Ice Thermal Storage System Research Articles

Performance analysis and multi-objective optimization for an integrated air separation, power generation, refrigeration and ice thermal storage system based on the LNG cold energy utilization

Against the backdrop of escalating resource depletion and the urgent quest for alternative sources, liquefied natural gas (LNG) is increasingly gaining prominence as a sustainable solution, particularly in refrigeration applications. However, its underutilization results in wasted resources. To efficiently harness the released cold energy from LNG gasification, this study proposes an integrated system comprising air separation, power generation, refrigeration, and ice thermal storage. The system undergoes optimization using the non-dominated sorting genetic algorithm II (NSGA-II) to determine the optimal operating parameters. The optimized system is comprehensively analyzed from energy, exergy, economic, and environmental perspectives. Results show that the system, with a 70t/h LNG capacity, achieves an energy efficiency of 42.52% and an exergy efficiency of 48.09%. Economically, the system incurs a cost of approximately 0.0711 $/kWh and can mitigate over 1.4504*107kg of CO2 emissions. Compared to traditional LNG utilization systems, the integrated system demonstrates a 22.32% improvement in energy efficiency, a 7.69% enhancement in exergy efficiency, and a cost reduction of 0.0049 $/kWh. In summary, this technologically advanced and economically viable system offers a significant alternative to optimize LNG cold energy utilization.

Design, analysis, and operation optimisation of a shipborne absorption refrigeration–ice thermal storage system based on waste-heat utilization

The integration of waste-driven absorption refrigeration technology into marine applications is recognized as a promising low-carbon solution. Nonetheless, its practical application does not inherently outperform electric compression technology, primarily due to the absorption system’s inherent thermal inertia and limited adjustability. This characteristic renders the system less responsive to the dynamic refrigeration requirements typically encountered on board vessels. In this study, a shipborne ammonia absorption refrigeration–ice storage system is proposed to balance the cooling load between supply and demand. To evaluate the efficiency of the integrated system for ice storage and cooling during ship sailing, key operational variables including refrigeration temperature, cooling water temperature, and generation temperature are analyzed to assess the thermal cycle performance of the system. A typical shipping route is considered for cooling operation optimisation of the absorption refrigeration–ice storage system. This paper explores four typical cooling-supply strategies and determines the operation modes for the ice storage period and the cooling period based on considerations of energy consumption, energy utilization, and economic factors. The final optimisation results indicate that the combined system has significant advantages based on energy consumption and operation cost. In comparison to compression and absorption refrigeration systems, the proposed system exhibits 52.4% and 8.31% reductions in energy consumption, respectively. Additionally, the operation costs are decreased by 12.27% and 27.41%, respectively, and the life cycle costs are lowered by 11.51% and 32.35%, respectively. The findings of this combined system can provide a technical reference for the design and operation of a ship waste-heat refrigeration system.

Mass flow rate prediction of a direct-expansion ice thermal storage system using R134a based on dimensionless correlation and artificial neural network

Accurately predicting the refrigerant mass flow rate through the electronic expansion valve (EEV) is crucial for improving the system's performance and achieving intelligent control. However, the refrigerant mass flow rate model applicable to the direct-expansion ice thermal storage (DX-ITS) system for a wide range of flow rates is rare in the open literature. In this study, Buckingham-π theorem and artificial neural network (ANN) are adopted to predict the refrigerant mass flow rate through the EEV of the DX-ITS system using R134a. The dimensionless π-groups and optimal number of neurons in hidden layers of ANN model are obtained. The obtained ANN model shows good accuracy, and over 95.7 % of the predicted data are within the 15 % error band. Results indicate that the EEV outlet pressure has a significant impact on the refrigerant mass flow rate compared with the inlet pressure, the average increase in refrigerant mass flow rate is 43.76 kg/h with an outlet pressure increase of 0.05 MPa. Moreover, the refrigerant mass flow rate gently rises with the increase of superheat temperature under fixed EEV inlet and outlet pressure. On average, every 2 °C increase in superheat temperature leads to an approximately 3.98 kg/h increase in refrigerant mass flow rate.

