Cool Storage System Research Articles

Design of a Cooling System Integrated with Ultraviolet Light for Preservation of Fruits and Vegetables at Variable Tropical Weather Conditions: A Case Study of Arusha, Tanzania

Post-harvest losses of fruits and vegetables pose significant challenges, especially in tropical climates. This study introduces the development and performance evaluation of a solar-powered evaporative cooling storage system integrated with ultraviolet light (UV) designed for preservation of perishable fruits and vegetables. The cooling chamber supplied with ultraviolet lamp was developed using locally available materials such as sisal, sponge, and bricks. The performance of the system was evaluated in terms of air temperature decrease, relative humidity increase, and evaporative cooling power capacity both for sunny and cloudy tropical weather conditions. The study reveals that activating the UV light considerably extends the shelf life of fruits and vegetables. The system was able to extend the shelf life of perishable products by up to 21 days when exposed to ultraviolet light and by 9 days when not exposed to ultraviolet light. On sunny days, active system operation leads to an average temperature reduction of 5.0 °C, along with a relative humidity increase of 23%. On the contrary, on cloudy days, the cooling impact diminishes slightly, resulting in temperature decrease of approximately 3.5 °C and relative humidity increase of 18%. These findings emphasize the potential of the solar-powered evaporative cooling system, combined with UV light treatment, as a viable approach to combat post-harvest losses in tropical environments.

Optimal operation of energy hubs including parking lots for hydrogen vehicles and responsive demands

Energy hubs (EHs) are units that enable the simultaneous supply of different types of energy demands by converting energy carriers, and using energy storage systems. Energy storage systems can significantly help maintain the balance between energy production and energy demand, while enabling the use of renewable energy resources, and improve the flexibility of energy hubs through the efficient management of energy supply. In this study, a stochastic model is designed for unit commitment (UC) in Energy hubs, which include hydrogen vehicle (HV) parking lot, electric heat pump (EHP), absorption chiller (AC), photovoltaic (PV) module, boiler, hydrogen electrolyzer (HE) and electric, thermal, cooling and hydrogen storage systems. Here, natural gas (NG) and electricity are the input of the EH and are used to supply electric, hydrogen, heat, cooling and NG demands. In this work, uncertainties of demands, the initial power of hydrogen vehicle tanks and PV power are modeled, and the impact of storage systems, parking lot and demand response on EH operation are also investigated. The proposed mixed integer linear programming (MILP) model is solved for unit commitment in EH using the CPLEX solver in the GAMS software. The results show that the EH operation cost is reduced by 27.58% in the presence of demand response, energy storage systems by 12.68%, and hydrogen vehicles by 2.9%. In addition, according to the results, it can be found that the cooling storage system by 6.19% has the significant impact on reducing EH operation costs compared to electrical, hydrogen and thermal storage systems, while electric demand response by 15.89% reduction in operation costs is more effective than others. Moreover, the impact of different contingencies on the EH operation is evaluated. The results indicate that the hydrogen demand is fully supplied despite the exit of the power grid. This is particularly due to the presence of hydrogen vehicles (HV tanks) in the model. Also, simulations show that the outage of the power grid leads to 1288.64 kW of energy not served.

Optimal and stochastic performance of an energy hub-based microgrid consisting of a solar-powered compressed-air energy storage system and cooling storage system by modified grasshopper optimization algorithm

Simultaneous operation of different energy generation and transmission infrastructures is a subject that has been considered under the concept of energy hub. This subject is highly regarded in the field of microgrids. One of the basic issues for investors is to properly utilize the energy hub for optimally managing energy carriers, especially in the energy price prediction. In the present paper, a new strategy is introduced for the energy hub in order to achieve the optimal performance of a microgrid (MG) that includes different energy carriers for each day. The objective of this strategy is to minimize the operation cost and consider the environmental issues. The proposed energy hub consists of a combined cooling-heating-power (CCHP) system along with a wind turbine and photovoltaic cells. The studied energy hub system is composed of an ice storage conditioner (ISC) system and an energy storage system (ESS) as the energy storage resource (ESR). One of the goals of the present work is to investigate the effect of solar-powered compressed-air energy storage (SPCAES) on the performance of the energy hub. The proposed strategy takes into account the uncertainty of the energy resources such as the wind and sun for meeting the electric, thermal, and cooling needs in different scenarios. In the present paper, to produce various scenarios, the Latin hypercube sampling (LHS) method is used. Also, the k-means method is used to reduce the number of scenarios. The objective function is solved using the modified grasshopper optimization algorithm (MGOA). According to the modeling results, the ESS can exhibit successful performance in the energy management strategy. • Considering the effects of the SPCAES and ISC on optimal performance of the energy hub. • Considering the effects of the SPCAES and ISC on the optimal performance. • Application of generations sources as PV, WT, CHP system, and TESS.

