Organic Working Fluids Research Articles

Exergoeconomic and exergoenvironmental analysis of a combined heating and power system driven by geothermal source

This paper develops a geothermal driven combined heating and power system to obtain multi-generation, in which power is generated by Organic Rankine Cycle and heating is supplied by radiant floor heating system. Comprehensive thermodynamic, exergoeconomic and exergoenvironmental models of the system are performed and the capital cost and environmental impacts of the system components are analyzed. Superheat degree of the organic working fluid and inlet pressure of the Organic Rankine Cycle turbine are selected as variables to assess the system performance. Multi-objective optimization is employed to obtain the maximum system net power output, minimum levelized cost per exergy unit and minimum levelized environmental impact per exergy unit of the system. Results show that the increase of the working fluid superheat degree and the Organic Rankine Cycle turbine inlet pressure would cause the decrease of the Organic Rankine Cycle turbine power output and the increase of the heat supplying. Cooling water holds the highest levelized exergy cost and geothermal water heat exchanger has the highest environmental impact reducing potential. Under the condition of 11 °C superheat degree and 833 kPa Organic Rankine Cycle turbine inlet pressure, the system obtains a better performance with system net power output 1.19 MW, levelized cost per exergy unit 4.80 $/GJ and environmental impact per exergy unit 16.0 mpts/GJ.

Design and Fabrication of Solar Organic Rankine Cycle Test Rig with Helical Coil Heat Exchangers and working fluid selection strategy

Organic Rankine Cycle (ORC) is a modified Rankine cycle which uses organic working fluid to convert heat into useful energy. ORC has proven its potential in the field of exploiting waste heat generated by process industries. Due to environmental concerns and power demand, researchers now started exploiting renewable energy sources like solar and geothermal energies as heat source for ORC. The research in the field of ORC has revealed that, the energy conversion efficiency of ORC is very low and depends on working fluids used in it. Although variety of organic working fluids are available in market, the Zeotropic working fluids have revealed the better performance in ORC systems due to their temperature glide characteristics in evaporator and condenser but the unknown thermophysical characteristics of these working fluids restricts their use in ORC. This motivates a researcher to explore new possibilities to use these working fluids and improve ORC efficiency. In this regard a systematic test setup is designed and developed to test the potential of Zeotropic working fluids with solar energy as heat source.

Economic and Exergo-Advance Analysis of a Waste Heat Recovery System Based on Regenerative Organic Rankine Cycle under Organic Fluids with Low Global Warming Potential

The waste heat recovery system (WHRS) is a good alternative to provide a solution to the waste energy emanated in the exhaust gases of the internal combustion engine (ICE). Therefore, it is useful to carry out research to improve the thermal efficiency of the ICE through a WHRS based on the organic Rankine cycle (ORC), since this type of system takes advantage of the heat of the exhaust gases to generate electrical energy. The organic working fluid selection was developed according to environmental criteria, operational parameters, thermodynamic conditions of the gas engine, and investment costs. An economic analysis is presented for the systems operating with three selected working fluids: toluene, acetone, and heptane, considering the main costs involved in the design and operation of the thermal system. Furthermore, an exergo-advanced study is presented on the WHRS based on ORC integrated to the ICE, which is a Jenbacher JMS 612 GS-N of 2 MW power fueled with natural gas. This advanced exergetic analysis allowed us to know the opportunities for improvement of the equipment and the increase in the thermodynamic performance of the ICE. The results show that when using acetone as the organic working fluid, there is a greater tendency of improvement of endogenous character in Pump 2 of around 80%. When using heptane it was manifested that for the turbine there are near to 77% opportunities for improvement, and the use of toluene in the turbine gave a rate of improvement of 70%. Finally, some case studies are presented to study the effect of condensation temperature, the pinch point temperature in the evaporator, and the pressure ratio on the direct, indirect, and fixed investment costs, where the higher investment costs were presented with the acetone, and lower costs when using the toluene as working fluid.

