Rankine Cycle Power Generation System Research Articles

Thermodynamic analysis of a cascade organic Rankine cycle power generation system driven by hybrid geothermal energy and liquefied natural gas

The combination of renewable energy and liquefied natural gas (LNG) cold energy can effectively improve energy utilization efficiency and achieve the goal of energy conservation and emission reduction, which is one of the important directions of future development. This work proposed a cascade organic Rankine cycle (ORC) driven by a geothermal heat source and an LNG heat sink. Seven organic fluids are chosen as candidates to form different working fluid pairs. The effects of the main design parameters on system performance are carried out through the thermodynamic analysis. Then, the optimal design conditions and fluid selection schemes are searched based on the single-objective optimization results. Finally, the exergy destruction study is conducted under the optimal design conditions and working fluid pair. Results showed that the cascade ORC system using the working fluid pair of R601/R290 had the highest exergy efficiency, which could reach 20.02%. At the same time, under the optimal design conditions, the secondary cycle condenser and LNG direct expansion brought high exergy destruction, which was respectively 29.3% and 25.8%, and followed by the two turbines in the cascade ORC system, which were 16.1%, 11.2% and 7.7%.

Review on the development of solar geothermal complementary power generation system

Nowadays, due to the burning of fossil energy has many negative impacts on the environment, people are looking for new sustainable energy sources that can replace fossil energy, and among them, geothermal energy and solar energy are more prominent, but the two energy sources alone have certain shortcomings, and since complementary solar geothermal energy systems compensate for some of the shortcomings of the two energy sources, much research has been done in this field. This essay summarizes the conclusion from those studies and identify the shortcomings. The largest losses in the system are always in the solar power system. The component with the highest losses may be the evaporator or the trough solar collectors with over 50%. In a solar-geothermal complementary power system, the two energy sources promote each other and the system is more efficient in the summer than in the winter. In a solar-geothermal Organic Rankine Cycle power generation system, Supercritical Organic Rankine Cycle can be a better option than subcritical Organic Rankine Cycle for solar geothermal hybrid power production and cost control. And hybrid power plants benefits will increase over time

Enhancing geothermal ORC power generation with SOFC: A comprehensive parametric study on thermodynamic performance

Geothermal energy is a promising renewable energy source due to its abundant global reserves. However, most geothermal resources are of low grade, severely restricting their power generation capacity and efficiency. In this study, the geothermal organic Rankine cycle power generation system is combined with a solid oxide fuel cell-gas turbine system to improve the overall power supply and heat utilization efficiency. The heat source and cycle temperature are upgraded using high-temperature solid oxide fuel cell waste gas, and the combined system’s efficiency is further improved through cascade heat utilization. Electrochemical-thermodynamic models are developed for the proposed system, and energy-exergy analysis is carried out. The effects of fuel cell current density, operating temperature and geothermal grade on the combined system’s performance are comprehensively analyzed. Compared to the standalone geothermal system, the energy efficiency and output power of the organic Rankine cycle increase by 8.11% and 7.95% respectively in the baseline case. Under the lowest geothermal temperature condition, the cycle output power is improved by 22.64%. The net power of the combined system can vary from 358 kW to 846 kW by adjusting the fuel cell current density from 1000 A m−2 to 8000 A m−2, demonstrating a flexible power supply capability. The optimal solid oxide fuel cell operating temperature is 1023.15 K, resulting in the highest system overall energy efficiency of 14.85%. The presented work provides essential guidelines for improving geothermal power generation performance and designing applicable combined systems.

