As a rule, large-scale combined cycle gas and steam power plants consume immense volumes of cooling water. In many cases consumption is so high that it makes sense to install hydroelectric facilities.

This is exactly what was decided for the CCPP Bandirma combined cycle gas and steam power station on the Marmara coast in Turkey. 15 m3/s of seawater are required here to keep the machinery cool. Just a few months ago, exploitation of this hydroelectric potential was made possible by the experienced Austrian hydropower specialists at Geppert as they provided and installed the electro-mechanical technology required. The Kaplan turbine is very well protected from the strongly corrosive effects of salty water and provides a constant power output of 3.5 MW. This job set the experienced Tyrolean turbine manufacturers a number of challenges.

The ceremonial state opening of the new Enerjisa Bandirma Natural Gas Combined Cycle Power Plant – or Bandirma CCPP for short – took place at the end of 2010 and was attended by the Turkish Prime Minister Recep Erdogan. Enerjisa is an immense energy producer and invested around 550 million Euros in the power station that – at full capacity – is capable of generating 916 MW and supplying an annual volume of 7000 GWh to the Turkish grid. In fact, the station is responsible for around 3.5% of Turkey’s total electricity supply and it’s the largest and most powerful power station run on natural gas in the entire country. Its overall efficiency rating of 59% also means it is the most modern and effective facility in Turkey.

Bandirma CCPP is situated in the port city of the same name on the southern edge of the Sea of Marmara. The city is home to 130,000 inhabitants and is an important business centre. The port is a particularly important transfer hub between Istanbul and Izmir. The new combined cycle gas and steam power station project was completed with the assistance of numerous established energy businesses, and attracted a large degree of international attention.

Salt water integral to the system
Seawater from the ocean below is used to cool down the thermic processes in the power station. It is pumped into the facility up a total climb of 30m and having been pumped through the heat exchange system, reaching a maximum temperature of 35°C, it is then fed back into the sea. It made good sense to use the remaining height difference of 26 metres for hydro-energetic exploitation. Obviously, the plant operators wanted to make the most out of this opportunity, so they decided to build a suitable hydropower turbine in the cooling water system. This meant facing a multiplicity of challenges posed by salty water and the local particularities of the site, which is why they called on the experience and products of one of the industry’s best known manufacturers. Not only has Geppert from Hall in Tyrol, Austria, been producing turbines for over 100 years, they have also gathered decades of experience in the management and implementation of international hydropower contracts. In May 2013 the Austrian company was awarded a contract to install the electro-mechanical facilities in Turkey. The system was successfully commissioned at the beginning of last summer.

Non-stop full power
‘The cooling water is pumped at a constant volume throughout the year. Hence, the combined cycle power plant is in permanent use at full capacity. The plan is to schedule 2 weeks of complete downtime every 2 years for repair and maintenance work’ said Geppert’s project manager, Thomas Marthe (Ing.), expanding on the framework of the agreement. In terms of machine construction this entailed optimising operational performance. Geppert’s designers constructed the Kaplan turbine to take these requirements into consideration.

However, this proved less of a problem than the use of salty seawater, which is extremely corrosive for metals in warm conditions of up to 35°C. Marthe continued: ‘It was the first time that we had dealt with a system that actively uses salt water, so we had to spend a considerable amount of time discovering which substances, materials and anti-corrosion  coatings best suited the task.’ Ultimately, the main parts of the turbine – the mill wheel, control device, main wheel ring and suction pipe – were all made of a high-grade rustproof Duplex steel alloy. The standard steel housing elements were coated with a very special anti-corrosion layer. This helped to ensure the parts would work reliably within the cooling system for many years.

Hydropower turbine increases environmental friendliness
The turbine was installed to take advantage of a net drop of 25 m and a maximum volume of 15 m3/s, and is usually taken to capacity by the 3.5 MW motor. In addition to the turbine the scope of delivery provided by Geppert also included the generator, the closing flap, a compatible cooling system, and all the electro-technical equipment. This station-within-a-station was provided as a turnkey project by a consortium led by Geppert, although a local construction company was responsible for all the building agendas.

The Tyrolean company has plenty of experience working on hydropower projects on foreign soil, so transporting the components did not pose any special challenges. Nevertheless, unpleasant obstacles were encountered. ‘For some inexplicable reason customs procedures were very slow-moving and complicated. This led to a construction schedule delay of around three weeks. Fortunately, were able to catch up during the assembly and commissioning phase, and managed to stay within the overall completion deadline’ recounted Thomas Marthe. The hydropower station within the cooling water system of the combined cycle steam power plant has now been in non-stop operation since last June, and the power it produces contributes in no small measure to the environmental friendliness of the Turkish high-performance steam power station.