Exergy Values Research Articles

Exergy Analysis of Hydrogen-Rich Syngas Production System Utilizing Palm Oil Empty Fruit Bunch using Pyrolysis Connected with Steam Methane Reformer

Fossil fuel consumption on a large scale continues to increase yearly, causing a shortage of energy sources. Hydrogen can help to overcome the shortage of energy sources. It can be produced from renewable energy sources, such as oil palm Empty Fruit Bunch (EFB) as biomass using pyrolysis processes equipped with steam methane reformer and water gas shift reactions. This research was conducted to determine the amount of hydrogen that can be produced and to analyze the exergy of the existing systems in the hydrogen production process. Aspen Plus has been used to design and analyze pyrolysis processes, steam methane reform, and water gas shift reactions. The results showed that when 6.54 kg Empty Fruit Bunch was used as raw material in a pyrolysis reactor, hydrogen could be produced in the amounts of 0.435 kg. The exergy values of raw materials and fuels are relatively high because the chemical exergy values of the compounds contained therein are also high. Based on the calculations, it is found that the combustion process is the process that experiences the most significant exergy destruction. The exergy efficiency of this hydrogen production process system is 22.77%.

Mathematical model for the exergy of the system ammonium nitrate–water

The exergy balance has recently been used more frequently for the energy analysis of technological processes and represents a considerable improvement over the evaluation according to the First law of thermodynamics, in which completely convertible and incompletely convertible forms of energy are taken into account equally. In order to carry out the exergy balance, the exergy values of the material flows involved in the process must be known. This article presents a mathematical model for calculating the exergy of ammonium nitrate in aqueous solution in the production of fertilizers. When carrying out the exergy model, it was assumed that the conditions are: ambient temperature 20 °C, pressure 101.325 kPa and that it consists of liquid water and crystalline ammonium nitrate, which has an exergy value of zero under these conditions. The model is based on Pitzer’s ion-interaction type equations for the dependence of the activity coefficient on the composition of the solution at a given temperature and pressure. This mathematical model is valid for aqueous solutions of ammonium nitrate up to saturation in the temperature range from 20 °C to 170 °C and offers the possibility to estimate the NH4NO3(aq) enthalpies at different temperatures and different compositions.

Experimental investigation of a new defrosting technique for sustainable refrigeration system

Defrosting can have a detrimental impact on the functioning of regularly used refrigeration systems. The primary objective of this study is to enhance the cooling efficiency by resolving the defrost process, which impacts the cooling performance due to the heat received from the system. A new solar PVT-assisted system, which includes a cold chamber, was created and tested for this specific purpose. Furthermore, a sophisticated automation scenario has been devised to function in five distinct modes, ensuring the successful execution of the defrost process. Two experiments, Experiment 1 and Experiment 2, were conducted. The average coefficient of performance (COP) and exergy values obtained were 2.29 and 2.25, and 25.74 % and 24.45 %, respectively. The maximum temperature change measured in the cold room during defrosting was 2 °C. In Experiment 1, the PVT collector produced a total energy of 2.85 kWh; Experiment 2 generated 2.79 kWh. Consequently, the defrosting procedure was effectively executed by directing hot air into the chilly chamber using the proposed sustainable method. This system is highly recommended because of its innovative defrosting mechanism, which guarantees optimal solar energy utilization.

Exergy Analysis in Highly Hydrogen-Enriched Methane Fueled Spark-Ignition Engine at Diverse Equivalence Ratios via Two-Zone Quasi-Dimensional Modeling

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH4). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO2) emissions. Given that using neat hydrogen (H2) containing nil carbon still possesses several issues, blending CH4 with H2 constitutes a stepping-stone towards the ultimate goal of zero producing CO2. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH4 to 50% vol. fraction H2, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H2 percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H2 and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H2 or EQR, the work transfer exergy curves acquire slightly higher values the higher the H2 and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H2 or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H2. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H2 fuel, which can prove to be game changer to attaining a clean energy environment transition.

