Refrigeration Demand Research Articles

Energy, exergy, environmental, and enviroeconomic (4E) analysis of cascade vapor compression refrigeration systems using nanorefrigerants

The refrigerants used in traditional vapor compression refrigeration systems are harmful to the ozone layer and contribute to global warming. The demand for refrigeration is increasing because of global warming. In this study, for the first time, an energy, exergy, environmental, and enviroeconomic (4E) analysis was performed using different refrigerants and nanoparticles to reduce the energy required in low-temperature vapor compression cascade refrigeration systems and to determine more environmentally friendly nanorefrigerants. The R290 refrigerant was used for the Low-Temperature Circuit (LTC), while the High-Temperature Circuit (HTC) used RE170, R1234yf, R600, R600a, and R450A refrigerants. The nanoparticles used in the analysis were Al2O3, CNT, CuO, TiO2, ZnO, and SiO2. The R600 nanorefrigerant performed the best, whereas the R1234yf nanorefrigerant performed the worst. The results indicate that the CuO nanoparticles provided the highest performance. In addition, the results showed that the R290+R600-CuO nanorefrigerant emitted 11 % less CO2 than the pure R290+R600 refrigerant. The nanorefrigerants provide a more environmentally sustainable option because of their high efficiency and lower energy consumption than conventional refrigerants.

ANÁLISE DE RENTABILIDADE DE INVESTIMENTOS EM SISTEMAS DE REFRIGERAÇÃO COM ALTA EFICIÊNCIA ENERGÉTICA

This study analyzes the profitability of investments in high-energy-efficiency refrigeration systems, addressing the economic and environmental impacts of these systems compared to conventional technologies. Energy efficiency is essential for reducing operational costs and promoting sustainability, especially in sectors with high continuous refrigeration demand. The objective is to evaluate the economic feasibility of efficient systems, highlighting variables that influence the return on investment. A descriptive and qualitative literature review was conducted, analyzing studies on energy efficiency, environmental impact, and cost-benefit in commercial and industrial sectors. The findings indicate that, although the initial investment in high-efficiency technologies is high, these systems significantly reduce energy consumption and operational costs over time. It concludes that adopting efficient refrigeration systems is economically viable across various sectors, especially those with high energy demand, and an effective strategy for meeting environmental requirements and reducing emissions.

Experimental study of an absorption-based refrigeration driven by ocean thermal energy

Establishing an island-based cold chain is essential for ensuring food storage, vaccine preservation, and fish freezing on islands, which is indispensable for the sustainable development of island communities. The compression-absorption refrigeration system that uses ocean-thermal-energy is ideal for cold storage on islands as it efficiently utilizes local renewable energy sources and can meet refrigeration needs below 0 °C. Therefore, a refrigeration prototype has been constructed and thoroughly experimentally investigated to obtain refrigeration characterization under variations of refrigeration demand and environmental conditions. The system's energy-saving potential is evaluated by conducting comparisons with conventional refrigeration techniques. The results indicate that refrigeration temperature plays a crucial role in determining refrigeration capacity, with an increase of approximately 8.2 % observed for every 1 °C rise in refrigeration temperature. Lower cold-seawater temperatures or higher warm-seawater temperatures do not have a significant effect on the refrigeration capacity, but contribute to a reduction in compressor power due to increased thermally-driven compression force. Consequently, for every 1 °C change, the refrigeration capacity per unit compressor power increases by approximately 4 %. Additionally, the refrigeration capacity of the system is three times greater than that of a vapor-compression-refrigeration-system. The findings provide theoretical and experimental guidelines for the design and operation of refrigeration using ocean-thermal-energy.

Modeling of magnetocaloric effect in RE2X2Y ternary compounds for cooling technology using hybrid intelligent learning computational methods

