Exergy Cost Research Articles

Exergoeconomics evaluation on optimal operation conditions in crude oil gathering and transportation system

ABSTRACT At present, most of the energy analysis of the engineering system is only from the energy point of view. In this paper, the theory of exergoeconomics is combined with the operation optimization of the gathering and transportation system. In terms of exergy flow distribution and the construction of each equipment, the exergy value of total 17 exergy flows and the non-energy cost of 6 main equipment in the process are calculated. An exergoeconomic model in technological process of gathering and transportation system is established. Combined with the exergoeconomic cost valuation strategy, 11 auxiliary equations are used to get the economic cost of each flow unit in the process. Taking the minimum operation exergy cost as the objective function, a mathematical model of operation optimization in exergoeconomics is established, and each decision variable is constrained on the basis of the actual site conditions. The objective function within the range of process requirements is solved by iterative method. The optimal water mixing temperature is 47.1°C, and the optimal water mixing volume is 840.7 m3/d under the actual working condition of the site in light of the calculation results.

System integration and evaluation of residual oil deep catalytic cracking process coupled with CO2 recycle to produce polypropyl carbonate

A system for the production of polypropyl carbonate (PPC) from residual oil deep catalytic cracking process coupled with CO2 recycle (DCC-P&CO2-PPC), based on the actual refinery (1.5 million tons of residual oil per year), is proposed in this work. The CO2 in the flue gas emitted from the factory is used as raw material to produce high-value-added PPC. The novel DCC-P&CO2-PPC simulation process is established and verified by Aspen Plus software, and the key parameters and process conditions of the system units are optimized. The feasibility and development potential of the DCC-P&CO2-PPC system are elucidated by analyzing the characteristics and composition of the economy, elemental flow, total exergy distribution, and exergy cost of the system. To sum up, the DCC-P&CO2-PPC system converts CO2 and primary product propylene into high-value-added PPC, expands the downstream industry chain of LPG, makes full use of the elemental complementarity between CO2 in flue gas and the refinery products and achieves the dual goals of low-carbon production and economic efficiency improvement of the refinery, thus providing a new technical route and practical solution for the low-carbon transition development of residue catalytic cracking refineries.

Energy, exergy, economic, environmental, and sustainability assessments of the CFM56-3 series turbofan engine used in the aviation sector

In this study, aviation, energy, exergy, environmental, exergoeconomic, and exergoenvironmental analyses are performed on a CFM56-3 series high by-pass turbofan engine fueled with Jet-A1 fuel. Specific fuel consumption and specific thrust of the engine are found to be 0.01098 kg/kN.s and 0.3178 kN/kg/s, respectively. Engine's energy efficiency is calculated as 35.37%, while waste energy ratio is obtained as 64.63%. Exergy efficiency, waste exergy rate, and fuel exergy waste ratio are forecasted as 33.32%, 33175.03 kW, and 66.68%, respectively. Environmental effect factor and ecological effect factor are computed as 2.001 and 3.001, while ecological objective function and its index are taken into account of −16597.22 kW and −1.001, respectively. Exergetic sustainability index and sustainable efficiency factor are determined as 0.5 and 1.5 for the CFM56-3 engine, respectively. Environmental damage cost rate is determined as 519.753 $/h, while the environmental damage cost index is accounted as 0.0314 $/kWh. Specific exergy cost of the engine production is found as 40.898 $/GJ from exergoeconomic analysis, while specific product exergy cost is expressed as 49.607 $/GJ from exergoenvironmental analysis. From exergoenvironmental economic analysis, specific exergy cost of fuel is computed as 10.103 $/GJ when specific exergy cost of production is determined as 40.898 $/GJ.

