Absorption Refrigeration Research Articles

Thermodynamic and exergo-economic evaluation of biomass-to-X system combined the chemical looping gasification and proton exchange membrane fuel cell

The resource utilization of biomass is of great significance to the adjustment of energy structure. The syngas produced by biomass gasification can be used for power generation and production of green chemical raw materials. In this paper, a biomass-to-X (BtX) system based on the chemical looping gasification and high temperature proton exchange membrane fuel cell (PEMFC) is proposed to produce methanol, electricity, heating and cooling. The heat produced by the BtX system is harnessed for the regeneration of the carbon capture solution, as well as to drive both the organic Rankine cycle and the double-effect absorption chiller, enabling cascade utilization of the energy. The thermodynamic and exergo-economic models are carried out to evaluate system performance. The relationship between the material, energy and cost flow from biomass to products is analyzed. Finally, the influence of key parameters on system performance is studied. The results show that the energy efficiency of the BtX system is 54.0 % and the exergy efficiency is 35.4 %. The yield rate of methanol with 99.2 wt% purity is 6.48 tons/h. The cost of equipment, propanol and biomass accounts for 34.9 %, 28.9 % and 28.1 % of the total investment cost, respectively, while the cost of the PEMFC stack represents 50.4 % of the equipment costs. The unit exergy cost of the electricity and methanol are 0.068 $/kWh and 0.049 $/kWh, respectively. The methanol, carbon capture and cooling costs are most sensitive to the change in the propanol cost, followed by the biomass cost. For every 0.05 increase in the hydrogen fraction to methanol production, the electricity decreases by 3.1 MW and the methanol yield increases by 0.23 kg/s.

Optimization and exergoeconomic analysis of a biomass-driven cogeneration system for power and cooling applications

Due to the increasing population and the expansion of industry in daily life, a significant depletion of fossil fuel resources is observed, accompanied by escalating environmental concerns. In response to these challenges, this study presents an optimized cogeneration system powered by renewable biomass, designed for simultaneous power and cooling generation. The system integrates a biomass gasification unit, a steam Rankine cycle, a helium-driven gas turbine cycle, and an ammonia-water-based two-stage absorption refrigeration cycle with a bleed line. Thermodynamic and exergoeconomic analyses reveal a net power output of 5356 kW, a cooling load of 360.9 kW, and an exergetic efficiency of 29.52 %. Financially, the system shows a net present value of 11.76 $M and a payback period of 6.51 years. A multi-objective optimization utilizing the gray wolf algorithm improves system performance through the employment of three diverse scenarios, which raises power output to 5864 kW, cooling load to 372 kW, and optimize net present to 14.28 $M with a reduced payback period of 5.96 years. The studied system is well-suited for industrial applications, rural electrification, and district energy systems, and offers a sustainable and economically viable energy solution.

Economic and technical optimization of a tri-generation setup integrating a partial evaporation Rankine cycle with an ejector-based refrigeration system using different solar collectors

Three collector types, namely parabolic trough solar collector (PTSC), linear Fresnel collector (LFC), and dish collector, are employed to drive a tri-generation configuration composed of a partial evaporation Rankine cycle (PERC), a hot water production unit (HWPU), and a cascade ejector-based compression refrigeration system (ECRS) for electricity, cooling, and heating production. The ECRS is integrated with the topping PERC through an absorption refrigeration system (ARS). Moreover, the collector is indirectly connected to the system by a storage tank to increase the operating hours of the system. The performance of the system is evaluated by thermodynamic and economic analysis. The three-objective optimization result is a testament to the fact that utilizing PTSC brings about the best performance of the system. The system exergy efficiency (ηex) in the case of PTSC is 8.1 % and 24.9 % higher than in the case of LFC and dish collector, respectively. The economic performance of the system in the case of PTSC is superior to that of the dish collector. Furthermore, the PTSC case results in a relatively similar economic performance to the LFC case. The system produces power, cooling, and heating at rates of 200.8 kW, 564.9 kW, and 795.7 kW in the optimum case of utilizing PTSC, respectively. Moreover, ηex, total cost rate (C˙tot), and specific cost of tri-generation (ctri) are obtained as 11.48 %, 204.7 $h−1, and 44.91 $GJ−1, correspondingly. The results indicate that ηex of the proposed layout in the case of PTSC is superior to a comparable tri-generation configuration introduced in the field by 2.78 % points.

