Design Of Organic Rankine Cycle Research Articles

Optimum Design of Shell and Tube Heat Exchangers using Modified Kinetic Gas Molecule Optimizer for the use of Low Temperature in Organic Rankine Cycles

Shell and Tube Heat Exchangers (STHEs) plays a crucial role in an effective design of Organic Rankine Cycle (ORC) power plants.The main aim of this research work is to design a cost-effective ORC in order to exploit low to medium temperature geothermal fluid or low grade industrial waste heat. In this research work, modified Kinetic Gas Molecule Optimization (KGMO) algorithm was developed forfinding the optimized parameter settings of the power plant. In modified KGMO algorithm, feedback learning stage was included for improving the fitness of individual worst particles. In addition, the proposed optimization algorithm was tested on two dissimilar fluids such asR245fa and R134a in order to show the effectiveness of proposed scheme. The experimental investigation showed that the proposed scheme effectively improved the heat exchanger performance as related to the existing schemes.The enhancement factor of proposed scheme was 2.8063 for R245fa fluid and 1.9346 for R134a fluid, which was better compared to the existing schemes; KGMO and Bell-Delaware method.

Toward the Integrated Design of Organic Rankine Cycle Power Plants: A Method for the Simultaneous Optimization of Working Fluid, Thermodynamic Cycle, and Turbine

Abstract The conventional design of organic Rankine cycle (ORC) power systems starts with the selection of the working fluid and the subsequent optimization of the corresponding thermodynamic cycle. More recently, systematic methods have been proposed integrating the selection of the working fluid into the optimization of the thermodynamic cycle. However, in both cases, the turbine is designed subsequently. This procedure can lead to a suboptimal design, especially in the case of mini- and small-scale ORC systems, since the preselected combination of working fluid and operating conditions may lead to infeasible turbine designs. The resulting iterative design procedure may end in conservative solutions after multiple trial-and-error attempts due to the strong interdependence of the many design variables and constraints involved. In this work, we therefore present a new design and optimization method integrating working fluid selection, thermodynamic cycle design, and preliminary turbine design. To this purpose, our recent 1-stage continuous-molecular targeting (CoMT)-computer-aided molecular design (CAMD) method for the integrated design of the ORC process and working fluid is expanded by a turbine meanline design procedure. Thereby, the search space of the optimization is bounded to regions where the design of the turbine is feasible. The resulting method has been tested for the design of a small-scale high-temperature ORC unit adopting a radial-inflow turbo-expander. The results confirm the potential of the proposed method over the conventional iterative design practice for the design of small-scale ORC turbogenerators.

Design of Organic Rankine Cycle (ORC) Power Plant Systems by Using Flat-Plate Solar Collector

Electrical energy is the most used energy today in daily activities and industry is increasing. In rural areas that do not have electricity still exists in Indonesia. In this study, it can be used as an alternative power plant that can be used by the countryside. The system used in this study is the new types of power plants, namely the Organic Rankine Cycle (ORC) system. In connection with the problems stated above, through this research, an effort will be made to design an ORC power generation system. The ORC power plant system that will be designed utilizes solar energy sources and working fluids. Solar power is used to heat the heating fluid in the form of water. This heating water is used to vaporize the working fluid which can evaporate at low temperatures and high pressures. So that the working fluid gas can be used to rotate the turbine shaft and produce electrical energy through a generator. Simulation is done using energy system software. In addition to simulations, examples of manual calculations are also needed for validation. The simulation results of the ORC generating system design on the two working fluids produce the greatest power at the pump outlet pressure of 6 bar with Ẇnet of 13.61 kW and the smallest power is generated by the pump outlet pressure of 5.03kW. While the design simulation of the ORC generating system produces power close to 10 kW at the pump outlet pressure of 5 bars with 11.38 kW. The flat collector solar-plate system gets the energy that is useful for collectors of 191.92 W and an efficiency of 9.8%.

