Exergy Destruction Research Articles

The feasibility study of cascade waste heat recovery in a molten carbonate fuel cell-driven system

The use of solid-state converters in power production, particularly in combination with molten carbonate fuel cells, holds promise for improving overall power generation efficiency. These systems are designed to capture and utilize the considerable waste heat generated during power production, leading to enhanced performance and energy recovery. The specific approach discussed in this investigation involves a solid-state system consisting of an alkali metal thermal electric converter and a thermally regenerative electrochemical cycle for waste heat recovery and additional power generation. The study conducts a comprehensive analysis of this combined system, focusing on various aspects, including energy, exergy, and economic considerations. One key variable investigated is the current density, which plays a significant role in determining system performance. The investigation considers sensitivity analysis by varying six design parameters, offering insights into how different factors affect the system's performance. One of the notable findings is the identification of the overall maximum power density, which reaches 2642 W/m2 at a specific current density of 4686 A/m2. Evaluating the overall performance of the system, the study reports energetic efficiency, exergetic efficiency, and exergy destruction rate density. The energetic efficiency stands at approximately 44.04 %, while the exergetic efficiency is notably higher at 47.09 %. Additionally, the exergy destruction rate density is reported at 2968 W/m2. The research highlights the significance of the operating temperature of the molten carbonate fuel cell, as it has a substantial impact on the overall performance of the system. Increasing the operating temperature of the fuel cell leads to improvements in system efficiency and performance. In summary, the investigation demonstrates the potential of a solid-state system with waste heat recovery components in combination with a molten carbonate fuel cell. This approach enhances power production efficiency, making it a promising solution for sustainable and efficient energy generation.

Energy and exergy analysis of the 1220 MW natural gas-fired Hamitabat combined cycle power plant

In this study, the energy and exergy analysis of the 1220 MW Hamitabat combined cycle power plant (CCPP) that was renovated in 2017 with a 520 million € project is carried out. A thermodynamic model is built by applying the conservation of mass and energy principles and operating data are obtained from the plant operators. Exergy analysis is performed with the exergy balance equation to determine the exergy efficiencies and improvement potentials of all components. Also, parametric analyses are carried out to investigate the methods to enhance the performance of the plant. The plant has thermal and exergy efficiencies of 59.70% and 58.52%, respectively and these values are 13.70% and 13.52% higher than the thermal and exergy efficiencies of the original plant, respectively. Results showed that the combustion chamber (CC) has the highest rate of exergy destruction, and it is responsible for 77.61% of the total irreversibilities. The improvement potential of the CC is found to be 67.992 MW, and the prevention of heat loss from CC can increase the thermal and exergy efficiencies of the plant by 3.88% and 3.80%, respectively. Parametric analyses showed that the plant performance can be enhanced by increasing the inlet temperatures of high- and intermediate-pressure turbines, and decreasing the pressures of condenser and high-pressure turbine.

A novel multi-generation system for sustainable power, heating, cooling, freshwater, and methane production: Thermodynamic, economic, and environmental analysis

Addressing environmental concerns and developing efficient systems pose significant challenges for researchers. This paper presents a groundbreaking multi-generation system designed to generate power, heating, cooling, freshwater, and methane. The system comprises a flash-binary power plant, a modified transcritical CO2 cycle, a proton exchange membrane electrolyzer, and a methanation unit. Integration of the modified transcritical CO2 cycle with the ejector refrigeration cycle, solar still desalination unit, and heating unit enhances its functionality. The proton exchange membrane electrolyzer supplies hydrogen to the methanation unit. The thermodynamic, economic, and environmental approaches are employed to analyze the system, and three scenarios are considered to assess the optimum state. Accordingly, the exergy efficiency, products' total cost, and exergoenvironmental impact rates are obtained at about 28.30%, 4.153 $/h, and 73.48 mPts/h, respectively. The gas heater unit has the highest exergy destruction rate and cost rate and exergoenvironmental impact rate by 37.6%, 36.4%, and 22.7% portions, respectively. The optimal state provides 33.25% exergy efficiency, 450.9 kW net power, 10.07 kg/h freshwater, and 2.149 kg/h methane. The cooling and heating production rates are attained 28.16 kW and 183.5 kW. The product's cost rate and exergoenvironmental impact rates are estimated at about 4.357 $/h and 76.64 mPts/h.

