Organic Rankine Cycle Cycle Research Articles

An exergy analysis of various layouts of ORC-VCC systems for usage in waste heat recovery onboard ships

An exergy based analysis is carried out for waste heat recovery from a marine Diesel engine using various layouts of organic Rankine cycles (ORCs) for driving a vapor compression refrigeration cycle. The ORC layouts studied are a simple organic Rankine cycle (ORC), an organic Rankine cycle with internal heat exchanger (RORC) and a serial cascade ORC cycle (SCORC). In addition to the well-known fluid R134a, two hydrocarbon-based refrigerants, namely butane (R600) and isobutane (R600a), are considered in the present study. It is found that sensible improvements are attained using the cascade ORC and the ORC with internal heat exchanger configurations compared to simple ORC under certain conditions. This improvement depends on both the heat source temperature and the working fluid considered. Moreover, the results indicate that R600 as working fluid has the best performance from a thermodynamic point of view. Finally, though R600, a pure hydrocarbon, is completely accepted by the environment, more attention should be paid to its flammability.

Analysis of Nanofluids Behavior in a PV-Thermal-Driven Organic Rankine Cycle with Cooling Capability

This paper discusses the performance of nanofluids in a PV Thermal-driven Organic Rankine Cycle (ORC) with cooling capabilities. This study was intended to investigate the enhancement effect and characteristics of nanofluids; Al2O3, CuO, Fe3O4 and SiO2 on the performance the hybrid system composed of PV Thermal, ORC and cooling coil. The quaternary refrigerant mixture used in the ORC cycle to enhance the ORC efficiency is an environmentally sound refrigerant mixture composed of R152a, R245fa, R125, and R1234fy. It was shown that the enhancement of the efficiency of the hybrid system in question is significantly dependent upon not only the solar radiation but also the nanofluids concentration and the type of nanofluid as well as the fluid temperature driving the ORC. A higher hybrid system efficiency has been overserved with nanofluid CuO. Moreover, it has been also shown that on the average, the hybrid system efficiency was higher 17% with nanofluid CuO compared to water as the heat transfer fluid. In addition, it was also observed that the higher cooling effect produced is significantly increased with the use of the nanofluid CuO compared to the other nanofluids under investigation and water as heat transfer fluid. The results observed in this paper on ORC efficiency and PV solar panel efficiency are comparable to what has been published in the literature.

The Performance of waste Heat Recovery Systems using Steam Rankine Cycle and Organic Rankine Cycle For Power Generation

This paper presents extensive modelling of an Organic Rankine Cycle (ORC) system for a combined cycle power plant and to compare and evaluate the performance of ORC and Steam Rankine Cycle (SRC). In addition, ORC as a second stage waste heat recovery system after SRC too was modelled. Conceptual design of an ORC was made to replace the SRC system used in the power plant and its performance was compared with that of the SRC above. Upon replacing the steam cycle with ORC, the system efficiency is 7.63 %. The total energy destruction is 5140.41 kW. The result shows that ORC delivers very low system efficiency. The steam cycle produces 202.5MW whereas the presented ORC produces just 1.016MW of power. On the other hand, if ORC is implemented on the chimney the system will produce 0.2% of extra power on top the current power production of 675MW. The efficiency of this system is 7.81%. It is recommended to add the ORC at the chimney to tap more useful energy from the otherwise waste energy rejected into the environment.

Efficiency analysis of refrigerant work fluid in the Organic Rankine Cycle (ORC) as an energy generating machine electricity 1 kW scale

At present, the depletion of fossil energy resources will have a significant impact on every aspect of life in Indonesia. One effort to overcome this problem is by conducting research to look for renewable energy sources. This study uses the Organic Rankine Cycle (ORC). The types of refrigerants used in this study are R141b, R245fa, and R123 using the Aspen plus Program Simulation. This study focuses on the working fluid R141b, R245fa, and R123 on the ORC as a 1 kW scale electric energy generator. The results obtained from the Aspen Plus Program Simulation in the ORC Cycle use working fluids R141b, R245fa, and R123 at a pressure of 3 bar to a pressure of 10 bar at a temperature of 95 ° C. The maximum efficiency produced is 8.65%, 7.79%, and 8.36%. The turbine power produced is 1005 watts, 896 watts, and 770 watts. From the simulation results used in the ORC working fluid R 141b has an Efficiency and Power value that is best used as a 1 kW electric energy generator with an efficiency value of 8.65% and 1005 Watt Power.