Features Design of Organic Rankine Cycle

This article discusses the design features of plants operating on the principle of organic Rankine cycle. Firstly, the choice of organic Rankine cycle as the most effective technology for utilization of low-potential heat by comparison and analysis with other technologies is justified. Secondly, the technique of selection and calculation of the installations working on the principle of an organic Rankine cycle, taking into account features of a choice of a working body, type of the expander, and also a configuration is offered. Third, an example of the calculation of the prototype of such a 4 kW unit operating on the thermal energy of hot water from the boiler, the simulation of which is performed in the program SmoWeb, the results of which it was designed. Fourth, the design for this technology takes

Organic Rankine Cycle Systems Design Using a Case-Based Reasoning Approach

Over the past several decades, the organic Rankine cycle (ORC) has been considered to be a promising technology for converting low-grade heat sources into electricity. ORC design is a knowledge-int...

Design and off-design optimization procedure for low-temperature geothermal organic Rankine cycles

In this paper, a two-step optimization methodology for the design and off-design optimization of low-temperature (110–150 °C) geothermal organic Rankine cycles (ORCs) is proposed. For the investigated conditions—which are based on the Belgian situation—we have found that the optimal ORC design is obtained for design parameter values for the environment temperature and for the electricity price which are both higher than the respective yearly-averaged values. However, the net present value is negative (−12.62 MEUR) which indicates that the low-temperature (130 °C) geothermal electric power plant is not economically attractive for the investigated case. Nevertheless, and demonstrated by the results of a detailed sensitivity analysis, a low-temperature geothermal power plant might be economically feasible for geological sites with a higher brine temperature or in a country with a more favorable economic situation; e.g., with higher electricity prices (∼70 EUR/MWh). The novelty of our paper is the development of a thermoeconomic design optimization strategy for low-temperature geothermal ORCs, accounting for the off-design behavior already in the design stage. The generic methodology is valid for low-temperature geothermal ORCs (with MW scale power output) and includes detailed thermodynamic and geometric component models, is based on hourly data rather than monthly-averaged data and accounts for economics.

Robust optimization for the preliminary design of solar organic Rankine cycle (ORC) systems

Organic Rankine cycle (ORC) powered by solar energy is a viable and effective option for a high efficiency conversion of solar thermal energy into electricity at a distributed scale but recurring fluctuations of the thermal energy often force solar-based ORC systems to operate at part-load conditions.With the aim of including the effects of the expected variations of the heat source and heat sink characteristics, even during the design phase, a novel optimization approach for the preliminary design of ORC systems integrated with concentrating solar collectors is presented and analysed. In particular, the minimization of the expected levelized cost of energy (LCOE) of the ORC unit is chosen as an objective function, while the generation of various scenarios is proposed to face the expected fluctuations on the heat source mass flow rate and temperature and cooling inlet temperature. In this way, the expected off-design performances are involved during the design step, giving robustness to the optimal design solution.The proposed methodology is tested by referring to the solar ORC system configuration of the Ottana solar facility. Firstly, the effect of a robust optimization on the preliminary ORC design is investigated by considering an increased number of scenarios for each of the three most significant ORC input variables (heat source mass flow rate and temperature and ambient temperature). Subsequently, the proposed methodology was applied to an ORC design case by considering a concurrent variation of the three variables and three different working fluids.The results of this study demonstrate that a multi-scenario approach drives towards an ORC configuration with lower performance under design conditions, but less sensitive to the variation of the main inputs. Less expensive solutions are therefore achieved by the proposed methodology, but the annual energy production obtained is comparable with those achieved by adopting a single scenario approach, with a consequent reduction of the LCOE.

Multi-objective optimization of Organic Rankine Cycle (ORC) design considering exergy efficiency and inherent safety for LNG cold energy utilization

Natural gas (NG) is an environment-friendly energy source with low CO2 and SOx emission. NG is usually liquefied during processing for transportation and storage, and then vaporized before consumption for multiple purposes. Usually, cold energy from the vaporization process is not utilized and hence wasted. One of the means of utilizing the cold energy is Organic Rankine Cycle (ORC), through which electricity can be generated from any grade of heat sources. Accordingly, ORC has been extensively investigated with the aim of increasing efficiency. However, although the ORC process has high potential risk of fatality, the safety aspect has not been previously studied.In this study, ORC design considering the thermodynamic and safety aspects is explored with a multi-objective optimization methodology. Exergy efficiency is used for the thermodynamic aspect, and risk distance is used for the safety aspect, with inherent safety techniques for designing safer processes in the conceptual design. Considering the working fluid as the main factor for optimal ORC design, six working fluids in three categories (pure component, binary components, ternary components) are investigated. Pareto optimal solutions are obtained from the multi-objective optimization method with two objectives based on working fluids for ORC design. Optimization variables include working condition (pressure), working fluid conditions (components). Moreover, the final optimal solution is selected using decision techniques, such as LINMAP and TOPSIS.