An Exploration of the Application to Buildings of an Organic Rankine Cycle Power Generation System Driven by Solar Evacuated Glass Tubes

Abstract Solar technologies are an efficient means of addressing environmental pollution and climate change challenges. In this study, an organic Rankine cycle (ORC) system driven by solar evacuated glass tubes named solar water power generation (SWPG) system was experimentally investigated to explore the performance of the SWPG system in powering buildings. For ORC, a new mixture called TD-3 was introduced for the experiment after comparing the thermodynamic characteristics of five working fluids using refprop software. The solar radiation intensity was simulated for solar collectors to determine the best installation angle of the evacuated glass tubes to be 30 deg in Tianjin, China. The power generating efficiency was tested as high as 4.5% at 1:00 pm on July 15. The optimization of operating parameters and the modification of generating equipment contributed to the increase in power generation. The SWPG system could achieve an optimal power output when the system guaranteed a small superheat and no more than 3 °C subcooling using the TD-3. The transmission ratio between the generator and expander also impacted power generation that the ratio of 2:1 helped optimize the power generation.

Pressure drop analysis for organic Rankine cycle power generation system using low-grade heat sources

Pressure drops are unavoidable when testing or applying power generation systems. Similar to any other system, the organic Rankine cycle (ORC) power generation system also experiences pressure drops. This study focused on analyzing the pressure drop in the plate heat exchanger of the evaporator, the condenser, and the piping to minimize the occurrence of a decrease in the system performance. Three scenarios, organic fluids R141b (scenario 1), R245fa (scenario 2), and R227ea (scenario 3), are used to determine the working fluid with the lowest pressure drop at a heat source with a temperature of 95 °C. The analysis was performed with data from an ORC system that had been installed in a laboratory. Pressure drop calculation was divided into cold and hot sides because of the presence of two fluid flows in the evaporator and condenser. Each side was divided into two zones because of a phase change in the evaporator and the condenser. The pressure drops from the plate and through the port were calculated in the evaporator and the condenser, and the pressure drop in the piping system completed the analysis. The analysis results showed that the total pressure drop in the evaporator and condenser for scenarios 1, 2, and 3 are 0.268 bar, 0.173 bar, and 0.134 bar, respectively. In addition, the total pressure drop in the piping system is 0.069 bar, 0.075 bar, and 0.081 bar for scenarios 1, 2, and 3. Therefore, scenario 3 had the lowest total pressure drop than other scenarios.

A Study on the Thermal Flow of Waste Heat Recovery Unit (WHRU) for Ship’s Organic Rankine Cycle Power Generation System using CFD Method

A Study on the Thermal Flow of Waste Heat Recovery Unit (WHRU) for Ship’s Organic Rankine Cycle Power Generation System using CFD Method

Heat current method for integrated analysis and optimization of thermodynamic systems

Performance analysis and optimization of thermodynamic systems are important in increasing the efficiency of energy systems, but traditional approaches cannot meet the demand of high-efficiency performance analysis for complex thermodynamic systems. Based on the entransy theory, the recently developed heat current method, combined with the specialized simulation algorithm, offers a new and attractive solution for performance analysis of thermodynamic systems. This paper first presents the standardized heat current modeling strategy for thermodynamic systems, taking a Rankine cycle power generation system as an example to present the modeling procedure. Combining flow constraints and physical property constraints of working fluids, the framework of construction of a global system mathematical model is then presented. In the proposed framework, linear, nonlinear explicit, and nonlinear implicit system constraints can be separated. Consequently, the number of constraints needing to be solved iteratively is minimized. Based on this separation feature, this paper further proposes and presents a hierarchical and categorized algorithm that could reduce calculation time greatly and improve calculation stability significantly. Finally, a triple-pressure steam power generation system is investigated to demonstrate the advantages of the proposed hierarchical and categorized algorithm compared with conventional methods from the aspects of the time required for calculation and the initial values required.

Exergy Analysis of Two-Stage Organic Rankine Cycle Power Generation System.

