(747b) Optimal Production of Power from Mid-Temperature Geothermal Sources: Scale and Safety Issues
In this work we use a superstructure optimization approach for the mathematical optimal design and operation of Organic Rankine binary Cycles for the recovery of energy from medium and low geothermal sources. We focus on the three fluids, Benzene, toluene and cyclohexane, that our previous study identified as the most promising from environmental, economic and safety points of view .In particular, we develop a superstructure for the heat exchanger network to use the hot brine from a geothermal well allowing double and single extractions to optimally design the best cycle, where the thermodynamics of the fluids is included through surrogate models for the enthalpies and entropies. Two solutions are presented, the first one optimizes the energy output and a second one where economic, environmental and safety considerations are included in a normalized objective function to evaluate their effect on the selection of the cycle and on the operating conditions. Finally, the effect of the scale on the investment and production costs is evaluated.
The economic optimization selects a two expansion cycle using toluene as organic fluid, producing 10.4 MW at 0.075â¬/kWh with an investment of 102Mâ¬. Safety considerations slightly change the operating conditions, reducing the pressures and temperatures, but not the selection of the working fluid. Sustainable and economic terms overcome safety issues. The results are competitive with other renewable-based technologies for thermal power production such as CSP or biomass.
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