Energy Analysis of a Proposed Wellhead Geothermal Plant in Menengai Field

Drilling in Menengai Geothermal Field started in February 2011 with the aim of harnessing steam for electricity power production(Suwai, 2011). It has been 9 years since and no installation of a conventional power plant has taken place. Looking at the case of KenGen, they had a similar situation and as stated by (Saitet and Kwambai 2015) decided to adopt the wellhead technology in the year 2012. They started with 5Mwe plants and have grown to own 15 geothermal wellhead power plants of condensing steam turbine type. The objective of this study is to analyze the feasibility of installing a wellhead power plant in Menengai. The single flash cycle with condensing turbine and combined binary cycle were analyzed. The study was conducted on well MW-18A which had undergone discharge tests for 4months. The optimum wellhead pressure was 18.5bara for a total mass flow rate of 105t/hr with an enthalpy of 1618kJ/kg. The reservoir temperature obtained from pressure and temperature logging tests was 280 . The energy analysis was conducted using EES. Power output and plant efficiencies for the single flash were 9,442 kW, 20.1%; binary plant 1,785 kW, 3.781% and combined flash binary cycle with the highest output of 11,227 kW, 23.79%.

Key words: Geothermal wellhead power plant, Single flash, Combined flash-binary cycle, Energy, EES