Organic Rankine cycle (ORC) power generation is an effective way to convert medium and low temperature heat into high-grade electricity. In this paper, the subcritical saturated organic Rankine cycle system with a heat source temperature of 100~150 °C is studied with four different organic working fluids. The variations of the exergy efficiencies for the single-stage/two-stage systems, heaters, and condensers with the heat source temperature are analyzed. Based on the condition when the exergy efficiency is maximized for the two-stage system, the effects of the mass split ratio of the geothermal fluid flowing into the preheaters and the exergy efficiency of the heater are studied. The main conclusions include: The exergy efficiency of the two-stage system is affected by the evaporation temperatures of the organic working fluid in both the high temperature and low temperature cycles and has a maximum value. Under the same heat sink and heat source parameters, the exergy efficiency of the two-stage system is larger than that of the single-stage system. For example, when the heat source temperature is 130 °C, the exergy efficiency of the two-stage system is increased by 9.4% compared with the single-stage system. For the two-stage system, analysis of the four organic working fluids shows that R600a has the highest exergy efficiency, although R600a is only suitable for heat source temperature below 140 °C, while other working fluids can be used in systems with higher heat source temperatures. The mass split ratio of the fluid in the preheaters of the two-stage system depends on the working fluid and the heat source temperature. As the heat source temperature increases, the range of the split ratio becomes narrower, and the curves are in the shape of an isosceles triangle. Therefore, different working fluids are suitable for different heat source temperatures, and appropriate working fluid and split ratio should be determined based on the heat source parameters.

Effects of thermophysical and thermochemical recuperation on the performance of combined gas turbine and organic rankine cycle power generation system: Thermoeconomic comparison and multi-objective optimization

In this paper, effects on the performance of a combined gas turbine and organic Rankine cycle (GT/ORC) system of using thermophysical and thermochemical recuperation based on methane steam reforming (MSR) process is investigated from the viewpoint of thermoeconomics. For this purpose, three power generation systems consisting of simple GT/ORC, GT/ORC with thermophysical recuperators (TPR) and GT/ORC with thermophysical and thermochemical recuperators (TPCR) are proposed and compared thermodynamically and economically. In addition, the multi-objective optimization using genetic algorithm is conducted for the systems and the systems characteristics at the final optimum design points are compared. Resultsreveals that the thermodynamic, economic and environmental performance of all three proposed power generation systems are enhanced as the combustion temperature raises. In addition, the power generation system with TPR shows the best performance from the thermodynamic perspective with the 22.86% and 27.52% improvement in the exergy efficiency compared to the simple GT/ORC and GT/ORC with TPCR, respectively. However, under the operating thermodynamic conations obtained by the multi-objective optimization approach, the product cost associated with the system using TPCR is less than that of the other configurations.

Experimental analysis of organic Rankine cycle power generation system with radial inflow turbine and R245fa

Small turbines must operate at high rotational speeds to generate adequate output power. In this study, a radial inflow turbine using R245fa as the working fluid is miniaturised and is designed to have a rotational speed of 30,000 r/min. The organic Rankine cycle system is not simplified, and a preheater and a superheater are installed. The turbine is experimentally analysed in the organic Rankine cycle system. The experimental results show that with an increase in the inlet pressure, the turbine output power and system efficiency increase; moreover, the turbine efficiency first decreases and then increases slightly after the pressure exceeds 1.5 MPa. The turbine efficiency decreases first and then increases and attains the minimum value at an inlet temperature of 100°C–105°C. When the flow rate is 0.82 m3/s, the speed reaches its maximum value of 28,000 r/min, and a maximum output power of 17.37 kW is generated. The maximum efficiency of the turbine is 0.885 and that of the system is 0.1625. The experimental data and design parameters of the turbine provide a reference for further design optimization.

Experimental study of a micro-scale solar organic Rankine cycle system based on compound cylindrical Fresnel lens solar concentrator

In the present study, a micro-scale solar organic Rankine cycle power generation system was developed. The system comprises of a solar collection system based on compound cylindrical Fresnel lens concentrator and an organic Rankine cycle power generation system integrated with a scroll expander. YD320 and R245fa were used as the heat transfer fluid and the working fluid, respectively. The effects of the evaporation pressure, the degree of superheat, and the mass flow rate of the working fluid were analyzed to evaluate the solar collection efficiency, the electric power output, the thermal efficiency and exergy efficiency of the system. The results illustrate that both the increasing evaporation pressure and decreasing superheat degree have positive impacts on solar collection efficiency. The electric power increases as the evaporation pressure increases, while the thermal efficiency and the exergy efficiency decrease. However, the system overall efficiency decreases slowly due to the increase of solar collection efficiency. The electric power increases with the increment of the working fluid mass flow rate. The increasing mass flow rate has no visible impact on the thermal and exergy efficiencies of organic Rankine cycle subsystem, whereas a slightly increase of the thermal and exergy efficiencies of the integrated system. The electric power decreases with the increase of the superheat degree, whereas the thermal and the exergy efficiencies of the system increase. The system works more suitably with a higher degree of superheat for the small mass flow rate condition.