Energy and exergoeconomic assessments of a renewable hybrid ERC/ORC integrated with solar dryer unit, PEM electrolyzer, and RO desalination subsystem

In this investigation, a zero-dimensional model of a renewable generation system encompassing a solar-geothermal driven Proton Exchange Membrane (PEM) electrolyzer integrated with Organic Rankine Cycle (ORC), Ejector Refrigeration Cycle (ERC) and Reverse osmosis (RO) unit is expressed with respect to energetic, exergetic, economic, and exergoeconomic points of view. Cooling and heating energies, electricity, distilled water, Hydrogen (H2), Oxygen (O2) are the key products of the mentioned system. In order to acquire the influences of the solar collector numbers, area ratio, and pressure drop of the ejector and working fluid of solar collectors on the efficiency of the hybrid unit, a set of equations were coded in MATLAB and Engineering Equation Solver (EES). The exergy destruction rate, exergy efficiency, and exergy destruction ratio of each subsystem and exergy flow diagram of all subsystems were evaluated in this study. Afterward, the results of the sensitivity analysis were used for multi-criteria optimization in three various layouts that the LINMAP as well as the fuzzy TOPSIS decision makings and Gray Wolf Optimizer (GWO), are considered to get the optimal result. The results have indicated that the main variables analyzed are more affected by the variation in the number of the flat plate solar collector. Besides, in the second optimization scenario, the TOPSIS selects the optimal solution of exergy efficiency and unit exergy cost of the product of 3% and 19.77 $/Gj, while the LINMAP selects 3.001% and 19.80 $/Gj point.

Integrate exergy costs and carbon reduction policy in order to optimize the sustainability development of coal supply chains in uncertain conditions

The coal supply chain in developing countries is supposed to have the lowest cost overall; however, in terms of sustainability (social, economic, and environmental aspects) and considering Joules rather than monetary objectives, does this assumption remain accurate? This research develops a sustainable model for coal supply chain in five countries by integrating exergy costs and carbon tax policy using the extended exergy accounting (EEA) method under an uncertain environment. This sustainable model is a single vendor multi-buyer economic order quantity (EOQ) model for coal supply chain with the objective of the least total exergy with the maximum carbon and imperfect quality items decrease. Additionally, some realistic suppositions such as waste disposal to the environment, the obtainable budget of buyers and stockout in the model are considered. Following this, four metaheuristic algorithms, such as WOA, GA, ACO, and SA, are suggested to solve the model, and their results are validated by the exact method (GAMS). Finally, to improve the model's sustainability, a sensitivity analysis with different exergy values is offered for coal supply chain in each country. According to the results, coal supply chains in Canada and Germany have better sustainability performance (in Joules) than Iran and Turkey.

Efficiency, economic and environmental impact assessments of a new integrated rail engine system using hydrogen and other sustainable fuel blends

Locomotives still use antiquated engines, such as internal combustion engines operated by fossil fuels which cause global warming due to their significant emissions. This paper investigates a new hybridized locomotive engine containing a gas turbine system, solid oxide fuel cell system, heat recovery system, and an on-board hydrogen production system. This new integrated engine is operated using five fuel blends composed of alternative fuels, such as hydrogen, methane, methanol, ethanol and dimethyl ether. The current investigation involves multiple studies, such as exergy analysis, exergoeconomic analysis and exergoenvironmental analysis to assess the integrated engine system from three perspectives: efficiency/irreversibility, cost and environmental impact. The present study results show that the net power of this new engine is 4948.6 kW, and it has an exergetic efficiency of 62.7% according to the fuel-product principle. In addition, this engine weighs about 9 tons and costs about $10.2 M, with a levelized cost rate of 147 $/h and 14.06 mPt/h of overall component-related environmental impact rate. The average overall specific fuel and product exergy costs are about 37 $/GJ and 60 $/GJ, and the minimum values are 13.3 $/GJ and 21.8 $/GJ using the methane and hydrogen blend, respectively. Also, the average overall specific fuel-product exergoenvironmental impacts are about 15 and 23 mPt/MJ, respectively. Furthermore, the on-board hydrogen production has an average exergy cost of 274 $/GJ with an environmental impact of 52 mPt/MJ. Moreover, the hydrogen blended with methane or methanol is found to be more economical with less environmental impact.