Optimal energy management of grid-connected PV for HVAC cooling with ice thermal storage system

Studies have shown that reducing cooling energy costs and increasing operational efficiency may be achieved by utilizing ice thermal energy storage (ITES) technology while maintaining the thermal requirements in space cooling facilities. Optimal control of the ITES system and integration of renewable energy (RE) sources such as PV and geothermal, depending on the availability of resources and application, can further improve the operation of HVAC's cooling systems and mitigate the increased energy cost required for ice formation and overall cooling energy.This study presented optimal switching control of the ice-build chiller for ITES charging and PV power source. Inputs to the model, simulations, and validations were implemented using the available data, which include the historical exogenous meteorological data, temperatures at the inlet and exit of the plant components, manufacturer's information, and readings from the plant's SCADA chosen for the case study.The main aim of the study was to develop an optimal control model that minimizes the energy consumption and cost in the Ice built chiller and other devices, such as pump fans in the HVAC system, by optimal charge and discharge of the ITES and supplementary utilization of the greener energy source PV source under the time of use (ToU) tariff and desired cooling load demand. The case study for a healthcare building was considered in implementing the model.Simulations were implemented in the MATLAB optimization toolbox with the Solving Constrained Integer Programs (SCIP) solver, which was chosen to address mixed integer programming (MIP) problems. It incorporates algorithms like a branch and cut conflict analysis and pre-solving techniques to handle intricate optimization problems involving continuous and discrete decision variables.The optimal switching control model yields approximately 33 % of energy cost savings during the summer months that involve using the HVAC with ITES compared to the current system control (baseline). Additionally, the ITES temperature remained below 0 °C to maintain thermal requirements as an operation constraint. The inclusion of PV and battery options as a source of power to the pumps accounted for 10–15 % of the overall energy usage of the system. Optimal control of the system to utilize the stored energy during peak pricing and high demand periods eliminated the extreme dependence on grid energy in some instances. Despite the additional capital required for the controller, solar PV, and batteries installation, the study projects a return on investment within two years, with a 20-year lifetime energy cost savings estimate of 35 % if inflation and annual electricity price increases are estimated at 5 % and 10 %, respectively.

Dynamic modelling and performance prediction of a novel direct-expansion ice thermal storage system based multichannel flat tube evaporator plus micro heat pipe arrays storage module

Direct-expansion ice thermal storage (DX-ITS) system can improve the energy efficiency ratio (EER) by integrating the evaporator and the storage module. In this paper, a dynamic model for a DX-ITS system is developed to predict system behavior. This system consists of multichannel flat tube evaporator plus micro heat pipe arrays storage module, a 4-HP compressor using R134a, an air-cooled condenser with 40 m2 area and an electronic expansion valve. On this basis, the influences of the condenser's cooled-air temperature, cooled-air flow rate, and compressor speed on the system energy and thermodynamics performance are studied. Results show that the EER and the charging power could reach 2.24 and 5.41 kW, respectively, under cooled-air temperature, cooled-air flow rate, and compressor speed of 28.5 °C, 4660 m3/h, and 1450 rpm. The exergy efficiency is more sensitive to cooled-air temperature, which decreases by 22.48% from 11.52% to 8.93% as the cooled-air temperature increases from 18 °C to 35.5 °C. Moreover, the compressor has the highest exergy destruction ratio of 40%–55% in the exergy analysis of the system component, while the condenser has the lowest exergy destruction ratio of 7%–15%, indicating that optimizing the compressor is the key to improving the system's performance.

