Exergy Efficiency Improvement Research Articles

Energetic/economic/scalability assessment of active solar energy and waste heat utilization in urban environments for H2/freshwater production: A CSP-centered multigeneration system with dual-loop power generation

The imperative to reduce greenhouse gas emissions has intensified the need for sustainable thermal energy systems. This study addresses this exigency by harnessing solar energy and exploiting waste heat to augment energy efficiency in urban settings. The proposed system integrates a concentrated solar power-based Brayton cycle with dual power generation, water desalination, and hydrogen production capabilities. Comprehensive technical and economic evaluations affirm the feasibility of this system. Additionally, transient codes have been utilized to ascertain the performance of the proposed configuration. The investigation reveals that the tower and receiver are the primary sites of exergy destruction, accounting for 48.1 % of the total, with the heliostat field, reverse osmosis, and proton exchange membrane electrolysis contributing 24 %, 8.8 %, and 6.9 %, respectively. The findings show that increasing the pressure ratio in the Brayton cycle leads to improved exergy efficiency and increased power output, but also leads to higher overall costs. A thorough economic evaluation shows that the solar unit, which includes the receiver, heliostat field, compressor, and gas turbine, is the main factor influencing costs, representing 62.6 % of the total system cost rate. The dynamic study conducted to forecast the annual system capacity in San Francisco indicates that electricity production peaks during summer at 242.15 MWh. Conversely, winter exhibits the lowest contribution at 17.3 % with 143.11 MWh.

Full analysis and deep learning optimization of a sustainable and eco-friendly power plant to generate green hydrogen and electricity; A zero-carbon approach

Among alternative energy sources for fossil fuels, hydrogen has emerged as a promising candidate; however, its production methods, reliant on fossil fuels, constrain its widespread adoption as a sustainable energy source. To transcend this limitation, researchers have proposed the concept of green hydrogen production, leveraging renewable energy sources, as a viable solution. This study presents a comprehensive techno-economic analysis that seeks to evaluate the feasibility of establishing a multi-generation green power plant in Iran. Extensive climate data from diverse locations across Iran were collected to determine the most influential design parameters. A mathematical model was developed to simulate the entire system, and an innovative neural network algorithm was employed to optimize the objective functions, given the substantial computational time required for the optimization process. The results of the optimization revealed Qeshm island as the optimal location for the green power plant, considering its favorable annual average temperature, wind speed, and solar radiation intensity. Remarkably, the proposed green power plant boasts a robust power generation capacity of 10.1 MW, enabling the production of 250 tons of hydrogen per year, exhibiting a 10 % improvement in exergy efficiency, and a 6 % reduction in LCOE, in comparison to similar studies. Furthermore, it exhibits an impressive total exergy efficiency of 41.6 %, resulting in a substantial annual income of $3.9 million and achieving a commendable payback period of 1.8 years.

Thermoeconomic analysis of novel hydrogen liquefaction assisted by absorption refrigeration utilizing heat from Brayton cycle

Abstract Current research presents a novel method for reducing the energy consumption of hydrogen liquefaction through heat recovery of hydrogen liquefier. An ammonia absorption refrigeration cycle on the hydrogen precooling utilizes the heat generated by the compressor intercooler and aftercooler of the reverse Brayton cycle of hydrogen liquefier to precool hydrogen feedstock. The system is analyzed from exergy, energy, and economic perspective. The results are compared with the reference case without a heat recovery system. The proposed system can reduce SEC (specific energy consumption) from 7.37 kWh/kgLH2 to 6.23 kWh/kgLH2 and exergy efficiency improvement from 55.2% to 60.90%. The economic analysis shows that the levelized cost of energy to produce 5.07 tons/day of liquid hydrogen for the reference and novel case is 5.88 USD/kgLH2 and 5.03 USD/kgLH2, respectively. The results imply that the proposed method can be a reference for designing an integrated hydrogen liquefaction system to minimize energy consumption.