Detailed assessment of specific exergetic costing, energy consumption, and environmental impacts of a rotary kiln in cement industry.

Türkiyeis one of the biggest developing countries and the second biggest cement exporter in the world. In 2021, the country exported around $1billion of cement, which is responsible for over 8% of emissions globally. In order to fulfill the EU norms, energy, emissions, and cost reduction investments continue in the country. The aim of this paper is to perform a detailed exergoeconomic assessment of a rotary burner to increase the energy and exergy performance and decrease energy consumption, exergy costs and environmental impacts of a real scale cement factory in Türkiye. During the 2-year period, detailed data has been obtained from the factory by real time detection of clinker manufacturing process. By applying the specific exergy costing (SPECO) method, energy and exergy destructions, and exergetic cost distributions for the rotary burner are calculated in detail. The 1st and 2nd law efficiencies of the overall factory, specific energy (SEC) and exergy (SExC) consumption, and SPECO for clinker production are calculated to be 59.84%, 39.04%, 4786.75MJ/ton, 5230.38MJ/ton, and 10.11 $/MJ, respectively. The use of magnesia-spinel composite refractory bricks and the anzast layer formation decreased the SPECO by 2.71% corresponding to a saving of $2,280,000 preventing 13.74 MtCO2 emissions yearly.

Thermodynamic rarity of electrical and electronic waste: Assessment and policy implications for critical materials

AbstractThe strategic relevance of extracting raw materials from waste from electrical and electronic equipment (WEEE) in the EU is increasing due to value chain risks caused by geopolitical instability, accessibility of specific minerals, and decreasing reserves due to growing extraction rates. This article examines the quantities of so‐called critical raw materials (CRMs) originating within WEEE streams from a depletion perspective. Presently, current recycling targets are based solely on mass collection and recycling rates. We examine the potential limitations of this approach using an exergy‐based indicator named thermodynamic rarity. This indicator represents the exergy costs needed for producing materials from the bare rock to market. The case of Italy is used to explore the application of the indicator at the macro (national) and micro (company) level for the product categories “small electronics” and “screens and monitors.” Our estimations show significant differences between the mass and rarity of materials within Italian WEEE streams. While iron accounts for more than 70% of the weight of the product categories analyzed, it accounts for less than 15% of the rarity. Similarly, several CRMs with a small mass have a higher rarity value, for example, tungsten with less than 0.1% of the mass and over 6% of the rarity. The policy context is reflected upon, where it is argued that thermodynamic rarity can provide novel insights to support end‐of‐life WEEE decision‐making processes, for example, target development and recycling standards setting to help prioritize material monitoring and recovery options.

An innovative compressed air energy storage (CAES) using hydrogen energy integrated with geothermal and solar energy technologies: A comprehensive techno-economic analysis - different climate areas- using artificial intelligent (AI)

The present study evaluates the optimal design of a renewable system based on solar and geothermal energy for power generation and cooling based on a solar cycle with thermal energy storage and an electrolyzer to produce hydrogen fuel for the combustion chamber. The subsystems include solar collectors, gas turbines, an electrolyzer, an absorption chiller, and compressed air energy storage. The solar collector surface area, geothermal source temperature, steam turbine input pressure, and evaporator input temperature were found to be major determinants. The economic analysis of the system showed that the solar subsystem, steam Rankine cycle, and compressed air energy storage accounted for the largest portions of the cost rate. The exergy analysis of the system demonstrated that the solar subsystem and SRC had the highest contributions to total exergy destruction. A comparative case study was conducted on Isfahan, Bandar Abbas, Mashhad, Semnan, and Zanjan in Iran to evaluate the performance of the proposed system at different ambient temperatures and irradiance levels during the year. To optimize the system and find the optimal objective functions, the NSGA-II algorithm was employed. The contradictory objective functions of the system included exergy efficiency maximization and cost rate minimization. The optimal Exergy round trip efficiency and cost rate were found to be 29.25% and 714.25 ($/h), respectively.