Thermo-economic analysis of a novel hybrid multigeneration system based on an integrated triple effect refrigeration system for production of power and refrigeration

Multigeneration systems provide substantial benefits in terms of improving efficiency and economics as well as environmental benefits. In this study, a multigeneration system is proposed for generating power and triple effect refrigeration at different evaporation temperatures. The system hybridizes a 25 MW recuperative Brayton cycle with an organic Rankine cycle (ORC) and an integrated refrigeration system that combines a branched generator–absorber heat exchange (GAX) absorption refrigeration system with a dual-evaporator cascade carbon dioxide-ammonia compression refrigeration system. The exhaust gas from the Brayton cycle is divided into two streams: one is supplied to the generator of the GAX cycle and the remaining is supplied to the ORC for additional power generation. Results show that additional power generation by ORC increases thermal efficiency from 0.394 to 0.510 and reduces the levelized cost of electricity from $75.5/MWh to $64.4/MWh. The integration of GAX cycle and cascade cycle is beneficial from both thermodynamic and economic viewpoints. Due to their integration, the coefficient of performance of the cascade cycle increases substantially from 2.37 to 4.69. Also, the levelized cost of cooling for the production of triple effect refrigeration decreases from $0.08/ton-hr to $0.059/ton-hr. Environmental analysis shows that the development of multigeneration system can lead to avoiding 24,185 tons of CO2 per year. The proposed multigeneration system brings a possibility to efficiently recover the waste energy for additional power generation and refrigeration production at different temperatures. Waste energy recovery by the ORC and GAX cycle as well as the integration of the GAX cycle with a cascade refrigeration cycle provide good potential for cleaner production of all products with improved efficiency, economics and environmental benefit.

Investigation of an efficient and environmentally-friendly CCHP system based on CAES, ORC and compression-absorption refrigeration cycle: Energy and exergy analysis

Combined cooling heating and power (CCHP) is a promising energy supply technology which is widely installed in buildings due to its feasibility from techno-economic, performance and environmental points of view. In present paper, a novel cogeneration system based on compressed air energy storage (CAES), organic rankine cycle (ORC) and hybrid compression-absorption refrigeration cycle is proposed. The main objective of the proposed system is to improve the efficiency of the CAES system by providing cooling capacity from the rest of hot gases in turbine exhaust through employing an ORC driven refrigeration system. Also, the effect of the maximum to minimum pressure ratio of CAES vessel as a critical parameter on CAES volume and round trip efficiency (RTE) has been scrutinized. Using the environmentally-friendly compression-absorption refrigeration system, high temperature thermal energy storage (HTES) and R407C as the organic working fluid decrease fossil fuel consumption and make the proposed system fully environmentally-friendly. The results indicate that 2280 kW electrical energy and 416.7 kW cooling capacity are simultaneously generated during peak period. As a result, with 13.15% RTE enhancement in comparison to the individual CAES system, it reaches to 65.15% based on the proposed modification. Also, the results show that the overall exergy efficiency and total exergy destruction of the components are 49.17% and 1419 kW, in which the pressure regulating valve and the air turbine have the highest irreversibility and exergy destruction.