Cooling technology that employs magnetocaloric effect of magnetic refrigerants has been lately recognized as a green system with immense potential to meet the global refrigeration demand. Hugeness of magnetocaloric impact is one of the major factors which determines the choice of magnetic refrigerants for cooling applications. This research endeavour explores and models magnetocaloric effect (MCE) in ternary system of compounds which combine rare-earth metals (RE = Tm, Er, Ho, Dy, Tb and Gd) due to the localized f-orbital electrons, transition metals (X = Co, Cu and Ni) due to their ferromagnetism near room temperature and other metals (Y = Al, Ga, In, Cd and Sn) using genetic algorithm hybridized support vector regression (GSVR) computational approach. The results of Gaussian transformation function-based hybrid model (G-MCE-GSVR) and polynomial transformation function-based hybrid model (P-MCE-GSVR) are compared with stepwise regression-based model (SR-MCE) using different performance metrics such as mean absolute error (MAE), correlation coefficient (CC) and root mean square error (RMSE). G-MCE-GSVR model outperforms P-MCE-GSVR model using testing data samples with improvement of 66.93 % for RMSE metric, 5.69 % for CC metric and 68.58 % for MAE metric. Similarly, the P-MCE-GSVR model performs better than SR-MCE with improvements of 60.36 %, 37.63 % and 63.41 % corresponding to performance metrics RMSE, CC and MAE, respectively. G-MCE-GSVR model was also employed for investigating the influence of applied magnetic field on magnetocaloric effect in system of RE2X2Y ternary materials. The outstanding performance demonstrated by the developed models coupled with the obtained huge magnetocaloric effect would be of great significance in strengthening practical implementation of magnetic cooling technology for addressing energy crisis and global refrigeration demand.

Research on origin-based cold storage location and routing optimization of fresh agricultural products based on hybrid whale algorithm

With the focus on the insufficient origin-based cold storage in China, this study investigates the location and routing problem (LRP) of origin-based cold storage for fresh agricultural products. This study considers the loss of fresh agricultural products in different environments during transportation and presents a cold storage LRP model. To address this issue, a hybrid whale algorithm with heuristic rules is designed, and the effectiveness of the algorithm is verified by standard instances. Finally, taking Chenggu County as a practical case, the influence of cold storage capacity and farmers’ demand for refrigeration are analysed. Experimental results show that the proposed algorithm has a good effect in solving medium-scale LRP. As the storage capacity increases, the total cost of the system can be increased by 0.086%. As farmers’ demand for refrigeration increases, the total cost of the system can be increased by 34.034%. Farmers’ demand has a greater impact on the system’s total costs than the cold storage capacity. When optimizing the cold storage layout, changes in fresh agricultural product output in the next few years can be roughly predicted, and the most economical optimization scheme can be obtained.

Environmental simulation and refrigeration demand analysis for shield tunnel construction in hot summer and cold winter regions

The thermal hazards generated during the tunnel boring machine construction process significantly impact the physical and mental health of personnel. A field test was conducted on the tunnel of Metro Line 1 in Changsha, China, where the average temperature in the work zone reached up to 33.16 °C, and the air velocity was generally below 0.2 m/s. These conditions were unfavorable for ventilation and heat dissipation. In this paper, a full-scale CFD simulation model was established to simulate the construction environment and analyze the cooling demand. The results indicated that increasing the fresh air velocity could lower the temperature in the work zone; however, this effect was limited. When the fresh air temperature exceeded a certain threshold, it actually raised the average temperature of the work zone. Consequently, there is a need for supplementary cooling of the fresh air during the hot summer months. At a fresh air velocity of 15 m/s, the maximum temperature in the work zone was recorded at 27.8 °C when the fresh air was cooled down to 22.5 °C through auxiliary cooling measures. This approach effectively controlled the temperature in the work zone, reduced flow dead zones, and significantly improved air distribution and heat dissipation. Additionally, it ensured the physical and mental well-being of the construction workers and the safe operation of the equipment. This study provides valuable guidance for managing thermal environments in underground tunnel construction.

Thermodynamic analysis of an enhanced ejector vapor injection refrigeration cycle for CO2 transcritical operation at low evaporating temperatures

The main drawback associated with CO2 refrigeration systems is related to their performance reduction during transcritical operation at warm climate conditions, which may be compensated by better cycle architectures such as the split-cycle with subcooling or the flash-tank configuration, among others. Specifically, the use of standard gas-ejectors together with parallel compressors provides even better efficiency improvements, not being able to use them with low-temperature evaporators to prevent the triple point inside the ejector. This paper proposes an enhanced cycle with a gas ejector for two-stage compressor architectures with vapor injection from the flash-tank, which is able to operate at low evaporating temperatures and that provides a greater performance improvement the more severe the climate conditions are. The methodology conducted is based on a thermodynamic analysis that includes parametric evaluation and cycle optimization, comparing the results to a conventional CO2 transcritical cycle with flash-tank and dynamic vapor injection architecture. The main results show that a maximum Coefficient of Performance improvement of 17.5% is achievable for transcritical operation at -40 °C evaporating temperature. The compressor displacement capacity required with the enhanced cycle is up to 9% lower for the same refrigeration demand, reducing the electrical consumption as well as the compressor expenditure. Moreover, greater vapor injection mass flow rates are obtained by the gas-ejector injection with discharge temperature reductions up to 18%, enhancing the system reliability.