Flexibility improvement of a coal-fired power plant by the integration of biogas utilization and molten salt thermal storage

This study presents a novel method to enhance the flexibility of coal-fired power plant (CFPP). The suggested integrated system comprises a CFPP integrated with molten salt thermal storage system and a biogas combustion and its waste heat utilization system. Molten salt can be used to heat high-pressure feedwater and expel steam into the turbine, quickly increasing the output of CFPP. The waste heat from biogas combustion is used to charge the molten salt, and further waste heat is recovered by ORC. Comparative analyses reveal compelling advantages. The power generation can be rapidly increased by 6.8 %. A substantial 1,342.45 kW increase in power generation and an impressive 9.52 % enhancement in energy efficiency. Exergy analysis demonstrates a notable 9.52 % improvement in overall exergy efficiency. The system yields an annual net income of 10,083.51 k$, boasting an exceptionally low dynamic payback period of 1.798 years and a substantial net present value of 51,427.34 k$ over its 10-year operational span. This research enhances understanding of the use of molten salt thermal storage to increase the flexibility of CFPPs and the biogas utilization.

Enhancing reliability and efficiency of solar chimney by phase change material Integration: An Experimental study

The Solar Chimney Power Plant (SCPP) presents an eco-friendly and straightforward technique for converting solar radiation into electricity. However, the performance limitations and reliability challenges of SCPPs are inherently linked to the variability and intermittency of solar radiation. To tackle this issue, using phase change materials (PCMs) can enhance the thermal energy storage and release capabilities of SCPPs. This study aims to explore the impact of PCM on the exergy efficiency and performance of a solar chimney. Two pilot solar chimneys with identical dimensions were constructed, each featuring a 4 m height chimney and a 5 m diameter collector. One solar chimney was equipped with hydrated salt PCM as an energy storage layer, while the other operated without PCM. Both systems' power production and ventilation potential were evaluated using theoretical turbines, and subsequent exergy analysis discerned the operational behavior and efficiency of the systems. Results indicate that PCM increased the average air mass flow rate through the solar system during the day. The average daily air mass flow rate was 0.045 kg/s with PCM and 0.033 kg/s without PCM. Notably, mean pressure drops resulting from the airflow through the turbine were 2.44 and 1.83 Pa in the presence and absence of PCM, respectively, over a complete day. Additionally, PCM improved exergy efficiency by about 19 % due to enhanced thermal energy storage.

Techno-Economic and Environmental Analysis of a Hybrid Power System Formed From Solid Oxide Fuel Cell, Gas Turbine, and Organic Rankine Cycle

Abstract Distributed energy technology is an essential pathway for future advancements in the field of energy technology. In the present study, organic Rankine cycle (ORC) is integrated with solid oxide fuel cell (SOFC)-gas turbine (GT) hybrid power system. The conventional metrics employed for assessing the performance of SOFCs, gas turbines, and organic Rankine cycles, such as voltage and gross real efficiencies, have some limitations as indices of merit. Contemporary second law concepts and economic and environmental analysis have been used to enhance hybrid power system evaluation. R1233zd(E) has been selected as the ORC working fluid. The outcomes reveal that, under certain conditions, the present configuration may reach 55.67% energy efficiency and 53.55% exergy efficiency. Economic and environmental analysis shows that the hybrid system's total cost rate and Emissions of CO2 gas (EMI) under design conditions are 36.09 $/h and 355.8 kg/MWh, respectively. Thermodynamic evaluation of present SOFC-GT-ORC configuration shows 11.72% improvement in exergy efficiency compared to hybrid SOFC-GT cycle. Consequently, the hybrid SOFC-GT-ORC system is far better than the hybrid SOFC-GT system. In the future, other ORC fluids like R123, R601a, and R245fa can be used as ORC fluids.

