Organic Rankine Cycle Working Fluids Research Articles

Parametric study of organic Rankine working fluids via Bayesian optimization of a preference learning ranking for a waste heat recovery system applied to a case study marine engine

This work presents an analysis of environmentally friendly organic Rankine cycle (ORC) fluids and their application in a marine waste heat recovery system (WHRS) to reduce the utilization of fuel, thus reducing the emission of harmful pollutants. The proposed WHRS consists of four subsystems: steam Rankine, organic Rankine, Seebeck effect heat to electricity conversion and desalination. Among the 80 ORC working fluids analyzed, R1233zd(E), Novec 649 and SES36 exhibit the best overall performance in terms of power output, efficiency, safety and environmental impact. The results indicate that the implementation of innovative energy efficiency systems that comply with MEPC.1-Circ.896, such as this proposal, can reduce the IMO technical energy efficiency index (EEXI) up to 7.26 % and the operational carbon intensity indicator (CII) up to 14.24 %.

Sensitivity analysis and working fluid selection for a biogas-fueled hybrid energy system based on nearly zero energy building concept: A case study

The concept of NZEB (Nearly Zero Energy Building) has a promising share to fulfill the future of sustainable development goals. However, exploiting renewable-based THESs (Trigeneration Hybrid Energy Systems) for providing the energetic demands of the building sector needs further attention. In this regard, the present paper proposes a sustainable THES driven by a biogas-fueled gas engine. The bottoming systems comprise absorption/electrical chillers (AC and EC), organic Rankine cycle (ORC), solar collector (PTC), and an auxiliary boiler. A detailed sustainability evaluation framework (technical and eco-environment) is derived to approve the performance of the THES. Within this procedure, the best working fluid of the ORC is firstly selected and then the sensitivity of the system performance to the design variables is assessed by a comprehensive parametric study. To make the derived framework more applicable, a case study building is considered and the proposed THES is sized to meet its electricity, heating, and cooling energies. The analyses proved that R123 shows the best techno-economic performance among six investigated ORC working fluids. The parametric study illustrated that the highest and lowest sensitivity of the THES's performance is related to the outlet temperatures of EC condenser and AC evaporator. Furthermore, the energy, exergy, and economic efficiencies of the THES for the case study building are 61.78%, 25.24%, and 44.77%. In this condition, discounted payback period is 7 years, demonstrating the feasibility of this proposal. The maximum CO2 emission is released in November, with a total electricity generation of 320 MWh.

Multi-criteria thermo-economic analysis of solar-driven tri-generation systems equipped with organic Rankine cycle and bottoming absorption refrigeration and Kalina cycles

Optimal thermo-economic integration of renewable energy sources with multi-generation energy systems is a prime research topic today. The present study proposes a multi-criteria evaluation method of such integration, based on combined heating and power (CHP), and combined cooling and power (CCP) scenarios, for three different solar intensities. Three novel solar-driven tri-generation systems are selected. They include different organic Rankine cycle (ORC) architectures and a Kalina cycle system (KCS) and a double-effect absorption refrigeration cycle as bottoming cycles. Evaluation of the tri-generation systems, both with and without the KCS system, indicates a performance improvement of up to 23% in various thermoeconomic characteristics when the KCS system is present. Selection of the suitable tri-generation system for each condition and optimization of the working fluid are carried out based on a multi-attribute decision-making method. P-xylene is found as the optimal organic working fluid for ORC and ORC (ORC integrated with internal heat exchanger) based systems, and benzene for the regenerative ORC-based system in both CHP and CCP scenarios. Multi-criteria analysis shows that ORC-based system outperforms other systems with net outranking flow of 0.44 (0.39) for CHP (CCP) application. The optimal configuration gives 95.6 M$ and 1.99 years for net present value and dynamic payback period, and 83.03% and 34.55% for energy and exergy efficiencies, respectively.