Thermoeconomic analysis of a microcogeneration system using the theory of exergetic cost

Cogeneration and trigeneration systems have been broadly employed as part of the strategies oriented toward rational energy use. The assessment of these systems must include simultaneous considerations of costs, irreversibility, energy losses, and their causes. This work presents a step-by-step thermoeconomic analysis of a microcogeneration unit, composed of an internal combustion engine and an NH3-water single-effect absorption refrigeration chiller. The research employed the Theory of Exergetic Cost method to determine monetary and energy costs and the exergy efficiency of equipment. It is therefore, possible to identify which pieces of equipment present the highest impact and focus on these to improve the overall performance of the energy system. Although not part of the Theory of Exergetic cost, exergoeconomic parameters can be calculated to expand the assessment further. The highest specific exergy cost is associated with the endothermic reaction inside the absorber (282 $/GJ), while the lowest specific exergy cost is due to electricity consumed by the pump of the refrigeration system (2.16 $/GJ). The highest exergy efficiency was identified at the condenser (almost 90%, while values under 40% were obtained for the engine, pump, and absorber. The combined analysis of exergoeconomic results indicates that the lowest performances are related to the generator, the absorber, the evaporator, and the regenerator.

Exergetic and exergoeconomic implications of a recuperative organic Rankine cycle plant for power production from an abandoned oil well

This study was aimed at assessing the exergetic and exergoeconomic implications of adopting a recuperative (SUB-REGEN) instead of a non-recuperative (SUB) organic Rankine cycle (ORC) plant for power production from an abandoned oil well. The geometric parameters of a typical oil well in Nigeria were adopted for simulating the heat source. The specific exergy costing (SPECO) approach was employed for the exergoeconomic assessment. Results showed that for the SUB ORC, the evaporator had the highest exergetic efficiency of about 86% and the condenser the highest cost rate of exergy destruction of about 47%. For the SUB-REGEN ORC, the condenser had the highest contribution ratio of 0.41 to the total irreversibility with a cost rate of about 19.1 k$/h. Overall, the integration of a recuperator would increase the ORC exergetic efficiency from around 55% to 58%, albeit with a consequent increase in the cost rate of system irreversibility by about 24%.

Exergoeconomic and sensitivity analyses of a gas turbine power plant using MINI-REFPROP and MATLAB simulink

In this paper, exergy, exergoeconomic, and exergoenvironmental analysis of a gas turbine cycle and its optimization have been carried out by MINI-Reference Fluid Properties (MINI-REFPROP) and Matrix Laboratory (MATLAB) SIMULINK. The parametric study was carried out based on the Specific Exergy Costing approach. The mathematical models were developed and presented regarding mass, energy, and economy. The Excel and MATLAB LIBRARY TOOLS BOX are used to perform thermodynamic properties and research analyses. The analyses lead to valuable economic status benchmarks. The exergoeconomic factor, relative cost, total cost of energy loss, and energy destruction for the combustion chamber and work output were determined. The parametric study was conducted, considering the effects of the gas turbine inlet temperature, air compressor inlet temperature, and compressor pressure ratio. For the considered case study status, the combustion chamber in the plant revealed the highest amount of energy destruction (85%), leading to the recommendation that more attention be paid to boilers in terms of design, selection, operation, and maintenance, while the combustion chamber has a high improvement potential (91%).