Experimental study on the prospect of low-temperature heat to power generation using Trilateral Flash Cycle (TFC)

In this paper, a trilateral flash cycle (TFC) based system has been developed and studied to find out its prospect for utilizing more energy and enhancing the power generation capacity. To hold simplicity and minimize the cost of system construction, an impulse turbine and a converging-diverging (CD) stationary nozzle setup have been used as the expander. The experimental study introduced impulse turbine incorporates with a stationary CD nozzle and organic working fluid, which showed a promising power generation capability from a heat source below 80 °C in spite of the increasing size of the heat exchanger, condenser, and pump. In addition to the use of proper impulse turbines, however, the power generation capacity of such type of system is basically a function of the nozzle isentropic efficiency, which lies on the nozzle geometry and the alignment with respect to the turbine. A case study on the application of the TFC system for commercial power generation in associate with economic analysis has also been included in this study which shows a payback time less than 10 years with typical operational life of 20 years, considering only 40% nozzle isentropic efficiency and by using more efficient nozzle, the capital cost per unit power generation could be minimized.

Techno-economic analysis of combined inverted Brayton – Organic Rankine cycle for high-temperature waste heat recovery

Many practical cases with waste heat recovery potential such as exhaust gases of reciprocating engines, cement kilns or heat-treating furnaces, are nowadays often integrated with organic Rankine cycle to convert waste heat to the mechanical power. However, when dealing with high-temperature waste heat, organic Rankine cycle faces efficiency limit due to the physical properties of the working and thermal fluids. That gives room for further enhancement of the waste heat recovery technologies via the investigation of different non-conventional schemes as one of the possible ways. In the present work, a system introducing the combined inverted Brayton plus organic Rankine cycle is under investigation. Aspen Hysys models of both conventional organic Rankine cycle and combined cycle were designed, orienting on waste heat recovery from the heavy-load gas-fueled reciprocating engine exhaust. In this way, the performance of the combined scheme was benchmarked versus the conventional organic Rankine cycle. An assessment of the organic Rankine cycle working fluids was provided, and pentane has shown the best thermodynamic performance. The study on inverted Brayton cycle defined the remarkable effect of the water condensation in the gas duct on the inverted Brayton cycle performance. Finally, both thermodynamic and economic optimizations of the models were conducted, setting the stage for the comparison of solutions. Results have shown the 10% advantage of the combined scheme over organic Rankine cycle in generated power and system efficiency. The levelized-cost-of-energy-based optimization for variable capacity factors has highlighted above 6% advantage of the investigated solution. The analysis of the sensitivity from machines’ efficiencies and heat exchangers’ pinches has shown that with some sets of parameters, the studied scheme may concede to the organic Rankine cycle.

Mechanism of thermal decomposition of HFO-1234ze(E) under supercritical fluid conditions

The supercritical organic Rankine cycle (SORC) system is a promising solution for the recovery of low-grade heat resources and for the utilization of geothermal energy. The thermal stability of the organic working fluid is one of most important criteria for establishing the SORC. Therefore, it is very important to understand the mechanism of thermal decomposition of the organic working fluid. In this study, decomposition experiments and theoretical calculations using the density functional theory (DFT) method were performed to evaluate the thermal stability and elucidate the mechanism of decomposition of a new-generation working fluid, (1E)-1,3,3,3-tetrafluoropropene (HFO-1234ze(E), CFHCHCF3). The main decomposition products included pentafluoroethane (CF2HCF3), 1,1,1-trifluoroethane (CH3CF3), and 2,3,3,3-tetrafluoropropene (CH2CFCF3). HF, the key molecule, is produced and consumed multiple times throughout the course of the decomposition reaction. HFO-1234ze(E) decomposed to C1C2 hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) under moderate operating conditions. On the other hand, under harsher operating conditions, the formation of long-chain HFCs and HFOs with C3C5 was experimentally observed, where these species can be produced from the reactions between the decomposition intermediates.