Effect of intake valve lift and binary alcohol (bioethanol+isobutanol) addition on energy, exergy, sustainability, greenhouse gas impact and cost analysis in a hydrogen/diesel dual fuel engines

Greenhouse gas emissions are a significant problem contributing to global warming and climate change and it is essential to increase the use of renewable and biomass-derived fuels in internal combustion engines to reduce greenhouse gas formation. Alcohol fuels and hydrogen have become prominent in recent years due to less harmful emission levels as a result of combustion. While there are very few studies in the literature on ternary mixture + hydrogen in terms of energy and exergy, there is a gap on the effect of the valve lift amount. The aim of this study is to investigate the effects of binary alcohol addition and variable intake valve lift (IVL) in hydrogen-diesel dual fuel mode on energy, exergy, sustainability, and greenhouse gas emissions. The experiments are conducted at variable torque conditions, involving three different IVL values (4, 4.46, and 4.9 mm) and four different fuel combinations (diesel, diesel + H2, diesel + binary alcohol, and diesel + binary alcohol + H2). The binary alcohol addition consists of 10% bioethanol and 10% isobutanol volumetrically, while in the dual-fuel mode, hydrogen is injected into the cylinder at a constant flow rate. When the results are examined, the highest energy and exergy values are obtained with the IVL-Diesel + H2 operation, providing on average 11% and 8% higher exergy efficiency compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively. Additionally, the exergy destruction in the IVL-Diesel + H2 study shows an average decrease of 16% and 12%, respectively, compared to the IVL 4-Diesel and IVL 4.46-Diesel studies. Additionally, significant reductions in emissions are achieved. In the IVL 4.9-EB20+H2 study, HC, CO, and CO2 emissions decrease by 28%, 40%, and 28%, respectively, compared to the IVL 4.0 study. When examining the GHG emission impact, it is analysed that operating a single-cylinder engine with EB20+H2 fuels under 4.9 mm IVL conditions emits, on average, 36% and 32% less GHG impact over a one-year period compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively.

Optimization of a combined gas turbine and steam Rankine cycle utilizing the chemical looping combustion (CLC) reactor for CO2 capture and Storage: Towards enhanced efficiency and Cost-Effectiveness

In recent years, CO2 released by fossil fuel power plants, through the process of capture and storage, has been tried to be separated from other combustion products and directed to the underground to prevent it from entering the environment. While various methods exist for this purpose, they are typically expensive and consume a significant amount of power. In this research, a proposed solution to study and optimize the capture and storage process involves a combined cycle power plant with two gas turbines and four steam turbines, equipped with a carbon dioxide capture and storage system using the chemical looping combustion (CLC) method. The storage of released CO2 is facilitated by four compressors operating in four stages. To begin, the developed model is validated in terms of energy, exergy, and economic factors. Subsequently, the system is optimized using an NSGA genetic algorithm, with two objective functions: exergy efficiency and total cost rate. Sensitivity analysis is conducted to define the decision variables. The results demonstrate that the optimization process has led to a 4.37 % increase in the system’s power output, from 379.75 MW to 396.37 MW. Moreover, the optimization has improved both the exergy and energy efficiency values, with these parameters rising from 51.97 % and 54.23 % to 54.24 % and 56.61 %, respectively. Furthermore, the total cost rate has slightly decreased from 46,267 to 46,020 $/hr as a result of system optimization.

COMPARATIVE EXERGY ANALYSIS OF ADIABATIC AND ISOTHERMAL HUMIDIFICATION IN A DIRECT-FLOW CENTRAL AIR CONDITIONING SYSTEM

Central air conditioning systems of buildings and structures are significant consumers of electric and thermal energy of different temperature levels and are the least economical in terms of energy consumption. When designing these systems, due attention is not always paid to assessing their energy efficiency and no variant design is carried out with a comparison of the relevant indicators. This is due to the lack of proven engineering methods. The exergy method of analysing energy-consuming systems provides a correct numerical assessment of energy efficiency and enables a comparative analysis of circuit solutions and system elements. In contrast to the energy method, the peculiarity of the exergy method in relation to air conditioning systems is the possibility of taking into account all available mass and energy flows in the system in exergy units. The extension of the exergy method to systems for creating and maintaining a microclimate in buildings and structures has not yet acquired the status of practical engineering support. This article presents an example of an exergy analysis based on the original methodology for comparing methods of humidification in a central air conditioning system for a public building in order to select the best method in terms of energy efficiency. Two traditional methods of air humidification for the cold season - adiabatic and isothermal - were used for the study and comparison. The results of analytical studies are presented in the form of relative values of exergy.