CFD modeling of a tubular three-pass solar air heater with phase change material: Investigating heat transfer enhancement and energy efficiency

The present study introduces a novel solar air heater design featuring a tubular surface with three passes arranged in a counter-flow configuration, aimed at improving compactness and enhancing heat transfer characteristics. The research involved the development and validation of a computational fluid dynamics (CFD) model, which was utilized to accurately depict the distribution of solar flux through the system components by comparing the model results with experimental data. The study involved conducting a comparative analysis between the tubular three-pass solar air heater with phase change material (TTPSAH_PCM) and conventional flat plate solar air heaters (FPSAH) to ascertain the superior design characteristics. A thorough investigation was carried out, encompassing evaluations of energy, exergy, outlet temperature, convection heat transfer coefficient, and useful heat gain. The findings indicate that the TTPSAH_PCM outperforms alternative geometries. For instance, when operating at a mass flow rate of 0.006 kg/s, the TTPSAH_PCM demonstrates substantial enhancements in several key metrics, including an 11.4 % increase in the system's daily thermal efficiency, a 17 % improvement in exergy efficiency, and a 4 % rise in outlet air temperature. The convection heat transfer coefficient of TTPSAH_PCM exhibited a 155.6 % increase compared to the FPSAH type. Moreover, the system being investigated demonstrates an 8.5 % rise in useful heat gain. The results underscore the enhanced efficacy of the TTPSAH_PCM system in contrast to alternative solar air heater arrangements, and its applicability for both drying operations and indoor heating applications.

Investigation of the effects of various nanoparticles on improvement of hydrogen production rate in a solar energy driven alkaline electrolyzer

Present paper aims to investigate effects of nanoparticle addition to thermal oil of parabolic trough collectors which are integrated to Kalina cycle for electricity generation to run an alkaline electrolyzer for hydrogen production. Thermodynamic models for Kalina cycle, thermal model for parabolic collectors and electrochemical models for water electrolyzer are developed for overall plant modeling. Three types of nanoparticles including: copper oxide, alumina and titanium oxide are considered and overall plant performance is investigated using these nanoparticles and is compared with basefluid. The nanofluid thermophysical properties are evaluated as a function of nanoparticles’ properties, volume fraction and the base fluid properties. The effects of key variables such as nanoparticle volume fraction, collector inlet temperature, evaporation pressure and ammonia concentration of Kalina system were evaluated on hydrogen production as well as exergetic efficiencies. Results revealed greater positive influence for CuO compared to TiO2 and Al2O3 on performance improvement for both hydrogen generation and its exergetic efficiency. Also, compared to basefluid (without nanoparticles) case, it was found that CuO particles result in a solar-to-H2 exergy efficiency improvement by 4.7%. Using this nanofluid with a volume fraction of 5%, the H2 production rate enhances from 0.633kg/hto0.664kg/h, indicating 4.9 % improvement.

Transcritical [formula omitted] precooled single mixed refrigerant natural gas liquefaction process: Exergy and Exergoeconomic optimization

This study proposes a two-stage transcritical CO2 pre-cooled single mixed refrigerant process to investigate the potential improvement in exergy efficiency and exergoeconomic performance. Two different objective functions, namely maximizing exergy efficiency and minimizing the unit cost exergy of LNG, were optimized using the particle swarm optimization algorithm to compare the performance of the CO2 pre-cooled single mixed refrigerant process with single mixed refrigerant process. The results of the first objective function indicate a higher exergy efficiency of the CO2 pre-cooled single mixed refrigerant process, with an increment of 7.56%. This improvement can be attributed to not only the lower total power consumption but also the better matching of the temperature-difference composite curve, particularly the location of the pinch temperature at the warm end of the heat exchanger. Additionally, the exergy destruction of the CO2 pre-cooled single mixed refrigerant process was 30.12% lower than that of the single mixed refrigerant process. The second objective function demonstrated that the CO2 pre-cooled single mixed refrigerant process had a unit exergy cost value of 7.46 $/GJ, which was 11.98% lower than the single mixed refrigerant process. In conclusion, the proposed process contributes to energy saving throughout the LNG chain. Previous studies on the transcritical CO2 precooling cycle were limited to only one-stage configuration paving the way for thermodynamic efficiency enhancement by modifying the design of the process. This study also considers the effects of two objective functions maximizing exergy efficiency and minimizing the unit exergy cost of LNG on the optimization of decision variables which has not been discussed yet in the literature. Moreover, innovative exergoeconomic analysis presents a comprehensive criterion for evaluating economic performance, providing guidance for the initial construction and sustainable development of LNG plants.

