Power Output Of Organic Rankine Cycle Research Articles

Dynamic power generation performance of enhanced geothermal system during life cycle in gonghe basin, china

Enhanced geothermal systems (EGS) can efficiently generate electricity from hot dry rock (HDR), the temperature of which will decrease during its life cycle. In this paper, the organic Rankine Cycle (ORC) experimental device and dynamic model are established to investigate the dynamic power generation performance with heat source temperature decrease, and the relative installed capacity ratio is defined to investigate the optimal mass flow rate of geothermal fluid. The results show that the temperature decrease of the heat source is detrimental to the power generation performance and energy efficiency of the system, but the isentropic efficiency of the expander increases with the decrease of the heat source temperature. The installed capacity and net power output of ORC is proportional to the mass flow rate of the geothermal fluid, but the life cycle of the EGS is inversely proportional to this. There is a mass flow rate that maximize the total power generation over the life cycle while having a high relative installed capacity ratio.

Combined heating and power generation performance of thermal station for electricity self-sufficient characterized by two-stage heat transfer

As the living standard improves, the demand for space heating has been increasing, leading to global warming and environmental problems. The thermal station consumes a large amount of electric power. A novel electricity self-sufficient thermal station based on the organic Rankine cycle (ORC) is proposed using the primary heating network supply water as the heat source and the secondary heating network return water as the heat sink. The mathematical model is established based on the laws of thermodynamics, and the performance of combine heating and power is numerically analyzed under the design condition. The results show that the power generation performance is directly proportional to the primary heating network supply water temperature. However, the power output of ORC is at the expense of reducing the same amount of heating capacity of secondary heating network. The novel self-sufficient thermal station in electric power lowers the irreversible loss of heat transfer between the primary and secondary heating networks to construct cascade heat transfer, therefore recovering the potential power generation being ignored and realizing the self-sufficient supply of electric power.

Evaluating the thermal efficiency and net power output of ORC for three wet fluids

Low-grade heat can be successfully recovered from waste energy sources for power production by an organic Rankine cycle (ORC). In this work, reheat ORC has been studied with three different wet organic fluids. The performance of R1270, R152a and Cyclopropane has been modelled in an ORC operated by a source of heat of 413.15K. The reheat ORC model contains economizer, evaporator, superheater, reheater, two turbine, pump and condensers. With variable turbine inlet temperature and reheat pressure, the net power output and thermal efficiency have been estimated. The results show that there exists an optimum temperature at the turbine inlet maximizing . The increase of reheat pressure gives only a marginal growth in the cycle efficiency, but it rises the with about 16.88 %, 16.26 % and 13.23 % for R1270, R152a and cyclopropane respectively.

Energy and exergy analyses of a hybrid system integrating solar-driven organic Rankine cycle, multi-effect distillation, and reverse osmosis desalination systems

This study analyzes the energy and exergy of a novel arrangement of a solar driven organic Rankine cycle (ORC), two reverse osmosis (RO) desalination systems, and a multi-effect distillation (MED) desalination unit. The ORC power is used as power sources of the high-pressure pump of the RO unit and pumping system of the MED unit. Also, the waste heat of the ORC condenser is utilized as the heat impetus of the MED unit. The results demonstrate that increasing the solar radiation intensity and collector module length leads to increase in the ORC power output, produced freshwater, and total exergy destruction. Increasing the volumetric flow rate of the collector reduces the temperature of the output fluid from the solar collector field, but the mass flow rate is increased, resulting in the highest net output power from the ORC system at a volume flow rate of 11000 lit/min. The exergy analysis reveals that the solar collector, as the system heat source, has the highest total exergy destruction share of 65% in the system. Also, among the organic fluids, toluene, n-decane, n-nonane and n-octane have the highest ORC power, the highest amount of produced freshwater, and the least exergy destruction for ORC, respectively.

