Thermo-Economic optimization of waste heat recovery Organic Rankine Cycles

Sylvain Quoilin (1) , Sébastien Declaye (1) , Bertrand F. Tchanche (2) , Vincent Lemort (1)

1 Université de Liège
2 Agricultural University of Athens

The present paper focuses both on the thermodynamic and on the economic optimization of a small scale ORC in waste heat recovery application. A sizing model of the ORC is proposed, capable of predicting the cycle performance with different working fluids and different components sizes. The working fluids considered are R245fa, R123, n-butane, n-pentane and R1234yf and Solkatherm. Results indicate that, for the same fluid, the objective functions (economics profitability, thermodynamic efficiency) lead to different optimal working conditions in terms of evaporating temperature: the operating point for maximum power doesn't correspond to that of the minimum specific investment cost: The economical optimum is obtained for n-butane with a specific cost of 2136 €/kW, a net output power of 4.2 kW, and an overall efficiency of 4.47%, while the thermodynamic optimum is obtained for the same fluid with an overall efficiency of 5.22%. It is also noted that the two optimizations can even lead to the selection of a different working fluid. This is mainly due to additional fluid properties that are not taken into account in the thermodynamic optimization, such as the fluid density: a lower density leads to the selection of bigger components which increases the cost and decreases the economical profitability.

Mots clés: Physical Sciences

Domaines: Thermique [physics.class-ph]; Thermique [physics.class-ph]

Sylvain Quoilin, Sébastien Declaye, Bertrand F. Tchanche, Vincent Lemort. Thermo-Economic optimization of waste heat recovery Organic Rankine Cycles. Applied Thermal Engineering, 2011, 31 (14-15), pp.2885. ⟨10.1016/j.applthermaleng.2011.05.014⟩. ⟨hal-00781353⟩