Quality retention and shelf‐life prolongation of cucumbers (Cucumis sativus L.) under different cool storage systems with passive modified atmosphere bulk packaging

AbstractStorage plays an important role in maintaining the post‐harvest shelf life of fresh fruits and vegetables. Cool storage of perishables is costly due to higher energy input. So, to reduce the operating cost and minimize the postharvest loss, a low‐cost on‐farm storage structure is required, especially in tropical developing nations. In this study, the effectiveness of different cool storage systems was validated by conducting shelf‐life studies on freshly harvested seedless cucumbers with (LDPE bags; 37.5‐μm thickness) and without packaging (open plastic crates) under ambient (25.0 ± 8°C; 55 ± 14% RH), cool storage (10.0°C; 90 ± 5% RH), and evaporative cool storage (ECS) systems (19 ± 3°C; 82.0 ± 9% RH). The shelf life and quality of cucumbers were determined based on weight loss, titratable acidity, total soluble solids, ascorbic acid, firmness, and total colour difference. Analysis of the data revealed that the effect of storage conditions and packaging on shelf life and quality was significant (p ≤ 0.05). It was found that the samples packaged in LDPE films had better firmness and lower weight loss as compared with unpackaged samples. Adoption of the evaporative cooling system helped in achieving temperatures of 8–10°C lower than the ambient depending on the environmental parameters. The relative humidity of the evaporative cooling system ranged from 75% to 90%, which is highly suited for the storage of fruits and vegetables. Although the shelf life of cucumbers was longer under cool storage (24 days), ECS could be used as an alternative for low‐cost on‐farm short‐term storage of fresh fruits and vegetables before marketing.

Optimal Economic Modelling of Hybrid Combined Cooling, Heating, and Energy Storage System Based on Gravitational Search Algorithm-Random Forest Regression

The hybridization of two or more energy sources into a single power station is one of the widely discussed solutions to address the demand and supply havoc generated by renewable production (wind-solar/photovoltaic (PV), heating power, and cooling power) and its energy storage issues. Hybrid energy sources work based on the complementary existence of renewable sources. The combined cooling, heating, and power (CCHP) is one of the significant systems and shows a profit from its low environmental impact, high energy efficiency, low economic investment, and sustainability in the industry. This paper presents an economic model of a microgrid (MG) system containing the CCHP system and energy storage considering the energy coupling and conversion characteristics, the effective characteristics of each microsource, and energy storage unit is proposed. The random forest regression (RFR) model was optimized by the gravitational search algorithm (GSA). The test results show that the GSA-RFR model improves prediction accuracy and reduces the generalization error. The detail of the MG network and the energy storage architecture connected to the other renewable energy sources is discussed. The mathematical formulation of energy coupling and energy flow of the MG network including wind turbines, photovoltaic (PV), CCHP system, fuel cell, and energy storage devices (batteries, cold storage, hot water tanks, and so on) are presented. The testing system has been analysed under load peak cutting and valley filling of energy utilization index, energy utilization rate, the heat pump, the natural gas consumption of the microgas turbine, and the energy storage unit. The energy efficiency costs were observed as 88.2% and 86.9% with heat pump and energy storage operation comparing with GSA-RFR-based operation costs as 93.2% and 93% in summer and winter season, respectively. The simulation results extended the rationality and economy of the proposed model.