Direct integration of an organic Rankine cycle into an internal combustion engine cooling system for comprehensive and simplified waste heat recovery

Cogeneration systems based on internal combustion engines (ICE) provide decent efficiency and flexibility. In order to further improve the efficiency, organic Rankine cycle (ORC) can be used to convert high temperature (waste) heat from flue gas to electricity. There is a large amount of heat in jacket cooling at lower temperatures for which there is often no demand so it has to be rejected into the ambient. Previous systems trying to utilise this heat in the ORC cycle end up as too complex and expensive. This study introduces an innovative jacket cooling method. In the cooling system of an ICE, instead of typical water or oil-based heat transfer fluids, the working fluid of an ORC is used as the engine coolant, recovering the low-potential heat. Preheated organic fluid is then directly used in the bottoming ORC with further heat input from the flue gas. This concept allows utilising both low and high potential heat from the cooling of the ICE and from the flue gas recovery, while omitting the intermediate heat-transfer circuits commonly found in ORC waste heat recovery applications. Presented thermodynamic analysis shows a strong dependency of the ORC utilisation efficiency on cooling fluid allowed pressure in the ICE jacket and on the heat flow ratio between the coolant and the flue gas of the ICE. A baseline study with a specific 83 kWe ICE with the novel configuration provides an improvement of nearly 10 kW in comparison with 7 kW of an ORC utilising only flue gas. More general parametric analysis has shown the potential of the ORC power output improvement by more than 60% for specific ICE types and higher pressures and temperatures in the engine cooling circuit. In a cogeneration regime, these benefits in electrical power output come at the cost of a very slight decrease in overall efficiency.

Thermo-economic analysis and optimization of ICE-ORC systems based on a splitter regulation

The traditional Organic Rankine Cycle (ORC) system recovering waste heat from Internal Combustion Engine (ICE) ignores the low-grade thermal energy of jacket cooling water. In this paper, a new ICE-ORC configuration is proposed to maximize the ORC net power output for different ICE rated power outputs. The comparative analysis between the ICE-ORC system based on a splitter regulation and two traditional ICE-ORCs is presented with ten different working fluids. The computational results demonstrate whether it is necessary to recover jacket cooling water waste heat with different working fluids, and cascade utilization of exhaust gas and jacket water waste heat by splitter regulation is validated with different Caterpillar series of ICE. Moreover, using pentane as working fluid has the best performance which ORC power output is 556 kW for all the three different ICE-ORC bottoming cycles and ten working fluids, and the ICE-ORC bottoming cycle efficiency is increased by 17% compared with single ICE generator set. This research provides information to increase the efficiency and power output of ICE-ORC configuration modification and determines the direction of further improvement.

Experimental investigation of an Organic Rankine cycle system using an oil-free scroll expander for low grade heat recovery

ABSTRACT Organic Rankine cycle (ORC) has become a promising energy harvesting technique to recover thermal energy from low-grade heat sources. In this study, a lab-scale ORC system has been designed, constructed, and tested to investigate the potential of utilizing the heat from hot water, which is used to simulate the jacket water of internal combustion engines. The ORC system employs an oil-free scroll expander with R245fa as working fluid. A wide range of operating conditions has been studied by adjusting the pump frequency, the load and the mass flow rate of cooling water. Effect of the superheat degree at the expander inlet was investigated and the results showed that the ORC system presented better performance with superheat of 0. It is concluded that the system should be controlled to maintain the least possible superheat degree to obtain higher power output and better efficiency. The maximum electric power output and the maximum thermal efficiency are 0.61 kW and 4.09%, respectively, when the heat source is 96.8°C. The power consumed by the pump ranges from 0.07 to 0.18 kW, which accounts for 22 to 39% of the power output of ORC.

Thermo-economic performance evaluation and multi-objective optimization of a screw expander-based cascade Rankine cycle integrated with parabolic trough solar collector

