Comparing binary ORC systems in a single unit and a modular cascade configuration, using an ORC model for a low temperature geothermal resource
Author: Hjörleifur Þór Steingrímsson
Year: 2022
Supervisors: Dr. María Sigríður Guðjónsdóttir
Abstract:
The organic Rankine cycle is the world’s most established technology to produce electricity from low-temperature geothermal sources. In recent years there have been several companies bringing to market modular small-scale ORC systems. Varmaorka is an Icelandic energy company that develops and operates geothermal power plants in Iceland. Kópsvatn is one of Varmaorka’s power plants, and it uses eight Climeon modular ORC systems to produce power. There are four units in a cascaded configuration, where the temperature of the resource fluid is gradually decreased. In this study, a thermodynamic model of an ORC process was made using a thermodynamic library called CoolProp in Python. That model was then used to evaluate the performance difference between a single unit ORC system and a modular ORC systems in a cascade configuration. The case study plant used was similar to the Kópsvatn power plant. A group of working fluids was compared, and the model was used to run performance evaluation for a given exit temperature range. The modular cascade setup exceeded the single-unit system in terms of power production. However, for some of the working fluids, the documented performance might not be achievable due to the sub-atmospheric pressures needed to achieve the system conditions.