Study of the soil temperature effect on the operation of a low-capacity power plant’s condenser

Every year, the share of decentralized energy generation in Russia is increasing. The following factors contribute to the development of this scenario: increased wear of the country’s energy system equipment, energy shortages, and lack of centralized energy supply in a number of regions and constantly rising tariffs. One of the methods of decentralized energy generation is the use of low-capacity power plants based on the Rankine cycle with an organic working fluid. The operation of such plants requires cooling and condensation of the working fluid by transferring its heat to the environment. This study discusses the design of such a power plant and the heat removal system to a cold source. is the authors consider the design of a condenser which is a horizontal pipeline placed in the ground. Seasonal fluctuations of the soil temperatures affect the operation of the condenser. Thereby, to ensure the stable operation of the power plant, it is necessary to quantitatively assess the effect of the annual dynamics of the soil temperature state on cooling and condensation of the coolant. The study of the temperature fields of the soil, pipeline and working fluid, as well as the lengths required for cooling and condensation of the working fluid, was carried out in the ANSYS CFX software package for numerical hydrodynamic modeling. A homogeneous flow model was chosen to simulate the momentum and condensation of a vapor-liquid medium. Also, the calculations were conducted in a one-dimensional formulation using an engineering method. A methodology for modeling complex processes of heat transfer to the soil using numerical modeling has been developed and verified. 12 calculations were made; the distributions of the steam dryness and temperature in the simulated region depending on the time of the year were obtained. The functions of the total length of the pipeline, cooling and condensation lengths on the soil temperature are analyzed. It has been established that the harmonic change in the temperature of the soil set as the initial condition determines a similar change in the lengths required for cooling and condensation of the working fluid. Using this technique, it is possible to calculate pipelines of more complex shapes. The obtained temperature distributions in cross sections allow to establish the optimal distance between the axes of the pipes when designing a condenser in the form of a bundle of horizontal pipes or a bent pipeline.

Exergy, Economic, and Life-Cycle Assessment of ORC System for Waste Heat Recovery in a Natural Gas Internal Combustion Engine

In this article, an organic Rankine cycle (ORC) was integrated into a 2-MW natural gas engine to evaluate the possibility of generating electricity by recovering the engine’s exhaust heat. The operational and design variables with the greatest influence on the energy, economic, and environmental performance of the system were analyzed. Likewise, the components with greater exergy destruction were identified through the variety of different operating parameters. From the parametric results, it was found that the evaporation pressure has the greatest influence on the destruction of exergy. The highest fraction of exergy was obtained for the Shell and tube heat exchanger (ITC1) with 38% of the total exergy destruction of the system. It was also determined that the high value of the heat transfer area increases its acquisition costs and the levelized cost of energy (LCOE) of the thermal system. Therefore, these systems must have a turbine technology with an efficiency not exceeding 90% because, from this value, the LCOE of the system surpasses the LCOE of a gas turbine. Lastly, a life cycle analysis (LCA) was developed on the system operating under the selected organic working fluids. It was found that the component with the greatest environmental impact was the turbine, which reached a maximum value of 3013.65 Pts when the material was aluminum. Acetone was used as the organic working fluid.

Study of Development Scenarios for Bottoming Unit Binary Cycle to Utilize Exhaust Steam from Back Pressure Turbine Geothermal Power Plant

Binary cycle using organic working fluid or ORC system has been applied in geothermal and some other industrial processes to recover low grade and waste energy to generate electricity. The conventional system to utilize geothermal energy is a condensing system or back pressure system which depend on a turbine used in the system. Two units of the power plant in Flores, Indonesia are using back pressure turbine, which means that there is still a chance to increase the electrical power of the steam which is released through the turbine. The amount of exhaust steam available from these two units power plant is more than 62,000 kg per hour with 99°C of temperature and around 2,430 kJ/kg enthalpy. This research is trying to get the optimum power that can be generated by the ORC regarding other consideration parameters such as ambient temperature, thermodynamics condition of resource steam, and energy conversion of each apparatus. It is the aim of this paper to present a thermodynamic study on the utilization of ORC as the bottoming cycle with various types of working fluids to produce additional electricity. Several working fluids are chosen to find the optimum ORC system to utilize this exhaust steam such as isobutane, butane, isobutene, isopentane, propane, propyne, neopentane, R245fa, R236fa, and R134a. ORC system used in this research is simple ORC with basic components such as Pre-Heater, Evaporator, Expander, Condenser, and Pump. The properties of working fluids are calculated by REFPROP. The results show that this binary cycle can generate up to 2.25 MW with the thermal efficiency around 10% depend on the working fluid used. Two working fluids in this scenario that provide the best power generated are Propyne and Isopentane. The type of working fluid must also be considered, propyne is a wet type while isopentane is a dry type working fluid.

