High Temperature Organic Rankine Cycle Research Articles

Silicon Tetrachloride as innovative working fluid for high temperature Rankine cycles: Thermal Stability, material compatibility, and energy analysis

Silicon Tetrachloride (SiCl4) is proposed as a new potential working fluid for high-temperature Rankine Cycles. The capability to overcome the actual thermal stability limit of fluids commercially employed in the state-of-the-art Organic Rankine Cycles (ORC) is demonstrated by static thermal stability and material compatibility tests. Experimental static test proves its thermo-chemical stability with a conventional stainless-steel alloy (AISI 316L) up to 650 °C. A preliminary material compatibility analysis performed with optical microscope on the AISI 316L cylinder, after exposure of 300 h to SiCl4 at temperature higher than 550 °C, confirms the potentiality of this fluid when coupled with high-grade heat sources. A thermodynamic analysis has been carried out accounting for the effect of operating conditions on the axial turbine efficiency. A comparison with fluids adopted in medium–high temperature ORCs is performed, evidencing that the proposed fluid could achieve more than + 10 % points as thermal efficiency gain compared to any commercial solutions when coupled with high-temperature sources such as solar, biomass, waste heat from industrial processes and prime movers. A 2 MW SiCl4 cycle operating full-electric at 550 °C reaches a thermal efficiency of 38 %, exceeding values attainable by any other working fluid under similar conditions and power size.

Feasibility study of the high‐temperature organic Rankine cycle in combined heat and power state from energy, exergy, and economic point of view

AbstractThe organic Rankine cycle (ORC) has received a lot of attention in recent years due to its wide application in energy recovery and the use of low‐temperature energy sources. In this article, the energy, exergy, and economic analyses of a high‐temperature ORC (HTORC) in combined heat and power production mode have been performed. In this system, the heating water at 90°C for domestic or industrial purposes is provided in the HTORC condenser. Two working fluids, hexamethyldisiloxane (MM) and siloxane mixture (MDM), have been evaluated and compared in HTORC. The system has been modeled in engineering equation solver software and key parameters such as energy efficiency and exergy of the system, output power, heat‐to‐power ratio, and levelized cost of electricity (LCOE) have been calculated. The energy and exergy efficiency of the system for the two working fluids MM and MDM are equal to 40.8%, 45.6%, 22.45%, and 19.3%, respectively. From the point of view of energy and exergy, the working fluid MM performs better. The LCOE of the system with MM working fluid is equal to 0.5946 US$/kWh, which is slightly higher than MDM working fluid (0.5702 US$/kWh).

Design and analysis of an axial turbine for high-temperature organic Rankine cycle

The organic Rankine cycle (ORC) system is of great importance to achieving the effective exploitation of waste energy. As the essential component of the ORC system, the expander is directly related to the performance and structure size of the ORC system, which deserves to be studied in detail. A single-stage axial turbine with a U-shaped volute is presented for the high-temperature ORC system in this paper. Based on preliminary design and modeling, the turbine aerodynamic performance under design and off-design conditions is investigated in numerical simulation. Results show that the turbine efficiency is 77% with a pressure ratio of 4.78 at the design point and the turbine efficiency can still be maintained above 70% as the pressure ratio reaches 6. It can be concluded that low Reynolds number flow and negative incidence angle are the main reasons for low turbine efficiency under the low pressure ratio, while the shock wave becomes the key factor influencing turbine efficiency under the high pressure ratio. In addition, blade profile optimization and shock wave management is the primary way to maintain high turbine efficiency under a high pressure ratio. Results indicate that the turbine proposed in this paper is proven suitable for high-temperature ORC systems and the relevant research has a certain guiding value for the efficient and compact single-stage axial turbine design.

