Thermodynamic and Techno‐economic Analysis of a Triple‐pressure Organic Rankine Cycle: Comparison with Dual‐pressure and Single‐pressure ORCs

Abstract

Investigation of a triple-pressure organic Rankine cycle (TPORC) using geothermal energy for power generation with the net power output of the TPORC analyzed by varying the evaporation pressures, pinch temperature differences (t pp ) and degrees of superheat (t sup ) aimed to find the optimum operation conditions of the system. The thermodynamic performance of the TPORC was compared with a dual-pressure organic Rankine cycle (DPORC) and a single-pressure ORC (SPORC) for geofluid temperatures ranging from 100°C to 200°C, with particular reference to the utilization of a hot dry rock (HDR) geothermal resource. Thermodynamic performances of the TPORC system using eight different organic working fluids have also been investigated in terms of the net power outputs. Results show that a higher geofluid mass flow rate can make a considerable contribution to shortening the payback period (PBP) as well as to decreasing the levelized electricity cost (LEC), especially when the geofluid temperature is low. For the temperature range investigated, the order from high to low based on thermodynamic and techno-economic performances is found to be TPORC > DPORC > SPORC. In terms of using geothermal resources within the given temperatures range (100°C-200°C), the TPORC system can be a better choice for geothermal power generation so long as the wellhead geofluid temperature is between 140°C and 180°C.

Thermodynamic Investigation and Economic Evaluation of a High-Temperature Triple Organic Rankine Cycle System

“…When the geothermal fluid temperature was 200 • C, the net power output was 3.8% and 2.4% higher than that of the single-stage and cascade cycles, respectively. The LEC of the TORC was approximately 0.04 USD/kWh [5].…”