In the present study, a cascade power generation system, consisting of a partial evaporation Rankine cycle (PERC), and an organic Rankine cycle (ORC) with a parabolic trough solar collector (PTSC) as the driver coupled with a storage tank, has been studied and optimized from energy and exergoeconomic viewpoints. Instead of using conventional steam turbine, a screw expander has been utilized in PERC, in order to facilitate coupling the PERC with the PTSC and the storage tank, operating near the recommended temperature of 300 °C, as well as to avoid producing superheated vapor in the upper Rankine cycle. This configuration is appropriate specifically because of the pressure limit at the inlet of expander (4 MPa), corresponding to a saturation temperature of 250 °C for steam. With toluene as the selected organic fluid among 4 candidates, parametric analysis was performed to investigate the effect of variations in solar radiation intensity, collector aperture area, PERC evaporation and condensation temperatures, and expander inlet steam quality on the thermoeconomic performance of the system, followed by a tri-objective optimization using genetic algorithm considering net power output, exergy efficiency and total cost rate as objective functions. The obtained results show that for the optimum design point, the studied solar power plant with aperture area of 5540 m2 and storage tank volume of 184.7 m3 can produce 782 kW of power with exergy efficiency of 18.61% and total cost rate of 228 $·h−1. The optimum design case indicates an improvement in net power output, exergy efficiency, and unit cost of electricity by 65%, 2.9%, and 27.26%, respectively, compared to the base case. Furthermore, at the optimal point, the power output of ORC (440.6 kW) is higher than that of PERC (349.2 kW). However, the unit cost of electricity production is lower for PERC (22.82 $·GJ−1) compared to ORC (37.19 $·GJ−1).

A Hot Water Split-Flow Dual-Pressure Strategy to Improve System Performance for Organic Rankine Cycle

The organic Rankine cycle (ORC) is widely used to recover industrial waste heat. For an ORC system using industrial waste hot water as a heat source, a novel hot water split-flow dual-pressure organic Rankine cycle (SFD-ORC) system is developed to improve the performance of the ORC. The maximum net power output was selected to compare three ORC systems, including basic ORC (B-ORC), conventional dual-pressure ORC (CD-ORC) and SFD-ORC. A genetic algorithm (GA) was used to optimize the parameters to search the maximum net power output of ORCs. The maximum net output power was taken as the standard of performance evaluation. The results show that, under the same hot water inlet temperature condition, the optimal hot water outlet temperature of B-ORC is much higher than that of CD-ORC and SFD-ORC, which indicates that less thermal energy could be utilized to convert to power in B-ORC. The optimal hot water temperature at the outlet of evaporator 1 in SFD-ORC is higher than that in CD-ORC, which means SFD-ORC could make more efficient use of the high-grade thermal energy of hot water. The SFD-ORC could obtain the highest net output power under the optimal parameter conditions, followed by the CD-ORC system, while the B-ORC has the lowest net output power. Moreover, with the increase in the hot water inlet temperature, the advantage of SFD-ORC becomes increasingly obvious. When the hot water inlet temperature is 90 °C, the net output power of SFD-ORC at is 6.22% higher than that of CD-ORC. The net output power of SFD-ORC at 130 °C increases to 9.7% higher than that of CD-ORC. The SFD-ORC presents better system performance and has great engineering application potential.

Optimization of an organic Rankine cycle constrained by the application of compact heat exchangers

Recovering waste heat from the exhaust gases of heavy-duty diesel truck engines by using the organic Rankine cycle can reduce both fuel consumption and greenhouse gas emissions. The design of such systems is constrained by the space available for installation; thus, an optimization procedure is required. In this research work, a two-objective optimization, based on the maximization of power output and minimization of the total heat exchanger surface area, is implemented in the Engineering Equation Solver software package. Application of the developed procedure is illustrated in a case with an exhaust gas temperature of 394.2 °C and mass flow rate of 0.306 kg/s. Configurations both with and without a recuperator are analyzed, and four working fluids (water, ethanol, toluene, and hexamethyldisiloxane) are compared. Of these fluids, ethanol could be recommended as the best when considering the organic Rankine cycle power output and the total area/volume of heat exchangers. For a total surface area of 10 m2 in the case without the recuperator, the power output values for ethanol, water, and toluene are 17.6 kW, 17.2 kW, and 15.8 kW, respectively; with the recuperator, the power output is slightly higher, but the total area of heat exchangers is considerably larger. Again, the best working fluid is ethanol: for a total surface area of heat exchangers of 24 m2, the power output values for ethanol, toluene, and hexamethyldisiloxane are 18 kW, 17.1 kW, and 15.8 kW, respectively. The presented procedure is useful both for the conceptual design of a complete waste heat recovery unit and for the optimization of all heat exchangers.