Analysis of heat transfer and irreversibility of organic rankine cycle evaporator for selecting working fluid and operating conditions

Organic Rankine cycle (ORC) is suitable to converting the normally hard to utilize low temperature thermal energies, such as geothermal energy, solar energy, and industrial waste heat, to electricity through utilizing low boiling organic working fluids. The performance of ORC system is dramatically affected by the selections of working fluid and working conditions. As a key component of waste heat recovery, the irreversible loss of evaporator also has great influence on the performance of ORC system. In this paper, we study the heat transfer performance in evaporator under the condition that the heat source parameters and pinch point temperature difference are identified. It is found that the heat transfer performance is affected by Cr, the ratio of heat capacity flow rates between the working fluid and the heat source fluid. The equivalent thermal resistance, deducing from the concept of entransy, to measure the irreversability during the heat transfer process is used. Then, the parameter ?r, the ratio between latent heat and sensible heat of working fluid is defined. With the parameters Cr and ?r, we investigate the relationship between the heat transfer and irreversible loss, and deduce the condition that maximum heat transfer and minimum equivalent thermal resistance occurs. Finally, a calculation method is established to choose the optimum working fluid and the evaporation condition.

Ledinegg instability analysis on direct vapor generation inside solar collectors

Compared with direct steam generation (DSG), direct vapor generation (DVG) system based on organic working fluid has better application potential in low and medium temperature distributed system. However, there is a lack of understanding of the two-phase flow instability that commonly occurs in DVG systems and can cause fatal damage to the system. In this paper, Ledinegg instability is considered as a common flow instability, and its occurrence characteristics and avoidance strategies are presented. First, a theoretical model was established to study Ledinegg instability of organic working fluid. Then, the effects of heat flux q, inlet subcooling Tc, length-to-diameter ratio L/D and fluid properties are analyzed. Particularly, a characteristic parameter RL representing the possibility of Ledinegg instability is proposed for the first time in performance evaluation of Ledinegg instability. The results show that as L/D decreases from 200 to 100, RL reduces from 0.88 to 0.25. As q increases from 10 kW/m2 to 30 kW/m2, RL increases from 0.54 to 1.03. When Tc is less than 3 °C, RL approaches 0 and Ledinegg instability disappears. With the increase of surface tension σ and the latent heat of vaporization r, the decreases of vapor-liquid density ratio ρsv/ρsl and the decreases of vapor-liquid viscosity ratio μsv/μsl, RL increases. The physical equation describing RL of Ledinegg instability is helpful to guide DVG system to reduce or avoid Ledinegg instability in design and operation.

Process Simulations of the Direct Non-Aqueous Gas Stripping Process for CO2 Desorption

The integration of the direct steam stripping (DSS) process with organic working fluid promises a significant reduction in the energy penalty for the CO2 capture process. This work investigates the mechanisms of the mass transfer enhancement in direct pentane stripping (DPS) process using simulation methods. Through regressing the molecule-molecule interaction parameters, a quaternary system thermodynamic model (QSTM) is developed to successfully predict the vapor-liquid equilibrium of Amine/CO2/Pentane/H2O system. Three typical solvents, monoethanolamine (MEA), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP) are studied in this work. The DPS process using 30 wt.% MEA, 30 wt.%MDEA, and 30 wt.% AMP exhibits the solvent regeneration energy of 2.55, 2.65, and 2.01 GJ/tCO2 under the optimal conditions, which is 34%, 32%, and 48% lower than of the conventional MEA-based process. DPS using MDEA shows an energy advantage over the other two solvents because of the high CO2 equilibrium partial p...