An optimization strategy for enhancing energy consumption performance in digital currency miner's building

AbstractCryptocurrencies, as a way of extraction, are categorized into two main groups of non‐mineable and mineable. Bitcoin (BTC), the most famous mineable digital currency, utilizes the Proof of Work (PoW) algorithm for maintaining network solidarity. Its mining process is done by devices known as application specific integrated circuits (ASICs), which consume electricity and turn it into heat. They shall operate within an accepted temperature range of around 25°C; otherwise, they will face an efficiency drop; consequently, all mining sites require a proper cooling system. This study aims to investigate the problem of high energy consumption for cooling in digital currency mining sites and to present a solution for that via optimizing the capacity and operation of the chiller and ice thermal storage system (ITS). The results show the utilization of the ITS system reduces the operational costs by 10%, and the ITS system provides 1320 kWh of cooling energy during peak hours. Finally, the sensitivity analysis results considering the impact of the electricity tariff on the size and operation of the system have confirmed that with an increase in peak time tariff, the role of the ITS system in cost reduction increases.

Energy and exergy analysis of a novel direct-expansion ice thermal storage system based on three-fluid heat exchanger module

Direct-expansion ice thermal storage (DX-ITS) system can overcome the mismatch between cold energy supply and demand, and also exhibit the characteristics of high energy efficiency, simple pipeline and minimal installation space. However, existing DX-ITS failed to achieve simultaneous high-efficiency heat transfer in the processes of charging and discharging, thereby limiting its widespread use. This study developed a novel DX-ITS system based on three-fluid heat exchanger modules employing micro heat pipe arrays to address the proceeding issue. Temperature distribution, pressure, charging and discharging power, energy efficiency ratio, exergy efficiency and ice packing factor during the charging and discharging processes at different compressor speeds, cooling-air temperature and flow rates were experimentally studied. Results demonstrated that maximum charging power, energy efficiency ratio, exergy efficiency, ice packing factor and discharging power of proposed system using a 4 HP compressor under experimental conditions reached 5.71 kW, 2.31, 11.12 %, 82.1 % and 4.99 kW, respectively. Moreover, cooling-air temperature had a more significant effect on system performance compared with cooling-air flow rate and compressor speed. The 11.7 %, 25.9 %, 24.3 %, and 20.6 % reductions in charging power, energy efficiency ratio, exergy efficiency, and ice packing factor were observed with an increase of cooling-air temperature from 18 °C to 35.5 °C.

A case study in the field of sustainability energy: Transient heat transfer analysis of an ice thermal storage system with boiling heat transfer process for air-conditioning application

A numerical study on transient heat transfer of shell and tube type ice thermal storage system is carried out based on the concept of a single u-tube borehole thermal network. Two tubes are arranged in the thermal storage tank in which glycol solution flows in one of the tubes, while a refrigerant flows in the other tube. In this study a boiling heat transfer of the refrigerant is considered to model the heat exchange among the ice storage, the refrigerant and the glycol solution which can be used for air-conditioning application. Temperature variation of all the three substances of the ice thermal storage system (i.e. the ice/water, glycol solution and the refrigerant) with depth has been determined for specified times. Also temperature history of all the three substances has been determined at specific depth of the thermal storage system. Finally the effect of mass flow rate of the refrigerant on the solidification process has been investigated with the numerical method. The transient boiling heat transfer of the refrigerant in the saturated region, the transient single-phase heat transfer process of the glycol solution and the refrigerant at the superheated region, and the solidification process of the ice thermal storage system were all investigated in this study.

Optimal Design of Integrated Chiller Capacity with Ice Thermal Storage for Commercial Buildings through Cooling System Cascade Analysis

Chilled water air conditioning system is used to supply cooling systems in large capacity for industrial processes and commercial buildings. Air conditioners contribute more than 60 percent of electricity consumption in buildings. District Cooling System (DCS) technology comprises a central chiller plant which provides advantage compared to local air conditioning system. It has higher efficiency, uses less power in system operation, allows more usable space in buildings, and can be operated with minimum manpower while handling same amount of cooling load. The integration of a chiller with ice thermal storage (ITS) offers more operational flexibility while reducing space cooling expenses. This paper presents a systematic framework for design and operation of District Cooling Plant (DCP) comprising an integrated chiller and ice thermal storage system. The Cooling System Cascade Analysis (COSCA) based on pinch analysis is constructed to determine the chiller optimal size and ice thermal storage capacity. The District Cooling System configuration for this study comprises a cooling tower, chiller (centrifugal, variable centrifugal, glycol) and ice thermal storage system. The application of this technique to fulfil 66,284 refrigerant tonne hour (RTH) cooling load demand from commercial buildings reveals the optimal capacity of the chiller is 3068.91 refrigerant tonne (RT), ice tank rating at 989 refrigerant tonne (RT) and ice tank capacity is 9892.75 refrigerant tonne hour (RTH).