An artificial intelligent approach for the optimization of organic rankine cycle power generation systems

<span>The study on Organic Rankine Cycle (ORC) power generation system has gained significant popularity among researchers over the past decade, mainly due to the financial and environmental benefits that the system provides. A good maximum power point tracking (MPPT) mechanism can push the efficiency of an ORC to a higher rate. In this research, a Self-Adjusted Peak Search algorithm (SAPS) is proposed as the MPPT scheme of an ORC system. The SAPS has the ability to perform a relatively detailed search when the convergence reaches the near-optima peak without jeopardizing the speed of the overall convergence process. The SAPS is tested in a simulation to track for a moving maximum power pint (MPP) of an ORC system. Experiment results show that the SAPS outperformed several other well-established optimization algorithm in tracking the moving MPP, especially in term of the solution accuracies. It can thus be concluded that the proposed SAPS performs well as a mean of an MPPT scheme in an ORC system</span>

Thermal and Exergy Analysis of an Organic Rankine Cycle Power Generation System with Refrigerant R245fa

In this paper, the performance of an organic Rankine cycle (ORC) power generating system operating with refrigerant R245fa was investigated when heat source temperature was below 200 °C. It was found the system thermal efficiency increased but the exergy efficiency of the evaporator decreased with the increase of the heat source temperature. It was also obtained that the exergy efficiency of the evaporator could reach70% when the heat source temperature was 80 °C, which was high enough to prove that the transformation efficiency between the waste heat and the electricity power was ideal. In the simulation model, the area of different parts of the heat exchanger were considered to be varied, flow rate of the waste heat and working medium, the system thermal and exergy efficiency of the evaporator were respectively calculated, the different parameter change regarding the performance influences of the ORC system were simulated. The results can be considered as a reference to research on the design of ORC power generating systems and heat exchangers.

Proposal for Development of a Novel 2kWp Solar Powered Rankine Cycle Power Generation System

Proposal for Development of a Novel 2kWp Solar Powered Rankine Cycle Power Generation System

Performance analysis of organic Rankine cycle power generation system for intercooled cycle gas turbine

Intercooled cycle gas turbine has great potential in improving the output power because of the low energy consumption of high-pressure compressor. In order to more efficiently recovery and utilize the waste heat of the intercooled system, an organic Rankine cycle power generation system is developed to replace the traditional intercooled system in this study. Considering the effects of different kinds of organic working fluids, the thermodynamic performance of organic Rankine cycle power generation system is investigated in detail. On this basis, the sensitivity analyses of some key parameters are conducted to study the operating improvements of organic Rankine cycle power generation system. The results indicate that the integration of organic Rankine cycle and intercooled cycle gas turbine not only can be used for waste heat power generation but also increases the output power and efficiency of intercooled cycle gas turbine by selecting the organic working fluids of n-butane (R600), n-pentane (R601), toluene, and n-heptane. And compared to the others, organic Rankine cycle power generation system with toluene exhibits the best performance. The maximum enhancements of output power and thermal efficiency are 6.08% and 2.14%, respectively. Moreover, it is also concluded that both ambient temperatures and intercooled cycle gas turbine operating conditions are very important factors affecting the operating performances of organic Rankine cycle power generation system.

