Energies Energies 1996-1073 ENERGA 7 2014 7 7 Thermal-Economic Modularization of Small, Organic Rankine Cycle Power Plants for Mid-Enthalpy Geothermal Fields Yodha Nusiaputra Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology (KIT), Karlsruhe 76021, Germany German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany Hans-Joachim Wiemer Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology (KIT), Karlsruhe 76021, Germany Dietmar Kuhn Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology (KIT), Karlsruhe 76021, Germany

The costs of the surface infrastructure in mid-enthalpy geothermal power systems, especially in remote areas, could be reduced by using small, modular Organic Rankine Cycle (ORC) power plants. Thermal-economic criteria have been devised to standardize ORC plant dimensions for such applications. We designed a modular ORC to utilize various wellhead temperatures (120–170 °C), mass flow rates and ambient temperatures (−10–40 °C). A control strategy was developed using steady-state optimization, in order to maximize net power production at off-design conditions. Optimum component sizes were determined using specific investment cost (SIC) minimization and mean cashflow (MCF) maximization for three different climate scenarios. Minimizing SIC did not yield significant benefits, but MCF proved to be a much better optimization function.

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