Efficient waste heat utilization in high-temperature proton exchange membrane fuel cell bus through integration of lithium bromide absorption refrigeration

Compression-type air-conditioning heat pump systems used in high-temperature proton exchange membrane fuel cell (HT-PEMFC) buses significantly increase the vehicle's hydrogen consumption. This study introduces a lithium bromide (LiBr) absorption refrigeration air-conditioning system into a fuel cell bus, aiming to convert the high-quality waste heat produced by the HT-PEMFC into cooling and heating capabilities for balancing the temperature within the vehicle cabin and recover waste heat. Modeling and co-simulation of the HT-PEMFC, LiBr absorption refrigeration system, vehicle thermal model, and compression-type air-conditioning heat pump system were conducted using MATLAB/Simulink. The simulation results indicate that, compared with the traditional compression-type air-conditioning heat pump system, the LiBr absorption refrigeration system can save 6.13–18.17 % of hydrogen and improve the electrical energy and exergy efficiencies by 3.58–10.74 % and 3.74–11.22 %, respectively, under different driving scenarios. Using the LiBr absorption refrigeration system significantly enhances the vehicle's overall fuel utilization efficiency and driving range.

Multi-criteria optimization next to a comparative analysis of a polygeneration layout based on a double-stage gas turbine cycle fueled by biomass and hydrogen

The significance and advantages of utilizing renewable energy sources are widely recognized. Upon examining past studies, it was revealed that there has been a lack of research on harnessing the waste energy from double-stage gas turbines powered by biomass-hydrogen hybrid fuel for polygeneration applications. Thus, a new configuration is proposed in the study for the multi-production of electricity, cooling, heating, and potable water. In the current research, a high-pressure turbine is driven by a combustion chamber fed by a biomass gasifier. Meanwhile, a low-pressure turbine is driven by a post-combustion chamber fed by hydrogen as fuel. The heat loss of the topping gas turbine cycle is recuperated by a supercritical Brayton cycle (SBC), a steam Rankine cycle (SRC), and a water heater. The waste heat of the supercritical Brayton cycle and steam Rankine cycle is recovered through an absorption refrigeration cycle and a thermoelectric generator, respectively. Thus, the heat loss of the topping system is completely recovered. The net power output of the gas turbine cycle is considered the electricity production of the system while the output power of the SBC and SRC is utilized in a reverse osmosis desalination system to produce potable water. The investigations conducted on the system are thermodynamic and exergy-economic assessments and three-objective optimization utilizing 5 gases (i.e., CO2, CO, Nitrogen, Air, and Helium) in the SBC. The final results reveal the superiority of Helium as the supercritical gas, bringing about an exergy efficiency () of 32.11%, a total cost rate () of 103 , a payback period (PP) of 0.159 years, and a specific cost of polygeneration () of 22.03 for the system. Although the levelized cost of products of the configuration is high due to the freshwater production, of the proposed system is higher than the previous systems based on a double-stage gas turbine cycle driven by biomass and hydrogen.

Design, multi-aspect investigation and economic advantages of an innovative CCHP system using geothermal energy, CO2 recovery using a cryogenic process, and methanation process with zero CO2 footprint

The significance of devoting attention to environmental pollution control strategies is widely recognized as an effective means of mitigating the harmful environmental effects caused by fossil fuels in industrial and power plant sectors. Carbon dioxide (CO2) capture and recovery technologies have opened up the possibility of utilizing this pollutant gas. Hence, the current study suggests a methodology for the CO2 hydrogenation of the flue gas leaving a power plant. This approach facilitates methane generation via a methanation reactor, subsequently is utilized as fuel for a power plant. For this purpose, a cryogenic method using liquefied natural gas cold energy facilitates CO2 recovery. Moreover, the whole system utilizes geothermal energy to launch a power plant for power generation and supply the power demands of a hydrogen production unit, relying on a water electrolysis process. The hydrogen generated is employed for CO2 hydrogenation, while the oxygen produced is utilized for the combustion reaction. Heating provider units and an absorption chiller are also included in the design. The system is modeled utilizing Aspen HYSYS software. This study incorporates a sensitivity analysis alongside energy, exergy, environmental, and economic assessments. The energy and exergy efficiencies, as determined by the thermodynamic analysis, are 30.87% and 48.61%, respectively. Additionally, according to the economic study, the levelized energy cost amounts to 16.65 $/MWh, demonstrating a substantial reduction of 87.6% compared to the power generation mode. One notable merit of the suggested system lies in its zero CO2 footprint framework, showing a noteworthy supremacy when compared with previous studies.