Relative exergy and energy analysis of DI‐CI engine fueled with higher blend of Azadirachta indica biofuel with n‐butanol and NiO as fuel additives

AbstractAlternate fuels are in high demand for current engines and such fuels are studied both property‐wise and tested as fuel in the current engines. In current work, diesel engines are studied for higher blend Neem (Azadirachta indica) biodiesel (NB) as fuel, and fuel additives such as n‐butanol and NiO nano additives are chosen. Experimentation was performed on the experimental stationary engine which is coupled to eddy current dynamometer for four test fuels under varying fuel injection timings. Four test fuels were chosen for experimental studies which are Diesel 90% (vol %) + n‐butanol (10%), pure Neem biodiesel, NB 90% (vol %) + n‐butanol (10%), and Neem Biodiesel 90% + 25 ppm of nickel oxide dissolved in solvent. The synthesis of nickel oxide nano additives was done using a homogenous grinding method and XRD, FESEM, and EDS characterization signifies the presence of NiO. The Neem biodiesel was derived from base catalytic process and was studied using Gas Chromatography and Mass Spectroscopy apparatus for its chemical composition. The experimentation results which were focused were on the energy, exergy derived, and expenditure at varying fuel injection timings. The exergy and energy usage were almost similar in nature and entropy produced during the chemical‐to‐mechanical energy transfer reduced with the advancement in fuel injection timing to 27° bTDC for Diesel 90% + Bt.10%, NB90 + Bt.10% and NB100 + 25 ppm of NiO by 2.2%, 2.9%, and 4.6% respectively. Also, the exergy destruction retarded when with advancement in fuel inlet timing to 27° bTDC by 2.1%, 3%, 6.2%, and 6.8% for the same fuels, respectively.

Downsizing strategy for an air-cooled indirect-fired single-effect ammonia-water absorption chiller in part-load operation in hot climates

A modular mathematical model has been created to simulate an ammonia-water absorption refrigeration system indirectly fired and air-cooled. The model includes governing equations based on mass, species, and energy balances, implemented for the main components of the system. It accounts for both thermal and mass resistances in the transfer processes that occur in the system. The study evaluates the performance of the ROBUR® absorption refrigeration system, model ACF60-00 LB, operating under part-load conditions, driven by hot water temperatures ranging between 160 and 210 °C, while the ambient temperature remains up to 40 °C. This refrigeration system is characterised by including an extra valve that allows active control of the pressure levels of the system. The analysis focusses on the effect of its active control on the size of the system. The results show that increasing the pressure loss in this valve reduces the size of the air-cooled absorber to 37.3 % of its nominal size at an ambient temperature of 40 °C, while the reduction in refrigerant mass flow is 18.5 %, while the condenser size decreases 3.1 times. Evaporator, air-cooled absorber and condenser effectiveness are minimally affected. Additionally, contribution of condenser and evaporator to exergy destruction is balanced.

Energy, exergy and exergo-economic analysis of a novel SOFC based CHP system integrated with organic Rankine cycle and biomass co-gasification

This paper proposes a novel SOFC based cogeneration system, consisting of biomass co-gasification, SOFC power generation and ORC waste heat recovery, to achieve the efficient and clean utilization of poultry litter. Based on the conceptual design, the energy, exergy and exergo-economic analysis are conducted, including sensitivity analysis, uncertainty analysis and multi-objective optimization. Results show that when using straw as the co-gasification biomass with poultry litter, the highest energy utilization efficiency of 44.70 % is obtained with the electricity and heat production of 162.02 kW and 52.41 kW, respectively. The biomass gasifier and the SOFC stack have the highest exergy destruction, accounting for 24.43 % and 19.99 % of the total. Sensitivity analysis presents complex results concerning mass fraction of poultry litter, water content, equivalent air ratio and water-carbon ratio, etc. The optimal solution for the current optimization problem is obtained. When poultry litter mass fraction is fixed at 25 %, TSOFC = 852 °C and uf = 0.73, the exergy efficiency is obtained as 41.95 % and the overall exergy cost per unit is obtained as 42.35 $/GJ. This paper investigates a novel cogeneration system relying on the biomass co-gasification of poultry litter, providing a new solution for poultry litter treatment and sustainable development of agriculture, forestry and husbandry.