Optimization of heat exchanger size of a 10 kW organic Rankine cycle system

Most of the heat exchangers design in a conventional Rankine cycle power generation system is based on the assumption of a fixed temperature difference between the heat source and the inlet temperature of the expander. Since the temperature difference between the evaporator and the condenser is high, the effect of this estimated temperature difference on the system performance is not important. However, for an ORC system, since the temperature of heat source is low, a minor difference on the temperature estimation will affect the system thermal efficiency significantly. This study provides an experimental measurement of a practical 10 kW organic Rankine cycle system using HFC-245fa as working fluid subject to the influence of heat exchangers with different NTU. The effect of NTU of evaporator on heat transfer rate, network output, system thermal efficiency and investment payback years were studied. The results show that with increasing NTU of evaporator leads to the increase of total heat transfer rate, work output and system thermal efficiency. However, since the system installation cost increases with increasing heat exchangers NTU, in combining with the increase of power output, an optimal heat exchanger NTU for the shortest investment payback years is found.

A cascade organic Rankine cycle power generation system using hybrid solar energy and liquefied natural gas

A cascade organic Rankine cycle (ORC) system utilizing solar energy and liquefied natural gas (LNG) for thermal power generation is proposed. Energy from solar collectors drives the evaporation of working fluid in the top cycle (I). The heat released by cycle I facilitates the evaporation of working fluid in the bottom cycle (II). LNG is the cold source of cycle II. The system is optimized with respect to a new index, i.e., the equivalent efficiency, which denotes the ratio of the extra electricity produced by adding collectors and the received solar irradiation. Its advantages are clarified in comparison with existing indices like thermal efficiency, cold energy efficiency, and exergetic efficiency. The effects of working fluids on the system performance are investigated. Flat plate collectors (FPC) and evacuated tube collectors (ETC) are exemplified. It is shown that the equivalent efficiency is the most suitable index to embody the effectiveness of combination of solar collectors and LNG. A maximum equivalent efficiency of 5.99% can be obtained on the use of isopentane/R125 and ETC. The volume ratio for each expander in the cascade ORC is much smaller than that in single-stage ORC, thereby resulting in easier design and manufacture of the expanders.

Selection of organic Rankine cycle working fluids in the low-temperature waste heat utilization

In the current study, simulations based on the engineering equation solver (EES) software are performed to determine the suitable working fluid for the simple organic Rankine cycle system in different temperature ranges. Under the condition of various temperatures and a constant thermal power of the flue gas, the influence of different organic working fluids on the efficiency of the subcritical organic Rankine cycle power generation system is studied, and its efficiency and other parameters are compared with those of the regenerator system. It is shown that the efficiency of the subcritical organic Rankine cycle system is the best when the parameters of the working fluid in the expander inlet are in the saturation state. And for the organic Rankine cycle, the R245fa is better than other working fluids and the efficiency of the system reaches up to 10.2% when the flammability, the toxicity, the ozone depletion, the greenhouse effect and other factors of the working fluids are considered. The R601a working fluid can be used for the high-temperature heat source, however, because of its high flammability, new working fluid should be investigated. Under the same condition, the efficiency of the organic Rankine cycle power generation system with an internal heat exchanger is higher than that of the simple system without the internal heat exchanger, but the efficiency is related to the properties of the working fluid and the temperature of the heat source.

Experimental verification of a rolling-piston expander that applied for low-temperature Organic Rankine Cycle

A kilowatt-sized rolling-piston expander is proposed for low-temperature Organic Rankine Cycle power generation system. The main purpose of this paper is to conduct a dynamic test of the proposed expander. A low-temperature ORC system using R245fa as working fluid is established for the performance evaluation of the proposed expander. In the experimental system, a hot-water boiler is applied to supply a low temperature heat source. A variety of working conditions are achieved by varying the feed pump capacity and the generator load. In these tests, experimental data such as the R245fa flow rate, the temperature of expander inlet and outlet, the pressure of expander inlet and outlet, the output power and rotation speed of the expander are measured and analyzed. The experimental results show that the proposed expander normally runs between 350rpm and 800rpm with a maximum output power of 0.35kW when the heat source temperature is below 90°C. Meanwhile, a maximum expander isentropic efficiency of 43.3% and a stable Rankine cycle efficiency of 5% are also obtained.