Designing and multi-objective optimization of a novel multigenerational system based on a geothermal energy resource from the perspective of 4E analysis

Over the past few years, a growing emphasis has been placed on providing sustainable energies to reduce carbon emissions and promote energy efficiency. This paper delved into energy, exergy, exergoeconomic, and exergoenvironmental investigation for a system that combines the Kalina cycle, a double-effect absorption chiller with a vapor compression refrigeration system coupled with an air handling unit driven by a geothermal renewable energy resource. This innovative system generated four distinct outputs: electricity, potable water, cooling load, and hot water. Key system performance variables, such as net power output, coefficient of performance, sum unit cost of the product, energy and exergy efficiencies, the temperature of supply air to the cold store, and potable water production in the base mode, are measured at 63.45 kW, 0.83, 56.74 $/GJ, 62.28 %, 45.67 %, 268.7 K and 20.82 lit/h, respectively. This research explored the impact of various parameters on the output variables, the exergy destruction and environmental impact rate of all components, and the net percent value of the proposed system. The multi-objective optimization significantly improved energy and exergy efficiencies by 6.83 % and 1.8 % from its base mode. Exergy and exergoenvironmental analysis revealed that the highest exergy destruction occurs in Re-injection, and the highest environmental impact rate associated with exergy belongs to the HPG component. Moreover, the geothermal section has the largest share of exergy destruction, approximately 58.5 % of the total exergy destruction of the system.

Exergoeconomic optimization of a proposed novel combined solar powered electricity and high-capacity cooling load production system for economical and potent generation via utilization of low-grade waste heat source

A novel system for combined electricity and cooling generation was introduced, integrating Flat Plate Solar Collectors (FPSC), Absorptional Heat Transformer (AHT), Organic Rankine Cycle (ORC), and Absorption Cooling Cycle (ACC) systems to utilize low-grade solar energy. The ability to use low-grade waste heat sources (70 °C–90 °C) via FPSC system for high-capacity integrated cooling and electricity generation in a more economical way, a feature not commonly addressed in conventional systems and previous literature studies, was a key advancement. The need for additional generators, boilers, and high-temperature heat sources was eliminated, resulting in substantial cost savings and a simplified system design. The FPSC-AHT integration, identified as having significant advantages over separate electricity and cooling load production, was comprehensively evaluated for its combined exergoeconomic and environmental benefits in multigeneration system design. The modeling was performed using Engineering Equation Solver (EES) and Transient System Simulation Software (TRNSYS) in Izmir, Turkey, with the aim of achieving the heightened economic efficiency and superior Coefficient of Performance (COP) values without high-temperature waste heat sources. Three configurations were examined, with the third demonstrating superior technoeconomic performance due to the increased thermal efficiency of solar hybrid photovoltaic-thermal (PV-T) systems. The higher cost per unit area in the PV-T system was effectively offset by the substantial electricity consumption, contributing to energy savings. Economic indicators for the third configuration included an initial investment of US$9.91 million, annual operational costs of US$1.29 million, a payback period of 4.2 years, an annual energy cost gain of US$9.25 million, a levelized cost of cooling (LCC) of US$0.014/kWh, and an electricity cost (LCE)of US$0.015/kWh. Through exergy analysis, toluene was identified as the optimal working fluid, revealing a total exergy destruction rate of 13245.46 kW. The performance of the proposed system was tested under different operation conditions, and based on these results, a sensitivity analysis and a comparison with the real-word studies were performed. In comparison to real-world data, the proposed system exhibits superior performance metrics, especially in terms of COP and exergy efficiency values. The optimal configuration, established using single and multiobjective optimization approaches based on exergoeconomic parameters, indicated annual electricity and cooling load production of 40,000 MWh and 300 GWh, respectively. The system’s efficiency in producing 1000 kW of electricity power and 4000 kW of cooling load at a comparable cost to systems generating only one output was highlighted. To determine the technoeconomic performance improvement of the proposed integrated system, the optimal configuration of the novel integrated system was compared to a reference plant for similar-scaled integrated power and cooling generation (UCI Trigeneration Plant). Compared to the UCI Trigeneration Plant, the proposed system demonstrated significant improvements in technoeconomic performance. Specifically, the proposed system achieved a 164.13 % increase in annual electricity production, a 97.38 % increase in annual cooling duty, a 60.36 % reduction in initial investment, a 57 % reduction in annual operational costs, and a 47.5 % reduction in payback period. Additionally, the levelized costs of electricity and cooling were 40 % and 22.22 % lower, respectively. Significantly higher electricity and cooling output highlights the system’s ability to meet demanding energy needs. Lower initial investment and operational costs, coupled with a reduced payback period, make the system financially attractive. Lower levelized costs for electricity and cooling increase the system’s competitiveness and affordability. The innovative integration of technologies provides new insights into the design of multigeneration systems, setting a new benchmark for sustainable energy solutions