A neural network approach to the combined multi-objective optimization of the thermodynamic cycle and the radial inflow turbine for Organic Rankine cycle applications

An optimization model based on the use of Neural Network surrogate models for the multi-objective optimization of small scale Organic Rankine Cycles is presented, which couples the optimal selection of the thermodynamic parameters of the cycle with the main design parameters of In-Flow Radial turbines. The proposed approach proved well suited in the resolution of the highly non-linear constrained optimization problems, typical of the design of energy systems. Indeed the use of a surrogate model allows to adopt gradient based methods that are computationally more efficient and accurate than conventional derivative-free optimization algorithms.The intensive numerical experiments demonstrate that assuming a constant efficiency for the In-Flow Radial turbine leads to an error in the evaluation of the performance of the system of up to 50% and that the optimization approach proposed improves the accuracy of the solution and it reduces the computational time required to reach it by two orders of magnitude. An holistic approach in which the turbine and the thermodynamic cycle are designed simultaneously and the use of multi-objective optimization proved to be essential for the design of Organic Rankine cycles that satisfy both size and performance criteria.

Working fluid selection for organic Rankine cycle power generation using hot produced supercritical CO2 from a geothermal reservoir

Geothermal heat mining simulations using supercritical CO2 (sCO2) were performed in this research. Working fluid selection criteria for power generation using sCO2 from a geothermal reservoir are then presented for subcritical, superheated and supercritical organic Rankine cycles (ORCs). Meanwhile, method of working fluid classification for ORC is proposed. To get the most feasible ORC design, this study introduces the concept of “turning point” for isentropic and dry working fluids, as well as minimum turbine inlet temperature for wet working fluids. A thermodynamic model was developed with capabilities to obtain the optimal working fluid mass flow rate, evaporation temperature, superheated temperature, and supercritical pressure, to evaluate the thermal performance of the three ORC approaches using hot produced sCO2. With this model, thirty potential working fluids with critical temperatures in the range from 50 to 225 °C were screened for utilizing hot produced sCO2 considering physical properties, environmental and safety impacts, and thermodynamic performances. Finally, the thermodynamic results were compared for all possible working fluids.

Integrated operation design and control of Organic Rankine Cycle systems with disturbances

Traditionally, the control design of Organic Rankine Cycle (ORC) is sequential. The operating condition is obtained first by steady-state optimization, and then the controller is designed around the operating condition. Since the fluctuating nature of the heat source is not considered in the design of operating conditions, it is easy to violate the constraints of the ORC system during the operation. It is, therefore, of paramount importance to integrate the closed-loop dynamic performance analysis into the design of operating conditions to make sure the dynamic feasibility. An integrated design and control approach of the ORC system is proposed based on the mechanistic nonlinear model of the ORC system. It maximizes the waste heat recovery and guarantees the safe operation in the presence of disturbances. The optimal operating conditions and the controller parameters are obtained simultaneously through a nonlinear constrained optimization problem. The performance comparison between the integrated design and control approach and the sequential control design reflects the advantages of the proposed integrated approach. Its results with different control strategies (PI controllers with static feed-forward and PI controllers without static feed-forward) show that a well-behaved controller can improve heat recovery and the effectiveness of the proposed method.

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.

A Novel Pinch Point Design Methodology Based Energy and Economic Analyses of Organic Rankine Cycle

A generalized methodology for pinch point design and optimization of subcritical and transcritical organic Rankine cycles (ORCs) using both wet and dry fluids is adopted in this study. The presented algorithm can predict the pinch point location in evaporator and condenser simultaneously and optimize the evaporator pressure for best performance with various heat source and sink conditions. Effects of pinch point temperature difference (PPTD), isentropic efficiency, subcooling, superheating and regenerator on the energy and economic performances are discussed for selected working fluids. System yields similar optimum design for both maximum power generation and minimum capital cost per unit power. At optimum condition, ammonia is best in terms of higher thermal efficiency and lower component size, R152a is best in terms of higher net power output and heat recovery efficiency (11.1%), and toluene is best in terms of lower capital cost and cost per unit power output (7060 $/kW). Effect of heat source and sink parameters on both energy and economic performances is significant. Contour plots are presented to select the best ORC design parameters for available heat source condition. PPTD and expander isentropic efficiency have significant effect on performances. However, the effect of subcooling, superheating and regenerator depends on working fluid.