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.

Análisis detallado de un motor diésel alimentado con mezclas de combustible diésel, aceite de linaza, biodiésel y etanol en el contexto termodinámico, económico y medioambiental

The growing demand for energy, coupled with volatile oil prices and the environmental damage caused by the harmful gases produced when it is used, has prompted countries to explore alternative energy sources. The transportation sector, an important end-user of petroleum, must adapt to the changing energy landscape and opt for new technologies to remain competitive. The study conducted a thorough thermodynamic analysis to assess the economic and environmental impact of using biodiesel (BD) made from cold-pressed linseed crude oil, commercial diesel fuel (DF), and ethanol in a compression-ignition (CI) engine. The study conducted a detailed thermodynamic analysis of performance and emission data recorded from a single-cylinder diesel engine. The analysis included energy, exergy, sustainability, exergoeconomic, exergoenvironmental, and exergoenviroeconomic parameters. The results pointed out that the fuel energy increases with the load, with B20E5 fuel reaching 6.887 kW at 25% load and 18.908 kW at 75% load. BD and blended fuels were found to have a higher fuel energy compared to DF. At 50% load, DF and B20 fuels have fuel energies of 10.765 kW and 10.888 kW, respectively. The analysis clearly demonstrates that commercial DF outperforms both DF-BD binary fuel blends and DF-BD-ethanol blends in terms of thermal and exergy efficiency values. Furthermore, DF exhibits lower entropy generation and exergy destruction than other binary and ternary blends. At maximum load, the exergy efficiencies of DF, B20, and B20E10 fuels were 28.5%, 25.8%, and 24.7%, respectively. The exergy losses were determined to be 10.495 kW, 12.317 kW, and 13.134 kW, respectively, under the same conditions. Binary and ternary fuel blends have a higher cost of power from the engine shaft due to the expensive market prices of ethanol and linseed oil-based BD compared to DF. However, B20 and B20E10 fuels have a lower environmental cost than DF, with B20 and B20E10 fuels estimated to be 2.8% and 5.3% lower than DF, respectively, at full load. These findings demonstrate the clear advantages of using B20 and B20E10 fuels over DF, both in terms of cost and environmental impact. Additionally, the infusion of ethanol into ternary blends reduces the environmental damage. This study provides a unique perspective on sustainable energy research and serves as a valuable reference for future studies.

The Exergy and Energy Analysis of Change Phase Steam in Patuha Geothermal Well Production

A Geothermal Power Plant Company in West Java Indonesia have capacity around 55MW. It company have increased the well production quality to keep up the Indonesia's energy demands. The power plant has been operated around ten years, it has ten geothermal production wells and two injection wells. The either of it wells has an abnormality. It wells has water dominated condition so, the separator equipment is required to separate the steam from water and vapor. Previous study indicated that subsurface water entering the broken reservoir pipe. That leaks in reservoir pipe was repaired in 2020. The impact after the pipe have been repaired it made the fluid characteristic of reservoir be vapor dominated. After that a separator as a steam separator is no longer required. The study compares the value energy and exergy power of the power plant. The calculations are performed from the well reservoir and all power plant equipment. According to the results of the energy study, the plant's energy efficiency after the transformation increased by 0.03%, from 19.48% to 19.52%. The exergy value of the brine in either wells (separated steam cycle) is also known to be 2.512,52 kW, beyond which the value will become zero.