Day-ahead scheduling of energy hubs with parking lots for electric vehicles considering uncertainties

Energy hubs (EHs) are units in which multiple energy carriers are converted, conditioned and stored to simultaneously supply different forms of energy demands. In this research, the objective is to develop a new stochastic model for unit commitment in EHs including an intelligent electric vehicle (EV) parking lot, boiler, photovoltaic (PV) module, fuel cell, absorption chiller, electric heat pump, electric/thermal/cooling storage systems, with electricity and natural gas (NG) as inputs and electricity, heat, cooling and NG as demands. The uncertainties of demands, PV power and initial energy of EV batteries are modeled with Monte Carlo Simulation. The effect of demand response and demand participation factors as well as effect of EVs and storage systems on EH operation are investigated. The results indicate that thermal demand response is more effective than electric and cooling demand response; as it decreases EH operation cost by 12%, while electric demand response and cooling demand response decrease it respectively by 9.3% and 4.2%. The results show that at low electric/thermal/cooling demand participation factors, an increase in participation factor sharply decreases EH operation cost, while the same amount of increase at higher participation factors leads to a smaller decrease in operation cost. The results also indicate that thermal storage system and cooling storage system have significant effect on reduction of EH operation cost, while the effect of electric storage system is trivial.

Experimental investigation on packed bed cool storage system for supply-demand management in building air-conditioning system suitable for micro thermal grid

In most of the developed nation, the increase in percentage share of renewable power in the total power generation causes major concerns over the integration of these renewable power with the grid resulting grid instability. Energy storage is a new frontier technology which is considered as the ultimate solution in developing micro-smart grid with distributed renewable power generation. Most of the hot countries like India spend nearly 24% of the electricity generated on air-conditioning and food preservation. Under such scenario, among the various types of storage systems, the cool thermal storage plays a vital role to promote renewable power in an economical way. Considering the importance in the present renewable energy scenario, in the present work, an experimental investigation was performed on a packed bed cool storage system integrated with a chiller system which has major advantages in central air-conditioning system for demand management strategies. The storage system consists of encapsulated spherical balls filled with a mixture of distilled water and pseudomonas (nucleating agent) as phase change material and a mixture of distilled water and mono-ethylene glycol as heat transfer fluid. The essential parameters such as reduction in subcooling, instantaneous, and cumulative heat transfer during the charging process are presented for the efficient operation.

Thermal performance enhancement of eutectic PCM laden with functionalised graphene nanoplatelets for an efficient solar absorption cooling storage system

The present work investigates the thermal enhancement of a binary eutectic phase change material (PCM) (150–200 °C), laden with different concentrations of COOH-functionalized Graphene nanoplatelets (f-GNP) for a multi-effect solar cooling thermal storage system. The novel nano-composite is prepared by varying the weight concentration of f-GNP from 1% to 5% in a pristine eutectic salt of LiNO3-KCl (50:50) using the standard nano synthesis protocol. The microstructure, dispersion uniformity are evaluated using scanning electron microscope (SEM) and thermophysical properties of the nano-composite are characterized using dynamic Differential scanning calorimetry (DSC). The thermal conductivity enhancement due to the doping of f-GNP is studied through a series of experimental trials conducted with Laser flash analysis (LFA). The obtained data is plotted and compared with a more robust theoretical thermal conductivity model. It is found that thermal conductivity rises by 104% with f-GNP dispersions, which reflects the improved thermal performance of the storage system. The specific heats of the solid and liquid phase show an increase of 80% & 38% respectively at f-GNP concentration of 5%. Finally, the effect of doping f-GNP on the conjugate heat transfer inside the PCM and fluid flow of HTF is investigated in a vertical shell and tube type storage system, suitable for the double effect solar cooling system. The f-GNP dispersions accelerate the heat storage process with a maximum decrease of 17.3% in the total melt duration. In addition, the role of increased viscosity on the natural convection is simultaneously studied with the increased thermal conduction due to nanoplatelets dispersions.