A data-and-knowledge-driven WNN modeling approach for the absorption refrigeration system

Given that the cooling capacity of the absorption refrigeration system depends on both the heat supply and the operating conditions, a data-and-knowledge-driven Wavelet Neural Network (WNN) modeling approach is proposed based on the analysis of its working principle and the coupling relationship between variables. This approach utilizes the Simple Particle Swarm Optimization (SPSO) algorithm instead of the gradient descent method to search the network parameters of WNN, which makes up for the defects of the gradient descent method that is easy to fall into the local optimum. Furthermore, the inequality constraints of energy and temperature are integrated into the loss function of model training as prior knowledge, and the model’s parameters are trained using experimental data, which reduces the training burden of the model and the model’s dependence on the training data, and increases the network’s interpretability and the model’s robustness. The experimental results show that the prediction accuracy and generalization of the WNN model are improved after replacing the optimization algorithm and incorporating the physical knowledge under the same working conditions, and its RMSE and MAE are reduced by 2.08% and 1.63%, respectively, compared with the original WNN model.

Development and Assessment of the Performance of a Novel Parabolic Trough Solar Collector-Driven Three-Stage Cooling Cycle

Abstract A gaseous flow is employed as heat transfer fluid (HTF) in a parabolic trough solar collector (PTSC) for simultaneous production of cooling at three different levels of temperature to meet the demands of air conditioning, refrigeration, and ultra-low-temperature refrigeration required to ensure the efficacy of some special vaccines. The combined system consists of five subsystems including PTSC, Kalina cycle (KC), ejector refrigeration cycle (ERC), cascaded refrigeration cycle (CRC), and absorption refrigeration cycle (ARC). A simulation through an engineering equation solver (EES) is conducted to assess the impact of internal tube diameter of absorber and solar irradiation on rise of HTF temperature and mass flowrate of Kalina cycle fluid. It is determined that for given solar irradiation, the temperature of HTF goes down when internal diameter of absorber tube is enlarged. The influence of weather conditions; solar irradiation and ambient temperature, type of HTF, and concentration of ammonia–water basic solution on thermal and exergy efficiencies of three-stage cooling cycle (TSC) are examined. The TSC with helium-operated PTSC delivers better results than air and CO2. Exergy analysis shows that solar collector (30.26%) dissipates the highest exergy, followed by the ejector (12.5%) and vapor generator subsystem (7.61%). The type of CRC fluid pair affects TSC cycle refrigeration capacity and cooling exergy efficiency. The promotion of solar irradiation from 850 to 1200 W/m2 increases the cooling exergy efficiency of the three-stage cycle from 6.72% to 9.52% when the evaporator temperature is set at −45 °C and CRC employs NH3-propylene.

Multi-variable optimization of a geothermal power plant integrated with water electrolyzer and methanol production