Simulation and experimental study of thermal storage systems for district cooling system under commercial operating conditions

The use of ice as a phase change material (PCM) for such latent thermal energy storage (LTES) systems has been well established in industrial thermal storage. Organic phase-change materials (PCMs) such as paraffin waxes present advantages over ice for LTES systems in commercial air conditioning application due to higher phase-change temperatures and negligible volume expansion. In this study, an encapsulated ice thermal storage (EITS) system was analysed, modelled via COMSOL and validated with operating data. The numerical model is employed to analyse a similar theoretical encapsulated PCM (EPCM) system under similar and altered operating conditions using experimentally-derived thermal properties. Key results from this work revealed that the EPCM system is able to attain higher cold energy storage capacity of up to 3 times that of a reference chilled water tank and 9.37% more than that of the EITS under high flow conditions due to greater degrees of solidification. The effect of heat transfer fluid flowrate on solidification ratio and energy charged is also observed to be more pronounced in EPCM systems as compared to EITS systems.

Study on optimal ice storage capacity of ice thermal storage system and its influence factors

This paper explores the impact of different control strategies and electric tariff structures on the optimal ice storage capacity in relation to system economy for four typical buildings of hotel, restaurant, mall and office. The ice storage rate and electric price ratio are introduced to denote the various ice storage capacities and the different electric tariff structures, respectively. Then the chiller capacity and economic evaluation index value corresponding to each typical building with various ice storage rates and electric price ratios under three control strategies (chiller priority, storage priority, and optimizing) are calculated. The results indicated that there is respective optimal ice storage rate corresponding to both the minimal chiller capacity and the minimal economic evaluation index value. The optimal ice storage rate in relation to minimal chiller capacity is constant value under each control strategy. Such optimal values under both chiller priority and optimized control strategies are equivalent and less than that under storage priority control strategy. However, the optimal ice storage rate in relation to minimal economic evaluation index value under each control strategy is significantly affected by the electric tariff structures. The corresponding optimal ice storage rates under both chiller priority and optimized control strategies are equivalent and increase to a definite value with the increase in the electric price ratio. While the optimal ice storage rate under storage priority control strategy will appear when electric price ratio is greater than 3. The results also showed that, when electric price ratio increases to a certain value, the optimal ice storage rates corresponding to both minimal economic expense and minimal chiller capacity under each control strategy for the four typical buildings are equivalent.

Effect of encapsulated ice thermal storage system on cooling cost for a hypermarket

Effect of encapsulated ice thermal storage system on cooling cost for a hypermarket

B-18 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第3報)

B-18 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第3報)

B-16 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第1報)

B-16 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第1報)

B-17 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第2報)

B-17 氷蓄熱を活用した大温度差空調システムの高効率運転の評価(第2報)

Discharging performance of a forced-circulation ice thermal storage system for a permanent refuge chamber in an underground mine

This study aimed to develop a proper control strategy for a forced-circulation ice thermal storage system (ITSS) designed for a permanent refuge chamber with an accommodation capacity of 50 persons. The heat transfer characteristics of the ITSS were investigated through theoretical and experimental approaches. A quasi-steady one-dimensional mathematical model for predicting the transient discharging power was proposed. On this basis, a control strategy was proposed to fulfill the minimum cooling requirement in consideration of both effective discharging time and human comfort. The minimum required velocity of the ITSS was analyzed; from this, the effective working time of the ITSS was determined to be 64.57h. Additionally, the heat load inside the chamber was found to be the main factor that affected the effective temperature control duration and the utilization ratio of the ice. Thus, a reserve factor, which is defined as a function of rated heat load and determined by the discharging performance model, is suggested for consideration during optimization.