Exploration of different water content on the performance of reactive-extractive distillation for separating the ternary azeotropic mixture

Reactive-extractive distillation (RED) has gained significant attention as an innovative approach for separating azeotropic mixtures. Although many studies have reported its positive benefits, no studies have explored the impact of varying water content on RED performance, a domain that has seen exhaustive exploration in conventional extractive distillation. In this study, we investigate how water content affects RED performance using the separation of ethyl acetate (EA), 1,4-dioxane (DIO), and water as a case study. We design diverse configurations tailored for feed compositions ranging from 0.35 to 0.8 water mole fractions using a double column reactive-extractive distillation (DCRED). These configurations are globally optimized and the performance is compared against the triple-column conventional extractive distillation (TCCED) based on economic, environmental, and thermodynamic efficiency considerations. The TAC and CO2 emission of TCCED schemes exhibit the linear decreases, reaching its lowest point at 50 mol.% water content. Beyond this threshold, both indicators increase significantly, even surpassing the reference case (20 mol.% water) at 80 mol.% water content. The thermodynamic efficiency of TCCED behaves inversely due to the intrinsic exergy destructions. Interestingly, the DCRED schemes show almost linear decreases in the trends of both economic and environmental indicators, and the notable deviations are then observed at 65 mol.% water content, accompanied with a slight decrease up to 80 mol.%. The thermodynamic efficiency of DCRED scheme gives an inverse trend, identical to those observed in TCRED. Overall, TCCED performs best at 50 mol.%, in which DCRED excels at 80 mol.% water content. This comprehensive study bridges a significant knowledge gap, offering insights into optimizing RED processes for varying water content, an unexplored topic despite widespread application of RED.

Design, evaluation, and optimization of an integrated proton exchange membrane and double flash geothermal based organic Rankine cycle multi-generation system fed by a biomass-fueled gasifier

This study introduces an innovative approach by formulating and evaluating a synergistic biomass-geothermal structure, emphasizing optimized inter-component connections. The research stands out for its thorough analysis of parameter impacts on the system and variables, addressing an unexplored aspect in integrated energy systems. The multi-generation systems are the integration of a combined gasification gas turbine cycle, double flash geothermal cycle, and proton exchange membrane cycle for the generating power and hydrogen. The overall system and its subsystems are studied to explore how the performance of thermodynamics and the total cost rate are influenced by operating parameters. The best operational conditions for both subsystems and the overall system have been determined by analyzing the impact of operating parameters on the thermodynamic behavior and environmental impact through parametric studies. The findings indicate while Sabalan's current efficiency is 16.26 %, the system energy efficiency reached 24.89 % when coupled with other renewable source. To enhance the system's efficiency, a genetics algorithm was utilized to simultaneously optimize the total cost of exergy destruction and investment cost. The outcome of the multi-objective optimization revealed that the exergy efficiency of optimal point for the system is 29.8 % and a total investment cost is 6 (M$/year).

Experimental Investigation of Energy and Exergy Assessment of Vapor Compression Refrigeration Unit Enhanced via Encapsulated Phase Change Material

Energy and exergy performance of simple vapor compression refrigeration unit is investigated experimentally with and without coupling heat exchanger of phase change material before the condenser. The hot outside air is cooled before entering the condenser throughout the day by flowing over the cooled phase change material structure that previously solidified during nighttime. Phase change material SP24 is employed because its melting/freezing range is suitable for most selected countries' climates. An experimental set‐up of an air‐phase change material heat exchanger coupled with the unit is constructed to examine its performance, including pressure–enthalpy curve, coefficient of performance, exergy performance, and power consumption including inflow air temperatures and flow rates impacts. Results affirm that the coefficient of performance, cooling capacity, power usage, and exergy destruction are improved by using phase change material. Compared to the unmodified unit, the maximum percentage of saved power and exergy destruction enhancement for the modified refrigeration unit with phase change material is about 8.8% and 10%, respectively. The maximum coefficient of performance and exergy efficiency rise is about 15.1% and 14.2%, respectively. Increasing the temperature differential across the phase change material heat exchanger, either by increasing inlet temperature or decreasing airflow, enhances the refrigeration unit power saving.