Renewable energy-based routes for methanol generation are recognized as essential strategies for eco-friendly energy conversion. Thus, the current study focuses on developing an innovative combined energy system for methanol production using direct carbon dioxide hydrogenation powered by geothermal energy. This is important because it addresses the need for sustainable and environmentally friendly methods of methanol production while also harnessing the potential of geothermal energy as a renewable resource. Therefore, in order to achieve multigeneration energy production, this work introduces and optimizes a novel configuration that benefits from an innovative heat design process. This configuration integrates an organic Rankine cycle, a single-flash geothermal power plant, an ammonia-water absorption chiller, a proton exchange membrane electrolyzer, and a methanol generation unit. Using the Aspen HYSYS tool, the multigeneration energy system is modeled and analyzed. As a result, the system is assessed using energy, exergetic, environmental, and economic evaluations. Furthermore, performance evaluations are carried out in the following modes: single generation, multigeneration, cooling, heat and power generation, and cooling. Furthermore, a genetic algorithm is employed to optimize the system in terms of economy and exergy. The energy and exergy efficiency are determined to be 32.57 % and 76.3 %, respectively, under the base case results. Furthermore, the rate of overall costs is 377.38 $/h. Furthermore, the precise output of carbon dioxide is −0.043 kg/kWh. The optimal unit cost and exergy efficiency for all items, taking into account the optimization scenario, are 3.34/GJ and 78.35 %, respectively. In addition, the optimum carbon dioxide and hydrogen rates for methanol generation are 92.49 mol/h and 200.51 mol/h, respectively.

Performance analysis of sub-cooled transcritical CO2 refrigeration system using vapour absorption refrigeration system and dew point evaporative cooling

Shifting towards natural refrigerants is expected to reduce the environmental damage in terms of refrigerants leaks, as they have zero ozone depletion potential as well as minimal global warming potential. A CO2 transcritical cycle is analysed thermodynamically in this study. Further, to improve the performance of the CO2 system, a vapour absorption refrigeration system (driven by the heat available at the exit of the compressor) has been integrated with it. Also, to counter the effects of hot climatic conditions, in Indian context, a dew point evaporative cooling system is further utilized to take up the heat from the gas-cooler. A thermodynamic and economic study of the proposed integrated system is performed. The effect of various performance parameters; such as ambient dry bulb temperature, relative humidity, evaporator temperature has been studied on the overall performance of the system. Compared to the base case, the coefficient of performance is improved in the range of 40%–270 %, for the hybrid systems, under the different climatic conditions. Moreover, the proposed system provided a low-cost performance of about 0.024 $/kWh, as compared to the base case consumption of about 0.05 $/kWh.

Numerical analysis of multistage ultrasonic atomization enhanced ammonia-water falling film absorption

The absorption refrigeration system is a widely used system that utilizes waste heat and is environmentally friendly. However, many current systems still suffer from challenges such as large volume, and high initial investment. Meanwhile, optimizing the absorber is crucial for enhancing system performance as it is one of the main components. In this study, a novel absorber model is proposed and its influencing factors of performance are comprehensively analyzed. In this model, the traditional falling film absorber is divided into multiple stages, with an ultrasonic atomizer (UA) installed in each stage to enhance absorption. In each stage, falling film and atomization absorption occur simultaneously, and their outputs are combined and weighted at the exit to maintain continuous droplet absorption, effectively utilizing the entire absorber volume. In this process, the vapor–liquid contact area is increased through atomization, and simultaneously, generated heat is removed by the cooling water during mixing. As a result, the absorber’s absorption capacity increases, and the outlet solution temperature decreases. The results demonstrate that compared to the traditional falling film absorber, the proposed absorber, when divided into two stages with a droplet diameter of 50 μm and an atomization rate x = 0.7, shows a 60.64 % increase in ammonia absorbed rate. Additionally, compared to double-stage absorber, triple-stage absorber increases the ammonia absorption by 9.52 %. As the number of stages increased, the strengthening effect persisted, albeit with a gradually diminishing rate of increase. Scaling up to ten stages results in a 152.63 % absorption rate increase and a size optimization of 60.43 %. In this paper, multi-stage ultrasonic atomization is innovatively introduced into the falling film absorber, which enhances ammonia absorption and reduces the volume of the absorber. Additionally, the multi-stage atomization offers an innovative method to improve the droplet absorption process.

Research on Energy-Saving Control Strategies for Single-Effect Absorption Refrigeration Systems

The automatic control device is a critical component of absorption refrigeration systems. Its functional enhancement can reduce operating costs, improve energy efficiency, and ensure long-term stable unit operation. Given that absorption refrigeration systems operate under various dynamic conditions, the rational design of control strategies is particularly important. This study analyzes the influence of changes in the cooling water and heat source water flow rates on the outlet temperature of chilled water in the unit based on the open-loop response characteristics of absorption refrigeration systems. It proposes a dual-loop energy-saving control strategy for single-effect hot water lithium bromide absorption refrigeration systems based on the setpoint comprehensive optimization algorithm. Considering the multiple variables, strong coupling, large inertia, long time delay, and nonlinear characteristics of absorption refrigeration systems, as well as the difficulties in modeling these systems, this study applies a model-free adaptive control algorithm to the system’s control. It derives both SISO and MIMO model-free control algorithms with time-delay components. Through simulations comparing MFAC, improved MFAC, and traditional PID control, the dual-loop energy-saving control strategy is demonstrated to effectively reduce system heat consumption by approximately 20%, decrease power consumption by about 10%, and enhance the system’s SCOP by approximately 19.3%.

