Working fluid selection and performance comparison of subcritical and supercritical organic Rankine cycle (ORC) for low-temperature waste heat recovery

Panel: 4. Undertaking high impact actions: The role of technology and systems optimisation

This is a peer-reviewed paper.

Authors:
Stephanie Jumel, EDF R&D, France
Van Long Le, Theoretical and Applied Energetics and Mechanics Laboratory, France
Michel Feidt, Theoretical and Applied Energetics and Mechanics Laboratory, France
Abdelhamid Kheiri, Theoretical and Applied Energetics and Mechanics Laboratory, France

Abstract

In the industrial and daily process, a big amount of energy is lost as waste heat. This heat source reduces not only the energy effectiveness of industrial process but it also contributes to greenhouse gases emissions and thermal pollution. In this context, the CERES project (Energy pathways for waste heat recovery in industrial systems), financed by the French National Research Agency, aims at developing a numerical platform to optimize waste heat recovery and valorization in industrial process. Through this platform, the comparison of various technologies (heat pumps, thermoelectricity, ORC…) based on technico-economic basis will be possible.

In the article, it is proposed to describe the principles of the CERES project (functionalities of the platform, industrial processes and technologies included…) and to focus on one of these technologies, the Organic Rankine Cycles (subcritical and supercritical cycle), which can be used to valorize low-temperature waste heat. Indeed, many thermodynamic cycles for converting low-grade heat into electrical power have been studied. Among them, the organic Rankine cycles (ORCs) are much less complex and require less maintenance.

The Organic Rankine Cycle performances were analyzed and compared via their thermal efficiencies and exergy analysis. Both of these cycles used a heat source simulated by hot air with an inlet temperature of 170 °C and a heat sink that is water at ambient temperature to cool down and condense the working fluid. The performance calculations and the cycle simulation were carried out by Engineering Equation Solver (EES).

Later, steady-state models of each ORC components developed in EES, relying on Modelica language and a fluid property database (eg. Refprop) are used to perform thermodynamic simulations.