Improving the efficiency of a cataphoresis oven with a cogenerative organic Rankine cycle unit

In process industries, large amount of medium and low grade heat is generated and wasted due to the absence of internal heat demand. However, in the last decades, several technologies have been proposed to convert waste heat into electricity. Among them, Organic Rankine cycles (ORCs) are, currently, the most technically mature and economically feasible process to convert the low-grade heat into electricity. Therefore, in this study, the ORC technology is proposed to generate electricity from the low-grade heat released by the oven of a paint and cataphoresis facility. To design the ORC unit and select the working medium, an “in-house” optimization tool has been developed. A single-objective optimisation approach is adopted to maximize the ORC electric power while the heat rejected by the ORC condenser is used to heat the pre-treatment vats line. The ORC purchasing costs are estimated by means of an economic analysis. The ORC design has been made using real data acquired during a 5-year monitoring project. A recuperative-ORC, operating with R245fa, guarantees to maximize the net electric power. The ORC nameplate power and efficiency are 31.2 kW and 11.2%, respectively while the payback time is approximate 4 years. Being ORC also able to heat the paint vat, the facility costs can be abated of 15–20 k$/years.

Reconstruction procedure of the thermodynamic cycle of organic Rankine cycles (ORC) and selection of the most appropriate working fluid

Organic Rankine cycles (ORC) are part of heat recovery technologies, which allow thermal wastes to be converted into a mechanical power. These systems are suitable for various applications characterized by a large range of source and sink temperatures. Nonetheless, the selection of the organic working fluid is essential during ORC design processes; they have a major impact on the overall engine performance. Several works have been intending to develop appropriate methodologies to determine the optimal working fluid. Recently, an optimization approach independent of the organic fluid, has been proposed in the open literature, where optimal operating conditions are expressed in terms of equivalent temperatures and overall heat transfer surface areas. However, at the end, the primitive variables under which the real system must operate, should be determined. Within this framework, for a given working fluid, this paper presents a reconstruction method of a traditional thermodynamic cycle that allows actual thermodynamic variables (pressures, temperatures, mass flow rates) to be calculated. Furthermore, a methodology is also proposed for selecting the most appropriate organic working fluid, subjected to environmental and practical engineering design criteria. To emphasize the potential of the proposed approach, the entire procedure is then applied to a particular case study.

Deterministic Global Optimization of the Design of a Geothermal Organic Rankine Cycle

Herein, a framework for deterministic global optimization of process flowsheets is adapted to the design of an organic Rankine cycle for geothermal power generation. A case study using isobutane as working fluid is considered for the optimal sizing of components and selection of operating conditions at different ambient temperatures. The framework can provide the global optimum in reasonable calculation times within tight tolerances. In contrast, most local solvers applied are found to be inadequate. The CPU times are substantially smaller compared to a state-of-the-art global solver. For the case considered, recuperation can increase net power output but not necessarily economics.

Integrating working fluid design into the thermo-economic design of ORC processes using PC-SAFT

To exploit the full thermo-economic potential of an Organic Rankine Cycle (ORC), the process, equipment and working fluid have to be optimized simultaneously. Today, working fluid selection and thermo-economic process optimization are commonly separated. This separation leads to suboptimal solutions if the prior working fluid selection fails. In this work, we present an approach for the integrated thermo-economic design of ORC process, equipment and working fluid using consistent thermodynamic modeling. The approach is based on the Continuous-Molecular Targeting-Computer-aided Molecular Design (CoMT-CAMD) approach. In CoMT-CAMD, the properties of the working fluid are modeled by the physically-based Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. A CAMD formulation allows the design of novel working fluids during the process optimization. So far, CoMT-CAMD was limited to equilibrium thermodynamics. Some of the authors recently developed models for the transport properties viscosity and thermal conductivity based on entropy scaling and PC-SAFT. The integration of these models allows designing the equipment within the CoMT-CAMD approach. In particular, the heat exchanger of the ORC can be designed using detailed correlations for single phase, evaporation and condensation heat transfer. Based on the equipment sizing, a thermo-economic objective function can be considered in the resulting mixed-integer nonlinear optimization problem. Thereby, the thermo-economically optimal working fluid is identified in a single optimization problem jointly with the corresponding optimal process and equipment. The resulting approach is illustrated for the design of a subcritical ORC for waste heat recovery. We show that the predicted specific purchased-equipment costs are in good accordance with real ORC applications.