Design and economic analysis of an innovative multi-generation system in different Countries with diverse economic contexts

This paper presents an innovative trigeneration system designed to maximize energy utilization by simultaneously producing power, cooling, and freshwater. The system integrates multiple energy sources, including biomass, natural gas, and geothermal energy, and comprises a modified gas turbine cycle, a geothermal power plant, a triple-effect absorption refrigeration cycle, and a multi-effect desalination unit. Performance metrics are evaluated from both thermodynamic and economic perspectives across four case studies: Australia, the USA, China, and Russia. The economic feasibility analysis utilizes real-state economic data, incorporating natural gas prices, electricity prices for households, interest rates, and inflation rates specific to each country. The system achieved impressive outputs, with net power, cooling, and freshwater production rates of 6299 kW, 140.1 kW, and 13.41 kg/s, respectively. Exergy analysis revealed that the combustion chamber, heat exchanger, and multi-effect desalination units exhibit the highest irreversibility, with exergy destruction rates of 2961 kW, 1125 kW, and 995.3 kW, respectively. The fixed capital investment cost is estimated at $13.5 million, resulting in a payback period of 6.75 years and a net present value of $7.287 million. In Australia, the system demonstrated a particularly favorable economic performance, with a payback period of 3.98 years and a net present value of $36.19 million. Conversely, in China, the payback period exceeds the system's expected lifetime, highlighting the economic challenges in certain environments. These results underscore the system's potential for profitability and sustainability, particularly in regions with favorable economic conditions.

Optimized multi-criteria performance of a poly-generation layout including a Stirling engine and a supercritical Brayton cycle using biogas and methane as two potential fuels of a topping gas turbine cycle

The combination of a supercritical Brayton cycle, an absorption chiller, a Stirling engine, a reverse osmosis desalination system, and a proton exchange membrane electrolyzer is investigated for waste heat recovery of a topping gas turbine cycle. The required electricity for hydrogen and freshwater production is supplied by the Stirling engine and supercritical Brayton cycle, respectively. In addition, the output power is provided by the gas turbine cycle, and the exiting cold stream of the Stirling engine is considered hot water for domestic utilization. A comparison is made between biogas and pure methane as two possible fuels for the system. Energy and exergy analyses, economic analysis using the specific exergy costing approach, and environmental analysis considering the carbon dioxide emissions are employed in the study. The three-objective optimization of the configuration discloses an exergy efficiency (ηex) of 39.49 % and 39.85 % in the cases of biogas and methane, respectively. The proposed system can improve ηex by 6.18 % points compared to the stand-alone GTC. The specific cost of poly-generation (cpoly) and the total cost rate (C˙tot) are obtained as 25.92 $GJ−1 and 249.5 $h−1 in the biogas mode, while these values are calculated as 36.75 $GJ−1 and 336.7 $h−1 in the methane case. The environmental cost rate (C˙env) of the system is 24.78 $h−1 in the case of biogas and 17.47 $h−1 in the methane mode. The results confirm the superiority of the methane case from the environmental viewpoint over biogas. However, the low values of cpoly and C˙tot in the biogas case indicate that biogas is superior to methane from a general standpoint. The utilization of the present setup for waste heat recovery of biogas-driven GTCs is recommended due to the higher ηex than the previous layouts.