Thermal decomposition mechanism and thermal stability prediction of n-pentane/n-butane mixture

Mixtures appear to hold more promise in organic Rankine cycle (ORC) system than pure working fluids due to their better performance. The key limiting factor for the screening of mixture in the medium- and high temperature ORC system is its thermal stability. ReaxFF reactive molecular dynamic simulations and density functional theory calculations are performed in this study to investigate the thermal decomposition mechanism of n-pentane/n-butane mixture and predict its thermal stability. The results show that the presence of n-butane improves the thermal stability of n-pentane. According to the initial decomposition time, decomposition rates and apparent activation energies of mixture and pure working fluids, n-pentane/n-butane mixture has a better thermal stability than n-pentane and worse than n-butane. Based on the decomposition temperature ranges of n-pentane and n-butane, it can be determined that the n-pentane/n-butane mixture is stable at 280 °C. Therefore, the safe use temperature of the mixture can be roughly predicted based on the thermal stability data of the known working fluids and comparing the thermal decomposition of the mixture with these known working fluids. This paper provides a simple, economical and fast way for the safe use temperature prediction of mixture.

Intrinsic-group-contribution PC-SAFT and its application in performance analysis of high-temperature organic Rankine cycle with siloxanes and alkanes

Thermodynamic property prediction of working fluids is of great importance on the performance analysis of high-temperature organic Rankine cycles (ORCs) for utilizing low-grade heat sources. In this study, an intrinsic-group-contribution perturbed-chain statistical associating fluid theory (iGC-PC-SAFT) is proposed for the high-temperature ORC performance analysis with 8 siloxanes and 10 alkanes. By adjusting the initial values and corresponding value ranges of PC-SAFT parameters repeatedly according to the changes in molecular structures, the PC-SAFT parameters were fitted to determine the initial iGC-PC-SAFT parameters. Afterwards, the final iGC-PC-SAFT parameters for each working fluid were obtained based on a global optimization algorithm. Furthermore, the iGC-PC-SAFT equation of state (EoS) was used to calculate the thermodynamic properties of working fluids. Compared with the results from Coolprop database, maximum relative deviations for the saturated liquid density and the compressibility factor in the superheated region are 0.95% for MM, and 0.84% for MD2M, respectively. Besides, the average absolute relative deviations of ORC performance parameters calculated by the iGC-PC-SAFT EoS at different input pressures of turbine, including the thermal efficiency, turbine power output, pump power consumption, heat rejection, mass flow, and exergy efficiency are less than 2.04% for siloxanes (except for MM) and 6.09% for alkanes, respectively.

Thermal stability of linear siloxanes and their mixtures

The working fluid thermal stability is one of the crucial features of an effective organic Rankine cycle. Hexamethyldisiloxane (MM - C6H18OSi2) and octamethyltrisiloxane (MDM - C8H24O2Si3) are siloxane fluids currently exploited in high temperature organic Rankine cycles. However, data about their thermal stability are scarce or absent in literature. This manuscript presents a study of their behavior and decomposition at operating temperatures in the range 270–420°C.The assessment of thermal stability can be performed with several methods, which are either based on pressure anomalous variation in isothermal stresses or on the deviation of the saturation curves experimentally obtained before and after the fluid is thermally stressed. An enhanced method is proposed here, based on chemical analysis of both vapor and liquid phases of the sample before and after it is subjected to thermal stress. A comparison of the pre- and post-stress vapor–liquid equilibrium curve complements the analysis.Results proved a higher stability for MM than for MDM. Moreover, due to the current interest in applying mixtures in organic Rankine cycles, an equimolar mixture of MM and MDM was also tested, which exhibit a behavior that appears to be different from the simple superimposition of pure fluid ones.