Investigation on a novel hybrid system based on radiative sky cooling and split thermoelectric cooler driven by photovoltaic cell

This paper develops a novel cooling and heating system by integrating a novel split thermoelectric cooler (STEC) with photovoltaic power generation and radiative sky cooling. The system uses photovoltaic driven STEC modules to generate cooling and heating combined with radiative sky cooling to improve cooling capacity. By harnessing the distinctive characteristics of photovoltaic technology and radiative sky cooling, the new system is capable of operating continuously for 24 h without requiring any additional energy input. The system mathematical model is established, and the effects of STEC module number, solar illumination intensity, area ratio and ambient temperature on the performance are studied. Results demonstrate that the cooling efficiency of the system is 3.02 and the heating efficiency is 1.86 when the number of STEC modules is 3. In a year, the monthly average heat production of the system fluctuates due to changes in the solar illumination intensity, while the fluctuation of cooling capacity is small. The system cold production is larger than heat production, which is more suitable for application in the area with high demand for year-round refrigeration. The new system has good energy and economic performance with payback time being shorter than that of the photovoltaic-air conditioning system.

Performance Evaluation and Cycle Time Optimization of Vapor-Compression/Adsorption Cascade Refrigeration Systems

The reliance on more sustainable refrigeration systems with less electricity consumption attracts a lot of attention as the demand for refrigeration increases due to population growth and global warming threats. This study examines the use of a cascade vapor-compression/adsorption refrigeration system in hot weather, focusing on condensing temperatures of 50, 55, and 60 °C, whereas an air-cooled condenser is in use due to practical considerations. A fully coupled transient model is developed using COMSOL Multiphysics to simulate the integrated system, considering the practical limitations of the vapor compression system (VCS) and the dynamic nature of the adsorption system (ADS). The model combines a lumped model for the ADS with the manufacturer’s data for a VCS compressor at different condensing and evaporating temperatures. It was found that the VCS is more sensitive to the change in the ADS’s condensing temperature, since when the temperature is raised from 50 °C to 60 °C, the VCS’s COP decreases by 29.5%, while the ADS’s COP decreases by 7.55%. Furthermore, the cycle time of ADS plays an important role in providing the cooling requirements for the bottoming cycle (VCS), and it can be optimized to maximize the energy conversion efficiency of the VCS. At optimum cycle time and compared to the conventional VCS, the cascade system can boost the cooling capacity of the VCS by 18.2%, lower the compressor power by 63.2%, and greatly enhance the COP by 221%. These results indicate that the application of the cascade VCS/ADS in such severe conditions is a more sustainable and energy-efficient solution to meet the growing need for refrigeration.

High performance dual-mode module for power generation and cooling based on optimized BiSbTe

Bismuth telluride is currently the most outstanding thermoelectric (TE) material near room temperature, and the high demand for solid-state refrigeration and low-grade waste heat recovery means there is an urgent need to improve its TE performance. This study investigates the enhanced TE performance of Bi0.4Sb1.6Te3 through the addition of Ag2Se. The introduction of Ag promotes an acceptor doping effect, leading to increased carrier concentration, while inhibiting lattice thermal conductivity together with Se doping. As a result, a notable enhancement in the figure of merit (ZT) to 1.35 at 373 K is achieved, with an average ZT of 1.17 spanning temperatures from 300 K to 523 K. More significantly, a 7-pair TE module was integrated using p-type Bi0.4Sb1.6Te3-0.00125Ag2Se and n-type extruded BiTeSe for cooling and power generation. A competitive conversion efficiency of 5.54 % at a temperature difference of 230 K and a maximum cooling temperature difference of 63.1 K at Th = 300 K are achieved, demonstrating the enormous practical application potential of this dual-mode module.