Co-gasification of biomass and plastic waste for green and blue hydrogen Production: Novel process development, economic, exergy, advanced exergy, and exergoeconomics analysis

A novel co-gasification process for biomass and plastic waste has been proposed to produce the blue and green hydrogen. For process feasibility, an Aspen Plus simulation model has been developed, and a sustainability analysis is being conducted, focusing on economic viability, exergy, advanced exergy considerations, and exergoeconomics evaluations. The current process has demonstrated economic sustainability, as evidenced by an internal rate of return (IRR) of 8 % at a process efficiency level of 70 %. The process with a waste capacity of 20 tons per hour has the potential to produce approximately 1079 kW-hours of electric power. The surplus electricity, exceeding the process requirements is utilized for green hydrogen production through an alkaline electrolysis cell (AEC). This surplus electricity has the potential to produce around 213.5 kg/day of hydrogen. The exergy analysis of this model highlights that the gasifier component exhibits the lowest exergy efficiency, resulting in the highest exergy loss, around 40 %. Furthermore, advanced exergy analysis identifies both the steam turbine and gasifier as primary sources of exergy destruction, with associated exergoeconomics costs of around $6,561.3 and $6,541.9 per hour, respectively. Consequently, improving the gasifier and steam turbine performance can enhance the overall sustainability of the process.

Energy, Exergy, Economic and Exergoeconomic Analyses of Chemical Looping Combustion Plant Using Waste Bark for District Heat and Power Generation with Negative Emissions

The greenhouse gas emissions from the boiler of pulp and paper industries can be minimized by adapting chemical looping combustion (CLC) technology. This work aims to analyze the energy, exergy, economic, and exergoeconomic performance of an industrial scale CLC plant for district heat and electricity generation using waste bark from the paper and pulp industry. The CLC plant with one natural ore and one industrial waste oxygen carrier (OC) is modeled using Aspen Plus. The performance of the CLC plant has been compared to Örtofta combined heat and power plant without CO2 capture and with post‐combustion CO2 capture as the reference cases. Results showed that the CLC‐based power plant is energetically, exegetically, and economically efficient compared to the reference cases. The circulating fluidized bed boiler unit contributes the highest exergy destruction (about 50–80%). Among the CO2 capture plants, the CLC plant with ilmenite has the lowest levelized cost of district heat (4.58 € GJ−1), and a payback period (9.69 years) followed by the CLC plant with LD slag (5.91 € GJ−1 and 11.84 years), and the plant with PCC (6.94 € GJ−1 and 13.58 years). The exergoeconomic analysis reveals that the CLC reactors have the highest cost reduction potential, followed by the steam turbine.

Optimizing power, cooling, and hydrogen generation: A thermodynamic and exergoeconomic study of an advanced sCO2 trigeneration system

This paper presents an innovative trigeneration system designed for efficient power, cooling, and hydrogen production. It combines a supercritical carbon dioxide (sCO2) power cycle with a Kalina cycle (KC) and an ammonia-water-based absorption refrigeration cycle (ARC), all integrated with a PEM electrolyzer (PEME) unit. The system optimally utilizes waste heat from the sCO2 power cycle to enhance power generation through the KC and provide cooling via the ARC. Additionally, it leverages the PEME system and KC-generated power for eco-friendly hydrogen production. Mathematical models, thermodynamic, and exergoeconomic analyses were performed, including parametric studies, optimization, and comparative analyses. The results indicate that the reactor experiences the highest exergy destruction rate, while components in the bottoming cycles exhibit lower exergy destruction. From an exergoeconomic perspective, the reactor and sCO2 turbine are ranked as the first and second most significant components. Under the optimal conditions, the system achieved a 9.76 % increase in exergy efficiency and a 6.63 % reduction in total product unit cost. The system also provides substantial net power output, cooling capacity, and hydrogen production rates of 261.74 MW, 123.95 MW, and 176.328 kg/h, respectively. These findings highlight the system's significant thermodynamic and economic advantages, making it a promising choice for diverse user needs.