Assessment and optimization of a novel waste heat stepped utilization system integrating partial heating sCO2 cycle and ejector refrigeration cycle using zeotropic mixtures for gas turbine

A waste heat stepped utilization system integrating a partial heating sCO2 power cycle and a thermally-driven ejector refrigeration cycle is proposed for gas turbine performance enhancement. The gas turbine exhaust heat is stepped utilized by two gas heaters in the sCO2 power cycle and a waste heater. Then, the exhaust CO2 heat is cascade utilized by the ejector refrigeration cycle using zeotropic mixtures (R245fa/R1234ze) as its working fluid. Detailed energy, exergy, and economic models are built to conduct the system performance investigation. The results show that the proposed system can improve the thermal and exergy efficiency by 28.23% and 2.65% compared with the single sCO2 cycle. The parametric study discloses that there are optimal turbine inlet temperature and compressor inlet pressure for power output and optimal refrigerant mixture ratio, around 0.30, for cooling capacity. Further, multi-objective optimization is implemented, and the overall system efficiency, bottoming system exergy efficiency, and levelized cost of exergy can reach 62.15%, 45.22%, and 0.076 $/kWh, respectively. Finally, to prove the superiority of the integrated system for different application scenarios, the system performance is optimized in the gas turbine part-load. The results reveal that the proposed system can effectively improve the gas turbine performance, especially in the part-load. Under all the gas turbine loads, the proposed system's levelized cost of exergy is no more than 0.076 $/kWh, which provides theoretical references for the development of the gas turbine combined system in practical engineering.

Exergy analysis of fusel oil as an alternative fuel additive for spark ignition engines

The present study conducted performance and exhaust emission tests of fuel blends prepared using gasoline and waste fusel oil at full load and different engine speeds in a spark-ignition engine. Additionally, energy, exergy, and exergoeconomic analyses were carried out using engine performance and exhaust emission values. In engine tests, the highest brake specific fuel consumption obtained was 433.12 g/kWh in F50 fuel at an engine speed of 3500 rpm. The brake specific fuel consumption of G100 fuel was 364.46 g/kWh at the same engine speed. Adding waste fusel oil into fuel blends was observed to reduce carbon monoxide, unburned hydrocarbon , and nitrogen oxide emissions. According to the thermodynamic analysis results, an increase in the ratio of fusel oil in fuel blends reduces thermal efficiency and exergy efficiency. The ratio of fusel oil in fuel blends positively affects exergy destruction. The lowest exergy destruction was calculated as 16.47 kW in F50 fuel at an engine speed of 1500 rpm. As the fusel oil ratio in fuel blends increases, the unit cost of exergy of useful work of the fuel blends decreases. The lowest cost is 6.195 $/GJ at 1500 rpm in F50 fuel. The low pump price of waste fusel oil indicates its advantages over gasoline in exergoeconomic analysis results.

A new solar, natural gas, and biomass-driven polygeneration cycle to produce electrical power and hydrogen fuel; thermoeconomic and prediction approaches

Nowadays, due to the limitations of fossil fuels utilization, renewable energies-driven polygeneration systems (PGSs) are becoming popular. In this article, the simulation and conceptual design of a PGS based on biomass and natural gas fuels to produce products such as electricity, hydrogen fuel, hot water (HW) and chilled water (CHW) is presented and discussed. The introduced PGS is integrated with units and cycles such as water electrolysis (based on polymer electrolyte membrane (PEM) electrolyzer), a ground source heat pump (based on geothermal well), and an absorption chiller. Additionally, in order to supply a fraction of the heat required for the cycle, a solar thermal unit (based on parabolic trough solar collectors, PTSCs) has been embedded. The proposed PGS is evaluated and analyzed from thermodynamic and exergoeconomic points of view. Moreover, as an innovative approach, a prediction on machine learning (ML) model is developed to predict and evaluate hydrogen production rate through biomass gasification. Besides, a state-of-art structure and configuration is considered for the proposed PGS, which had not been reported in the literature. The outcomes indicated that the considered PGS is capable of generating nearly 3.71 MW of electricity, 11.42 kg/h of hydrogen fuel, 5.7 kg/h of oxygen gas, 5.9 MW of CHW, and 2.95 MW of HW. In such a context, the energy and exergy efficiencies of PGS are yielded 74.2 % and 32.3 %, respectively. It is estimated that the implementation of such a system will require an investment cost of almost $ 3.9 million. It was also found that the HW unit exergy cost is approximately 37.8 % higher than that of CHW. Besides, the unit exergy cost of hydrogen fuel is almost 4.4-fold higher than that of electricity. In addition, a detailed parametric research is conducted to analyses the influence of the costing metrics on the PGS behavior under consideration. Finally, the results demonstrated that ML model had acceptable accuracy and could predict the hydrogen production rate through biomass gasification.