Case study of variable speed photovoltaic direct-driven ice-storage air conditioning system in Wuhu

In order to meet the contradiction between the growing demand for refrigeration and energy scarcity, this paper proposes a novel photovoltaic ice storage air conditioning system. The system is directly driven by a photovoltaic array. The performance of the system was studied through experiments, and a mathematical model was constructed for comparative verification. The experimental results show that the daytime cooling COP of the system is 1.18, the photovoltaic conversion efficiency is 6.29 %, and the nighttime cooling time is 9 h, which basically meets the cooling needs. Through simulation, the performance of the system was optimized, and the results showed that an increase in the initial water volume and temperature of the ice storage tank would increase the cooling COP; the spacing between evaporator pipes increased from 45 mm to 60 mm, resulting in a 7.11% increase in COP; the optimal spacing between evaporator fins is 9 mm, which improves performance by 9.11 %.

Energy and Conventional Exergy Analysis of an Integrated Transcritical CO2 (R-744) Refrigeration System

This study analyses the performance of an integrated transcritical CO2 (R-744) refrigeration system operating in winter conditions within a supermarket in Trento, north Italy. This system fulfils multiple functions, providing the heating (for domestic hot water and space heating), cooling, and freezing capabilities for the supermarket. Energy analysis reveals that the average value of the total coefficient of performance, total COP, over the entire study period is calculated at 2.47. Notably, the medium-temperature (MT) compressor rack exhibits the highest power consumption, especially in sub −5 °C conditions. The auxiliary (AUX) compressor rack and the gas cooler (GC) fan contribute significantly to the electrical power usage. The air conditioning (AC) heating load is consistently high, averaging 41.6 kW, while the domestic hot water (DHW) heating load remains stable at approximately 5 kW. The refrigeration demands include an average MT cooling load of 25.86 kW and a low-temperature (LT) freezing load of 10–15 kW, with an average of 13.76 kW. The current study also delves into exergy analysis, disclosing an overall system exergy efficiency of 22.4%. The AUX compressor rack is identified as the primary exergy destructor, followed by the GC, AC coils, MT compressor rack, and the ejector. The LT compressor rack has the highest exergy efficiency, followed by the MT and LT expansion valves.

Recent trends in solar thermal cooling technologies

The issue of the impact of global warming and climate change is at an alarming stage, along with the increasing demand for air conditioning and refrigeration in warm weather regions. The use of integrated renewable energy technologies, such as solar thermal technology for cooling and refrigeration, has proven to be a key solution for overcoming problems associated with conventional resources. Solar cooling technologies do not impose negative environmental impacts and can alleviate the burden on electric utilities. Numerous studies on solar-assisted cooling systems are underway to achieve reductions in cost, improvements in performance, and greater compactness compared to conventional systems. This paper presents a review of various available solar cooling methods and technologies, detailing their working principles, Coefficients of Performance (COP), types of collectors, working pairs, and their advantages and disadvantages based on previous literature. The focus is primarily on solar thermal and solar electrical technologies, highlighting their different attributes and providing essential knowledge for selecting appropriate solar cooling technology for specific applications. Additionally, several references, including experimental and simulation investigations, are summarized.

Experimental analysis of the temperature distribution inside vaccine freezer compartment based on hybrid refrigeration system

Recently, the demand for refrigeration globally has been increasing in the fields of vaccine storage, medical services, food preservation, and cooling for electronic components. This has resulted in the generation of more electrical power and thus releasing more CO2 around the world which has led to many climatic changes, such as global warming. The vapour compression refrigeration cycle (VCC) is the most common as it has a high coefficient of performance (COP), although it only operates down to temperatures of around −20 °C. The thermoelectric cooler (TEC) modules offer a featured method for cooling technology, which is not mainly considered by energy efficiency but offers distinctive merits in specific applications. Although the TEC system is not conventionally known for incomparable energy efficiency, it offers a range of exceptional attributes that make it a desirable option for certain scenarios. Therefore, this work aims to assess the performance of the innovative hybrid vaccine freezer system depending on how well the VCC system and the TEC work together. Also, the temperature distribution within the freezer compartment has been investigated under various operating conditions. The newly developed hybrid vaccine refrigerator system consists of four pieces of TEC-12706 modules that function well at low temperatures. The results indicate that the best coefficient of performance (COP) of 1.05 is achieved with a total power consumption of 172.8 W when the TEC is operating at 5.5 V and the fan is running at 12 V. The cooling capacities of the freezer and cooler compartments are 9.2 W and 165 W, respectively. Furthermore, the best distribution and lowest temperatures were obtained, with temperatures in the lateral area of −40 °C compared with −37 °C in the central area.