Optimization and analysis of Building Combined Cooling, Heating and Power (BCHP) plants with chilled ice thermal storage system

Thermal Energy Storage (TES) systems in Building Combined Cooling, Heating and Power (BCHP) plants are attracting more attentions nowadays in China. In this paper, a simple linear programming optimization model is developed for BCHP systems with an Ice Storage System (ISS), a hybrid Electric Chiller (EC) and Absorption Chiller (AC). Two BCHP systems (one with TES and the other without TES) are compared with the conventional system in a super high-rise building in Shanghai city. The design and operation of both BCHP systems are optimized with the linear programming tool. The results show that natural gas price is the most important factor regarding the economic performance of the BCHP plants, followed by electricity utility price and the price of the prime motor. In this case study, both BCHP options show higher energy use efficiency and better economic performance than the conventional solution. Compared with the BCHP system without TES, the one with TES has similar energy efficiency level, but lower operation cost due to its load shifting capability. Thus, considering the overall life cycle cost, the BCHP system with TES option is suggested to be used in similar high-rise buildings in Shanghai city.

Design and analysis of an ice thermal storage system for residential air-conditioning applications

In recent years, owing to electricity consumption growth in Iran particularly during warm seasons, problems have emerged in the electricity distribution networks like electricity shortage. Studies show that a large portion of the Iranians' electricity consumption during warm seasons is related to the air-conditioning systems. These systems operate higher during warm hours of the day which often coincide with periods of high electricity consumption. To balance the energy consumption of air-conditioning systems, the ice-storage technology is utilised to move the energy consumption away from the on-peak hours. A case study has been carried out on a residential apartment in the north of Iran to compare the performance of the system compared with that of a conventional air-conditioning system. The results signify that using an ice-storage system can reduce the energy consumption during the on-peak hours by 56% and the cooling charge by approximately 18.6%.

Parametric study of ice thermal storage system with thin layer ring by Taguchi method

A numerical study of material, thickness and arrangement of thin layer ring has been comparatively conducted to achieve heat transfer enhancement in the building thermal storage system. The parameters of thin layer ring from three perspectives have been numerically investigated and optimized by the Taguchi method to find the optimal combination. Nine combinations of model are carried out by combining different levels of each factor, and ice generated area of each combination has been statistically analysed. The results show that material and arrangement of thin layer ring have the most significant impact on the ice formation, but the thickness of thin layer ring has trifling effects on the ice formation. From this study, the optimal combination (A3B2C1) is acquired, and the reproducibility of the results is verified by two analytical results.

Numerical study of thin layer ring on improving the ice formation of building thermal storage system

Ice thermal storage systems have been widely used in HVAC&R systems for improving energy efficiency and reducing energy costs around the world. In this paper, a numerical model is developed to simulate the ice formation in a typical ice thermal storage system. The first study is to investigate the effect of a cooled cylinder placed in a rectangular space filled with water on the ice formation process. The validated numerical model can predict temperature distribution associated with liquid fraction during the process. Based on the result obtained from the first study, further research is focused on the novel structure of thin layer ring. The computational solutions can demonstrate that the thin layer ring structure can successfully increase an ice generated area and shorten the ice formation period in a typical ice thermal storage system. Finally, a parametric study was carried out to investigate the effect of material, thickness, and arrangement of thin layer ring. It predicted that the heat transfer performance of the thin layer ring is dependent on its material, thickness, and arrangement. Ice formation with novel thin layer ring can be improved by increasing the thermal conductivity of a material. A copper ring has the best performance among aluminum, stainless steel, magnesium alloy. The results show that the ice formation rate can be increased by increasing the thickness of the ring from 0.25 mm to 1 mm, while slowed by increasing from 1 mm to 2 mm and has the best performance with 3 mm ring in this study. Finally, the staggered arrangement of ring shows the best results of the ice formation compared to one parallel and two parallel cases.