Combustion and interaction mechanism of 2,3,3,3-tetrafluoropropene/1,1,1,2-tetrafluoroethane as an environmentally friendly mixed working fluid

Organic Rankine cycle (ORC) is an effective way to improve energy efficiency, and 2,3,3,3-tetrafluoropropene (R1234yf) is considered as a promising working fluid for ORC. However, the development of R1234yf in ORC is limited by its flammability, and the addition of 1,1,1,2-tetrafluoroethane (R134a) is an effective method to inhibit its flammability. In this paper, the combustion and interaction mechanism of R1234yf/R134a were investigated. Firstly, the combustion products of R1234yf/R134a were measured using an improved experimental device, the results showed a substantial reduction in the concentrations of CO, CO2, and HF with an increasing proportion of R134a. Then, the combustion mechanism of R1234yf/R134a was studied by ReaxFF-MD simulation. The initial decomposition time of R134a was found to be later than that of R1234yf, and a reduction in the production rate of combustion products was achieved with the addition of R134a. Furthermore, the combustion reaction was promoted by the increase in temperature. Finally, the main reaction pathways of working fluids were analyzed. The abstraction reaction of R134a with radicals and the scavenging of active radicals by flame retardant radicals were the key to inhibit the combustion reaction. The results have universal guiding significance for the safe application of R1234yf/R134a.

Simultaneous working fluid and expander selection method for reaching low‐threshold technology organic Rankine cycle (ORC) design

AbstractMaximizing the utilization of an available source serves as the ideal approach, provided that only technical factors are considered. For sources with low heat flux, however, cost‐effective solutions are more suitable due to the minimal net power generated, regardless of the effectiveness of the energy conversion. In such cases, utilizing low‐threshold technology may be the most fitting solution, the layout of these cycles should be simple and inexpensive. In the case of organic Rankine cycles (ORCs)‐based power cycles, this means the omission of superheaters or recuperative heat exchangers and the use of simple expanders and small heat exchangers. Simplifying the design, however, requires additional considerations about the elementary steps of the cycle. This work presents a procedure to select favorable working fluids for ORC while considering the expander's internal efficiency. The criteria for favourability is to have a nonideal expansion process starting and ending in (or very near) saturated vapor states to avoid problems related to wetness/dryness between the given maximal and minimal expansion temperatures. It is demonstrated that the design can be simplified under the simultaneous working fluid and expander selection method presented in this study, regardless of the type and isentropic efficiency of the expander. The resulting methodology applies the novel classification of working fluids using the sequences of their characteristic points on temperature‐entropy space. The proposed approach is illustrated with a case study finding optimal working fluid for an ORC system fitted to industrial waste heat, a low‐temperature geothermal, and a cryogenic heat source.

Energy, exergy, economic and environmental analysis of a regasification system integrating simple ORC and LNG open power cycle in floating storage regasification units

A thermodynamic, economic and environmental analysis of a regasification system including a simple Organic Rankine Cycle (ORC) and an Open Organic Rankine Cycle (OC) to utilise the liquefied natural gas (LNG) cold energy is carried out in the present paper. The proposed system, called ORC-OC, uses ambient seawater as heat source (open loop) and is implemented on board a Floating Storage Regasification Unit (FSRU) in order to reduce the greenhouse gas (GHG) emissions associated with the electricity generation plant, i.e., dual fuel (DF) engines. Regarding the ORC working fluids analysed, an ethane/propane zeotropic mixture is applied. The ORC-OC is compared with the simple ORC architecture, giving the first one better energy (lower specific energy consumption), exergy (higher exergy efficiency) and environmental (lower CO2e emissions) results. When compared to the regasification systems installed on board, the ORC-OC system reduces the specific energy consumption by 86.99 % and increases the exergy efficiency by 17.82 % with respect to the most efficient conventional system installed on FSRUs (direct seawater regasification system), leading to a reduction of CO2e emissions of more than 80 %. In addition, the ORC-OC system is more cost-effective than conventional regasification systems when the LNG price is above 6,508 USD/MMBtu.

Analysis of Different Organic Rankine and Kalina Cycles for Waste Heat Recovery in the Iron and Steel Industry.