Parametric Optimization and Thermodynamic Performance Comparison of Organic Trans-Critical Cycle, Steam Flash Cycle, and Steam Dual-Pressure Cycle for Waste Heat Recovery

Compared with the basic organic and steam Rankine cycles, the organic trans-critical cycle (OTC), steam flash cycle (SFC) and steam dual-pressure cycle (SDC) can be regarded as the improved cycle configurations for the waste heat power recovery since they can achieve better temperature matching between the heat source and working fluid in the heat addition process. This study investigates and compares the thermodynamic performance of the OTC, SFC, and SDC based on the waste heat source from the cement kiln with an initial temperature of 320 °C and mass flow rate of 86.2 kg/s. The effects of the main parameters on the cycle performance are analyzed and the parameter optimization is performed with net power output as the objective function. Results indicate that the maximum net power output of SDC is slightly higher than that of SFC and the OTC using n-pentane provides a 19.74% increase in net power output over the SDC since it can achieve the higher use of waste heat and higher turbine efficiency. However, the turbine inlet temperature of the OTC is limited by the thermal stability of the organic working fluid, hence the SDC outputs more power than that of the OTC when the initial temperature of the exhaust gas exceeds 415 °C.

A Combined Binary-Cycle Geothermal Power Plant with a Secondary Flash Steam Superheating System: Choice of Optimal Working Fluids

The article presents the results from numerically modeling the process circuit of a combined binary-cycle double-flash geothermal power plant (GeoPPs) with the use of secondary flash steam superheating by means of a hydrogen–oxygen steam generator. Geothermal heat carrier from substandard wells of the Mutnovsk geothermal field, as well as separated steam and waste brine from the Mutnovsk GeoPP, were taken as the primary heat source. Numerical investigation results have shown that the application of secondary flash steam superheating by means of a hydrogen–oxygen steam generator makes it possible to increase the steam turbine’s power output and its flow path efficiency owing to the steam wetness reduced by more than a factor of two. In addition, reduced steam wetness helps prevent erosion damage to the last-stage turbine rotor blades. Data on the effect that the use of different organic substances has on the efficiency and power output of the binary installation and of the GeoPP as a whole are given. Optimization investigations have shown that the highest power output and efficiency values of the binary installation used as part of a combined binary-cycle GeoPP at the lowest specific brine flowrate are achieved in using organic substances from the groups of nontoxic fire- and flame-proof (R-31-10 and RC-318) and low-toxic fire- and flame-proof ones (R-227ea, R-236fa, R1318, and R-134a) as working fluids. It has been established that the highest power output values of a combined binary-cycle double-flash GeoPP with secondary flash steam superheating by means of a hydrogen–oxygen steam generator are achieved in using the organic working fluids R-31-10, R‑227ea, and RC-318. In so doing, the optimum design pressure in the expander-separator at which the highest efficiency and power output of the studied GeoPP are obtained makes 0.47 MPa. In solving optimization problems on selecting the working fluids for binary combined-cycle GeoPP installations, it is proposed to use multiaxial composite diagrams of the relative values of geothermal power plant parameters and characteristics. An example of drawing a multiaxial composite diagram for the relative values of parameters and characteristics for a combined binary-cycle GeoPP for the R-290, R-31-10, R-32, and RC-318 working fluids is given. The numerical investigation results can be used in designing new and modernizing the operating GeoPPs that use steam geothermal sources.

Математическое моделирование конденсации рабочего тела в системе отдачи тепла холодному источнику энергоустановки малой мощности

The purpose of the paper is to offer a method for reducing the temperature and condensation of the working fluid circulating in the power plant due to the fact that the Russian Federation is characterized by uneven provision of electricity and heat (the problem of energy shortage is most acute in the Far East and the Far North regions). The major shortcomings of the current centralized energy supply are great losses during energy delivery and transformation, as well as the possibility of de-energizing a large number of consumers in case of an accident at the сentral power plant. In this regard, the idea of decentralized energy production free from the named shortcomings due to its autonomy and proximity to the places of consumption is becoming increasingly relevant. One of the methods of decentralized generation of heat and electricity is the use of Rankine cycle-based low-capacity power plants with an organic working fluid. Their design includes a boiler heating the working fluid, a turbine driving the electric generator, condenser and a pump. To condense the coolant the organic Rankine cycle must be provided with heat dissipation to the environment. This paper deals with the method of lowering the temperature and condensation of the working fluid circulating in the power plant (by means of a horizontal pipeline plunged to a certain depth in the ground). It is assumed that available temperature potential of the soil provides complete condensation of the working fluid without excessive overcooling. The study of intensity of working fluid cooling and condensation in the pipeline is carried out using a homogeneous and ring flow model. The temperature fields and steam dryness degree are determined by two approaches: in the software package of finite element modeling ANSYS CFX and by the finite difference method (engineering calculation methods). The paper also presents the analysis of the results obtained in the course of solving the problem by means of the finite element analysis and engineering calculation by the finite difference method.