Development and assessment of an integrated multigenerational energy system with cobalt-chlorine hydrogen generation cycle

This study aims to develop and assess a new multigeneration system where nuclear heat is utilized as the energy source. The multigeneration system is further designed to generate power, cooling, freshwater and hydrogen. In the present multigeneration system, five main subsystems, including high-temperature gas-cooled pebble bed nuclear reactors, a Rankine cycle, a cobalt-chlorine thermochemical cycle, a multi-effect desalination system and an ammonia-water absorption refrigeration system are integrated for synchronized operation. The analyses of the present system are carried out with the approaches of energy and exergy. This integrated system uses a total of 1000 MW thermal energy that is obtained from four units of high-temperature gas-cooled pebble bed nuclear reactor. Using all the thermal energy that comes from the nuclear reactors, a total of 346.99 MW of electricity, a total of 1.59 MW of cooling, a total of 384.67 kg/s of freshwater, and a total of 0.25 kg/s of hydrogen are produced. The energetic and exergetic performance coefficients of the ammonia-water absorption refrigeration system are 0.74 and 0.83, respectively. While the energy efficiency for the overall system is calculated as 37.83%, the exergy efficiency is found to be higher as 46.32% with the multiple useful outputs which help exergetically improve the overall system.

Assessment of a solar-powered trigeneration plant integrated with thermal energy storage using phase change materials

This study presents a comprehensive thermodynamic assessment of a trigeneration plant producing electricity, fresh water through multi-effect desalination (MED), and cooling through an absorption refrigeration cycle. The MED and absorption refrigeration systems utilize the rejected heat from the power cycle, driven by concentrated solar power (CSP). Situated in Qatar, the present system leverages the abundant solar irradiance to optimize the efficiency of electricity generation, water desalination, and cooling. The design features parabolic trough collectors with synthetic oil as the heat transfer fluid, direct thermal storage, and a Rankine steam turbine cycle with three turbine stages. The system also incorporates phase change materials (PCMs) based thermal energy storage (TES) to improve the system performance and offset the mismatch between demand and supply. The present system evaluation is based on energy and exergy analyses, while the Aspen Plus is used to simulate the power production and desalination operations, providing detailed insights into its efficiency and potential for large-scale implementation. The proposed system operates with an energy efficiency of 56.72 % and an exergy efficiency of 31.24 %, respectively.

Machine learning optimization and 4E analysis of a CCHP system integrated into a greenhouse system for carbon dioxide capturing

The world has seen an increase in the popularity of renewable-based energy systems. However, because of their erratic nature, fossil fuels cannot be entirely phased out. Utilizing carbon dioxide in greenhouses close to power plants and generating extra power electricity from dissipated thermal energy are appealing strategies that cause us to have a cleaner environment and affordable power electricity. To exploit the high enthalpy of expelled gases from a gas turbine, the gas turbine was coupled with an absorption refrigerant cycle and an organic Rankine cycle and analyzed. Additionally, a deep artificial neural network method was used to calculate all functions in a rapid optimization and accurate 4E analysis. The carbon dioxide emissions subsided from 0.9183 to 0.41 kg CO2/s, and the optimization time improved 257 times after using the trained machine learning model. An adsorption technique for CO2 separation is used for the proposed system because of its lower energy consumption. The maximum exergy and energy efficiencies were attained at 36.71 % and 49.2 %, respectively, and parametric studies are being assessed. Due to increases in harvests and efficiencies, the net annual interest has increased by 21.8 %, up to 22.5 million dollars.

Deep eutectic solvents and traditional refrigerants in absorption refrigeration cycles using molecular approaches

Absorption Refrigeration Cycles (ARC) represent a sustainable technology capable of effectively producing cold with modest energy consumption from waste heat or renewable sources. However, the right choice of working fluid pair absorbent–refrigerant is essential for the system to work properly. This contribution is devoted to analysing the performance of an ARC using a wide variety of refrigerants in combination with selected deep eutectic solvents (DES) as absorbents. Three choline chloride-based and one ionic liquid (IL)-based DESs as absorbers are combined with sixteen refrigerants. The PC-SAFT equation of state is employed to assess the thermophysical properties. Accurate modelling of the absorption cycle has revealed that the phase behaviour of the working mixture significantly constrains the temperature and pressure range within which the cycle can operate. Idealised ARCs are insufficient for accurately representing the capabilities and limitations of these systems. Of the sixty-four working pair mixtures, only eighteen are suitable for ARCs based on technical and thermodynamics criteria. The Coefficient of Performance (COP) has been updated with additional key performance indicators that consider environmental and safety factors. The maximum values of the COP for this mixture are around 0.92, while many options lie in ranges around 0.60. This comprehensive analysis helps establish a ranking of the best options. The results have shown that the IL-based DES using R227ea or R236ea is the most efficient system among all the systems studied, with performances of 0.92 and 0.74.