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20 mins
Integrated computer-aided working-fluid design and thermoeconomic ORC system optimisation
Martin White, Oyeniyi Oyewunmi, Maria Anna Chatzopoulou, Antonio Pantaleo, Andrew Haslam, Christos Markides
Session: Session 2C: Working Fluid Selection
Session starts: Wednesday 13 September, 14:20
Presentation starts: 15:00
Room: Building 27 - Lecture room 03

Martin White (Imperial College London)
Oyeniyi Oyewunmi (Imperial College London)
Maria Anna Chatzopoulou (Imperial College London)
Antonio Pantaleo (Imperial College London)
Andrew Haslam (Imperial College London)
Christos Markides (Imperial College London)

The successful commercialisation of organic Rankine cycle (ORC) systems across a range of power outputs and heat-source temperatures demands step-changes in both improved thermodynamic performance and reduced investment costs. The former can be achieved through high-performance components and optimised system architectures operating with novel working-fluids, whilst the latter requires careful component-technology selection, economies of scale, learning curves and a proper selection of materials and cycle configurations. In this context, thermoeconomic optimisation of the whole power-system should be completed aimed at maximising profitability. This paper couples the computer-aided molecular design (CAMD) of the working-fluid with ORC thermodynamic models, including recuperated and other alternative (e.g., partial evaporation or trilateral) cycles, and a thermoeconomic system assessment. The developed CAMD-ORC framework integrates an advanced molecular-based group- contribution equation of state, SAFT-γ Mie, with a thermodynamic description of the system, and is capable of simultaneously optimising the working-fluid structure, and the thermodynamic system. The advantage of the proposed CAMD-ORC methodology is that it removes subjective and pre-emptive screening criteria that would otherwise exist in conventional working-fluid selection studies. The framework is used to optimise hydrocarbon working-fluids for three different heat sources (150, 250 and 350 ◦C). In each case, the optimal combination of working fluid and ORC system architecture is identified, and system investment costs are evaluated through component sizing models. It is observed that optimal working fluids that minimise the specific investment cost (SIC) are not the same as those that maximise power output. For the three heat sources the optimal working-fluids that minimise the SIC are isobutane, 2-pentene and 2-heptene, with SICs of 4.03, 2.22 and 1.84 £/W respectively.