Integrated design of ORC process and working fluid using process flowsheeting software and PC-SAFT

Integrated design of ORC process and working fluid for transient waste-heat recovery from heavy-duty vehicles

The integrated design of the heat exchanger network (HEN) and organic Rankine cycle (ORC) system with new working fluids is a complex optimization problem. It involves navigating a vast design space across working fluid molecules, ORC processes, and networks. In this article, a new two‐stage reverse strategy is developed. The optimal HEN‐ORC configurations and operating conditions, and the thermodynamic properties of the hypothetical working fluid are identified by an equation of state (EOS) free HEN‐ORC model in the first stage. With two developed group contribution‐artificial neural network thermodynamic property prediction models, working fluid molecules are screened out in the second stage from a database containing more than 430,000 hydrofluoroolefins (HFOs). The presented method is employed in two cases, where new working fluids are found. The total annual cost of Case 1 is 12%–22% lower than the literature, and the power output of Case 2 is 5%–8% higher than the literature.

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

The performance of Organic Rankine cycle (ORC) systems is defined by the system design as well as working fluid selection. Integrated thermo-economic optimisation of both can unlock maximum system potential in terms of power generation at a minimal cost. However, such optimisation is associated with uncertainties related to the underlying thermodynamic fluid models, ORC system models, and equipment cost correlations. In this paper, the main sources of uncertainty are quantified and their impact on optimal system design and working fluid selection is analysed. A computer-aided molecular and process design (CAMPD) optimisation framework based on first-law system design models is developed and validated with experimental data. Results reveal that the developed framework can identify promising working fluid candidates with high probabilities, even considering the most important sources of uncertainty. In a case study of industrial waste-heat utilisation, it was found that while uncertainties challenge the strict discrimination of the most promising working fluids, they mainly affect absolute performance values, rather than the overall ranking of working fluids. Propane was identified as having a 94-% probability of being among the best 3 working fluids. Furthermore, although the overall specific investment costs are highly uncertain (mean: 3810 £/kW, standard deviation: 720 £/kW), the results are less sensitive to uncertainties in fluid equilibrium and transport properties (standard deviation: 160 £/kW), with the impact of equipment cost uncertainties being dominant. The analysis of uncertainties in working fluid selection also applies to other CAMPD problems, and other applications of group-contribution-based equations of state.

The Organic Rankine Cycle (ORC) power cycle is a well-established solution for harnessing heat sources to generate energy. Presently, ORC systems predominantly employ hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) as working fluids. However, these substances possess significant greenhouse gas effects and are slated for future bans. To address this, it is imperative to establish rational selection criteria and corresponding techniques for evaluating working fluids suitable for industrial ORC applications. This chapter presents the working fluid selection criteria and screening methods for environmentally friendly working fluids. The chapter is organized as follows: (1) The fundamentals of working fluids section provide a broad introduction to the core principles of working fluids; (2) the working fluid section outlines reasonable selection criteria for identifying potential alternatives; (3) the screening of ORC working fluids section discusses possible working fluid candidates, simulation approach, and thermodynamic models in detail, which is very important to access the thermodynamic performance of ORC cycle; and (4) an example of the simulation of an ORC for working fluid selection section demonstrates the strategy for the selection of a working fluid considering a defined ORC architecture.

Organic Rankine Cycle system performance targeting and design for multiple heat sources with simultaneous working fluid selection

How to give a full play to the advantages of zeotropic working fluids in organic Rankine cycle (ORC)

In off-shore oil and gas platform efficiency, the reliability and fuel flexibility are the major concerns when selecting the gas turbine to support the electrical and mechanical demand on the platform. In order to fulfill these requirements, turbine inlet temperature and pressure ratio are not increased up to the optimal values and one or more redundant gas turbines may be employed. With increasing incentives for reducing the CO2 emissions off-shore, improving the thermal efficiency has become a focus area. Due to the peculiar low turbine outlet temperature and due to space and weight constraints, a steam bottoming cycle is not a convenient solution. On the contrary, organic Rankine cycles (ORCs) present the benefits of high simplicity and compactness. Furthermore, the working fluid can be selected considering the temperature profile at which the heat is supplied; hence the heat transfer process and the thermal efficiency of the cycle can be maximized. This paper is aimed at finding the most optimal ORC tailored for off-shore applications using an optimization procedure based on the genetic algorithm. Numerous working fluids are screened through, considering mainly thermal efficiency, but also other characteristics of the fluids, e.g. stability, environmental and human health impacts, and safety issues. Both supercritical and subcritical ORCs are included in the analysis. The optimization procedure is first applied to a conservative ORC where the maximum pressure is limited to 20 bar. Subsequently the optimal working fluid is identified by removing the restriction on the maximum pressure. Different limits on hazards and global warming potential (GWP) are also set. The study is focused on the SGT-500 gas turbine installed on the Draugen platform in the Norwegian Sea. The simulations suggest that, when a high hazard is accepted, cyclohexane is the best solution. With a turbine inlet pressure limit of 20 bar, the combined gas turbine-ORC system presents an efficiency of 43.7%, corresponding to an improvement of 11.9%-points with respect to the gas turbine efficiency. With no upper pressure boundary, cyclohexane at 55.5 bar is the preferable working fluid with a combined thermal efficiency of 44.3%. The supercritical CO2 cycle with a maximum pressure of 192.9 bar is found to be the best alternative if an extremely low hazard is required.

The organic Rankine cycle (ORC) is an established thermodynamic process that converts waste heat to electric energy. Due to the wide range of organic working fluids available the fluid selection adds an additional degree-of-freedom to the early design phase of an ORC process. Despite thermodynamic aspects such as the temperature level of the heat source, other technical, economic, and safety aspects have to be considered. For the fluid selection process in this paper, 22 criteria were identified in six main categories while distinguishing between elimination (EC) and tolerance criteria (TC). For an ORC design, the suggested method follows a practical engineering approach and can be used as a structured way to limit the number of interesting working fluids before starting a detailed performance analysis of the most promising candidates. For the first time, the selection process is applied to a two-stage reference cycle, which uses the waste heat of a large reciprocating engine for cogeneration power plants. It consists of a high temperature (HT) and a low temperature (LT) cycle in which the condensation heat of the HT cycle provides the heat input of the LT cycle. After the fluid selection process, the detailed thermodynamic cycle design is carried out with a thermodynamic design tool that also includes a database for organic working fluids. The investigated ORC cycle shows a net thermal efficiency of about 17.4% in the HT cycle with toluene as the working fluid and 6.2% in LT cycle with isobutane as the working fluid. The electric efficiency of the cogeneration plant increases from 40.4% to 46.97% with the both stages of the two-stage ORC in operation.

Thermodynamic analysis of a simple Organic Rankine Cycle

Selection of working fluid for low enthalpy heat source Organic Rankine Cycle in Dholera, Gujarat, India

Identification of key affecting parameters of zeotropic working fluid on subcritical organic Rankine cycle according limiting thermodynamic cycle

Parametric optimization of regenerative organic Rankine cycle (ORC) for low grade waste heat recovery using genetic algorithm

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

Energy harvesting using solar ORC system and Archimedes Screw Turbine (AST) combination with different refrigerant working fluids