Surrogate Models Applied to Optimized Organic Rankine Cycles

Icaro Figueiredo Vilasboas,Julio Augusto Mendes Da Silva,Armando Sá Ribeiro,Victor Gabriel Sousa Fagundes Dos Santos

doi:10.3390/en14248456

Icaro Figueiredo Vilasboas, Julio Augusto Mendes Da Silva + Show 2 more

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https://doi.org/10.3390/en14248456

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Journal: Energies	Publication Date: Dec 15, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Universidade Federal da Bahia

Abstract

Global optimization of industrial plant configurations using organic Rankine cycles (ORC) to recover heat is becoming attractive nowadays. This kind of optimization requires structural and parametric decisions to be made; the number of variables is usually high, and some of them generate disruptive responses. Surrogate models can be developed to replace the main components of the complex models reducing the computational requirements. This paper aims to create, evaluate, and compare surrogates built to replace a complex thermodynamic-economic code used to indicate the specific cost (US$/kWe) and efficiency of optimized ORCs. The ORCs are optimized under different heat sources conditions in respect to their operational state, configuration, working fluid and thermal fluid, aiming at a minimal specific cost. The costs of 1449.05, 1045.24, and 638.80 US$/kWe and energy efficiencies of 11.1%, 10.9%, and 10.4% were found for 100, 1000, and 50,000 kWt of heat transfer rate at average temperature of 345 °C. The R-square varied from 0.96 to 0.99 while the number of results with error lower than 5% varied from 88% to 75% depending on the surrogate model (random forest or polynomial regression) and output (specific cost or efficiency). The computational time was reduced in more than 99.9% for all surrogates indicated.

Highlights

Energy, environmental, and economic issues have guided researchers into the optimization of available energy sources
Over the years organic Rankine cycles (ORC) systems have demonstrated some important advantages when compared to conventional power generation technologies including: (1) lower operational pressure; (2) supercritical cycles at lower temperature and pressure; (3) the possibility of selecting positive condensing pressure; (4) the possibility of selecting a fluid appropriated to the thermal source available; (5) efficient systems at small sizes; and (6) simpler cycle configurations [5]
Fluid selection and operational optimization were carried out to minimize specific cost for four ORC configurations subjected to a wide range of heat sources

Summary

Introduction

Environmental, and economic issues have guided researchers into the optimization of available energy sources. The use of waste heat and low temperature renewable sources to generate electricity using organic Rankine cycles (ORCs) has gained attention in the last decade. Several works have reported the use organic fluids in Rankine cycles and highlighted the contributions of Luigi d’Amelio, who developed an experimental turbine using ethyl chloride in 1954, and Harry Zvi Tabor and Lucien Bronicki, whom tested small solar ORC units (2 kWe and 10 kWe) with monochlorobenzene in 1961 [2,3,4]. Over the years ORC systems have demonstrated some important advantages when compared to conventional power generation technologies including: (1) lower operational pressure; (2) supercritical cycles at lower temperature and pressure; (3) the possibility of selecting positive condensing pressure; (4) the possibility of selecting a fluid appropriated to the thermal source available; (5) efficient systems at small sizes; and (6) simpler cycle configurations [5]. Other companies can be highlighted such as Exergy, Turbine Air Systems (TAS), General

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