This study analyzed waste heat of two sections including the rolling section and electric arc furnace with low and medium temperature ranges, respectively. Organic Rankine cycles (ORCs) and Kalina cycles are the best technologies for the conversion of low-quality and medium-quality thermal energy to electrical power. The ORC applies the principle of the steam Rankine cycle, but it uses organic working fluids with low boiling points to recover heat from lower temperature heat sources. Also, in the Kalina cycle, ammonia water is selected as the working fluid because of its variable boiling point and thermodynamic properties. This study employs the thermo-economic method using the genetic algorithm to optimize the performance of three different ORC systems including a basic ORC (BORC) system, a single-stage regenerative ORC (SRORC) system, and a double-stage regenerative ORC (DRORC) system using five different working fluids and a basic Kalina cycle with KCS34 and complex cycle under the same waste heat conditions. Based on the energy and exergy analysis, the complex Kalina cycle shows the best performance among all studied cycles. The next best performance was exhibited by KCS34 and DROC, respectively. In general, Kalina cycles and ORCs are suitable for low-temperature and medium-temperature heat sources, respectively. According to the thermo-economic analysis, KCS34 in the rolling section and DRORC in EAF show optimum performance for heat recovery. R11 and R113 are selected as the best working fluids for ORCs, and ammonia with a concentration of 0.9 in the mixture is the optimal solution for Kalina cycles.

Thermal stability of a mixed working fluid (R513A) for organic Rankine cycle

Organic Rankine cycle (ORC) is an effective way to utilize low-grade energy, with R1234yf being considered a promising working fluid for ORC for its low global warming potential (GWP). Nevertheless, the weak thermal stability has limited the application R1234yf in ORC, emphasizing the necessity to find a way preventing the its pyrolysis in ORC. In this connection, a systematic study on the mechanism of R134a affecting the thermal stability of R1234yf in ORC was conducted in this work. Our experimental results indicate that the pyrolysis temperature of R513A (R1234yf/R134a) is in the range of 190–210 °C. Further, ReaxFF simulations and density functional theory (DFT) calculations were performed on the pyrolysis process of R1234yf, R134a and R513A. It is revealed that the main pyrolysis reaction pathways of working fluids can be divided into three types: the reactions of working fluid molecules collision with F radical (FCR) or H radical (HCR), and the self-decomposition reactions of working fluid molecules (SDR). In R513A, F and H radicals are the origin for the affected thermal stability of R1234yf. The results are of great significance to guide the selection of additive species to enhance the thermal stability of HFO working fluid.

An examination of super dry working fluids used in regenerative organic Rankine cycles

Thermodynamic and economic performance of an Organic Rankine Cycle (ORC) system is closely related to the thermophysical properties of its organic working fluid. Super dry working fluids are especially suitable for regenerative ORC. Setting a recuperator in an ORC not only improves its thermodynamic performance, but also increases the investment cost of heat exchanger that accounts for the highest proportion in the whole ORC system. Based on the above consideration, this paper presents an examination of super dry working fluids used in regenerative ORC. The suitable super dry working fluid used in a regenerative ORC is determined and selected for common medium/low-temperature heat sources. Based on different types of heat sources, the optimal single-stage extraction pressure and extraction temperature of each super dry working fluid in regenerative ORC is determined according to the net power output and thermal efficiency of regenerative ORC, respectively. The results show that heptane may match the closed heat source best with an optimal extraction condition at 0.45 MPa and 478.64 K. While pentane, hexane, propylcyclohexane, undecane and o-xylene may match five different open heat sources. Their corresponding optimal extraction conditions are 0.85 MPa/408.78 K, 0.6 MPa/445.33 K, 0.35 MPa/570.22 K, 0.175 MPa/584.25 K and 0.4 MPa/544.32 K.

Power, cooling, freshwater, and hydrogen production system from a new integrated system working with the zeotropic mixture, using a flash-binary geothermal system

The current paper proposes a new hybrid system based on a binary-geothermal system to generate power, cooling capacity, freshwater, and hydrogen. This system includes an internal integration of the organic Rankine cycle and ejector refrigeration cycle with zeotropic working fluids, proton exchange membrane electrolyzer, and reverse osmosis desalination unit. The system is analyzed by developing a precise model in the Matlab software, and then a multi-objective grey wolf optimization is employed to optimize the proposed system performance. The net present value, payback period, and sum unit cost of products are considered the system's economic performance criteria to study the system's feasibility for investment. Results indicate that the Isobutene-R114 provides the best net output power, and the R12-R114 combination has the best cooling performance. Also, the R12-R114 reports the best overall performance as the organic Rankine cycle working fluid. Based on optimization results, the exergy and thermal efficiency reached 17.84% and 34.24%, respectively. The system could provide 856.06 kW net output power, 2410.54 kW cooling capacity, 0.743 kg/h hydrogen, and 40.22 kg/s freshwater with a sum unit cost of 25.5 $.GJ−1, and the total profit and payback period of 6.82 $M and 3.76 years.

