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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.

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.