Comparative Analysis of Small-Scale Organic Rankine Cycle Systems for Solar Energy Utilisation

Small-scale organic Rankine cycle (ORC) systems driven by solar energy are compared in this paper, which aims to explore the potential of power generation for domestic utilisation. A solar thermal collector was used as the heat source for a hot water storage tank. Thermal performance was then evaluated in terms of both the conventional ORC and an ORC using thermal driven pump (TDP). It is established that the solar ORC using TDP has a superior performance to the conventional ORC under most working conditions. Results demonstrate that power output of the ORC using TDP ranges from 72 W to 82 W with the increase of evaporating temperature, which shows an improvement of up to 3.3% at a 100 °C evaporating temperature when compared with the power output of the conventional ORC. Energy and exergy efficiencies of the ORC using TDP increase from 11.3% to 12.6% and from 45.8% to 51.3% when the evaporating temperature increases from 75 °C to 100 °C. The efficiency of the ORC using TDP is improved by up to 3.27%. Additionally, the exergy destruction using TDP can be reduced in the evaporator and condenser. The highest exergy efficiency in the evaporator is 96.9%, an improvement of 62% in comparison with that of the conventional ORC, i.e., 59.9%. Thus, the small-scale solar ORC system using TDP is more promising for household application.

Technoeconomic analysis of internal combustion engine – organic Rankine cycle cogeneration systems in energy-intensive buildings

Abstract Organic Rankine cycle (ORC) systems are a promising technology for converting heat to useful power, especially in combined heat and power (CHP) applications with significant quantities of surplus heat that would otherwise be wasted. Beyond the technical performance of these systems, their economic feasibility is crucially important for their wider deployment. In this study, a technoeconomic optimisation of CHP systems is performed in which ORC engines convert heat recovered from internal combustion engines (ICEs), and specifically from both the ICE hot-water output and exhaust-gas stream. The overall aim is to evaluate the impact of the ORC power output and of the components’ design and capital cost on the financial viability of a relevant project, while evaluating a range of candidate working fluids. Results indicate that ORC designs optimised for maximum power output correspond to higher specific investment cost (SIC), with the best performing fluids achieving a SIC of £2100 per kW. In contrast, optimisation for minimum SIC returns values as low as £1700 per kW, or 20% lower. For systems designed and optimised for maximum power, a large fraction of jacket water heat is recovered, while for minimum SIC the utilisation drops to minimise the size and cost of the heat exchangers. The best-performing ORC designs for minimum SIC have discounted payback periods (DPPs) of 4 – 5 years, while those optimised for power output have DPPs of 6 – 7 years, however, the net present values (NPVs) of the latter designs are up to 27% higher than the former. Therefore, there is a trade-off to consider over the project life between high-capacity ORC engines with a high SIC and longer DPP, and designs with minimal SIC but lower power output, shorter DPP and lower NPV. The effect of increasing the amount of hot water required by the building is also analysed, and the ORC engine is shown to be sensitive to this factor for some working fluids.

Thermo-economic analysis of using an organic Rankine cycle for heat recovery from both the cell stack and reformer in a PEMFC for power generation

Distributed power generation is gaining attention as a solution for the transmission loss and site selection in centralized power generation. Polymer-electrolyte membrane fuel cells (PEMFCs) are suitable as a distributed power source for residential areas because of their high efficiency and low environmental impact. This study proposes a combined power generation system for recovering waste heat from both the cell stack and the reformer of a PEMFC by applying an organic Rankine cycle (ORC). The best working fluid with the highest ORC power output (i.e., the highest combined system efficiency) was identified through a parametric study of different working fluids. An economic analysis was also performed for different working fluids, waste heat sources, and types of system operation. The results show that the installation cost of the ORC can be recovered within the fuel cell's lifetime in all design cases. Greater cumulative profit can be generated by maintaining the same power output as the stand-alone PEMFC system for greater efficiency than when increasing the power output to sell surplus power. The results demonstrate that the optimal heat recovery from the PEMFC system is both thermodynamically and economically beneficial.