A simplified economic model and case study for recovery ventilation based on SPECO method

Covid-19 further revealed the significance of ventilation by air conditioning systems. Most common split heaters and resistance heaters recirculate the indoor air without ventilation process. Ventilation wastes energy consumption by the building. However, adding an air-to-air heat recovery unit seems a quick solution to reduce the wasted heat of the ventilation process. Nonetheless, recovery unit means further pumping power (pressure drop through the air-to-air heat exchanger), capital cost, additional fans and their electricity consumption, exergy costs and so on. Hence, the profitability of the recovery unit depends on outdoor temperature, desired indoor temperature, electricity price of the region, exergy loss and also the aforementioned factors. In this research the general standard Specific Exergy Costing theory is employed and simplified as an economic strategy for recovery ventilation. The model not only is able to predict the profitability of the ventilation process using air-to-air heat exchanger, but also it is an optimization tool for air-to-air heat recovery units as provided as a case study in this paper.

Effects of plastic-grocery-bag derived oil-water-diesel emulsions on combustion, performance and emission characteristics, and exergoeconomic aspects of compression ignition engine

Waste generation from non-biodegradable plastic-grocery bags (PGB) has raised concerns in recent years due to their massive production and consumption. The other pressing issues include the depletion of fossil fuels, rising prices, and environmental pollution from compression ignition (CI) engines. In the context of reducing emissions from CI engines, emulsified fuel is becoming increasingly popular. Given the above two flaws and the potential of emulsification, this study looks into the prospects of PGB-derived oil-water-diesel emulsions for CI engine application. Three emulsions were prepared at varying diesel percentages. The average water droplet size ranged between 215.4 and 397.4 nm, with more than 93 % stability after 75 days. The lower heating value of the emulsions increased the brake-specific fuel consumption (BSFC). However, the neat BSFC of all the blends was lower than diesel. All the emulsion blends also decreased the nitrogen oxide and smoke emission simultaneously; additionally, the heat sink effect also reduced the exhaust gas temperature. The blend with 10 % diesel incorporation exhibited the lowest increment in carbon monoxide and unburnt hydrocarbon emissions w.r.t diesel. Additionally, it has also the highest exergy efficiency and sustainability index and the lowest specific exergy cost for shaft work amongst the emulsion blends.

Comparative study of steam injection modes for a proposed biomass-driven cogeneration cycle: Performance improvement and CO2 emission reduction

Biomass fuel energy can be utilized in cogeneration cycles through the gasification process. This reduces pollution and increases the efficiency of conventional cycles, and makes use of renewable energy instead of fossil fuels. In this paper, in order to generate both electricity and cooling, a cogeneration system has been proposed using biomass fuels. Then, various ways of injecting steam into each proposed cycle are proposed in order to improve its efficiency and performance. The following cycles are suggested and modeled: CHP with the steam injection into the combustion chamber, CHP with the steam injection into gasifier, and CHP with the steam injection into the gasifier and combustion chamber simultaneously. All proposed cycles are initially analyzed from energy, exergy, exergoeconomic, and environmental perspectives. Following analyses of the cycles, results are compared and discussed to select the cycle with the best balance in terms of thermodynamics, economics and pollutant emissions. Then, a parametric study is discussed in which, along with determining the influence of changing an important thermodynamic parameter on cycle performance, the simultaneous influence of two parameters is calculated and verified. The results show that the steam-injected gasifier cycle is about 5.43% more efficient than the steam-injected combustion chamber cycle, and its carbon dioxide emissions are about 5.2% lower. Also, the cycle by simultaneous injection of steam into both the gasifier and combustion chamber offers the highest efficiency and pollution reduction. Additionally, by simultaneously increasing the mass flow rates of steam injection into the proposed system with simultaneous steam injection into both the gasifier and combustion chamber, the exergy efficiency and costs are increased by 11.2% and 3.5% respectively, and CO2 emission are reduced by 12.5%.

