Combined cycle

www.modernpowersystems.com | MODERN POWER SYSTEMSNovember 2013 23

The economic growth and development of Korea, from one of the poorest countries in the world during the 1960s

to its status as an established industrialised nation today is truly incredible. In 2004, South Korea became a member of the elite trillion-dollar club of world economies and is currently ranked as the twelfth largest economy in the world.

However, Korea’s energy sector faces a major challenge stemming from this rapid development: the country’s high dependence upon imported fuels. Korea is not well endowed with domestic energy resources and consequently has become the world’s second largest importer of liquefied natural gas (LNG). And with many gas fired power plants under construction or planned Korea’s gas consumption will continue to rise significantly in the coming years.

Korea is experiencing a fast rise in the demand for electricity, which is why it is planning to expand its power generation capacity from 95 GW today to more than 150 GW by 2030. Gas-fired power plants are expected to account for approximately one-third of this installed capacity, while coal’s share of the power generation fuel mix is expected

to fall from the current level of 40% to around 16% by 2030. This means that South Korea’s power generation related CO

2 emissions are projected to decrease by about a third by 2030 even though power consumption is forecast to increase by around 25% over the same period.

Independent power producers (IPP) are playing an increasingly important role in South Korea with their primary fuel to date being liquefied natural gas (LNG).

South Korea’s first IPP, GS EPS, is operating successfully and continuing its track record of innovation. It was in October, 1997 that GS EPS awarded the contract for a new power plant at its site in Dangjin-City, Chungchong Nam-do Province, which is

approximately 120 km south of Seoul. This power plant, Dangjin 1 (formerly Bugok 1) was a first pioneering step. It was the first power plant in Korea to feature F class gas turbines, the Siemens SGT6-4000F. At the time of its commissioning in 2000, Dangjin 1 was the most efficient power plant in Korea.

Then in 2006, GS EPS awarded Siemens a follow-on order for an extension of the Dangjin power plant, the Dangjin 2 project (formerly Bugok 2). This power plant, featuring an upgraded model of the same SGT6-4000F gas turbine, was supplied on a turnkey basis in collaboration with GS E&C as consortium partner. The installation and commissioning were completed one month

Why efficiency matters in KoreaJohn Goss (CeeJay, Hong Kong), reports from Dangjin, where a new Siemens H class combined cycle plant has recently entered commercial operation

Dangjin 3 completed (source: Siemens)

Dangjin site plan (source: GS EPS)

Combined cycle

MODERN POWER SYSTEMS | www.modernpowersystems.com November 201324

ahead of schedule, in February 2008. The Dangjin 2 combined cycle plant, in a 2+1 multi-shaft arrangement, with a net capacity of 565 MW and a net efficiency of 58.6%, was then the most efficient and environmentally friendly power plant in Korea.

Continuing its sustained record of technology leadership at Dangjin, GS EPS partnered with Siemens again in March 2010, this time in a joint venture to bring Siemens H class gas turbine technology to Korea. In collaboration with GS E&C, Siemens supplied a complete turnkey H class single-shaft combined cycle plant for Dangjin 3 (formerly Bugok 3) (which was profiled in MPS, September 2011, pp 14-20).

Dangjin 3, which entered commercial operation on 19 August 2013, has achieved a combined cycle efficiency of over 60% (LHV basis/net), a first for Asia.

It is also the first deployment of the 60 Hz SGT6-8000H gas turbine and corresponding combined cycle technology in a single-shaft arrangement (SCC6-8000H 1S) and furthermore the first single-shaft plant in Korea.

The plant produces over 415 MWe on its one shaft, which has the gas turbine at one end, then generator, SSS clutch and, at the other end, the steam turbine.

The high efficiency levels at Dangjin 3 will serve to help GS EPS save up to 20 000 m3 of natural gas per year relative to generation of the same amount of power using the technology of Dangjin 2. “At today’s LNG import prices of around $15-17/MMBtu this amounts to $43 million in fuel savings over the turbine’s lifetime and predestines the plant to provide baseload power supply,” said Ki Hwan Cho, the GS EPS project manager for the Dangjin’s 3 expansion project. Put another way this corresponds to one complete LNG tanker load every eight years.

“Power plants with high power density are becoming increasingly important as the country attempts to optimise use of its limited space,” said W.K. Lee, CEO of GS EPS, and H class technology also has major advantages in this respect.

As well as high efficiency and power density, the Dangjin 3 plant also has enormous operational flexibility and is able to start up in less than 30 minutes to full load (hot start on-the-fly mode), to de-load very quickly, and to provide excellent frequency response capabilities. Having the SSS clutch between the generator and steam turbine helps with flexible start-up.

The plant’s HRSG with its Benson®-type HP stage also contributes to the fast cycling performance. The HRSG achieves live steam and RH temperatures of 585°C, deploying alloy T91 in the SH and RH sections.

Another four combined cycle power plants employing Siemens H technology are under construction in Korea, at Ansan, Andong, Posco and Daegu, with plans for more in development. MPS

A new Siemens study, presented at the World Energy Congress in Daegu, South Korea, in October 2013, notes that Korea, with its population of 50 million, has for years ranked number four in the list of countries with the highest coal imports in the world – only China, Japan and India import more. So it is no wonder, says Siemens, that Korea is planning to drastically reduce the coal contribution to its power generation fuel mix, to about 16% in 2030, compared with about 40% now, reducing the CO2 emissions from the country’s power sector by around a third (even though power consumption is likely to increase by about a quarter over the same period).

But Siemens thinks the Koreans could go even further, and additional changes in the power mix could even make it possible to reduce the power sector’s CO2 emissions by up to two thirds, as scenario analyses performed in the context of the new study indicate.

For instance, building even more high-efficiency gas-fired power plants than already planned could lower CO2 emissions still further, and increased exploitation of renewable energy resources would also help reduce both emissions and the country’s dependence on imported fuels even more. A further possibility for diversification of the energy mix, and, thus, for enhancing the security of supply while lowering the CO2 footprint could be offered by placing greater emphasis on nuclear energy.

If Korea were to dispense completely with coal-fired power plants in favour of modern gas-fuelled units by 2030, the power sector’s CO2 emissions would drop by a further third, and the country could save 9 million tons of imported oil equivalent per year, the Siemens study notes.

Possible scenarios for Korea’s future power generation fuel mix (source: Siemens study for WEC 2013)

Korea without coal?

Siemens H class projects to date > 24 gas turbines under contract (as of end September 2013) (source: Siemens)