A hybrid short-term load forecasting model and its application in ground source heat pump with cooling storage system

This paper proposed a hybrid hour-ahead forecast model, which combines multiple superimposed long and short term memory (LSTM) network and back-propagation neural network (BPNN), for the purpose of the load forecast on a building-level. The model (hybrid LSTM-BPNN) takes full consideration of the influence of the meteorological information, time information, the information of persons and devices and indoor thermal parameters. A method (LSTM-BPNN + BPNN) is further developed based on the forecasting advantages of sensible heat by hybrid LSTM-BPNN and latent heat by BPNN, in which the cooling load was split into sensible heat and latent heat to forecast separately. The results show that the method achieves the best performance for hour-ahead load forecasting compared with several classic forecasting models. An operation strategy based on the proposed LSTM-BPNN + BPNN method and LSTM model is applied to an improved ground source heat pump system integrated with cooling storage (GSHPs-CS) which was equipped with two storage tanks to achieve the variable volume control of stored chilled water. The system model is established by TRNSYS. Compared to conventional GSHPs-CS, the energy consumption and operating cost of the improved GSHPs-CS system were reduced by 11.5% and 7.5%, respectively. • A hybrid short-term load forecasting model and method is proposed. • Proposed model improved forecasting accuracy than classical models. • The forecasting models and method were applied to an improved GSHP-CS system. • The forecasting model can achieve a predictive control and realize energy saving.

Encapsulation surface roughness effect on the performance of cool storage systems

Cool Storage is a well-known technique that been used to increase the energy efficiency of cooling systems. This paper represents a novel experimental work for the effect of internal capsules surface roughness on the performance of encapsulated cool storage systems. In this study, distilled water was used as a phase change material inside capsules. Internal surface roughness of 0, 3, 7 and 12 μm were tested using the same heat transfer fluid Characteristics. Heat transfer fluid (HTF) composed of 50–50 wt. of (water–ethylene glycol) was used with a fixed volume flow rate of 12 L/min LPM and four different inlet temperatures of −6, −8, −10 and −12 C. The solidified mass fraction, charging rate and energy storage were calculated and plotted versus the charging time to determine the surface roughness effect on the cooling performance of the system. Results showed that the internal surface roughness of capsules had adverse effect on the system performance through increasing the total freezing (charging) time. Results also indicated that the charging time increased by 14–17% at inlet flow temperature of −12 and −6 ̊C, respectively at the higher roughness values compared with the smooth surface capsule e.g. zero roughness parameter.

Experimental study on the thermal performance of solar air conditioning system with MEPCM cooling storage

Solar powered air conditioning system is a hot issue in the study field of building energy conservation. An experimental platform of solar powered air conditioning with microencapsulated phase change material (MEPCM) cooling storage system was carried out to evaluate the efficiency of the solar powered air conditioning system and the coupled relation with the solar radiation intensity. The outdoor and indoor environmental test system was used to collect the performance parameter data of test room to verify the cooling energy storage effect. The solar air conditioning combined with MEPCM cold storage system which was tested in Chengdu city, China. According to the analysis result, the transient thermal efficiency would decline with the rising normalized temperature difference. The transient thermal efficiency has the same variation trend with the solar radiation. The indoor air temperature of the test room was maintained between 18°C and 22°C. MEPCM cold storage system could maintain the indoor air temperature in the stable range. The energy saving rate of the completed system could reach at 30.5%. The research result could help to improve the study of solar powered air conditioning system and its application.

Policy recommendations for using cool thermal energy storage to increase grid penetration of renewable power sources (1607-RP)

The majority of U.S. states have adopted policies intended to increase renewable energy generation. Because of the intermittent nature of wind and solar resources, in particular, several states have also adopted energy storage policies. Energy storage serves to bridge mismatches between intermittent electricity production and demands from end-use electricity consumers. Because building air-conditioning loads commonly drive peak electric grid demands, storage in the form of thermal energy is an attractive alternative to electric storage technologies. Cool thermal energy storage systems have been used successfully for decades by building owners seeking to shift air-conditioning system electric consumption to off-peak time periods when electricity rates are low. In the current article, the authors present a strategy for controlling cool thermal energy storage systems to enable an increased penetration of intermittent wind and solar generation. It was found that cool thermal energy storage systems operated using this strategy have not only reduced life-cycle costs compared to air-conditioning systems without cool thermal energy storage, but they more effectively utilize the renewable resource. Because cool thermal energy storage is a mature technology and the results show that cool thermal energy storage is more cost-effective than electric energy storage technologies currently in widespread use, policies that aim to increase renewable energy generation should also support increased deployment of cool thermal energy storage as an enabling technology.

