The Efeler geothermal power plant (GPP) located in Aydin, Turkey, is the biggest of its kind in the country, with a power generation capacity of approximately 162.3MW. It is currently undergoing a major expansion, which will increase the plant’s installed capacity to 259.9MW.

The 97.6MW expansion involves the addition of three new GPP units at an estimated cost of £288m ($350m). The project will help Turkey achieve a stable baseload geothermal power generation capacity of 810 gigawatt-hours (GWh) a year in 2022.

Gürmat Elektrik Uretim, which owns Mogan Enerji Yatirim Holding (85%), Güriş Holding (4.72%), Güriş Inşaat ve Muhendislik (4.72%), Gurenerji Elektrik Uretim (0.56%), and Mr. Müsfik Hamdi Yamantürk (5%), operates the Efeler geothermal power plant.

Efeler GPP location

The Efeler power project site encompasses the Germencik geothermal field, one of the hottest geothermal areas in Turkey.

The property lies in the western portion of the Buyuk Menderes Graben, an active rift basin situated in western Turkey. The region is characterised by the presence of water-bearing reservoirs and abundant geothermal activity.

Plant make-up

The Efeler GPP comprises two operational facilities, namely the Gürmat-1/Germencik, also known as Galip Hoca, and the Gürmat-2 encompassing the Efe-1, Efe-2, Efe-3, and Efe-4 GPP units.

Gürmat-1 became operational in 2009, while Gürmat-2 was commissioned in 2014.

Each GPP unit includes a turbine, an air-cooled condenser, and a non-condensable gas discharge system for handling the carbon dioxide (CO2) and hydrogen sulphide (H2S) produced in the process.

Gürmat-1 is a 47.4MW dual flash type plant, while the 114.9MW Gürmat-2 includes a 47.4MW dual flash type Efe-1 GPP unit and three binary GPP units named Efe-2, Efe-3, and Efe-4, each capable of producing 22.5MW of electricity.

Details of the expansion

The expansion project was launched under Turkey’s Ministry of Energy Market Regulatory Authority (EMRA) strategic plan (2015-2019), which encourages the development of renewable energy potential in the country.

Efeler’s Gürmat-2 expansion involves the construction of three additional binary GPP units namely the 22.6MW Efe-6, the 25MW Efe-7, and the 50MW Efe-8 along with associated transmission lines, boreholes (22 production wells and 20 reinjection wells), and a pipeline network interconnecting the powerhouse and production wells.

The Efe-6 unit came online in August 2017, followed by the Efe-7, which began commercial operations in October 2018.

The environmental impact assessment (EIA) of the Efe-8 was approved after reconsideration by the Turkish government in December 2018. EMRA issued the license for the final unit in 2019.

The expansion will be completed with the commissioning of Efe-8 in October 2020.

Technology used by Efeler geothermal power plant

The Efeler facility produces energy by tapping the high-temperature groundwater (220°C) contained at the lower depths of the geothermal reservoirs. Hot water coming out of the production wells separates into steam and liquid phases.

The steam then moves to the heat exchangers/evaporators for converting n-pentane, which is the system’s secondary working fluid, into steam without any contact. Vaporised secondary working fluid drives the steam turbines to generate electricity.

The pentane, which is released as the exhaust steam from the turbines, is reused for pre-heating the pentane present in the heat exchanger before condensation in an air-cooled condenser. Once used, the geothermal water is reinjected back to maintain the reservoir efficiency.

Infrastructure and transmission

The primary infrastructure of the project includes the power plant units consisting of conventional steam turbines, borewells, pipelines, and emergency ponds to collect the geothermal fluids during a crisis.

The electricity generated by Efe-6 is fed to the national grid via the existing 3.9km-long 154kV overhead transmission line of the Gürmat-1 GPP, while Efe-8 will use the existing 154kV Gürmat-2 transmission line.

Interconnection with the transmission grid requires the construction of two new switchyards adjacent to the Efe-6 and Efe-8 site.

Efe-7 is interconnected to the grid without any switchyard using a 31.5kV underground cable system that is 0.9km-long.

Financing for Efeler geothermal power plant expansion

A group of international and local banks including the European Bank for Reconstruction and Development (EBRD), the Asian Infrastructure Investment Bank (AIIB), and the Black Sea Trade and Development Bank (BSTDB), Isbank, Industrial Development Bank of Turkey, and ICBC Turkey will finance the expansion project.

Under the financing arrangement, AIIB, EBRD, and BSTDB will provide loans of $100m, $60m, and $20m respectively to Gürmat Elektrik for the Efeler expansion project.

Turkey’s most significant commercial lender Isbank will provide a loan of $90m, while ICBC Turkey and Industrial Development Bank of Turkey (TSKB) will lend $20m and $50m respectively for the project.