Experimental study of the organic rankine cycle under different heat and cooling conditions

A small-scaled organic Rankine cycle (ORC) system using R123 as working fluid was experimentally investigated. For ORC and regenerative organic Rankine cycle (RORC), the impacts of the evaporating and condensing temperatures on the performances of main components (i.e., the expander, the pump, and heat exchangers) and the system were tested. The comparison between these two systems under identical working conditions was also carried out. The results showed that the expander shaft power of ORC is greater than that of RORC under the identical evaporating temperature and condensing temperature. When the evaporating temperature is relatively low, the expander shaft power is more sensitive to the condensing temperature, and the thermal efficiency of ORC is higher than that of RORC. With the increasing of the evaporating temperature, the thermal efficiency of RORC exceeded that of ORC. Therefore, ORC is recommended for the low temperature heat source, while for the high temperature heat source, RORC is recommended for its higher thermal efficiency.

Design and Analysis of a Single-Stage Transonic Centrifugal Turbine for organic Rankine cycle (ORC)

The recovery of low temperature heat sources is a hot topic in the world. The ORC system can effectively use the low temperature heat source. As its main output device, the performance of the turbine is very important. The single stage transonic turbine has the characteristics of small size and large output power. In this paper, the complete design process of a transonic centrifugal turbine with R245fa in low working temperature condition is introduced. At the design conditions, the shaft power and the wheel efficiency of the centrifugal turbine can reach 1.12 MW and 83.61%, respectively. In addition, a thermodynamic ORC cycle is presented and the off-design conditions of the turbine and its influence on the system are studied in detail. The results obtained in the present work show that the single-stage transonic centrifugal turbine can be regarded as a potential choice to be applied in small scale ORC systems.

Comparison of different layouts for the integration of an organic Rankine cycle unit in electrified powertrains of heavy duty Diesel trucks

In the last years an increasing interest has grown about the organic Rankine cycle (ORC) for waste heat recovery from the engine exhausts, as a feasible way to improve the efficiency of internal combustion engines (ICE). However, the highly variable working conditions in which an engine usually works make the operation of the ORC unit very challenging. In the management of ORC units, optimization and control are considered as an essential step in order to attain good performance during the whole operation of the ICE on a driving cycle. In this paper a GT-Power model of a 12.6 l turbocharged Diesel engine is used as a typical heavy duty Diesel engine to retrieve the temperature and the mass flow rate of the exhaust gases during a heavy heavy-duty driving cycle. An optimization process is performed to maximize the power output of the ORC as a function of the revolution speeds of the pump and of the turbine. For powertrain electrification purposes, two different ORC layouts are proposed in this paper, both seeking to store the recovered energy into a battery pack. The first layout is optimized based on mean values of exhausts temperature and mass flow rate, while the second layout is designed to control independently the revolutions of the pump and of the turbine of the ORC unit toward optimal values for maximum net power output. Both the layouts allow to recover an interesting amount of energy, in spite of a straightforward control strategy. Nonetheless, results show that optimizing the net power of the ORC cycle by decoupling the turbine and the pump may not ensure the maximization of the recovered energy. In fact, the storable energy from the ORC unit is strongly affected by the conversion efficiencies related to the specific layout.

Enhanced performance and reduced payback period of a low grade geothermal-based ORC through employing two TEGs

In this paper, a novel integrated system is proposed to improve the performance of a conventional low-grade geothermal-based organic Rankine cycle (ORC). The main idea is to utilize two TEG units to recover the waste heat of the condenser and geothermal brine. The proposed model is investigated and compared with simple ORC from the energy, exergy, and exergoeconomic viewpoints through the parametric study. Furthermore, the payback period of the systems is calculated to investigate the economic aspects of the model in more details. Results show that the exergy efficiency of the proposed system would be 56.81% at the base case (4.67% higher than the simple geothermal-based ORC system) and the total product cost of the proposed integrated system is 24.55 $/GJ at the base case (5.5% lower than simple ORC), while the payback period of the suggested system is 2.422 years (15 days lower than the simple ORC cycle). Furthermore, the net power output of the novel proposed system is 75.24 kW (9% higher than the simple ORC cycle). Comprehensive paramedic study and comparison of the exergy and exergoeconomic aspects reveal that the proposed system is a promising method to optimize such systems from exergy/exergoeconomic viewpoints.

