, the ratio of direct refrigeration by the refrigeration compressor to the release of cold from the cold storage device is dynamically adjusted to maintain a stable temperature inside the greenhouse and meet the dormancy requirements of the crops.

9. The ice storage cooling and energy-saving system for greenhouses in Gansu Province according to claim 8, characterized in that, The control logic flow of the automatic control system includes: S1. Input local real-time temperature data, greenhouse parameters, and electricity price time period division information; S2. Calculate the hourly temperature change trend inside the greenhouse and the corresponding cooling demand based on the input data; S3. Determine the current electricity price period and execute the corresponding operation control strategy; S4. After completing the operation for the current time period, determine whether there is a next time period. If there is, return to S2. If not, calculate the total electricity cost for the day and the amount of electricity saved compared to the traditional direct cooling method, and complete a full operation cycle.

10. The ice storage cooling and energy-saving system for greenhouses in Gansu Province according to claim 8, characterized in that, The greenhouse monitoring points are located around the greenhouse and in the center.

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