A conceptual design of a geothermal combined cycle and comparison with a single-flash power plant for well NWS-4, Sabalan, Iran

Abstract

The Sabalan geothermal area in NW-Iran is a water-dominated field. The calculated parameters indicate that the potential capacity of the NW-Sabalan resource has a mean value of 209 MWe. The average calculated energy density for the whole area is 11 MW/km2. Five exploration wells have been drilled. The Ministry of Energy in Iran is planning to build a pilot power plant in order to confirm that a geothermal power plant can be operated in Iran. Simultaneously, there will be drilled fourteen production wells, one exploration well and one injection well. In this report, a model is presented for a single-flash power plant, using well NWS-4 as a production well and optimizing the separator pressure with respect to net power output. In addition, a new power generation cycle is proposed which is a combination of a geothermal power plant and a conventional gas turbine power plant. In Iran, gas turbine power plants produce 20% of the electricity. The exhaust from these power plants is, in many cases, not used but could be used to enhance fluid temperatures in the many medium-temperature geothermal fields in Iran. Model is presented for this new cycle using the EES program and calculations done for two scenarios in the model. Finally, some suggestions are made for optimizing the geothermal combined cycle.