Parametric and economic analysis of high-temperature cascade organic Rankine cycle with a biphenyl and diphenyl oxide mixture

High-temperature organic Rankine cycle (ORC) systems have the potential to improve the heat-to-power conversion efficiency and expand the temperature range for heat recovery, heat battery and solar power generation. Restricted by the critical temperature of the commonly used organic working fluids, the current ORC technology has a maximum working temperature of around 300 °C. This paper proposes a high-temperature cascade organic Rankine cycle (CORC) system using a biphenyl and diphenyl oxide (BDO) mixture as the top cycle fluid and conventional organic fluids for the bottom cycle. The BDO mixture has excellent heat stability over a wide operation condition from 12 °C to 400 °C in single-phase and binary-phase states. However, at present a detailed study on the ORC using the mixture is lacking. In this paper, a parametric analysis of the high-temperature CORC system is conducted. A mathematical model based on the equivalent hot side temperature is built to simulate the ORC efficiency. The thermodynamic and exergetic performances of the novel CORC system under different bottom ORC working fluids, mixing chamber temperatures, evaporation temperatures, and condensation temperatures are investigated. The results show the maximum thermal efficiency of the CORC system is 38.74 % and 40.26 % at top ORC evaporation temperatures of 360 °C and 400 °C. The largest exergy destruction takes place in the heat exchanger between the top and bottom ORCs. Besides, the heat regenerators have a significant impact on the thermodynamic performance and can elevate the CORC efficiency by about 4 %. The proposed system has a higher efficiency and a lower equipment cost than conventional steam Rankine cycle at 400 °C while eliminating the challenges of wet steam turbines.

Thermodynamic Modeling and Exergy Analysis of A Combined High-Temperature Proton Exchange Membrane Fuel Cell and ORC System for Automotive Applications

A combined system consisting of a high-temperature proton exchange membrane fuel cell (HT-PEMFC) and an organic Rankine cycle (ORC) is provided for automotive applications in this paper. The combined system uses HT-PEMFC stack cathode exhaust gas to preheat the inlet gas and the ORC to recover the waste heat from the stack. The model of the combined system was developed and the feasibility of the model was verified. In addition, the evaluation index of the proposed system was derived through an energy and exergy analysis. The numerical simulation results show that the HT-PEMFC stack, cathode heat exchanger, and evaporator contributed the most to the total exergy loss of the system. These components should be optimized as a focus of future research to improve system performance. The lower current density increased the ecological function and the system efficiency, but reduced the system's net out-power. A higher inlet temperature and higher hydrogen pressures of the stack and the lower oxygen pressure helped improve the system performance. Compared to the HT-PEFC system without an ORC subsystem, the output power of the combined system was increased by 12.95%.

Shock losses and Pitot tube measurements in non-ideal supersonic and subsonic flows of Organic Vapors

The present work documents extensive experimental campaigns involving the first ever L-shaped Pitot tube measurements in non-ideal subsonic and supersonic flows of siloxane MM (hexamethyldisiloxane, C6H18OSi2), a fluid commonly employed in high-temperature Organic Rankine Cycles (ORCs).The objective is to establish reliable methodologies for pressure probes usage in flows relevant to ORCs, contributing to power generation efficiency through the improvement of current components design and plant regulation capabilities.Experimental campaigns were carried out on the Test-Rig for Organic Vapors (TROVA) at Politecnico di Milano, with a total-static Pitot tube designed according to ISO 3966, in non-ideal subsonic flows at Mach numbers M=0.2,0.5 with total pressure and temperature in the range PT=1−7bar, TT=195−205°C and a corresponding compressibility factor ZT≥0.8. Adequate performance of the complete system was verified and Pitot tube behavior was found to be unaffected by flow non-ideality, requiring no calibration in the investigated conditions.A simple Pitot tube was then employed for direct total pressure loss measurements across normal shock waves in non-ideal supersonic flows at M≃1.5, with total conditions of PT=1.5−12.8bar, TT=212−233°C and ZT≥0.66. The good agreement between measured losses and theoretical ones calculated from conservation equations attests the validity of the developed methodologies even with supersonic flows.