Numerical simulation of flow boiling heat transfer characteristics of R134a/Ethane binary mixture in horizontal micro-tube

The cryogenic organic Rankine cycle (ORC) is appropriate for recovering the cold energy of liquefied natural gas (LNG) for power generation. However, pure working fluids in ORC are challenging to match the evaporation curve of LNG appropriately, which causes a large amount of exergy loss. Thus, adopting mixture working fluid is a good option due to their temperature-varying evaporation and condensation process. This study investigates the heat transfer characteristic of R134a/ethane (widely adopted in cryogenic ORC as pure working fluid) binary mixture in the horizontal micro-tube through numerical simulation. The law of boiling heat transfer characteristics with vapor quality, heat flux, mass flow, ethane mole fraction, and other factors are obtained. The simulation illustrated that the boiling heat transfer coefficient increases with the heat flux and mass flow. Furthermore, compared with R134a, ethane has higher thermal conductivity, lower vapor density, and latent heat of vaporization. Hence, the heat transfer coefficient of the R134a/ethane mixture increases with the ethane’s mole fraction. The fluid disturbance mainly influences the pressure drop and the turbulence intensity significantly when the fluid is transformed into a gas–liquid flow. This study could provide insights into boiling heat transfer improvement of binary mixtures for ORC power generation applications.

Modelling and integration of multi-parallel organic Rankine Cycles into total site

Organic Rankine Cycle (ORC) is a promising technology for exploiting the industrial low-grade waste heat. When trying to implement ORCs, proper integration with background waste heat sources is one of the crucial matters that should be considered. Research on ORC integration has been carried out during the last few decades. However, it is observed that the existing methodologies for integrating ORCs into industrial sites are still insufficient. Lots of the research efforts deal with ORC integration problems assuming only one single ORC participates, while the options of applying multi-parallel ORCs are rarely taken into account. Besides, existing research mainly focuses on the direct integration of ORC(s) (i.e. waste heat is transferred directly from heat sources to ORC working fluids), whereas the option of utilizing intermediate heat carriers indirectly is neglected. As such, this study proposes a model-based methodology for the indirect integration of multi-parallel ORCs. The overall model covers both waste heat extraction and ORC power generation. For heat extraction modelling, a modified superstructure based on (Isafiade and Fraser, 2008) [1] is proposed, which simplifies the construction of a heat extraction network (HEN) and reduces computational time. For thermodynamics, the Peng-Robinson Equation of State is adopted. The overall model leads to a mixed-integer nonlinear programming (MINLP) problem and can be solved by a General Algebraic Modelling System, e.g., the GAMS software. Two case studies are performed in this work to validate and illustrate the application of the proposed method, the results of which show that applying multi-parallels ORCs instead of using a single ORC can decrease the overall annualized cost effectively.

Comparative study, working fluid selection, and optimal design of three systems for electricity and freshwater based on solid oxide fuel cell mover cycle

In this paper, a novel electricity and freshwater cogeneration system is proposed in which an organic Rankine cycle (ORC) is utilized for recovering the wasted heat of a Solid Oxide Fuel Cell (SOFC). The electricity generated in the recovery unit is used to derive a Reverse Osmosis (RO) water desalination unit. Also, three different configurations are considered for the ORC unit. At the first step, a robust three-objective genetic optimization is applied for all three configurations and the best one is selected to have the maximum generated power, minimum total productions cost, and minimum pollutant emissions, simultaneously. The second step is focused on selecting the best working fluid of the optimal ORC (among five different working fluids). The results demonstrated that the regenerative configuration with the R123 working fluid has the best performance. For this optimal layout, the outputs are included 649.2 kW of the net generated power and 34.5 m3/h of freshwater At this condition, the optimal exergy efficiency, product unit cost, and pollutant emission factor are 46.29%, 28.59 US$/GJ, 0.2587 kg/kWh, respectively.