Exergy analysis of thermodynamic performance of a gas turbine unit

BACKGROUND: Gas turbine units are the most widespread type of power plants used in almost all industries. Such a wide distribution in combination with a high level of energy characteristics, high specific power and flexibility determine the relevance of research in the field of assessing their operating parameters.
 AIM: Determining the exergy characteristics (exergy efficiency and exergy dissipation factor) of a gas turbine plant and evaluation the efficiency of energy use in a gas turbine plant, as well as analysis of the influence of ambient temperature on the selected parameters.
 METHODS: The paper presents the results of an exergy analysis of the gas turbine plant as part of the Jandar Thermal Power Plant, Syria. To evaluate the described parameters, the method of exergy analysis of the thermodynamic characteristics of a gas turbine plant based on the first and second laws of thermodynamics in conjunction with the laws of conservation of mass and energy was used. An important feature of the study, which also emphasizes its novelty, is taking into account the chemical exergy of combustion gases during the exergy analysis.
 RESULTS: Based on the results of the study, it was found that the maximum exergy efficiency was 92.8% and was typical for a turbine as part of a gas turbine, while the highest exergy dissipation was observed in the process of fuel combustion in the combustion chamber and was equal to 80% (117.3 MW). The lowest exergy values corresponded to the compressor — 6.0% (9 MW). For the gas turbine unit as a whole, the total exergy dissipation was 147.3 MW and the exergy efficiency was 53.3%. In this case, the main sources of irreversibility in the gas turbine unit are the combustion chamber and combustion gases.
 CONCLUSION: Exergy analysis is a convenient method for evaluating the thermodynamic perfection of gas turbine units. As a further line of the study, it is necessary to evaluate the effects of various conditions, such as air humidity or compressor pressure ratio, on the exergy characteristics of the gas turbine fuller.

Exergoeconomic analysis of ultrasound-assisted extraction of tannins from acorn fruit

Acorn fruit (AF) is a valuable yet tannin-rich forest byproduct. The removal of bitter-tasting tannins is essential for its use as food. This study investigated exergoeconomic analysis of ultrasound-assisted extraction (USAE) with varying amplitudes (20%-60%-100%) and duty cycle conditions (20%-60%-100%) to extract tannins from AF. Conventional solvent extraction (CSE) was used as comparison. AF, mixed with water (1:10 w/v), subjected to ultrasound until tannin content reached 0.0274 mg TAE/mg DM. The study evaluates process conditions' impact on performance and tannin's unit extraction cost. Exergoeconomic analysis was conducted by considering the exergy values, operating costs, investment costs, and extraction time. CSE requires 300 min for target tannin content, while USAE reduces this time to 40-fold. The highest energy efficiency (84.44 ± 2.97) and exergy efficiency (83.68 ± 3.61) were determined at 20% amplitude-20% duty cycle. USAE reduces extraction costs by 25% compared to CSE. USAE has the potential for rapid tannin extraction and cost reduction.

Optimization and 3E analysis on variable operational conditions of a large, medium and small size Green Methanol Plant

This paper presents a technical optimization and comprehensive economic, exergy and exergonomic (3E) analysis of green methanol synthesis plants designed for large, medium, and small production capacities: 285,400; 56,700; and 16,300 tons/year, respectively. The optimization process explores operational parameters that encompass both economic and production aspects. The 3E analysis evaluates economic factors influenced by plant operational conditions, exergy assessment to evaluate the optimal efficiency and performance, and exergonomic assessment of the cost-performance relationship. A validated mathematical model in MATLAB and ASPEN Plus is utilized for process optimization and evaluation. The findings indicate the large and medium-sized plants as the most viable options, with levelized costs of 714.97 and 705.67 €/ton and methanol yields of 0.663 and 0.584 [-], respectively. The key factors influencing costs and production are H2 usage and reactor operational pressure. The plant performance evaluations show exergy efficiencies of 73%, 73%, and 71.4%, with destroyed exergy values of 78,676 kW, 15,965 kW, and 5070 kW for the large, medium, and small-sized plants, respectively.

