Design and Testing of n-Pentane Turbine for 2 kW Model of Binary Cycle Power Plant

Abstract

Design, manufacture and testing of a 2 kW n-pentane turbine were carried out. This project is dedicated to support the study of the 2 kW model of binary cycle power plant using geothermal brine as the energy source. Brine defined in this study is separated hot water at a separated steam geothermal plant. Currently, 100% of brine is injected into injection wells. Injected brine generally has a temperature higher than 1000 C and mass flow rate of hundreds of tons/hour. A quick estimation showed the content of rejected energy is around several hundred million watts.

A binary cycle plant is an advantageous technology for recovering this energy waste. In this plant, thermal energy from brine is transferred via a heat exchanger to a working fluid for using in a fairly conventional Rankine cycle. The aim of the whole study is to recover the unused energy in order to optimize the efficiency of a conventional geothermal power plant.

From a design analysis, the turbine used is a single-stage impulse turbine with five convergent nozzles, 382.3 mm rotor diameter, 60 blades, 16.5 mm height of blade, and 10 mm width of blade. This turbine is designed to operate at 3000 rpm and 65.6% of turbine efficiency. The turbine test was conducted using BPPT’s 2 kW system of research-scale-binary-cycle power plant. The experimental result shows that the turbine produced power of 1.2 kWe successfully. It is 8.5% lower than the efficiency of the original design. Therefore it is reasonable to conclude that the turbine is well designed.