Performance analysis of an Organic Rankine Cycle system with superheater utilizing exhaust gas of a turbofan engine

Waste heat recovery is recognized as one of the methods to overcome this energy saving issue. In this paper, the Organic Rankine Cycle (ORC) system has been introduced for the waste heat recovery. The main objective of the study is to convert the unused heat into useful power, which could reduce the fuel consumption and also minimize the harmful exhaust transmission. A thermodynamic model of the waste heat recovery cycle is developed and validated. The eventual results depict a reasonable agreement for the ORC power output and its thermal performance, especially at higher turbine inlet pressure. Consequently, this ORC model is then connected to a turbofan engine. The performance analysis of the engine depicts that the lowest Thrust Specific Fuel Consumption (TSFC) is at 0.68 lbm/lbf.h with the thrust force of 7000 lbf, thus lower than the base cycle without ORC as waste heat recovery.

Thermodynamic optimisation of a high-electrical efficiency integrated internal combustion engine – Organic Rankine cycle combined heat and power system

Organic Rankine cycle (ORC) engines are suitable for heat recovery from internal combustion engines (ICE) for the purpose of secondary power generation in combined heat and power (CHP) systems. However, trade-offs must be considered between ICE and ORC engine performance in such integrated solutions. The ICE design and operational characteristics influence its own performance, along with the exhaust-gas conditions available as heat source to the ORC engine, impacting ORC design and performance, while the heat-recovery heat exchanger (ORC evaporator) will affect the ICE operation. In this paper, an integrated ICE-ORC CHP whole-system optimisation framework is presented. This differs from other efforts in that we develop and apply a fully-integrated ICE-ORC CHP optimisation framework, considering the design and operation of both the ICE and ORC engines simultaneously within the combined system, to optimise the overall system performance. A dynamic ICE model is developed and validated, along with a steady-state model of subcritical recuperative ORC engines. Both naturally aspirated and turbocharged ICEs are considered, of two different sizes/capacities. Nine substances (covering low-GWP refrigerants and hydrocarbons) are investigated as potential ORC working fluids. The integrated ICE-ORC CHP system is optimised for either maximum total power output, or minimum fuel consumption. Results highlight that by optimising the complete integrated ICE-ORC CHP system simultaneously, the total power output increases by up to 30% in comparison to a nominal system design. In the integrated CHP system, the ICE power output is slightly lower than that obtained for optimal standalone ICE application, as the exhaust-gas temperature increases to promote the bottoming ORC engine performance, whose power increases by 7%. The ORC power output achieved accounts for up to 15% of the total power generated by the integrated system, increasing the system efficiency by up to 11%. When only power optimisation is performed, the specific fuel consumption increases, highlighting that high-power output comes at the cost of higher fuel consumption. In contrast, when specific fuel consumption is used as the objective function (minimised), fuel consumption drops by up to 17%, thereby significantly reducing the operating fuel costs. This study proves that by taking a holistic approach to whole-system ICE-ORC CHP design and operation optimisation, more power can be generated efficiently, with a lower fuel consumption. The findings are relevant to ICE and ORC manufacturers, integrators and installers, since it informs component design, system integration and operation decisions.

Thermodynamic Analysis of ORC and Its Application for Waste Heat Recovery

The analysis and optimization of an organic Rankine cycle (ORC) used as a bottoming cycle in the Brayton/ORC and steam Rankine/ORC combined cycle configurations is the main focus of this study. The results show that CO2 and air are the best working fluids for the topping (Brayton) cycle. Depending on the exhaust temperature of the topping cycle, Iso-butane, R11 and ethanol are the preferred working fluids for the bottoming (ORC) cycle, resulting in the highest efficiency of the combined cycle. Results of the techno-economic study show that combined Brayton/ORC cycle has significantly lower total capital investment and levelized cost of electricity (LCOE) compared to the regenerative Brayton cycle. An analysis of a combined steam Rankine/ORC cycle was performed to determine the increase in power output that would be achieved by adding a bottoming ORC to the utility-scale steam Rankine cycle, and determine the effect of ambient conditions (heat sink temperature) on power increase. For the selected power plant location, the large difference between the winter and summer temperatures has a considerable effect on the ORC power output, which varies by more than 60% from winter to summer.

