A multi-criteria approach for the optimal selection of working fluid and design parameters in Organic Rankine Cycle systems

The worrying effects of climate change have led, in the last decades, to the improvement of innovative solutions for low greenhouse emission energy conversion, among which, is the use of micro-ORC (Organic Rankine Cycle) systems for distributed generation, in the framework of combined heat and power applications and renewables exploitation. However, micro-ORCs environmental impact, due to high GWP (global working potential) working fluid leak rate, is an issue still to overcome. Neverthless the interest in using new low GWP refrigerants and their blends is increasing, new fluids have not yet been properly tested into ORC. Numerical studies reveal that low GWP fluids do not always guarantee the same performance of typically used fluids, leading to indirect emissions related to the use of fossil fuels to compensate the lower power production. This study proposes to investigate performance and impact of an innovative micro-ORC test bench when working with HFCs (HydroFluoroCarbons), low GWP fluids and mixtures, with the main aim of comprehensively evaluating its impact due to both direct and indirect greenhouse gas emissions produced in a typical annual operation.

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Improving the economy-of-scale of small organic rankine cycle systems through appropriate working fluid selection

Applied Energy ◽

10.1016/j.apenergy.2016.09.055 ◽

2016 ◽

Vol 183 ◽

pp. 1227-1239 ◽

Cited By ~ 13

Author(s):

Martin White ◽

Abdulnaser I. Sayma

Keyword(s):

Organic Rankine Cycle ◽

Rankine Cycle ◽

Working Fluid ◽

Economy Of Scale ◽

Cycle Systems ◽

Working Fluid Selection

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Exergy analysis and working fluid selection of organic Rankine cycle for low grade waste heat recovery

Energy ◽

10.1016/j.energy.2014.06.040 ◽

2014 ◽

Vol 73 ◽

pp. 475-483 ◽

Cited By ~ 82

Author(s):

R. Long ◽

Y.J. Bao ◽

X.M. Huang ◽

W. Liu

Keyword(s):

Heat Recovery ◽

Waste Heat Recovery ◽

Exergy Analysis ◽

Waste Heat ◽

Organic Rankine Cycle ◽

Rankine Cycle ◽

Working Fluid ◽

Low Grade ◽

Working Fluid Selection ◽

Selection Of

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Conversion of Low-Grade Heat from Multiple Streams in Methanol to Olefin (MTO) Process Based on Organic Rankine Cycle (ORC)

Applied Sciences ◽

10.3390/app10103617 ◽

2020 ◽

Vol 10 (10) ◽

pp. 3617 ◽

Cited By ~ 1

Author(s):

Danchen Wei ◽

Cheng Liu ◽

Zhongfeng Geng

Keyword(s):

Organic Rankine Cycle ◽

Rankine Cycle ◽

Exergy Efficiency ◽

Working Fluid ◽

Low Grade ◽

Maximum Output ◽

Methanol To Olefin ◽

Thermodynamic Performance ◽

Selection Of ◽

Mto Process

The organic rankine cycle (ORC) has been widely used to convert low-grade thermal energy to electricity. The selection of the cycle configuration, working fluid, and operating parameters is crucial for the economic profitability of the ORC system. In the methanol to olefin (MTO) process, multi-stream low-temperature waste heat has not been effectively utilized. The previous study mostly focused on the optimization of a single stream system and rarely considered the comprehensive optimization of multi-stream ORC systems which have multi-temperature heat sources. This paper proposes five kinds of system design schemes, and determines the optimal output work and the highest exergy efficiency through the selection of working fluid and optimization of system parameters. In addition, the influence of mixed working fluid on the thermodynamic performance of the system was also investigated. It is found that there is an optimal evaporation temperature due to the restriction of pinch temperature. At the optimal temperature the ORC system obtains the maximum net output power of 4.95 MW. The optimization results show that the working fluid R227EA selected from seven candidate working fluids shows the optimal thermodynamic performance in all the five design schemes, and obtains the maximum output work and exergy efficiency.

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Parametric Optimization of Zeotropic Mixtures Used in Low-Temperature Organic Rankine Cycle for Power Generation

Volume 3B: Oil and Gas Applications; Organic Rankine Cycle Power Systems; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2014-26664 ◽

2014 ◽

Author(s):

H. Xi ◽

M. J. Li ◽

Y. L. He ◽

W. W. Yang ◽

Y. S. Li

Keyword(s):

