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Standardized Geothermal Turbines Could Reduce Plant Capital Costs

October 23, 2018

Currently, the geothermal turbine market is driven by developer demand for plant efficiency and consists of custom turbines designed specifically for the varying conditions at different geothermal fields.

In practice, a standard turbine design would likely operate at off-design conditions, resulting in lower efficiencies, less electricity generation, and less revenue than a custom turbine design. However, the upfront capital cost savings could offset future revenue losses. In order to determine the commercially favorable operating range of a standard geothermal Organic Rankine Cycle (ORC) turbine compared to custom design, we created a process flow model at a given design point of the standard size (5-MW) turbine by using an off-design efficiency curve.

Line graph showing turbine efficiency, gross turbine power, and net plant power percentages with working fluid mass flowrate ratio.

Off-Design Turbine Efficiency Curve for 5 MW Geothermal ORC Turbine

We analyzed over 63 off-design cases by changing inlet geothermal brine temperature and inlet mass flow rate. The results showed that the net capital cost savings from a standard design versus a custom design turbine at the standard design turbine point for the modeled 5-MW case study may reach up to $2.3 million, while the difference in net present value (NPV) could reach up to $1.4 million

Temperature chart showing geothermal brine mass flow rate.

NPV Difference Between Standard and Custom Design Scenarios of 5-MWe Geothermal ORC Turbine

Access the highlights, or the full report titled "Global Value Chain and Manufacturing Analysis on Geothermal Power Plant Turbines."