On the CAMD method based on PC-SAFT for working fluid design of a high-temperature organic Rankine cycle

Working fluid is of great importance on the performance of organic Rankine cycle (ORC). Novel working fluids can be designed based on the computer-aided molecular design (CAMD) method. In this study, a working fluid design approach using CAMD for a high-temperature ORC is investigated. First, the molecular structures of 129 working fluids are obtained. Then, the thermodynamic performances are determined using the group-contribution PC-SAFT and the results of the top 10 working fluids are analysed. Finally, the feasibility of three correlations for a quick selection of the working fluid is estimated and the relation between the PC-SAFT parameters and the ORC performance is discussed. The results indicate that a high prediction accuracy on the net power of ORC is achieved by PC-SAFT Equation of State with a deviation of less than 5%. However, certain deviations exist for the PC-SAFT parameters when the group contribution method is used. Meanwhile, the PC-SAFT parameters of the top 20 working fluids distribute in a large space and the conventional two-stage optimization algorithm may ignore some suboptimal working fluids. With regard to the high-temperature ORC for exhaust heat recovery, the designed top 5 working fluids are toluene, ethynyl cyclohexane, benzene, propenyl cyclopentane, vinyl cyclohexane. It is better to select the suitable working fluid from a candidate set containing the top 10–20 fluids such that the negative impact of the uncertainties originated from the group-contribution PC-SAFT method is avoided.

Thermodynamic Optimization of Advanced Organic Rankine Cycle Configurations for Geothermal Energy Applications

The Organic Rankine Cycle (ORC) is commonly accepted as a viable technology to convert from low to medium temperature geothermal energy into electrical energy. In practice, the reference technology for converting geothermal energy to electricity is the subcritical simple ORC system. Over time, geothermal ORC plants with more complex configurations (architectures) have been developed. In the open literature, a large number of advanced architectures or configurations have been introduced. An analysis of the scientific literature indicates that there is some confusion regarding the terminology of certain advanced ORC system architectures. A new categorization of advanced configurations has been proposed, with a special emphasis on the application of geothermal energy. The basic division of advanced plant configurations is into dual-pressure and dual-stage ORC systems. In this study, the real potential of advanced ORC architectures or configurations to improve performance as compared with the simple ORC configuration was explored. The research was conducted for a wide range of geothermal heat source temperatures (from 120 °C to 180 °C) and working fluids. Net power output improvements as compared with the basic subcritical simple ORC (SORC) configuration were examined. The ability to produce net power with different ORC configurations depends on the magnitude of the geothermal fluid temperature and the type of working fluid. At a lower value of geothermal fluid temperature (120 °C), the most net power of 18.71 (kW/(kg/s)) was realized by the dual-pressure ORC (DP ORC configuration) with working fluid R1234yf, while the double stage serial-parallel ORC configuration with a low-temperature preheater in a high-temperature stage ORC (DS parHTS LTPH ORC) generated 18.51 (kW/(kg/s)) with the working fluid combination R1234yf/R1234yf. At 140 °C, three ORC configurations achieved similar net power values, namely the simple ORC configuration (SORC), the DP ORC configuration, and the DS parHTS LTPH ORC configuration, which generated 31.03 (kW/(kg/s)) with R1234yf, 31.07 (kW/(kg/s)) with R1234ze(E), and 30.96 (kW/(kg/s)) with R1234ze(E)/R1234yf, respectively. At higher values of geothermal fluid temperatures (160 °C and 180 °C) both the SORC and DP ORC configurations produced the highest net power values, namely 48.58 (kW/(kg/s)) with R1234ze(E), 67.23 (kW/(kg/s)) with isobutene for the SORC configuration, and 50.0 (kW/(kg/s)) with isobutane and 69.67 (kW/(kg/s)) with n-butane for the the DP ORC configuration.