Second law analysis of an internal combustion engine for different fuels consisting of NaBH4, ethanol and methanol mixtures

This study was carried out to investigate the effects of NaBH4, which is not used as an internal combustion engine fuel in the literature, on system energy and exergy when used in internal combustion engines. In the study, fuels containing oxygen and hydrogen (MSG12.5, EG12.5, ESG12.5 and MG12.5) and pure gasoline (G100) were tested at different engine speeds and the changes in the energy and exergy analyzes of the system were investigated. In the experimental study, the energy and exergy values of gasoline used as fuel were at the highest values with 33.21 kW and 35.62 kW, respectively, while the energy and exergy efficiencies were 27 % and 25 %, respectively. MG12.5 fuel used in the study showed the best performance among all fuels with 38 % energy efficiency and 35 % exergy efficiency. On the other hand, it was seen that boron added ESG12.5 % fuel was the second best fuel with 35 % energy efficiency and 33 % exergy efficiency. Another fuel, boron added MSG12.5 fuel, performed better than gasoline in terms of both energy and exergy efficiency. In addition, it was determined that more than 50 % of the exergy of the fuel entering the system was lost due to exergy destruction and the exergy destruction of the fuels used in the experiments was determined at least in MG12.5, ESG12.5, EG12.5 and G100, respectively.

Exergy Analysis of Coal-Based 2 X 7 MW Steam Power Plant

In this study, an analysis was conducted on a steam power plant system with a capacity of 2 x 7 MW based on coal. The coal fuel used by the majority of refined sizes is not in accordance with the recommendations of the American Society of Mechanical Engineers (ASME). The main objective of the study was to analyze the system components separately and to measure the exergy value of the components, covering the electrical energy so that it is known which equipment experiences the greatest energy loss as well as knowing the efficiency value of the equipment used. Efficiency and exergy are calculated using plant operation data. The results of the study found that the largest exergy destruction occurred in boilers, meaning that there was the largest energy loss in this section with a value of 37.34 MW (16.71%), while the destruction of the smallest exergy occurred in condensers of 0.58 MW (99.24%).

Exergy and energy analysis of Organic Rankine Cycle integration in the carbon black industry using pinch technology

Industrial Carbon black production is a petrochemical process that has high level of waste heat and emissions. Main points of CB process include furnace and stack lines. Also, the use of different feedstocks can be effective in level of waste heat and amount of emission pollutants. So the main objective of this research use from the pinch technology in CB process in order to minimize the level of waste heat by utilization of waste heat recovery (WHR) applications for power generation. By numerical investigation and modelling of WHR in furnace and stack points, can be defined best location for power generation in CB process. Moreover, through the analysis of Organic Rankine Cycle (ORC) systems integrated with WHR from both energy and exergy perspectives, second target to enhance their thermal efficiency. The results indicate that the presence of blowers on stacks leads to an increase in RoHR and RoHC. In order to determine the optimal location for power generation cycle installation, an ORC energy and exergy analysis was conducted. The results showed that the energy and exergy values at the SLC stack were higher than those at the HLC point. Also, numerical results showed the points that have suitable thermal efficiency and rate of exergy of WHR where have higher temperature gradient than other points. So SLC (ĖxWHR=166.7kW) and HLC (ĖxWHR=136.1kW) stacks integrated with blower are the optimal location for WHR utilization in the CB production process.

Comparative energy and exergy analysis of a CPV/T system based on linear Fresnel reflectors

Abstract An energy generation system that is highly appealing is the integration of a photovoltaic system with linear Fresnel reflectors, especially when combined with a cooling thermal system. This research study involves a comparative analysis of energy and exergy of a CPV/T system that uses traditional linear Fresnel reflectors. The calculations indicate that, given the prevailing weather conditions and an average instantaneous solar radiation of 559 W/m2 at the location, the system can generate an average of 271.23 kWh of electricity and 613.63 kWh of thermal energy per month by utilizing highly efficient, long-lasting, and cost-effective monocrystalline solar cells in the considered the CPV/T system. The overall efficiency of the system is determined to be 54.1 %. According to exergy analysis, the setup experiences some loss of exergy in both its thermal and electrical components. The overall exergy efficiency is calculated as 54.96 %. Thus, on average, the system experiences an exergy loss of 1.01 kWh per day due to thermal factors and 1.70 kWh due to electrical factors. Although the system appears to be more efficient in exergy than energy, the exergy values highlight the need to reduce energy and exergy losses in order to improve the overall system performance.