Organic Rankine Cycle ◽

Internal Heat ◽

Implementation Process ◽

Rankine Cycle ◽

Working Fluid ◽

Heat Sources ◽

Design And Optimization ◽

Internal Heat Exchanger ◽

Algorithm Implementation ◽

Selection Of

In the design and optimization of the ORC system, the selection of working fluid is one of the most important factors that should be considered. In this work, considering different heat sources with their temperatures ranging from 80 to 120 °C, 8 different zeotropic mixtures were proposed and their thermodynamic and economic performance for two types of traditional ORC systems (i.e. basic organic Rankine cycle, BORC and organic Rankine cycle with internal heat exchanger, IHORC) were investigated. Firstly, economic analysis were performed for both systems; Secondly, genetic algorithm (GA) was then introduced to determine the optimal fractions and other operation parameters for zeotropic mixtures under different working conditions and systems, the algorithm implementation process was described. Thirdly, the optimization studies were performed by using annual cash flow as the objective function. The optimal thermodynamic performance of different zeotropic mixtures and their components were both calculated and compared. For the different heat sources temperatures, the optimal zeotropic mixtures and their optimal fraction were recommended according to the calculated results.

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A Preliminary Turbine Design for an Organic Rankine Cycle

Volume 2: Aircraft Engine; Coal, Biomass and Alternative Fuels; Cycle Innovations ◽

10.1115/gt2013-94481 ◽

2013 ◽

Cited By ~ 4

Author(s):

T. Efstathiadis ◽

M. Rivarolo ◽

A. I. Kalfas ◽

A. Traverso ◽

P. Seferlis

Keyword(s):

Organic Rankine Cycle ◽

Rankine Cycle ◽

Operating Conditions ◽

Design Parameters ◽

Working Fluid ◽

Energy Sources ◽

Small Scale ◽

Choked Flow ◽

Turbine Speed ◽

Turbine Design

An increasing trend in exploiting low enthalpy content energy sources, has led to a renewed interest in small-scale turbines for Organic Rankine Cycle applications. The design concept for such turbines can be quite different from either standard gas or steam turbine designs. The limited enthalpic content of many energy sources enforces the use of organic working media, with unusual properties for the turbine. A versatile cycle design and optimization requires the parameterization of the prime turbine design. In order to address the major challenges involved in this process, the present study discusses the preliminary design of an electricity-producing turbine, in the range of 100 kWel, for a low enthalpy organic Rankine cycle. There are many potential applications of this power generating turbine including geothermal and solar thermal fields or waste heat of PEM type fuel cells. An integrated model of equations has been developed, accordingly. The model aims to assess the performance of an organic cycle for various working fluids, including NH3, R600a and R-134a. The most appropriate working fluid has been chosen, taking into consideration its influence on both cycle efficiency and the specific volume ratio. The influence of this choice is of particular importance at turbine extreme operating conditions, which are strongly related to the turbine size. In order to assess the influence of various design parameters, a turbine design tool has been developed and applied to preliminarily define the blading geometry. Finally, a couple of competitive turbine designs have been developed. In one approach, the turbine speed is restricted to subsonic domain, while in the other approach the turbine speed is transonic, resulting to choked flow at the turbine throat. The two approaches have been evaluated in terms of turbine compactness and machine modularity. Results show that keeping the crucial parameters of the geometrical formation of the blade constant, turbine size could become significantly smaller decreasing up to 90% compared its original value.

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The Application of Rotary Vane Expanders in Organic Rankine Cycle Systems—Thermodynamic Description and Experimental Results

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4023534 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 37

Author(s):

Zbigniew Gnutek ◽

Piotr Kolasiński

Keyword(s):

Power Systems ◽

Thermodynamic Description ◽

Organic Rankine Cycle ◽

Rankine Cycle ◽

Test Stand ◽

Working Fluid ◽

Cycle Systems ◽

Set Up ◽

Domestic Power ◽

Small Capacity

Small (10–100 kW) and micro (0.5–10 kW) Organic Rankine Cycle (ORC) power systems are nowadays considered for local and domestic power generation. Especially interesting are micropower applications for heat recovery from dispersed low potential (85–150 °C) waste and renewable heat sources. Designing and implementing an ORC system dedicated to energy recovery from such a source is difficult. A proper working fluid must be selected together with a suitable expander. Volumetric machines can be adopted as a turbine alternative in small-capacity applications under development, like, e.g., domestic cogeneration. Scroll and screw expanders are a common choice. However, scroll and screw expanders are complicated and expensive. Vane expanders are mechanically simple, commercially available and cheap. This paper documents a study providing the preliminary analysis of the possibility of employing vane-expanders in mini-ORC systems. The main objective of this research was therefore a comprehensive analysis of the use of a vane expander for continuous operation with a low-boiling working fluid. A test-stand was designed and set up starting from system models based on thermodynamic analysis. Then, a series of experiments was performed using the test-stand. Results of these experiments are presented here, together with a model of multivane expanders and a thermodynamic-based method to select the working fluid. The analysis presented in this paper indicates that multivane expanders are a cheap and mechanically simple alternative to other expansion devices proposed for small-capacity ORC systems.

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