High Performance Thermoelectric Power of Bi0.5Sb1.5Te3 Through Synergistic Cu2GeSe3 and Se Incorporations.

Bi2Te3-based alloys are the benchmark for commercial thermoelectric (TE) materials, the widespread demand for low-grade waste heat recovery and solid-state refrigeration makes it imperative to enhance the figure-of-merits. In this study, high-performance Bi0.5Sb1.5Te3 (BST) is realized by incorporating Cu2GeSe3 and Se. Concretely, the diffusion of Cu and Ge atoms optimizes the hole concentration and raises the density-of-states effective mass (md *), compensating for the loss of "donor-like effect" exacerbated by ball milling. The subsequent Se addition further increases md *, enabling a total 28% improvement of room-temperature power factor (S2σ), reaching 43.6µWcm-1K-2 compared to the matrix. Simultaneously, the lattice thermal conductivity is also significantly suppressed by multiscale scattering sources represented by Cu-rich nanoparticles and dislocation arrays. The synergistic effects yield a peak ZT of 1.41 at 350K and an average ZT of 1.23 (300-500K) in the Bi0.5Sb1.5Te2.94Se0.06 + 0.11 wt.% Cu2GeSe3 sample. More importantly, the integrated 17-pair TE module achieves a conversion efficiency of 6.4%, 80% higher than the commercial one at ΔT=200K. These results validate that the facile composition optimization of the BST/Cu2GeSe3/Se is a promising strategy to improve the application of BST-based TE modules.

Investigating the heating and air conditioning provision capability of a supermarket to neighboring buildings: Field measurement analysis and economic evaluation

This study explores the capability of a supermarket to fulfill the thermal demands of neighboring buildings. The research combines field measurements analysis, obtained from a Swedish supermarket which covers the neighbors' thermal demands, with theoretical calculations, using thermodynamic models of the refrigeration system and the ground source thermal storage. In contrast to previous studies, this work is unique in its use of demonstrating a real-life built case study rather than only theoretical approach. Results demonstrate that integrating ground source storage in a supermarket can meet the thermal demands of neighboring buildings without requiring additional equipment. The refrigeration system accounts for 80% of the total heat demand, while the ground serves as a heat source for the rest. This approach results in 67% annual operating cost savings for the neighboring buildings. In addition, ground source subcooling provides 9% annual energy savings to supermarket's refrigeration system. By exporting heat to neighboring buildings, the proposed solution emits 90% less CO2 in Uppsala and 67% less in Stockholm compared to solutions in which the refrigeration system only meets the refrigeration demands. Summing up, the concept of utilizing supermarkets to meet thermal demands offers a more energy-efficient operation for both supermarkets and property owners while significantly reducing annual energy consumption and emissions.

Quantifying agricultural productive use of energy load in Sub-Saharan Africa and its impact on microgrid configurations and costs

The use of advanced energy technologies for agricultural purposes—such as irrigation, refrigeration, crop processing, and egg incubation—has the potential to increase crop yield, reduce vulnerability to changing precipitation patterns, increase shelf life, strengthen income and employment opportunities in rural areas, and reduce emissions by displacing fossil fuel-based technologies. These productive uses of energy (PUE) in remote areas could potentially be powered by microgrids that additionally serve otherwise unelectrified communities, most of which are located in rural Sub-Saharan Africa. In this paper, we use high-resolution geospatial data to estimate the end-use electricity demand for a range of agricultural PUE across Sub-Saharan Africa, and we share these data in an open-access mapping tool. Next, we use REopt®, a techno-economic optimization model of energy systems, to determine the cost and system sizing implications of incorporating agricultural PUE into microgrid designs in Kenya and Zambia. We estimate the upper bound of agricultural PUE demand for irrigation, milling, shelling, refrigeration, and egg incubation across Sub-Saharan to be 16.8 TWh/yr. We find that incorporating local agricultural PUE into microgrid system designs increases the required system sizing while having minimal impact on the levelized cost of energy of these systems. Our analysis is the first to demonstrate the PUE potential in the agricultural sector at a 10x10-kilometer resolution across Sub-Saharan Africa and to show, at scale, how site-specific PUE can impact the cost and sizing of microgrids that are otherwise deployed to serve local household and community load.