Energetic and exergetic analysis of a Vapour compression refrigeration test rig in varying concentrations of (TiO2-SiO2/MO) hybrid nano-lubricants and R600a refrigerant charges

ABSTRACT Every residential refrigerator employs a Vapor Compression Refrigeration (VCR) technology. The performance of a VCR system is mostly determined by the input power and refrigeration effect. In present study, effects of varying concentrations of TiO2-SiO2/MO hybrid nano-lubricant (0.1, 0.2, 0.3, and 0.4 g/L), and mass charge of refrigerant R600a (80, 100, and 120 g) investigated by the authors. The performance parameters of the VCR test rig optimized at 0.2 g/L of hybrid nano-lubricant concentration using 100 g mass charge of R600a refrigerant. At this optimum condition, the percentage increase in coefficient of performance was 37.83% compared to the pure lubricant using 80 g mass charge of R600a refrigerant. The percentage reduction in input power at optimum condition was 13.46% compared to pure lubricant case using 80 g R600a, refrigerant mass charge. The maximum value of second law efficiency and the least value of exergy lost were found at 0.2 g/L concentration of hybrid nano-lubricant using 100 g charge of R600a refrigerant, with values of 77% and 96.90W, respectively. In conclusion, performance of VCR test rig altered when the concentrations of hybrid nano-lubricant and refrigerant mass concentrations changed.

Design and multi-objective optimization of a multi-generation system based on PEM electrolyzer, RO unit, absorption cooling system, and ORC utilizing machine learning approaches; a case study of Australia

The geothermal systems' capability to produce various products persuades the design of a novel hybrid system, including power, cooling, freshwater, and hydrogen. Australia, with numerous geothermal sources and the tendency of hydrogen utilization as fuel, is considered a case study. The designed system is analyzed from energy, exergy, and economic viewpoints. Also, the artificial neural network is implemented to optimize the system's operation. Hence, the accuracy of four artificial neural networks in optimizing and predicting systems' performance is compared. Furthermore, four double-objective and four triple-objective optimization scenarios are considered to achieve the best optimum state from different viewpoints. The mean absolute Error value of 2.28×10−14 to predict the exergetic efficiency in the testing procedure is the best algorithm. The system provides 1263 kW net power with 39.89% exergy efficiency and 2.13 years of payback period at the base condition. The exergy efficiency-net present value scenario represents the best performance in which the net power, hydrogen, and freshwater production rates reach 3946 kW, 8.73 kg/h, and 152 kg/h, respectively. Subsequently, the exergy efficiency, payback period, and net present value are estimated at 46.27%, 1.84 years, and 19.52 M$.

Obtaining mathematical equations for energy, exergy and electrical efficiency: A machine learning approach

ABSTRACT In this study, in which the energy, exergy, and electrical efficiency values of the photovoltaic thermal panel are modeled with different machine learning algorithms, mathematical equations that can calculate the efficiency values have been obtained as an innovative approach. Data sets consisting of environmental parameters (temperature, wind speed, solar radiation, humidity) of the environment in which the experiments were carried out were used in the models. Thus, the effects of environmental parameters on collector efficiency values were observed, and mathematical equations were produced using these parameters with the help of the decision tree algorithm and Pace regression. In addition, environ-economic analyzes of the panels were made and the coefficient of performance values were examined. In the experiments, two data sets were obtained. With one of these data sets, the efficiency values were modeled with machine learning algorithms, and the accuracy of the mathematical equations obtained with the other data set was proven. The mean absolute percentage error values of the energy, exergy and electrical efficiency models created with the decision tree are 8.04%, 1.76%, and 1.43%, respectively. Similarly, Pace model error values are 3.83%, 2.54%, and 2.1%. The high accuracy values of the obtained efficiency equations under different experimental conditions show that these equations can be used under different conditions and in different solar energy systems.