Simulation of the Melting Process of Ice Slurry for Energy Storage Using a Two-Fluid Lattice Boltzmann Method

Abstract: Ice slurry can be used as the thermal storage media in latent cool storage systems for both residential and commercial buildings. This paper presents the investigation of the phase change characteristics of the ice slurry using a two-fluid Lattice Boltzmann Method (TFLBM). The melting and migration processes of the ice slurry are simulated by improving the equilibrium distribution function and matching the relevant parameters such as the kinetic viscosity of ice particle cluster and cross-collision coefficient. The sensitivity analysis of the ice slurry viscosity and cross-collision coefficient are achieved through six numerical experiments, and the ice melting in the internal-melt ice-on-coil thermal storage device is then calculated. The results could be potentially used to guide the design of the ice slurry for cooling both residential and commercial buildings.

Phase Change Material with Thermal Energy Storage System and its Applications: A Systematic Review

Objective: The purpose of this review leads to use of Energy conservation technologies. Methods: There are so many systems which are used for energy saving among them thermal storage system with Phase Change Material (PCM) is well known. In this review majority focuses on the human comforts. It was observed that maintaining the human comfort is the challenging task for living spaces like room, offices etc. such type of required energy which is satisfied by thermal storage PCM based system. If the Phase change materials are applied to building applications they can be used for peak load shifting in cool storage system. Findings: Development of the new techniques for getting thermal comfort for building (lowering the heating and cooling demand is required. Also it includes the expenses behind development, maintenance and installation. Moreover this review finds the effective phase change materials. Improvements: Such thermal storage system has a potential to replace the conventional methods but the effectiveness or efficiency of that system is less. So it is required improvement in the selection of thermal storage system and phase change material. Also this review presents the potential of the phase change material system.

Modeling of Potato Shelf Life on Evaporative Cooling Storage

A model of evaporative cooling storage system was designed to increase potato shelf life for improving potato storage system. Two cultivars of potato ‘Diamant’ (100 gm and 51 gm per tuber) and ‘LalPakri (23 gm and 11 gm per tuber) were placed on four shelves of the bin. Each shelf holds 240 kg of potato from 23 march 2013 to December 2013. Potato spoilage, sprouting, shrinkage, moisture content, vitamin C and total sugar content of potato were measured. Experimental results revealed that potato spoilage progressively increased from April to November and sprouting of potato gradually increased from June to October, but stopped in November. The cumulative spoilage and sprouting were much lower in the improved bin compared to traditional farmer’s practices. Shrinkage of potato was found higher in farmer’s practice than that of storage bin from October to November. Moisture content of potato was higher during May and reduced gradually to the lowest value during November in both of practices. No significant difference was found in two practices on vitamin-C content. Sugar content of ‘Diamant; potato was lower in the storage bin during November. According to data analysis and regression curve storage bin model was more appropriate for both cultivars than farmer practice and significantly more appropriate for ‘LalPakri’ potato.

Optimal Cooling Load Sharing Strategies for Different Types of Absorption Chillers in Trigeneration Plants

Trigeneration plants can use different types of chillers in the same plant, typically single effect and double effect absorption chillers, vapour compression chillers and also cooling storage systems. The highly variable cooling demand of the buildings connected to a district heating and cooling (DHC) network has to be distributed among these chillers to achieve lower operating costs and higher energy efficiencies. This problem is difficult to solve due to the different partial load behaviour of each chiller and the different chiller combinations that can cover a certain cooling demand using an appropriate sizing of the cooling storage. The objective of this paper is to optimize the daily plant operation of an existing trigeneration plant based on cogeneration engines and to study the optimal cooling load sharing between different types of absorption chillers using a mixed integer linear programming (MILP) model. Real data from a trigeneration plant connected to a DHC close to Barcelona (Spain) is used for the development of this model. The cooling load distribution among the different units is heavily influenced by the price of the electricity sold to the grid which rules the duration of the operation time of the engines. The main parameter to compare load distribution configurations is the primary energy saving indicator. Cooling load distribution among the different chillers changes also with the load of the whole plant because the chiller performance changes with load.