Techno-economic analysis of a new thermal storage operation strategy for a solar aided liquid air energy storage system

The SA-LAES system is an economical and efficient energy storage solution that combines solar energy with LAES. However, the inherent instability of solar energy can result in uncertainty regarding heat storage, thereby compromising the stability of the energy storage system. The development of more economical, efficient, and stable strategies for the SA-LAES system represents a challenging task. The present study puts forward a novel thermal storage operation scheme (Strategy 2) for SA-LAES systems integrated with electric heating during valley periods, thereby achieving long-term stable operation of the energy storage system via the alternating utilization of two full molten salt tanks and one empty molten salt tank. Theoretical and case studies are conducted based on thermodynamic and economical technical indicators, and detailed comparisons are made with the traditional strategy (Strategy 1) of only changing the solar multiple and capacity. The results show the exergy destruction of Strategy 1 mainly occurs in air turbines under off-design operating conditions. The exergy destruction of Strategy 2 is mainly in the electric heater part. The single-day analysis found that the new strategy has a more significant advantage in terms of exergy efficiency than Strategy 1 when the direct normal irradiance (DNI) is below 650 W/m2. In the case study, the levelized cost of energy (LCOE) values for Nanning, Beijing, and Hami regions in Strategy 2 are 0.118 $/kWh, 0.077 $/kWh, and 0.062 $/kWh, respectively. The LCOE values of Strategy 2 are decreased by 10.97 %, 27.49 %, and 3.40 % compared to Strategy 1, respectively. The payback periods for investments in the Beijing and Hami regions have decreased by 67.63 % and 16.41 %, respectively. The research presented in this article provides an economical, efficient, and stable operating strategy for thermal storage in the SA-LAES system.

4-E analysis and multiple objective optimizations of a novel solar-powered cogeneration energy system for the simultaneous production of electrical power and heating

Owing to its natural and rich advantages, exploration of solar energy technology has become increasingly popular in recent years to counter the growing crude oil prices. However, its universal adoption is still limited, not only due to environmental restrictions but also due to lower overall efficiency. Rankine cycle is optimised to conduct 4-E (Exergy, Energy, Economic and Ecological) analysis. Furthermore, three sets (R-113, R-11, and R-1233zd) of refrigerants are prioritised and ranked on the basis of 4-E analysis as outcomes. The contemporary study addressed all critical factors and explains the impact of solar irradiance, mass flow rate of molten salt and steam, turbine inlet pressure, and turbine inlet temperature which are eventually weighed and prioritised using combined multi-criteria decision making (MCDM) techniques. The energy efficiency, exergetic efficiency, power/ cost of electricity, and ecological emissions are taken as the indicators of the combined cycle, respectively. The energy efficiency of the hybrid system is improved to 75.07% after including cogeneration cycle, with an increment of 54.58%. In comparison to conventional thermal powerplant setups, the power/cost of electricity and ecological efficiency have been reduced by 68% and upgraded by 16%, correspondingly. Direct normal radiation is the most critical factor followed by turbine inlet temperature. Further, the result indicates that maximum exergy destruction that occurs in the central receiver declines to 39.92%, followed by heliostat and steam turbine which was 27% and 9.32% respectively. In conclusion, the hybrid cycle can furnish cheaper electricity, with lower carbon imprint in sustainable manner with better efficiency.