Options for using solid oxide fuel cell technology in complex integrated biomass gasification cogeneration plants

The aim of this paper is to draw readers' attention to potential new technological solutions for effective utilisation of dispersed biomass resources in distributed community-scale applications. In the paper conceptual system, that consists of allothermal wood gasifier, solid oxide fuel cell (SOFC), internal combustion piston engine (ICE) and Organic Rankine Cycle (ORC) for waste heat recovery, is proposed. Configuration of such systems is nowadays possible due to availability individual small-scale energy conversion technologies that can be integrated into complex structures. In the studied case the anode exhaust gas of the syngas fired SOFC module, that still contains combustible gases, is considered a secondary fuel for a bottoming ICE. The ORC cycle module is driven by the heat recovered from process gas coolers as well as from SOFC cathode and ICE exhaust gases. The system has been theoretically evaluated in terms of energy conversion efficiency and profitability using thermodynamic and economic analysis. Relevant robust mathematical models of key components have been developed. Through the modelling the most important performance parameters are addressed. Electric power of the sample system is below 1 MW what makes it suitable for utilisation of locally available biomass. Simulations revealed potentially high value of the net biomass energy to electricity conversion efficiency of 37%–40% depending on the ORC cycle configuration. Financial analysis revealed positive values of profitability indices at current level of market prices. The results are compared with a real biomass-fired ORC cogeneration project. The system also addresses issues related to external effects of the project, such as global emission reduction and primary energy savings.

Exergy Analysis and Performance Improvement of a Subcritical/Supercritical Organic Rankine Cycle (ORC) for Exhaust Gas Waste Heat Recovery in a Biogas Fuelled Combined Heat and Power (CHP) Engine Through the Use of Regeneration

In the present study, a subcritical and supercritical regenerative organic Rankine cycle (rORC) was designed. The designed rORCs assist a combined heat and power (CHP) engine, the fuel of which is biogas produced from anaerobic digestion of domestic wastes in Belgium. R245fa was selected as the working fluid for both the subcritical and supercritical rORC. During the parametric optimisation, the net power production, mass flow rate, exchanged heat in the regenerator, total pump power consumption, thermal and exergetic efficiencies of rORC were calculated for varying turbine inlet temperatures and pressures. After parametric optimisation of the rORC, the results were compared with the results of the previous study, in which only a simple ORC is analysed and parametrically optimised. Moreover, the effect of the regenerator was revealed by examining all results together. Finally, the exergetic analysis of the best performing subcritical and supercritical rORC was performed. Furthermore, the results of the present and previous studies were considered together and it is clearly seen that the subcritical rORC shows the best performance. Consequently, by using the subcritical rORC, the disadvantages of the using simple ORC (low performance) and supercritical cycle (safety, investment) can be eliminated and system performance can be improved.

Performance analysis of ED-PR system with dual expanders and ORC for pressure energy recovery

Natural gas (NG) from the gas factory is delivered with abundant pressure energy to various industrial users and residents. The Throttle Valve Pressure Regulation (TVPR) configuration can only achieve stable downstream pressure. Additional expanders installed could recover the pressure energy, but hard to present a high efficiency and utilize the cold energy. This work innovatively proposes dual expanders and Organic Rankine Cycle (ORC) based on our previous EDNGPR (Expander-Depending Natural Gas Pressure Regulation) configuration. This configuration can not only regulate the NG pressure but harvest more pressure energy than that of the EDNGPR configuration. Thermodynamic analyses are conducted on the ED-PR configuration, the DED-PR configuration, the ORC-ED-PR configuration and the ORC-DED-PR configuration. Results show that the daily round-trip efficiency increased obviously by integrating the dual expander and the ORC. With the same NG volume flow, the daily round-trip efficiency of the configuration C2, C3 and C4 were increased up to 46.73%, 39.79% and 50.48% from 36.91% of the base configuration C1 respectively, while the daily power output was increased by 26.7%, 5.6% and 33.98% from 556.5KW of the base configuration C1 respectively. In addition, the daily exergy efficiency was 50.52%, 39.5%, 55.06% and 42.13% respectively for the configuration C1, C2, C3 and C4. Also, the results show that the contribution of the dual expander is far below that of the ORC cycle powered by solar energy.