Dual-objective optimization of biofuel-based solid oxide fuel cell energy system for hydrogen fuel and desalinated water production

In this research study, the combination of both mentioned solutions and their effects on the efficiency of the system, its environmental concerns, operation cost, and maintenance cost are explored. The intended purpose of the current study was to propose a regenerative cycle that implements multiple sub-cycles to enhance the first and second-law efficiencies of the system and reduce the cost rates. The aforementioned system consists of a gas turbine (Brayton) cycle, a steam turbine (Rankine Cycle), an ORC, a single-effect Li-Br absorption chiller, a reverse osmosis desalination unit, a SOFC, and thermoelectric generators to obtain higher efficiency and electricity, even from the system low-grade waste heat. The dual-objective optimization considering the minimum cost rate and maximum exergy efficiency of the system is proposed. To achieve this goal, a genetic algorithm is implemented for better optimization and the Pareto frontier is represented along with a scatter of distribution plots to determine the optimum outputs of the function and their respective values for the decision variables. The optimization using design parameters lead to the best point with the exergy efficiency of 61.3% and cost rate of 0.27$/s for an interest rate of 12%. Although the environmental aspects are not included in the optimization, the design of the system is tried to be as environmental-friendly as it can be. The decision variables were the most crucial ones that affect the system the most. Isentropic efficiencies of pumps, compressors, and turbines along with the fuel mass flow rate, and pressure ratio in pumps and compressors are considered decision variables. The other decision variable which plays an undeniable role in the efficiency of the system is the temperature difference between the inlet and outlet of the Rankine Cycle HRSG. In the end, the optimizations were repeated for four different interest rates. The projected results illustrated the negative effect of increasing interest rates on both the exergy efficiency and cost rate of the system.

Efficient waste heat recovery of a hybrid solar-biogas-fueled gas turbine cycle for poly-generation purpose: 4E analysis, parametric study, and multi-objective optimization

In the present theoretical study, a steam Rankine cycle (SRC) and a modified organic flash cycle (MOFC) are used as bottoming systems for a gas turbine cycle (GTC). Then, the waste energy of the compression stage of the GTC is recuperated by a hot water unit, and the waste energy of the SRC and MOFC is recovered in a single effect LiCl-H2O absorption chiller and a thermoelectric generator, correspondingly. Furthermore, the power produced in the SRC and MOFC is transmitted to a proton exchange membrane electrolyzer and a reverse osmosis desalination unit to produce hydrogen and freshwater. Thus, the system is converted into a ploy-generation layout. In the parametric study section, the effects of changes in the pressure ratio of the GTC, inlet temperature of the solar power tower, number of heliostat mirrors, methane content of biogas, inlet temperature of the gas turbine, and direct normal irradiance on the energy, exergy, exergy-economic, and environmental output parameters are investigated. The results show that solar power tower is the most influential component in the exergy destruction and cost rates. Furthermore, the exergy efficiency, total cost rate, the unit cost of products, and payback period are obtained as 24.34 %, 6390 $/h, 20.17 $/GJ, and 0.687 years in the base case. Considering exergy efficiency and total cost rate as the objective functions, these two parameters improved by 14.87 % and 11.01 % in the optimum case, respectively.