4E analysis and triple objective NSGA-II optimization of a novel solar-driven combined ejector-enhanced power and two-stage cooling (EORC-TCRC) system

This study proposed an innovative combined ejector-enhanced organic Rankine cycle and two-stage compression refrigeration cycle (EORC-TCRC), to investigate its potential to revolutionize energy utilization and offer a sustainable solution for the current energy challenge. Energy, exergy, economic, and environmental (4E) analysis of the novel EORC-TCRC system was conducted first. The performance appraisal of the novel system compared to the conventional combined power and ejector refrigeration system has been evaluated. The evolutionary non-dominated Sort Genetic (NSGA-II) optimization algorithm was implemented to ascertain triple-objective optimal system operating conditions. The results revealed a significant improvement in refrigeration output, energy, and exergy efficiency with values of 220.06 kW, 11.67%, and 17.07%, respectively, compared to the conventional Rankine power and ejector refrigeration system. By different selections of the objective functions, four groups comprised of Multi-Objective CT–ղex, Multi-Objective CT–ղTh, Multi-Objective ղex–ղTh, and Triple-Objective mode presented to sought NSGA-II optimization results. The optimization results of Multi-Objective CT–ղTh mode indicated that the best thermal efficiency and overall system cost rate operating conditions are 28.25% and 78,820 ($/year), respectively. While the optimal system operating condition occurs in the Triple-Objective ղex- ղTh-CT with the exergetic efficiency of 41.69%.

Experimental investigations of a novel solar still with heat storage materials - energy, exergy, economic and environmental analyses

Current study aims in finding the combined effect of using rectangular fins, gravels (G) and phase change material (PCM) on the performance of pyramid solar still. Two solar stills, one of conventional type (CSS) and other of modified solar still (MSS) which uses fins and PCM inside the basin, are fabricated. Experiments are conducted at Greater Noida (28°28′N, 77°30′E) of Uttar Pradesh, India, during May 2023. The influence of solar still design modifications (CSS and MSS) and adding gravels (CSS + G and MSS + G) on the performance of solar stills is investigated in terms of productivity, energy, exergy, economic, and environmental parameters. Experimental results show an enhancement of about 84 %, 38 % and 32 % in daily productivity for MSS + G, CSS + G and MSS, respectively, than CSS. The MSS + G shows the highest improvement in energy (81.1 %) and exergy efficiency (273 %) with significant reduction in costs per liter of yield produced (29.2 %) and payback period (29 %) when compared with CSS. About 76 % rise in carbon credits earned is observed for MSS + G than CSS while mitigating the CO2 emission of 19.14 tons. Conclusively, the innovative design (MSS + G) not only offers cost-effective yield production but also plays a crucial role in promoting environmental sustainability by reducing CO2 emissions.

Machine Learning-assisted Prediction and Optimization of Exergy Efficiency and Destruction of Cumene Plant under Uncertainty

Machine Learning (ML)'s growing role in process industries during the digitalization era is notable. This study combines Artificial Neural Networks (ANNs) and Aspen Plus to predict exergy efficiency, exergy destruction, and potential improvements in a cumene plant under uncertain process conditions. An optimization framework, using Particle Swarm Optimization (PSO) and Genetic Algorithm (GA), was developed to enhance exergy efficiency amid uncertainty. Initially, a steady-state Aspen model evaluates exergy efficiency, irreversibility, and potential improvements. The proposed model is transitioned to a dynamic mode, introducing artificial uncertainties into key variables. An ANN model predicts exergy efficiency and exergy destruction under uncertainty. The PSO and GA-based optimization methods improve exergy efficiency and reduce exergy destruction. This work demonstrates the potential real-time application of intelligent methods in plant analysis.