Thermodynamic optimization for dissociation process of gas hydrates

The dissociation process of gas hydrates is also the discharging process of the gas hydrate cool storage system. In order to reduce the entropy generation rate of the gas hydrate dissociation process, this paper takes the entropy generation minimization as the optimization objective to perform thermodynamic optimization for the related process. By establishing thermodynamic optimization model of the gas hydrate dissolution process based on entropy generation analysis, both the optimal control strategy and the optimal heating rate of the gas hydrate dissolution process are determined. The entropy generation rate related to the optimal heating rate decreases by 7.5% compared with normal situation. The research results can provide important guidelines for optimal design and operation of the dissolution process of gas hydrates related to the gas hydrate cool storage system.

Evaluation of combined cooling, heating and power (CCHP) systems with energy storage units at different locations

Incorporating energy storage units (ESUs) enables components of Combined Cooling, Heating and Power (CCHP) systems to operate stably as well as to decrease the system scales. In the premise of “priority of providing cooling” regime, two potential locations of ESUs which individually represent different energy storage technologies were involved to study their location and performance impacts on energy saving rates (ESRs) of CCHP systems. Detailed discussions were undertaken to study how critical parameters (Efficiency of Energy Utilization and Coefficient of Performance) affect ESRs of CCHP systems. Theoretical analysis has indicated that how the electrical demand is satisfied will have distinct influence on the final results. When CCHP systems can solely satisfy the electrical demand, a cooling storage system is recommended to be installed between absorption refrigerator and the CCHP user. If supplementary electricity from the grid is required to meet the electrical demand, the selections of ESU locations will depend on efficiencies of both the grid and the power generation unit of the CCHP system. Furthermore, the authors also demonstrate the existence of boundaries of Efficiency of Energy Utilization and show the upper and lower limit values.

Comparative study on AL2O3 nanoparticle addition on cool storage system performance

Adding nanoparticles almost enhance the thermal transport properties in thermal storage system. Nanoparticles could be used in two manners, the first one with Phase Change Material (PCM) as a nucleation agent to help the fast formation of crystals in solidification process. The second manner with Heat Transfer Fluid (HTF) to enhance the rate of heat transfer through the heat transfer process. In the present study a comparison between adding Al2O3 nanoparticles to either distilled water as PCM, and to aqua ethylene glycol solution of 50% wt as a HTF on the performance of cool storage system.A spherical capsule with 85% filling of its internal volume with PCM is used as a tested platform. A set of experiments to study the effect of adding Al2O3 nanoparticles to HTF at different volume fraction concentrations up to 1% for different HTF inlet temperature and volume flow rates on the solidified mass fraction, surface heat flux and complete solidification time, was performed. Comparing the present results with those for nanoparticles with PCM, it could be concluded that adding the nanoparticles to PCM alone is much beneficial to cool storage system than adding it to HTF alone.

Development of a Solar Powered Evaporative Cooling Storage System for Tropical Fruits and Vegetables

A solar powered evaporative cooling storage system (SPECSS) was developed to improve the shelf life of fruits and vegetables for small-holder farmers in rural Nigeria where an electrical power distribution network is almost nonexistent. The capacity of the SPECSS chamber was 0.39 m3. A suction fan (24 W) and a water pump (18 W) were powered through solar panels (182 W) with a battery (130 Ah) used to store charge and maintain the system's operation. Tomatoes, mangoes, bananas and carrots were then stored in the chamber for 3–4 weeks. The SPECSS chamber temperature depression and relative humidity from ambient conditions varied from 7.8 to 15.4C and from 44 to 96.8%, respectively. The shelf lives of tomatoes, mangoes, bananas and carrots stored inside the SPECSS chamber were 21, 14, 17 and 28 days, respectively, as against 6, 5, 5 and 8 days for ambient storage. Practical Applications Erratic power supply and inadequate facilities hinder storage of perishable crops, leading to postharvest losses. This study was designed to develop a solar powered evaporative cooling system for the storage of perishable crops. Extending produce quality for longer periods makes the solar powered evaporative cooling system suitable for use in rural communities where there is no electricity.