Evaluation of Organic Rankine Cycle Geothermal Power Plant and Considerations

The objective of this work is to evaluate the feasibility of an Organic Rankine Cycle (ORC) power plant to generate electricity from low flow rates of a geothermal resource (~875 gpm) at low temperatures (T~100°C). A model of ORC was developed using HYSYS process simulator. DOE’s Cost of Renewable Energy Spreadsheet Tool (CREST) model was used for economic modeling of the power plant. First law efficiency of the power plant was studied using energy analysis. Exergy analysis was used to study the second law efficiency of the power plant. A comparison was made between shell and tube heat exchangers and plate and frame heat exchangers for performance and cost evaluation. Plate and frame heat exchangers have advantages such as higher overall heat transfer co-efficient and smaller footprint compared to shell and tube heat exchangers. The quality of water used with respect to geothermal development was investigated, including dissolved solids, toxic minerals, additives, scale formation, corrosion and non-condensable gas. This paper will summarize the results of this study.