Multiaspect analysis and optimization of a power and cooling cogeneration plant integrated with a multilevel waste heat recovery system

Abstract This study focuses on the development and improvement of a new combined power and cooling system called the power-cooling cogeneration system (PCCS). The PCCS incorporates a tri-tier waste heat recovery system that includes an organic Rankine cycle (ORC) system and an ejector-driven refrigeration mechanism. The cogeneration system design incorporates a thorough assessment of thermodynamic efficiency, cost-efficiency, and environmental consequences. A dual-objective optimization technique is developed to decrease expenses while simultaneously improving exergy efficiency. In addition, the complex behavior of PCCS is compared to a standard system that uses a one-stage recovery-ORC system and a compressor-based refrigeration approach. Also, the effectiveness of the PCCS was evaluated through the utilization of several environmentally friendly refrigerants. Environmental evaluations employ two metrics: total equivalent-warming impact (TE-WI) and life cycle-climate performance (LC-CP), emphasizing substantial reductions in environmental harm through improved waste heat recovery. The results demonstrate that the R1234-yf refrigerant achieves the best possible performance in both configurations, resulting in a significant increase of roughly 10.1% in exergetic efficiency compared to the standard system. Simultaneously, the PCCS experiences a decrease in exergy loss and annual costs of around 7.25% and 21.16%, respectively, as compared to the baseline. Incorporating an ejector into the refrigeration cycle has the potential to reduce carbon dioxide emissions by up to 11.41 × 106 kg.

Modeling and thermal economy analysis of the coupled system of compressed steam energy storage and Rankine cycle in thermal power plant

To facilitate the integration of greater amounts of renewable energy into the power grid, it is crucial to enhance the peak shaving capabilities of conventional thermal power units. This paper proposes a novel system that combines compressed steam energy storage with the Rankine cycle of a thermal power plant (referred to as the coupling system), and focuses on modeling a 200 MW thermal power unit. The performance evaluation and parameter selection of the coupling system are conducted through comprehensive energy analysis, exergy analysis, and economic analysis. The results indicate that the energy storage cycle in the coupled system can prevent boilers and turbines in the Rankine cycle from operating at extremely low loads during deep peak shaving. Specifically, when the boiler and steam turbine operate at 66.45 % of their design load, the external power of the coupling system can be reduced to 30 % of the rated power. This results in a reduction of coal consumption by 63.42 g/W * h compared to direct peak shaving of the original thermal power unit, and an improvement in exergy efficiency by 2.99 %. In this study, a 1300 m3 energy storage circulating water storage tank capacity is used as an example, and it is found that the 200 MW unit can achieve continuous deep peak regulation operation for 8.58 h. The study also reveals that a 1 % increase in the isentropic efficiency of energy storage cycle compressors can lead to a reduction in coal consumption by 2.4 g/kW*h. Moreover, economic analysis suggests that maintaining a compressor efficiency of 86 %, utilizing 7 compression stages, and prioritizing the effectiveness of the heat exchanger are optimal for maximizing the system's revenue. These factors collectively result in a shorter payback period for the coupling system and an overall increase in total income.

Innovative modification process of a natural gas power plant using self-sufficient waste heat recovery and flue gas utilization for a CCHP-methanol generation application: A comprehensive multi-variable feasibility study