Thermoeconomic Analysis of Different Exhaust Waste-Heat Recovery Systems for Natural Gas Engine Based on ORC

Waste-heat recovery (WHR) systems based on the organic Rankine cycle (ORC) improve the thermal efficiency of natural gas engines because they generate additional electric power without consuming more gas fuel. However, to obtain a cost-effective design, thermoeconomic criteria must be considered to facilitate installation, operation, and penetration into real industrial contexts. Therefore, a thermo-economic analyses of a simple ORC (SORC), ORC with recuperator (RORC) and a double-pressure ORC (DORC) integrated with a 2 MW Jenbacher JMS 612 GS-N. L is presented using toluene as the organic working fluid. In addition, the cost rate balances for each system are presented in detail, with the analysis of some thermoeconomics indicator such as the relative cost difference, the exergoeconomic factor, and the cost rates of exergy destruction and exergy loss. The results reported opportunities to improve the thermoeconomic performance in the condenser and turbine, because the exergoeconomic factor for the condenser and the turbine were in the RORC (0.41 and 0.90), and DORC (0.99 and 0.99) respectively, which implies for the RORC configuration that 59% and 10% of the increase of the total cost of the system is caused by the exergy destruction of these devices. Also, the pumps present the higher values of relative cost difference and exergoeconomic factor for B1 (rk = 8.5, fk = 80%), B2 (rk = 8, fk = 85%).

Optimization Investigations of a Combined Binary-Cycle Geothermal Power Plant with Two Separation Pressures and Flashed Steam Superheating Using a Hydrogen–Oxygen Steam Generator

The article considers the specific features of and prospects for improving the efficiency of geothermal power plants (GeoPPs) that use a steam–water mixture from geothermal fields and steam superheating as an energy source. The process flow diagram of a combined binary-cycle GeoPP with two separation pressures and flashed steam superheating with the use of a hydrogen–oxygen steam generator is proposed. The advisability of using a separator downstream of the high-pressure section for decreasing the steam moisture at the turbine condenser inlet is substantiated. The article also presents the results from numerical optimization investigations of the effect that the choice of organic working fluid has on the efficiency, safety, and environmental characteristics of the binary installation used as part of a combined-cycle GeoPP. The following groups of organic substances as possible candidates for use as working fluid are considered: nontoxic, nonflammable, and nonexplosive ones (group I); low-toxic, nonflammable, and nonexplosive ones (group II); nontoxic inflammable ones (group III); and low-toxic, inflammable, and explosive ones (group IV). Typical dependences characterizing the effect that the pressure in the expander and the saturation pressure in the evaporator have on the binary turbine net power output, on the specific flowrate of separated geothermal brine per unit power capacity, on the binary cycle efficiency, and on the GeoPP efficiency as a whole are shown taking as examples the use of cyclobutane and octafluoropropane as a working fluid. For a few working fluids, the existence of extremes in the above-mentioned dependences is established, which determine the binary installation optimal power values and the minimal geothermal brine specific flowrate. Based on the numerical analysis results, limitations are imposed on the admissible maximum and minimum pressure values in the binary circuit. Bar charts of calculated process characteristics influencing the binary turbine flow path’s design and efficiency are plotted. A priority (according to the maximum net power output criterion) list of working fluids relating to the group of environmentally friendly organic substances for the combined-cycle GeoPP binary installation with flashed steam superheating taking into account process-related limitations is drawn up.