Sizing the Thermal Energy Storage Device Utilizing Phase Change Material (PCM) for Low-Temperature Organic Rankine Cycle Systems Employing Selected Hydrocarbons

Thermal energy storage (TES) looks to be a promising technology for recovering waste heat or other intermittent heat sources, especially if it is coupled with the organic Rankine cycle (ORC) system. This system may use a variety of heat storage materials, including solids, liquids, and phase change materials (PCM). This article discusses the use of PCM as a thermal energy storage material in TES systems coupled with ORC systems. Other TES configurations may be used in ORC; however, in this article, the TES is solely used in heat exchangers, i.e., evaporator and liquid heater. The goal of this research is to establish a dimensionless storage mass parameter for sizing TES-evaporator (TES-EVA) or TES-liquid heater (TES-LH) devices for ORCs. Furthermore, the model of this system was created in the MATLAB environment using the chosen hydrocarbons as ORC working fluids. The obtained modelling results provide a novel point of view that scientists and engineers may employ while developing the TES-EVA or TES-LH utilizing PCM for ORC.

Multi-objective optimisation of supercritical CO<SUB align=right>2 combined cycles based on energy-exergy-economy balanced analysis

In this paper, the supercritical CO2 (sCO2) recompression cycle combined cycles are analysed, where the bottom cycles include transcritical CO2 (tCO2), organic Rankine cycle (ORC) or trilateral flash cycle (TFC). The working fluid for the ORC and the TFC can be R123, R245fa, or n-Pentane. We implemented four sub-models in our calculation: 1) thermodynamic model; 2) heat transfer model; 3) economic model; 4) exergoeconomic model. The specific exergy costing (SPECO) method is utilised in the exergoeconomic model, and the multi-objective genetic algorithm is adopted to give the Pareto front of total unit exergy cost of the product (cPtot) and the thermal efficiency. Our model has been validated with the existing literature. The results show that the thermal efficiency standalone CO2 achieved 41.66% while attaching the tCO2, ORC, or TFC bottom cycle could improve the thermal efficiency by 1.1%, 1.68%, or 0.05%, respectively. In the meantime, the (cPtot, which is the representation of the cost, decreased by 0.2$/GJ for ORC and increased by 0.06$/GJ and 1.05$/GJ for tCO2 and TFC respectively. The influence of different working fluids for ORC and TFC is not obvious. Therefore, attaching the ORC as the bottom cycle will bring about the best performance and lowest cost.

Techno-economic analysis of a foil-based solar collector driven electricity and fresh water generation system

For medium-scale dispatchable (on demand) power and fresh water generation, a concentrated solar energy powered system with thermal energy storage is an attractive option. However, currently used concentrated solar power technologies (parabolic trough collector, solar power tower, linear Fresnel reflector) use heavy and very expensive glass mirrors and receivers. Recently, a novel micro-structured polymer foil-based concentrating solar collector system, with the advantages of a low installation cost and a low operation and maintenance cost, has been proposed. This system, which generate heat by focusing sunlight like magnifying glasses, can be effectively used for applications with temperatures up to about 350 °C. Techno-economic analysis and optimization of a micro-structured polymer foil-based concentrating solar collector powered organic Rankine cycle based electricity and multi-effect distillation based fresh water generation system is presented in this paper. The proposed system has a lot of potential for the places with electricity and water crisis. The results indicate that cyclopentane is the most appropriate organic Rankine cycle working fluid for the plant, achieving a levelized cost of electricity of 0.116 €/kWhe and levelized cost of fresh water of 1.13 €/m3 for Antofagasta, Chile and 0.163 €/kWhe and 1.62 €/m3 for Cape Town, South Africa.

Thermodynamic, Economic and Sustainability Analysis of Solar Organic Rankine Cycle System with Zeotropic Working Fluid Mixtures for Micro-Cogeneration in Buildings

Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost.

Key parameter influence mechanism and optimal working fluid screening correlation for trans-critical organic Rankine cycle with open type heat sources

Trans-critical organic Rankine cycles (ORC) are promising for low to medium temperature heat recovery. To achieve a better cycle performance, the screening of optimal working fluids is quite significant. The optimal working fluids vary with the heat sources, working conditions and performance criterion, and it is difficult to build a general optimal working fluid screening criterion for the trans-critical ORC. Finding the relationship between the working fluid thermodynamic properties and the cycle performance is an effective way to establish general method for optimal working fluid screening. This paper provides theoretical analysis of how the key working fluid thermodynamic properties influence on the cycle performance under a wide temperature range of open type heat sources using various working fluids. Especially the influence of ‘uniformity of cp’ on the heat source utilization is originally analysed. In addition, a relatively general quantitative correlation for selecting the optimal working fluid for trans-critical ORC with heat source temperatures from 150 to 350 °C is presented.