Feasibility assessment of a CO2 based power, cooling, and heating system driven by exhaust gas from ocean-going fishing vessel

The research presents a novel CO2 transcritical trigeneration system for ocean-going fishing vessel. Cascade ejectors are employed to decrease the exergy destruction caused by the dual evaporators, enhancing the cooling capacity of the system. By recovering the waste heat of exhaust, the system is designed to cover refrigeration demand of a refrigerated sea water (RSW) tank, the domestic hot water demand at different temperature levels onboard, as well as the power for sailing. The performance of the system is investigated from both thermodynamic and economic perspectives. The feasibility of applying the proposed system to replace the original refrigeration system of a RSW tank is evaluated in different periods, including prechilling, chilling, and chilling maintenance. Analysis show that sufficient cooling can be provided to a RSW tank under most typical engine operation modes, which is significantly influenced by the split ratio and refrigeration capacity ratio. Constraint multi-objective genetic algorithm under engine load of 100% is conducted to determine the maximum potential of the system under the optimum working condition and ensure the smooth operation of the system under all typical engine load. It is estimated that a cooling capacity of 619.9 kW can be offered to the RSW, and the cooling provided to the cold room (502.8 kW) can realize the freezing of 25018 kg fish. After covering the power consumed by compressor and pump, the system still can reach a net power output of 97.32 kW. The thermal efficiency of the engine integrated with the proposed system is improved by 2.89%, and the brake specific fuel consumption is reduced by 5.88%. And the heat rejected by the system can be used to heat water from 25 °C to 45 °C (11.93 kg/s) and 90 °C (2.18 kg/s), respectively. The proposed system shows better overall performance compared to the basic system without ejectors.

Choosing an optimized refrigeration system based on sustainability and operational scenarios applied to four supermarket architectures in three European countries

The growing global demand for refrigeration requires the design of more sustainable systems. However, despite environmentally promising technologies in refrigeration, there are still barriers to their widespread adoption. In this paper, a generic approach able to describe the multiple performances (energy, environmental, economic, social) of refrigeration systems is proposed to assess their potential of adoption. To propose a realistic study framework, four architectures of supermarket refrigeration systems are modelled and simulated using ground data with different climatic conditions and electricity mixes (France, Sweden, Spain). The overall results of these operational scenarios show that the electricity mix is the most influential parameter on cost and environmental impact. In addition, architecture using CO2 refrigerant shows interesting performances regardless of location and despite degraded regimes during heat peaks. However, the maintenance score can be a limiting factor for installing more energy efficient systems. Two other scenarios are studied: with photovoltaic panels; with financial support. Photovoltaic panels help improving cost and environmental performances, but also strongly depend on maintenance performances. Financial support helps facilities using low-global-warming-potential refrigerant to be more competitive than those using high-global-warming-potential refrigerant.

A New Approach to Air Conditioning System Using the Photovoltaic System in Combination With Electricity – Driven Heat Pump and Vapor Compression Chiller

Solar cooling systems have the benefit of the correlation between hours of cooling demand and the availability of solar radiation which can help to minimize electricity usage in buildings. Cooling and/or heating are the major requirements in houses, depending on local climatic conditions and construction style. As well as the impacts of global warming and climate change, air conditioning and refrigeration demands have risen. The development of cooling by using green energies, such as solar panels, is also a crucial solution for electricity and environmental problems. In this research, a solar air conditioning system using pv- vapor compression chiller is proposed. The objectives of this research is to design a system structure to reduce the energy consumption and electricity bill, investigate the performance of the proposed structure through simulation software, implement a hardware prototype based on the proposed design, and to evaluate the simulation and implementation data to validate the experimental results. Finally the data will be validating by the results from other works and simulation as well. DOI: 10.7176/JETP/13-1-04 Publication date: January 31 st 2023