Exergy and economic assessments of solar organic Rankine cycle system with linear V-Shape cavity

In this research, a parabolic trough concentrator with linear V-Shape cavity receiver was studied as the heat source of an organic Rankine cycle system. The solar organic Rankine cycle system was evaluated under exergy and economic analyses. Thermal oil was used as the solar working fluid, and ethanol was used as the organic working fluid under different turbine inlet temperatures and turbine inlet pressure. The influence of different operational parameters, including solar radiation, mass flow rate, and inlet temperature of solar working fluid was investigated on the performance of the solar organic Rankine cycle system. It was found that exergy gain and exergy efficiency of the solar system improved with increasing solar radiation, increasing inlet temperature, and decreasing the flow rate of the solar working fluid. The highest organic Rankine cycle efficiency and total efficiency were found to be 35%, and 25% at turbine inlet temperature of 592 K and turbine inlet pressure of 6 MPa, respectively. Finally, the lowest levelized cost of electricity, and the lowest payback period were calculated equal to 0.0716 (€/kWh), and 8.79 (years) for the optimum condition of the developed solar organic Rankine cycle system, respectively. The present study is beneficial for improving the performance of the solar organic Rankine cycle systems with parabolic trough concentrators in a simple and convenient way and the development of solar thermal technologies.

Experimental and Techno-Economic Analysis of Solar-Geothermal Organic Rankine Cycle Technology for Power Generation in Nepal

The current research study focuses on the feasibility of stand-alone hybrid solar-geothermal organic Rankine cycle (ORC) technology for power generation from hot springs of Bhurung Tatopani, Myagdi, Nepal. For the study, the temperature of the hot spring was measured on the particular site of the heat source of the hot spring. The measured temperature could be used for operating the ORC system. Temperature of hot spring can also further be increased by adopting the solar collector for rising the temperature. This hybrid type of the system can have a high-temperature heat source which could power more energy from ORC technology. There are various types of organic working fluids available on the market, but R134a and R245fa are environmentally friendly and have low global warming potential candidates. The thermodynamic models have been developed for predicting the performance analysis of the system. The input parameter for the model is the temperature which was measured experimentally. The maximum temperature of the hot spring was found to be 69.7°C. Expander power output, thermal efficiency, heat of evaporation, solar collector area, and hybrid solar ORC system power output and efficiency are the outputs from the developed model. From the simulation, it was found that 1 kg/s of working fluid could produce 17.5 kW and 22.5 kW power output for R134a and R245fa, respectively, when the geothermal source temperature was around 70°C. Later when the hot spring was heated with a solar collector, the power output produced were 25 kW and 30 kW for R134a and R245fa, respectively, when the heat source was 99°C. The study also further determines the cost of electricity generation for the system with working fluids R134a and R245fa to be $0.17/kWh and $0.14/kWh, respectively. The levelised cost of the electricity (LCOE) was $0.38/kWh in order to be highly feasible investment. The payback period for such hybrid system was found to have 7.5 years and 10.5 years for R245fa and R134a, respectively.

WITHDRAWN: Techno-economic analysis of combined inverted Brayton - Organic Rankine cycle for high-temperature waste heat recovery

Abstract Many practical cases with waste heat recovery potential such as exhaust gases of reciprocating engines, cement kilns or heat-treating furnaces, are nowadays often integrated with organic Rankine cycle to convert waste heat to the mechanical power. However, when dealing with high-temperature waste heat, organic Rankine cycle faces efficiency limit due to the physical properties of the working and thermal fluids. That gives room for further enhancement of the waste heat recovery technologies via the investigation of different non-conventional schemes as one of the possible ways. In the present work, a system introducing the combined inverted Brayton plus organic Rankine cycle is under investigation. Aspen Hysys models of both conventional organic Rankine cycle and combined cycle were designed, orienting on waste heat recovery from the heavy-load gas-fueled reciprocating engine exhaust. In this way, the performance of the combined scheme was benchmarked versus the conventional organic Rankine cycle. An assessment of the organic Rankine cycle working fluids was provided, and pentane has shown the best thermodynamic performance. The study on inverted Brayton cycle defined the remarkable effect of the water condensation in the gas duct on the inverted Brayton cycle performance. Finally, both thermodynamic and economic optimizations of the models were conducted, setting the stage for the comparison of solutions. Results have shown the 10% advantage of the combined scheme over organic Rankine cycle in generated power and system efficiency. The levelized-cost-of-energy-based optimization for variable capacity factors has highlighted above 6% advantage of the investigated solution. The analysis of the sensitivity from machines’ efficiencies and heat exchangers’ pinches has shown that with some sets of parameters, the studied scheme may concede to the organic Rankine cycle.