Analysis of a combined trilateral cycle - organic Rankine cycle (TLC-ORC) system for waste heat recovery

A combined Trilateral Cycle-Organic Rankine Cycle (TLC-ORC) system for waste heat recovery is proposed in this paper in order to obtain a better matching performance between the heat source and working fluid. Working fluid selection including Cyclohexane, Toluene, Benzene and water for the high temperature cycle is analyzed based on thermodynamic model under different evaporating temperature of high temperature cycle and low temperature cycle. Results show that Toluene has the best performance among the studied four high temperature working fluid. The net power output, thermal efficiency and exergy efficiency increases with Tevap,HT or Tevap,LT increasing at any a high temperature working fluid. The maximum net power output 11.3 kW, thermal efficiency 24.2% and exergy efficiency 63.2% are achieved by Toluene at Tevap,HT =530 K and Tevap,LT =373 K at the same time. It is also found that evaporator 1 has the largest exergy destruction while condenser 1 has the smallest one among all the components. Meanwhile, the condenser 2 has the lowest exergy efficiency while condenser 1 has the highest one. These results show us the direction to optimize the system parameters to improve the total efficiency of the whole system.

Design of structure and optimization of organic Rankine cycle for heat recovery from gas turbine: The use of 4E, advanced exergy and advanced exergoeconomic analysis

This paper presents the evaluation and optimization of an organic Rankine cycle (ORC) approached from four different perspectives: (1) selecting the ORC Cycle; (2) selecting the working fluid in accordance with the thermodynamic properties and environmental impacts; (3) analyzing energy and exergoeconomic; and finally, (4) advanced exergy and advanced exergoeconomic. The working fluid is selected based on the thermal source temperature and the environmental impacts including the reduction of ozone depletion (ODP) and global warming potential (GWP). Then, the selected working fluids in different cycles are investigated in terms of the thermodynamic properties based on energy and exergy concepts. The parameters of the selected cycles (from the perspective of energy and exergy), including the temperature and pressure of the input working fluid of the turbine, the pinch and approach temperature, and so on, are optimized by a genetic algorithm. Two objective functions of price and exergy efficiency are selected as the objective functions for optimal cycles. The results of this study reveal that single-pressure and dual-pressure cycles with recuperator and the R123 working fluid have the highest power and the lowest cost. It is indicated that the net power generation of dual pressure cycle with recuperator, single pressure with recuperator, and dual pressure cycle with two working fluids are 2.2 kW, (R123: 2.31 kW, R600: 1.72 kW) and 2.26 kW, respectively. Also, the cost of generated electricity for dual pressure cycle with recuperator, single pressure cycle with recuperator, and dual pressure cycle with two working fluids are 14.59, (R123: 13.03, R600: 21.95) and 16.78 (Cent/kWh), respectively. In addition, the results show that the cycles of dual pressure with recuperator and single pressure with recuperator with R123 as a working fluid have the highest exergy efficiency. The advanced exergy analysis indicated that the HRSG and turbine components are important to be improved based on exergetic performance.

Multi-objective optimization and exergetic analysis of a low-grade waste heat recovery ORC application on a Brazilian FPSO

This paper presents an analysis of the application of an Organic Rankine cycle (ORC) for power generation of a Brazilian FPSO (Floating Product Storage Offload). The peculiarity of this analysis is the investigation of power generation using low-temperature waste heat sources. Low-grade sources represent a significant amount of heat rejected on the platform. The primary production in the platform processes was evaluated using ASPEN-HYSYS® software v.8.6. The main sources of low-temperature residual heat were preliminarily identified, and the highest potential for energy recovery was: the heat rejected in the intercoolers and aftercoolers of the compression processes in the Main Compression Unit and the CO2 Compression Unit. For the development of this study, a computational tool was elaborated in MATLAB® to evaluate the thermodynamic performance and to predict the design of the heat exchanger of the ORC. A multi-objective optimization was conducted to verify the ORC application at the established sources. The higher net power was obtained at Main Compression Unit heat recovery, operating with R245CB2 as working fluid. This application allows to generate up to 2063 kW with a heat transfer area of 2997 m2, providing a 23.6% increase in exergy efficiency of the system. The results of this study suggest that the application of ORC cycles on FPSO platforms for heat recovery from low-temperature sources allows an essential increase in the energy and exergetic efficiency of the production processes of the platform. Although the ORC doesn’t give a substantial increase in the supply of electricity, they contribute to less gas consumption in gas turbines. In this way, contributing to a significant reduction of GHG emissions.

