Off-Design Modelling of ORC Turbines for Geothermal Application

Lorenzo Talluri,Giampaolo Manfrida,Zekeriya Özcan,Özgür Ekici,Pietro Ungar

doi:10.1051/e3sconf/202131211015

Lorenzo Talluri, Giampaolo Manfrida + Show 3 more

Open Access

https://doi.org/10.1051/e3sconf/202131211015

Copy DOI

Abstract

In this study, turbine modelling of a geothermal sourced organic Rankine cycle (ORC) power plant is aimed. Thermodynamic model of the plant is constructed with the help of design and off-design plant data from an existing two-cycle power plant in southwestern Anatolia. Utilizing statistical analysis tools such as maximum likelihood estimation and probability distribution, plant variables are obtained within their standard deviations. Stodola curves and probability calculations demonstrate that both turbines are most likely to have two stages. Average losses are 2.3 MW and 1.2 MW from Turbine-I and Turbine-II respectively throughout the different seasons. After the determination of losses, overall turbine efficiencies demonstrate a reverse trend with increasing reduced mass flow rate. This may be associated with the increased choking of the turbine. Correlations estimate rather fixed efficiency values at off-design conditions (84% for Turbine-I and 77% for Turbine-II); that is an expected outcome since these correlations are influenced mainly by the design isentropic efficiency, which is a constant value. On the other hand, these correlations are most likely to be proposed for non-choking conditions which are invalid for off-design conditions of existing ORC turbines. Datapoint dispersion in Turbine-II does not demonstrate a strong correlation with physical constraints such as -pressure ratio and reduced mass flow rate- as it does for Turbine-I; this phenomenon may need further attention for future work.

Highlights

Power extraction from geothermal sources has been a subject of attention since the early twentieth century due to the increasing demand of electricity
The aim of this paper is to model organic Rankine cycle (ORC) turbine curves sourced by an existing geothermal source at off-design conditions under part-load
With the help of off-design datasets from different seasons of different years, thermodynamic and statistical models are constructed under part-load conditions

Summary

Introduction

Power extraction from geothermal sources has been a subject of attention since the early twentieth century due to the increasing demand of electricity. Depending on the source temperature, flash steam and binary steam methods are other most common methods for geothermal applications. Binary steam targets low and moderate source temperature ranges (i.e. 100-180 oC). In this method, enthalpy of extracted brine is transferred in heat exchangers to a second medium with a lower boiling point, which is cycled in closed systems. Enthalpy of extracted brine is transferred in heat exchangers to a second medium with a lower boiling point, which is cycled in closed systems Based on this principle, state of art demonstrates two common cyclic systems namely- organic Rankine cycle (ORC) and Kalina cycle (KC)-.

Objectives

Results

Conclusion