Waste heat recovery holds significant importance in the context of natural gas power plants, as it facilitates the utilization of energy loss, leading to enhanced overall performance and mitigating adverse environmental effects. By harnessing and employing waste heat, power plants possess the capability to modify and optimize their operation, making a substantial contribution toward sustainable power/energy generation. Therefore, this study proposes a novel and eco-friendly approach to utilizing the flue gas emitted by a natural gas power plant. In addition to recovering waste heat, this method involves harnessing the flue gas for methanol production. The proposed system consists of an organic Rankine cycle, and absorption chiller, heating provider units, an electrolyzer for hydrogen generation, and a methanol synthesis unit. The novel method is implemented through computer-aided simulation using the Aspen HYSYS software and is subjected to an extensive analysis encompassing energy, exergy, environmental, and economic viewpoints. The simulation results exhibit producing 2712 kg/h of methanol with a purity of 99.97 mol%, 395.67 kg/s of hot water, 378 kg/s of chilled water, and 12253.57 kW of power. In this process, the energy and exergy efficiencies are 94.35% and 31.74%, respectively. Parametric study results demonstrate that reducing the gas turbine pressure and increasing the working fluid temperature in the evaporator of the absorption chiller cycle leads to improved exergy efficiency. Moreover, the multigeneration scenario shows a carbon dioxide footprint of 0.1564 kg/kWh and a total unit cost of product of 0.0485 $/GJ.

The optimization and energy efficiency analysis of a multi-tank solar-assisted air source heat pump water heating system

This article undertakes an optimization study of a solar-assisted air source heat pump water heating system by harnessing the advantages inherent in a multiple water tank arrangement. The Hooke-Jeeves algorithm was adopted to optimize the system parameters. The optimization variables encompass pivotal parameters such as water tank volume, collector area, dip angle, azimuth angle and heat pump power, while the objective function is the annual value of life cycle cost. By research and analysis of the monthly power consumption, electricity cost, solar fraction, average coefficient of performance (COP) and annual value of carbon emissions of the single-tank, dual-tank, and triple-tank system, it is discovered that the triple-tank system exhibits superior performance in overall aspects. Compared to the pre-optimized version, it achieves an annual energy consumption reduction of approximately 3.9%, leading to a 22.5% decrease in electricity expenses. Furthermore, it brings a 5.2% reduction in the annual lifecycle cost and a 6.3% decrease in carbon emissions, while simultaneously improving exergy efficiency by 4.8%.

Comprehensive analysis of combined power cycles driven by sCO2-based concentrated solar power: Energy, exergy, and exergoeconomic perspectives

Integrating Brayton cycles, utilizing supercritical carbon dioxide (sCO2) as a working medium, with a concentrating solar power (CSP) system is an attractive solution to enable high-temperature clean production of electricity. In this study, different power cycle configurations were coupled with the CSP system to examine and compare their energy, exergy, economic, and exergoeconomic performances to express a comprehensive view. A study of the impact of different parameters was also carried out to inspect the performance of each system under different operating conditions. The governing equations characterizing system performance and economics have been rigorously solved using MATLAB® R2021a, ensuring accuracy and reliability in the present analysis. Energy assessment reveals that, in indirect systems, the thermal efficiency of the recompression Brayton cycle (RBC) surpasses direct cycles by 0.9%, while the organic Rankine cycle (ORC) in dual cycles exhibits a 2% thermal efficiency advantage over triple cycles. For CSP, direct systems enhance efficiency by approximately 1.5%, compared to indirect systems, with dual cycles outperforming single and triple cycles. Exergy analysis indicates a 1.3% exergy efficiency increase for RBC in indirect systems, compared to direct systems, while ORC demonstrates an exceptional 35.66% exergy efficiency improvement in dual systems. Direct CSP systems exhibit higher exergy values than indirect counterparts. Overall exergy efficiency rankings place triple systems at the top (27%), followed by dual (25%) and single cycles (20%) for both direct and indirect systems. Exergoeconomic analysis reveals that the indirect triple cycle (ITC) system bears the greatest expense, totaling 56,968 USD per annum. Compared to the ITC systems, the indirect single- and dual-cycle systems reduce the cost by 8.2% and 1.15%, respectively.