Optimization of an organic Rankine cycle as bottoming cycle of a 1 kWe GENSET for residential applications

A novel 1 kWe GENSET featuring an internal combustion engine (ICE) operating on Spark-Assisted Compression Ignition (SACI) combustion of natural gas is under development to achieve an overall power generation efficiency of 40%. The aim is to create an efficient electricity generation system that can provide the energy necessary for light residential use at high thermal efficiency and low user cost. In order to achieve such power generation efficiency for a small-scale energy/heat production unit, an organic Rankine cycle (ORC) has been proposed as a bottoming cycle to recover heat from the exhaust of the small internal combustion engine. The ORC has been optimized to operate with a heat source inlet temperature of 400 ºC, which is necessary for use with the integrated catalytic converter evaporator proposed for the system. By means of a thermodynamic cycle model, the final cycle architecture has been identified along with the design of a novel two-stage scroll expander integrated with working fluid pump. Results showed that by employing R1233zd(E) as the working fluid, the theoretical ORC thermal efficiency is as high as 14.79% with a net ORC power output of 148.6 W.

Integration of Organic Rankine Cycle with Lignite Flue Gas Pre-drying for Waste Heat and Water Recovery from Dryer Exhaust Gas: Thermodynamic and Economic Analysis

Abstract The flue gas pre-drying of lignite produces a moisture rich dryer exhaust gas which can be further cooled to recover the waste heat and water vapor. An environmental friendly power system is investigated in the present work, which integrates the lignite flue gas pre-drying system with an organic Rankine cycle (ORC) to utilize the waste heat to generate power and capture the condensed water. Simulation models of the integrated system are developed, incorporating thermodynamic and economic evaluation indicators. The optimal energy and exergy efficiencies of the ORC system are calculated to be 3.10% and 24.57%, respectively, for an evaporation temperature of 51 °C when R245fa is used as the working fluid. Accordingly, the ORC power output is 3.61 MW and the absolute plant efficiency improvement is 0.27% points. Moreover, 55.17% of the water vapor can be recovered. The economic performance significantly relies on the specific investment cost of ORC and the electricity selling price. Typically, the break-even points of the specific investment cost are 2300 €/kW and 3700 €/kW when electricity selling prices are 0.05 €/kWh and 0.08 €/kWh, respectively.

Off-design performance analysis of organic Rankine cycle using real operation data from a heat source plant

There has been increasing demand for cogeneration power plants, which provides high energy utilization. Research on upgrading power plant performance is also being actively pursued. The organic Rankine cycle (ORC) can operate with mid- and low-temperature heat sources and is suitable for enhancing performance of existing power plants. In this study, an off-design analysis model for the ORC was developed, which is driven by waste heat or residual heat from a combined cycle cogeneration plant. The applied heat sources are the exhaust gas from the heat recovery steam generator (Case 1) and waste heat from a heat storage unit (Case 2). Optimal design points of the ORC were selected based on the design heat source condition of each case. Then, the available ORC power output for each case was predicted using actual long-term plant operation data and a validated off-design analysis model. The ORC capacity of Case 2 was almost two times larger than that of Case 1. The predicted average electricity generation of both cases was less than the design output. The results of this paper reveal the importance of both the prediction of electricity generation using actual plant operation data and the need for optimal ORC system sizing.

Investigation on the fluid selection and evaporation parametric optimization for sub- and supercritical organic Rankine cycle

ORC (Organic Rankine cycle) is a promising technology for recovery of low-grade heat. In the previous studies, different conclusions for working fluid selection criterion can be found and relatively few work for supercritical ORC has been made. Therefore, this paper investigates the net power output of ORC utilizing waste flue gas with various evaporation parameters and 12 working fluids in both subcritical and supercritical condition. The results indicate that the variation of the net power output with evaporation pressure is related to the heat source temperature, and the maximum net power output appears at supercritical condition rather than subcritical condition if the heat source temperature is about 25–40 °C higher than the working fluid's critical temperature. Besides, the parametric optimization is performed, and the most suitable working fluids for various flue gas inlet temperature of 150–250 °C have been found. It can be found that the most suitable working fluids have a critical temperature about 40–65 °C lower than flue gas inlet temperature, and the optimum condition is always supercritical. For subcritical ORC, it is better to adopt the working fluids with low evaporation latent heat and high liquid specific heat to pursue a high net power output.