Optimization waste heat recovery and power generation for industrial sustainability: A comparative study of supercritical CO2 Brayton, organic Rankine, and inverted Brayton cycles with synthesis natural gas as heat source

Generated waste heat in industrial processes, which is not applied in any functional work, is discharged into the environment by conduction, convection, and radiation from industrial products, processes, and equipment. Harnessing the waste heat carries significant attention because of its potential to decrease fossil fuel consumption and deterring of atmospheric pollutants. This study aims to provide an alternative for natural gas and reduce air pollution, serving the waste heat from the synthesis natural gas (SNG) production as the heat source for the cycles namely CO2 Brayton cycle, organic Rankine cycle, and Inverted Brayton cycles-organic Rankine cycle to the calculation of generated power, efficiencies, and total product unit cost of distinct layouts. By doing so, a comparison of the cost of synthetic natural gas between the two states can be made. Power output is analyzed concerning temperature and pressure, while exergy destruction calculations highlight the synthesis natural gas production process as the major contributor. Cost balance equations are applied to compute the cost of synthesized natural gas and total product unit cost. Objective functions encompass net power output, first law efficiency, and total product unit cost. Optimization employs the genetic algorithm method in MATLAB software. Results reveal that supercritical CO2 Brayton cycle achieves 17,100 kW power output, 0.8894 first law efficiency, and 26.32 $GJ total product unit cost. Conversely, with the inverted Brayton cycle-organic Rankine cycle, the outcomes are slightly lower, yielding 15,430 kW power output, 0.879 first law efficiency, and 25.41 $GJ total product unit cost.

Investigation of the geothermal flash cycle developed by a thermoelectric generator and PEMFC: 3E analysis and optimization

Investigations have revealed that geothermal organic Rankine cycles (ORCs) have a low efficiency and high exergy destruction rate, especially in the heat exchangers network, which drastically reduces the whole system's performance. To tackle this problem, in the present research, the effects of employing thermoelectric generators (TEG) and proton exchange membrane fuel cell (PEMFC) on the performance of a geothermal ORC will be discussed from thermodynamic and economic points of view. In this study, three geothermal flash cycles are investigated. The first system, GFC, is a geothermal flash cycle. The second system is the GFC boosted by a TEG thermoelectric generator, which is applied instead of the condenser (GFTC). The third system is GFTC, developed using a PEMFC (GFTPC) before the evaporator. These systems are compared from energy, exergy, and economic perspectives. Parametric analysis is conducted for the system with the best performance and the effects of the evaporator temperature, evaporator quality, flash temperature, and PEMFC temperature on the system performance. Based on the results, the net power outputs of the GFTC and GFTPC are 10.21 % and 40.49 % higher than those of the GFC, respectively. GFTC and GFTPC have higher energy and exergy efficiencies and lower LCOE and payback period than GFC. In the GFTPC, a 32.86 % increase in the net power output, 20.81 % enhancement in the energy efficiency, and 0.22 % increase in the exergy efficiency are observed with an increase in the PEMFC temperature from 75 to 115 °C. Moreover, The PEMFC temperature increment reduces the LCOE and payback period of the GFTPC system. Also, the multi-objective optimization for GFTPC design with three decision variables has been done.

Thermodynamic and environmental analysis of an integrated multi-effect evaporation and organic wastewater supercritical water gasification system for hydrogen production

Organic wastewater poses significant environmental and human health risks. Supercritical water gasification (SCWG) presents a promising approach for converting organic waste into hydrogen-rich mixed gases. Nevertheless, the high moisture content present in organic wastewater hampers the energy efficiency of the SCWG process. To tackle this challenge, we have designed and developed an organic wastewater SCWG hydrogen production system incorporating a multi-effect evaporator. The developed system demonstrates the ability to achieve autothermal conditions for the treatment of swine wastewater with a solids concentration of 4.3%. Notably, this system exhibits impressive energy efficiency, reaching a maximum value of 44.88%, along with an exergy efficiency of 33.90% when processing 7% swine wastewater. Exergy analysis further reveals that the incorporation of a multi-effect evaporator leads to a reduction in exergy destruction within the gasification unit, oxidation unit, and heat exchanger. These improvements highlight the positive impact of the multi-effect evaporator on the overall performance of the supercritical water gasification system. Sensitivity analysis indicated that suitable concentrated concentration and an appropriate amount of preheated water can improve hydrogen production. The system minimum GWP reaches 5.27 kgCO2-eq/kgH2 after adding the CCUS. This work expands the range of applicable feedstocks for the autothermal SCWG process.