Cascade utilization of LNG cold energy by integrating cryogenic energy storage, organic Rankine cycle and direct cooling

Utilizing LNG cold energy in different temperature ranges with distinctive approaches is a promising option to achieve a high thermodynamic efficiency. This paper proposed a novel LNG cold energy cascade utilization (CES-ORC-DC-LNG) system by integrating cryogenic energy storage (CES), organic Rankine cycle (ORC), and direct cooling (DC) to recover LNG cold energy in the low, middle, and high temperature ranges, respectively. The optimal components and their respective fractions of the mixed working fluids in ORCs, and other key parameters were simultaneously determined by a simulation-based optimization approach which was developed in this study. Then, comprehensive energetic and exergetic analyses were conducted to compare the proposed system performance with the system in the literature to highlight the superior thermodynamic performance. The results indicated that the net power output of the CES-ORC-DC-LNG system was 103.30 kW, which was 22.48% higher than the base case. The optimal compositions of the mixed working fluids in ORC-1 (ethane: 23.73%, ethylene: 15.01%, R134a: 20.17%, and R152a: 41.09%) and ORC-2 (ethylene: 60.14%, R134a: 38.73%, R1270: 0.54%, and R134a: 0.59%) were distinctive with the net power output of 13.89 and 14.46 kW, respectively. The round trip efficiency of the proposed system was 141.88% with 19% increment compared with the base case. Furthermore, the exergetic efficiency of the CES-ORC-DC-LNG system was 73.92% which was 5.17% higher than the base case. Thus, the CES-ORC-DC-LNG system is an energy efficiency LNG cold energy cascade utilization system and can be a potential technology for large-scale cryogenic energy storage.

Comparison of different optimized heat driven power-cycle configurations of a gas engine

Among different technologies in internal combustion engines, waste heat recovery from the lost energies has great potential to improve fuel economy and reduce CO2 emission. In the present work, to achieve the optimal design parameters for a waste heat recovery system of a gas engine, a multi-objective optimization evolutionary algorithm is employed. The system consists of different types and combinations of the Organic Rankine/Kalina cycle as the waste heat recovery system of gas engine exhaust gas and the waste heat of cooling water is recovered by the trilateral flash cycle. The objective functions are chosen to maximize exergy efficiency and minimize the specific investment cost of the system. Cyclohexane, Toluene, and Benzene have been investigated and compared to the organic Rankine cycle working fluid. To evaluate different cycle configurations and working fluids, the Pareto front solutions related to 18 studied cases are compared. Meanwhile, the “Linear Programming Technique for Multidimensional Analysis of Preference” decision-making approach has been used as an optimal point in all cases. This work is aimed to compare the optimal design operating conditions of the studied configurations to choose the best configuration for waste heat recovery from a gas engine. The results reveal that, among the decision parameters, the organic Rankine cycle turbine inlet temperature is the most important in terms of the specific investment cost of the system. Also, considering the exergy and energy efficiency of the system, organic Rankine cycle turbine inlet temperature as well as organic Rankine cycle and trilateral flash cycle turbine isentropic efficiencies are of great importance. The Pareto front comparison for each configuration indicates that toluene is the most suitable fluid for the organic Rankine cycle in all configurations. Comparing the selected optimal points in different combinations reveals that, the configuration of organic Rankine cycle with internal heat exchanger-trilateral flash cycle, due to its lower payback period and specific investment cost as well as the higher exergy efficiency and net power output in optimal point, is the prominent compared to the other combinations. Furthermore, the optimized configuration of the organic Rankine cycle with the internal heat exchanger-trilateral flash cycle shows a 14.31% increase in the exergy efficiency and an 8.2% decrease in the specific investment cost of the system compared to the base case. Employing the optimized configuration of the organic Rankine cycle with internal heat exchanger-trilateral flash cycle as waste heat recovery of the gas engine leads to a 7.8 kW increment of net power output, equivalent to an increase of 18.85% exergy efficiency of the whole system including engine and bottoming cycle. On the other hand, additional equipment to the engine, impose 3061$/kW specific investment cost which takes 2.2 years to be paid back.