4E analysis and optimization of a novel hybrid biomass-solar system: Focusing on peak load management and environmental emissions

Renewable energies are available as clean sources to replace fossil fuels. Providing continuous power without compromising the environment through hybridizing solar and biomass source is one of the promising solutions. This paper seeks to address thermodynamic, economic, and environmental analysis of a multi-generation system with the aim of supplying heating, cooling, electricity, fresh-water, and hydrogen. To do this, the considered system is divided into on-peak, mid-peak, and off-peak periods and modeled based on the consumption pattern at different hours of the day and night. Due to the availability of renewable energy during peak consumption periods, biomass, solar, and hybrid biomass-solar energies are used as energy sources. This leads to a reduction in biomass consumption and carbon dioxide emissions through storing approximately 10 tons of biomass during the day. A sensitivity analysis of the factors affecting the system’s function indicated that a growth in solar radiation from 600 to 1000 W/m2, results in a 35% improvement in exergy efficiency, a 2.7% raise in the total cost rate, and a 32.4% drop in CO2 emissions of the system. Moreover, by changing the biomass flow rate from 0.5 to 1.5 kg/s, the exergy efficiency and total cost rate improved by 9.28%, 1.3%, respectively, and the CO2 emissions rate increased from 0.41 to 1.14 tons/MWh. In addition, focusing on addressing economic and environmental concerns, the optimization of the proposed hybrid system is performed in two categories of objective functions. In the second category optimization, exergy efficiency, fresh water production, total cost rate and CO2 emissions are determined as 31.75%, 74.75 kg/s, 324.60 $/h and 3.55 tons/MWh, respectively.

A Novel Cascade Utilization System of Liquid Hydrogen Cold Energy: Energy, Exergy, and Economic Analysis

In order to effectively improve the cold energy recovery efficiency and thermodynamic performance of liquid hydrogen regasification process, a novel type of liquid hydrogen cold energy cascade utilization (RC-HT-AS-DI-CS-AC) system is proposed, which includes Rankine cycle power generation (RC), hydrogen turbine power generation (HT), air separation (AS), production of dry ice (DI), cold storage (CS) and air conditioning (AC). A comprehensive energy, exergy and economic analysis is carried out to compare the proposed system with a comparison system scheme (CSS). For RC-HT-AS-DI-CS-AC system, the energy efficiency of overall system is 79.74%. The cold energy provided by the hydrogen stream achieve 182.31 kW, which is 61.18% increase compared with the CSS. The acquired exergy and exergy efficiency of the RC-HT-AS-DI-CS-AC system increase by 119.6% and 115.9% compared with the CSS. It reveals the importance of liquid hydrogen pressurization to improve exergy efficiency for overall system. However, in the economic analysis, the total annual cost (TAC) of the system of RC-HT-AS-DI-CS-AC system is 278,400 US $, which is significantly higher than TAC of CSS. As a result, the IRR of CSS and RC-HT-AS-DI-CS-AC systems are 87.39% and 15.10% respectively. Therefore, from a commercial point of view, CSS is more worthy of industrialization.

Energy and exergy analyses of a recompression supercritical CO2 cycle combined with a double-effect parallel absorption refrigeration cycle

In this study, a new cogeneration system is presented that can make optimal use of the waste heat from the sCO2 power cycle using a double-effect parallel absorption refrigeration cycle (DEARC), generating electricity and refrigeration simultaneously. A comparative study between the proposed (sCO2/DEARC) system and the stand-alone sCO2 power system is conducted to show its advantages and potential. The performances of the sCO2 and sCO2/DEARC systems are evaluated from the energetic and exergetic points of view using an in-house developed thermodynamic simulation platform via Engineering Equation Solver (EES) software. Variables such as pressure ratio, turbine inlet temperature, and evaporator temperature are also used for parametric analysis. The results indicate that the proposed system can generate of 132.72 MW cooling capacity. Also, the results show that the proposed sCO2/DEARC system can achieve a 55.8% and 5.2% improvement in thermal efficiency and exergy efficiency, respectively, with a negligible decrease in net power output (Wnet) compared to the stand-alone sCO2 power plant.