Energy and Exergy Analyses of a Solid Oxide Fuel Cell-Gas Turbine-Organic Rankine Cycle Power Plant with Liquefied Natural Gas as Heat Sink.

An exergy analysis of a novel integrated power system is represented in this study. A Solid Oxide Fuel Cell (SOFC), which has been assisted with a Gas Turbine (GT) and Organic Rankine Cycle (ORC) by employing liquefied natural gas (LNG) as a heat sink in a combined power system is simulated and investigated. Initially in this paper, the integrated power system and the primary concepts of the simulation are described. Subsequently, results of the simulation, exergy analysis, and composite curves of heat exchangers are represented and discussed. The equations of the exergy efficiency and destruction for the main cycle’s units such as compressors, expanders, pumps, evaporators, condensers, reformers, and reactors are presented. According to the results, the highest exergy destruction is contributed to the SOFC reactor, despite its acceptable exergy efficiency which is equal to 75.7%. Moreover, the exergy efficiencies of the ORC cycle and the whole plant are determined to be 64.9% and 39.9%, respectively. It is worth noting that the rational efficiency of the integrated power system is 53.5%. Among all units, the exergy efficiency of the LNG pump is determined to be 11.7% the lowest exergy efficiency among the other investigated components, indicating a great potential for improvements.

Energy and exergy analyses of a combined cycle Kalina and organic Rankine cycles using waste heat

In current research, wasted heat from a reactivity controlled compression ignition (RCCI) engine provides driving energy for organic Rankine cycle (ORC) and Kalina cycle. After developing a numerical model for this system, the effects of some decision variables on the energy and exergy efficiencies are studied. The obtained results show that, by adding ORC and Kalina cycles, energy and exergy efficiency values are increased while, brake specific values of oxides of nitrogen (NOx) and carbon monoxide (CO) emissions are decrease in selected three engine operation modes (4, 9 and 23 bar indicated mean effective pressure) without changing in fuels consumption.

Energy and exergy analyses of a combined cycle Kalina and organic Rankine cycles using waste heat

In current research, wasted heat from a reactivity controlled compression ignition (RCCI) engine provides driving energy for organic Rankine cycle (ORC) and Kalina cycle. After developing a numerical model for this system, the effects of some decision variables on the energy and exergy efficiencies are studied. The obtained results show that, by adding ORC and Kalina cycles, energy and exergy efficiency values are increased while, brake specific values of oxides of nitrogen (NOx) and carbon monoxide (CO) emissions are decrease in selected three engine operation modes (4, 9 and 23 bar indicated mean effective pressure) without changing in fuels consumption.

Thermodynamic analysis of design and part-load operation of a novel waste heat recovery unit

Organic Rankine Cycle (ORC) thermodynamic optimization is of critical importance while developing new plants. Optimization procedures may be imed at the highest efficiency as well as cost or sizing minimization. Optimization process is generally carried out for plant nominal rating. At the same time, part-load operation has to be carefully considered in case of waste heat recovery from flue gases coming from internal combustion engines or gas turbines. Gas mass flow and temperature variations are specific to this application, significantly influencing ORC plant performance. Secure prediction of part-load operation is of particular importance for assessment of plant power output, providing stability and safety and utilizing proper control strategy. In this paper design and off-design cycle simulation model is proposed. Off-design performance of the ORC cycle recovering waste heat from gas turbine unit installed at gas compressor station is considered. Major factors affecting system performance are outlined.