Shock loss measurements in non-ideal supersonic flows of organic vapors

This paper presents the first ever direct measurements of total pressure losses across shocks in supersonic flows of organic vapors in non-ideal conditions, so in the thermodynamic region close to the liquid–vapor saturation curve and the critical point where the ideal gas law is not applicable. Experiments were carried out with fluid siloxane MM (hexamethyldisiloxane, C_6H_{18}OSi_2), commonly employed in medium-/high-temperature organic Rankine cycles (ORCs), in the Test Rig for Organic VApors (TROVA), a blowdown wind tunnel at the Laboratory of Compressible fluid dynamics for Renewable Energy Applications (CREA lab) of Politecnico di Milano. A total pressure probe was inserted in superheated MM vapor flow at Mach number sim 1.5 with total conditions in the range 215-230~^circ hbox {C} and 2-12~hbox {bar} at varying levels of non-ideality, with a compressibility factor evaluated at total conditions between Z_text {T}=0.68-0.98. These operating conditions are representative of the first-stage stator of ORC turbines. Measured shock losses were compared with those calculated from pre-shock quantities by solving conservation equations across a normal shock, with differences always below 2 % attesting a satisfactory reliability of the implemented experimental procedure. An in-depth analysis was then carried out, highlighting the direct effects of non-ideality on shock intensity. Even at the mildly non-ideal conditions with Z_text {T}gtrsim 0.70 considered here, non-ideality was responsible for a significantly stronger shock compared to the ideal gas limit at same pre-shock Mach number, with differences as large as 6%.Graphical abstract

Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Organic Rankine Cycle (ORC) is an effectively technology for the utilization of industrial waste heat and renewable energy. Zeotropic working fluids are more attractive than pure working fluids due to their lower exergy losses, higher cycle efficiencies and higher work outputs. The thermal stability is the major limitation factor for the selection of working fluid in the high temperature ORCs. This paper investigates the thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid by using ReaxFF reactive molecular dynamic simulations and density functional theory calculations. The thermal decomposition process, the effects of temperature and HFC-227ea to n-hexane ratio on the thermal decomposition of HFC-227ea/n-hexane zeotropic working fluid, and the interaction between HFC-227ea to n-hexane for the thermal stability of zeotropic working fluid were investigated. The results showed that the hydrogen bond formed between HFC-227ea and n-hexane in HFC-227ea/n-hexane zeotropic working fluid improved the thermal stability of n-hexane and weakened the thermal stability of HFC-227ea. Therefore, the thermal stability of the HFC-227ea/n-hexane zeotropic working fluid is better than that of pure n-hexane and weaker than that of pure HFC-227ea.

Determination of Optimum Pinch Point Temperature Difference Depending on Heat Source Temperature and Organic Fluid with Genetic Algorithm

In this study, the effect of evaporator pinch point temperature difference (∆TPP,e) value in Organic Rankine Cycle (ORC) on system performance was determined. Under different applications of ORC, optimum ∆TPP,e value has been determined in ORC systems designed with different heat source temperatures. By changing the ∆TPP,e value, the heat input provided to the system, the mass flow of organic fluid, the evaporation pressure and the enthalpy drop in the turbine are affected. In thermodynamic optimization, the objective function is determined as turbine power maximization. Genetic algorithm optimization technique is used. Within the scope of low and high temperature ORC applications, the optimum ∆TPP,e value of different organic fluids under 10 different heat source temperatures (Low, 90-130 °C; High, 250-290 °C) has been determined. Low temperature organic fluids have been selected from dry, isentropic, wet and new-generation categories. High temperature organic fluids have been selected from the alkane, aromatic hydrocarbon, and siloxane categories. The effect of ∆TPP,e on fluids of different categories was determined for low and high temperature ORCs. It has been determined that taking the ∆TPP,e value constant regardless of the heat source temperature and organic fluid causes performance loss in ORC.