Pumped heat electricity storage: potential analysis and orc requirements

The rising share of renewable energy sources in power generation leads to the need of energy storage capacities. In this context, also some interest in thermal energy storages, especially in a concept called pumped heat electricity storage (PHES), arises. One possible design of such a PHES system consists of a compression heat pump, a thermal storage and an organic Rankine cycle (ORC). The present work analyses the general thermodynamic potential and limits of such a system and deals with the unusual requirements for the ORC. The potential analysis starts with the optimal case of combining two Carnot cycles with irreversible heat transfer. It is found that the efficiency of the entire process increases with increasing storage temperature and in general roundtrip efficiencies up to 70 % are predicted. Afterwards the cycles are transferred to cycles that are more realistic by considering technical aspects and a hypothetical working fluid which is optimized by an inverse engineering approach. This leads to lowered roundtrip efficiencies, which now, decrease with increasing storage temperatures. In a second step the specific ORC requirements as part of a PHES are considered, emphasizing the working fluid parameters. Especially, the use of a latent thermal energy storage leads to an ORC design differing from common (e.g. geothermal) applications. It is shown that the efficiency of the ORC and of the entire process strongly depends on the superheating at the expander inlet; here, the superheating must be held as small as possible, contrary to ORCs using common heat sources.

Modeling and simulation of a shell-and-tube heat exchanger for Organic Rankine Cycle systems with double-segmental baffles by adapting the Bell-Delaware method

In respect of an efficient design of Organic Rankine Cycle (ORC) power plants, the heat exchange equipment plays an important role. Shell-and-tube heat exchangers are widely used in such energy conversion systems. The TEMA (Tubular Exchanger Manufacturers Association) E shell type with single-segmental baffles is a relatively simple and the most common design. For this configuration the shell-side heat transfer coefficient is in general determined by the Bell-Delaware method. However, in case of applications with low mean temperature differences like geothermal ORC systems, more advanced flow configurations are applied. In this work a TEMA NFN shell-and-tube heat exchanger with double-segmental baffles is analyzed for single-phase flow. For this design, the standard version of the Bell-Delaware method is not applicable. In this context, the Taborek version of the Bell-Delaware method is adapted to the specific heat exchanger design by adjusting the calculation methods for the main geometrical parameters like cross flow area, leakage areas and effective number of tubes in the overlapping region. The entire heat exchanger is simulated in DYMOLA 2015 FD01. Thereafter, the obtained temperature profiles are validated by real power plant data and deviate from operational data by up to −1.14%. Subsequently, a novel correlation for an enhancement factor Jx is developed. Due to the application to other shell-and-tube heat exchangers with double-segmental baffles, high accuracy is achieved. In addition, a heat exchanger baffle section is simulated in ANSYS FLUENT 15.0 in order to validate locally the novel adaption of the Taborek version of the Bell-Delaware method (main approach) by CFD simulations. The obtained heat transfer coefficients show a sufficient agreement.

Organic Rankine cycle design and performance comparison based on experimental database

The Organic Rankine Cycle (ORC) is a technology commonly used for low-grade thermal energy conversion in electricity. This technology is mature for large power scale and last research focused on small scale units for domestic or onboard applications. This paper presents an extensive open-access database of more than 100 ORC experiments collected from about 175 scientific literature references. Data harmonization and database frame are presented. Clear and consistent components and ORC performance criteria are proposed and applied to the data set of various ORC. An overview of the ORC experimental state-of-the-art is displayed and major trends are drawn. Efficiency of key components such as expanders and pumps are analyzed and used for ORC parametric optimization case study. Correlations of some parameters with ORC performances are statistically investigated, performance improvement of novel fluid or cycles is evaluated.