Design and 4E analysis of heat pump-assisted extractive distillation processes with preconcentration for recovering ethyl-acetate and ethanol from wastewater

The separation of ternary azeotropes with a high content of one component using extractive distillation is energy intensive, and the introduction of preconcentration can significantly improve process economy. In this paper, the conventional three-column extractive distillation (TCED), four-column extractive distillation (FCED) with preconcentration, and three-column extractive distillation with integrated distillation column (TCED-IDC) are established and economically optimized to minimize the total annual cost (TAC) for recovering ethyl-acetate (EAc) and ethanol (EtOH) from wastewater containing a large amount of water. The preconcentration and solvent recovery functions can be integrated in IDC. Following that, the vapor recompression heat pump (VRHP) is introduced to further reduce energy consumption for the TCED-IDC process. The two VRHP-TCED-IDC processes are correspondingly designed. Simultaneously, the processes proposed are evaluated in terms of economy, energy consumption, environment and exergy destruction (4E analysis). The environmental analysis is performed via calculating Global Warming Potential (GWP) index using Life Cycle Assessment method. The two VRHP-TCED-IDC processes demonstrate superior performances with regard to 4E analysis. The most efficient VRHP-TCED-IDC process reduce over 32.0 %/16.0 %/6.8 % of TAC, 53.4 %/42.4 %/33.7 % of energy consumption, 62.0 %/53.0 %/45.9 % of GWP, and 49.7 %/35.7 %/29.3 % of exergy destruction compared to the TCED/FCED/TCED-IDC processes, respectively.

Experimental Investigation of Chilled and Hot Water Inlet Temperature, and Mass Flow Rate Influence on Energy and Exergy Efficiency in a Prismatic Adsorbent Bed Cooling Systems

Adsorption technologies offer a promising solution for managing high electricity demand in building by leveraging waste heat recovery and renewable energy sources. The prismatic adsorbent bed adsorption water cooling system investigates energy and exergy analyses for cooling application. With hot water temperature of 80 °C, cooling water inlet temperature 30 °C, and chilled water inlet temperature 14 °C, the system achieves an energy efficiency of 45.2% while demonstrating an energy storage density of ≈340 kJ kg−1. As a result, the exergy efficiency reaches 12.2%, and the mass fraction at the end of the adsorption process is a significant value of 0.13kgadsorbate/kgadsorbent. Increasing the water mass flow rate in the evaporator results in a decrease in exergy efficiency, while simultaneously causing an increase in energy efficiency. With an increase in the chilled water inlet temperature of the evaporator and the hot water inlet temperature of the adsorbent bed, there is an increase in the energy storage density, energy efficiency, and exergy destruction due to irreversibility and losses. According to this study, the impact of the chilled water inlet temperature on the energy and exergy performances of the evaporator is more significant compared to the effect of the water mass flow rate.

Energetic and exergetic performances of a multi‐effect desalination unit driven by a gas turbine

AbstractDesalination can provide additional water resources in water‐stressed zones and also in zones suffering from water pollution or insufficient/overexploited groundwater. This study carried out the energy and exergy assessments of a multi‐effect desalination unit driven by a gas turbine based on the specific exergy cost (SPECO) approach. The chemical exergies of brine and seawater are explicitly considered (most studies consider the same specific heat for input seawater and output brine). In addition, the enthalpy of each flow of the desalination unit is considered according to its salt concentration (results are then compared to the constant specific heat model). The highest exergy rates of fuel and product are obtained at the combustion chamber, and its exergy efficiency is 67.83%. The lowest exergy efficiencies were obtained at the condenser, followed by the first effect of the desalination unit, and the heat recovery steam generator. The overall exergy efficiency of the multi‐effect distillation unit is 21.49%. Regarding exergy destruction, as expected, the highest rate was obtained at the combustion chamber, which contributed with 41% to the overall exergy destruction, followed by the regenerator and heat recovery steam generator, with contributions of 16% and 11%, respectively, to overall exergy destruction.