Determination of Chopped Fruits Freshness with High Accuracy by Using Electronic Nose

In this study, the effect of evaporator pinch point temperature difference (∆TPP,e) value in Organic Rankine Cycle (ORC) on system performance was determined. Under different applications of ORC, optimum ∆TPP,e value has been determined in ORC systems designed with different heat source temperatures. By changing the ∆TPP,e value, the heat input provided to the system, the mass flow of organic fluid, the evaporation pressure and the enthalpy drop in the turbine are affected. In thermodynamic optimization, the objective function is determined as turbine power maximization. Genetic algorithm optimization technique is used. Within the scope of low and high temperature ORC applications, the optimum ∆TPP,e value of different organic fluids under 10 different heat source temperatures (Low, 90-130 °C; High, 250-290 °C) has been determined. Low temperature organic fluids have been selected from dry, isentropic, wet and new-generation categories. High temperature organic fluids have been selected from the alkane, aromatic hydrocarbon, and siloxane categories. The effect of ∆TPP,e on fluids of different categories was determined for low and high temperature ORCs. It has been determined that taking the ∆TPP,e value constant regardless of the heat source temperature and organic fluid causes performance loss in ORC.

Performance assessment of a dual loop organic rankine cycle powered by a parabolic trough collector for ammonia and hydrogen production purpose

Energy systems used in the future will need to be cleaner and more sustainable. The use of liquid ammonia as a potential medium for hydrogen storage is an efficient solution from an economic, practical and environmental point of view. In this work, a new approach linked to the production of hydrogen and ammonia using a system combining an alkaline water electrolysis, an air separation unit and a Haber Bosch reactor is proposed. The electricity necessary to carry out this process is provided by a dual loop organic rankine cycle supplied by a parabolic trough collector and an auxiliary heater system. The survey was carried out by developing mathematical models on the different components of the combined system. The discrepancies between numerical and experimental results did no exceed 2% for the parabolic trough solar collector. Results demonstrated that hydrogen and ammonia flow rates increased as evaporation temperature of working fluid in the high –thermodynamics cycle increased. Results also showed that the thermal performance of the parabolic trough collector increased as inlet temperature and concentration factor increased. It was pointed out that the overall electrical efficiency of the combined system ranged from 15 to 20.28%. The specific energy consumption of the Back-up heater decreased as mass flow rate of Therminol® VP-1 decreased and its values ranged from 0 to 35 kWh.kg-1 of ammonia. Ammonia production efficiency and electricity consumption ratio varied between 59 to 63% and 8.25 to 8.67 kWh.kg-1of ammonia, respectively. Overall results showed that Cyclohexane, Octane, Toluene and Benzene can be used effectively as working fluid for the high temperature loop organic rankine cycle supplied by parabolic trough collectors for hydrogen and ammonia production purpose.

Cogeneration of power and hydrogen using Scramjet cooling system :Energy and exergy analyses

In the current study, a new integrated system is provided to prevent waste energy and reduce power consumption. This system consists of a cascade refrigeration system (for cooling) and an Organic Rankine cycle(ORC) (for power generation). These two cycles are combined through a heat exchanger. In fact, this heat exchanger acts as a condenser for the cascade refrigeration cycle and evaporator for ORC. The waste heat of the cascade refrigeration cycle is used to handle the ORC. In this way, a part of the power consumption of the cascade refrigeration cycle is satisfied by ORC. Thermodynamic simulation of the proposed system is carried out via Engineering Equation Solver(EES) software. A parametric study is done to evaluate the effects of the operational parameters on the performance of the integrated system. In addition, different working fluids are used in cascade refrigeration and ORC cycles. The results showed that by using the working fluids of R245fa, R717, and R141b in order in the low-temperature refrigeration cycle, high-temperature refrigeration cycle and ORC, one can produce cooling at -50 ° C and also reduce the power consumption up to 48.69% in the cascade refrigeration cycle.

Performance characteristics and working fluid selection for high-temperature organic Rankine cycle driven by solar parabolic trough collector

Abstract In present paper, thermodynamic analysis and techno-economic assessment of an organic Rankine cycle (ORC) coupled with solar parabolic trough collector (PTC) are investigated. The thermodynamic and economic models, based on the principles of thermodynamics and heat transfer, as well as dynamic economic analysis, are developed for the components of the combined system. By performing a parametric study, the effects of outlet temperature (TPTC,out) and temperature difference between inlet and outlet of PTC (ΔT) and pinch point temperature difference of heat exchangers on the thermo-economic performance are evaluated. Moreover, under reasonable thermodynamic boundary conditions, the optimal operational parameters are obtained via a Pareto frontier solution. It is indicated that the improving TPTC,out is beneficial to the thermo-economic performance. Among the fluid candidates, toluene yields the best energy, exergetic and economic performance. There exists an optimal ΔT at which the thermal and exergy efficiency achieve the maximum. The optimal ΔT is 19–26°C for the screened working fluids. The pinch point temperature difference of evaporator has different impact on the system performance compared with that of condenser. The evaporator pinch point temperature difference has slight influence on the economic performance when it is larger than 10°C. While there is optimized condenser pinch point temperature difference (7–8°C), the economic performance is the optimal. The PTC and heat exchanger are the main source of total investment cost, account for more than 75%. The Pareto frontier solutions can provide a design guide for the decision maker.

Process Systems Engineering Evaluation of Prospective Working Fluids for Organic Rankine Cycles Facilitated by Biogas Combustion Flue Gases

The organic Rankine cycle (ORC) has recently emerged as a practical approach for generating electricity from low-to-high-temperature waste industrial streams. Several ORC-based waste heat utilization plants are already operational; however, improving plant cost-effectiveness and competitiveness is challenging. The use of thermally efficient and cost-competitive working fluids (WFs) improves the overall efficiency and economics of ORC systems. This study evaluates ORC systems, facilitated by biogas combustion flue gases, using n-butanol, i-butanol, and methylcyclohexane, as WFs technically and economically, from a process system engineering perspective. Furthermore, the performance of the aforementioned WFs is compared with that of toluene, a well-known WF, and it is concluded that i-butanol and n-butanol are the most competitive alternatives in terms of work output, exergy efficiency, thermal efficiency, total annual cost, and annual profit. Moreover, the i-butanol and n-butanol-based ORC systems yielded 24.4 and 23.4% more power, respectively, than the toluene-based ORC system; in addition, they exhibited competitive thermal (18.4 and 18.3%, respectively) and exergy efficiencies (38 and 37.7%, respectively). Moreover, economically, i-butanol and n-butanol showed the potential of generating 48.7 and 46% more profit than that of toluene. Therefore, this study concludes that i-butanol and n-butanol are promising WFs for high-temperature ORC systems, and their technical and economic performance compares with that of toluene. The findings of this study will lead to energy efficient ORC systems for generating power.

Thermoeconomic analysis of a multigeneration system using waste heat from a triple power cycle

Multigeneration systems represent an appealing concept, due to their multiple benefits compared to standalone systems, which has motivated researchers to develop different types of multigeneration systems for several applications. Considering their significance, in this study, a novel multigeneration is proposed that uses the waste heat of a thermodynamically efficient triple power cycle with a 100 MWe capacity. The proposed system, which can generate power, freshwater, cooling, and domestic hot water concurrently, is evaluated using detailed thermodynamic and economic analyses. The triple cycle includes a simple Brayton cycle coupled with a supercritical carbon dioxide recompression cycle and a high-temperature organic Rankine cycle. The waste energy of the recompression and organic Rankine cycles is recovered by a half effect absorption chiller, a multi-effect distillation unit, and two heat exchangers. The results show that for an optimized triple cycle, up to 1,804 kW cooling and 8,472 m3/day of hot water can be generated from the hot supercritical carbon dioxide stream with a levelized cost of cooling and hot water of 0.0362/ton-hr and $0.6823/MWth, respectively. The integration of a multi-effect distillation unit with 7 effects can generate 4,167 m3/day freshwater with a levelized cost of water of $1.142/m3. Overall, the proposed multigeneration system offers a very promising application and a number of benefits such as a generating multiple useful products with no adverse effect on the thermodynamic efficiency of the triple power cycle.