Technology case study: Sihwa Lake tidal power station
The west coast of South Korea, with its winding rias, many-sized inlets and wide tidal range, is a rich repository of tidal energy resources. This is the setting for the world’s largest operating tidal power station: the 254 MW Sihwa Lake project.
Sihwa Lake is a 43.8 km² artificial lake constructed as a land reclamation project by the South Korean government in 1994, using a 12.7 km long seawall at Gyeonggi Bay. It was created to provide reclaimed land for the nearby metropolitan area, flood mitigation, and secure irrigation water by converting the costal reservoir to fresh water.
Yet once the seawall was closed and the natural tidal currents were cut off, water quality deteriorated. This was due to a combination of factors, including low natural freshwater inflows and the increase of wastewater from the industrial complexes.
Delays in the construction of local wastewater treatment facilities further exacerbated the situation, and by 1997 the Sihwa Lake was so contaminated that the water could no longer be used.
In response, the government transitioned Sihwa’s operating strategy from a freshwater to a seawater lake by periodically opening up the seawall’s sluice gates to flush the basin by circulating seawater in an effort to improve the water quality.
However, seawater circulation via the sluice gates alone is limited. K-water, the Korean governmental water authority, commissioned the first feasibility study for the construction of a tidal power plant at the site which would improve seawater circulation by about 200 per cent. Approval was received in 2002 and construction began in 2004.
The 552.7 GWh of electricity generated from Sihwa tidal power plant is equivalent to 862,000 barrels of oil, or 315,000 tons of CO2 – the amount produced by 100,000 cars produce annually."
The tidal power plant facility
The feasibility of tidal energy generation in South Korea was first investigated in the 1970s. At the time, potential developments were not deemed profitable and were postponed. In the early 21st century, tidal energy generation gained increasing attention as a strategy to counter rising international oil prices and reduce greenhouse gas emissions.
The Sihwa tidal power plant generates one-way power twice a day at high tide. The sluice gates are closed as the tide comes in which isolates the reservoir at its lowest level. When the tide is high, water then flows from the West Sea to Sihwa lake via the ten turbines, generating electricity.
With ten water turbine generators each with an installed capacity of 25.4 MW, the power plant produces 552.7 GWh of electricity annually – enough to support the domestic needs of a city with a population of 500,000.
LocationSihwa embankment, Ansan City, Gyeonggi-do, KoreaPower capacity254 MW (10 x 25.4MW turbines)Gates8 sluice gates (15.3m×12m, Culvert type)Annual generation552.7 GWhProject construction period2003–11 (commercial operation began in 2011)Project costUSD 560 million
Effect of the construction
With limited energy resources and a need to develop pollution-free, clean energy, South Korea is looking to tidal power as a potential alternative to fossil fuels. Tidal power offers some strong advantages in comparison to other renewable sources, such as its periodicity and long-term predictability of tidal patterns.
The 552.7 GWh of electricity generated from Sihwa tidal power plant is equivalent to 862,000 barrels of oil, or 315,000 tons of CO2 – the amount produced by 100,000 cars produce annually.
The most remarkable impact has been the recovery of water quality and ecosystems. Approximately 160 million tons of water flows in and out of the floodgate and waterwheel, accounting for about half of the total water quantity in Sihwa Lake. The continuous circulation of water between the lake and the outer sea during the power generation process has improved the water quality.
In 1998, the chemical oxygen level in Sihwa Lake was 17ppm, but has since been reduced to 2ppm, resulting in an improved habitat for all species of fish.
This site has become a very popular site for learning about lively ecosystems, with over 146 bird species including stork and mallard, and some 23 million birds living in and around the lake.
The Sihwa embankment, 12.7 km in length, is also a popular spot for leisure activities and sports. The tidal power station and surrounding area today attract some 1.5 million people annually.
The future of Korean tidal power generation
Based on the success of the Sihwa tidal power plant and the utilisation of large tides by K-water, other companies in South Korea have taken the impulse to plan new tidal power plants in the West Sea off the country’s western coast.
Since 2006, the Korean government has pursued studies in tidal energy development at Incheon Bay in the Yeongjongdo Island and Ganghwado Island district, in order to establish a foundation for the development and commercialisation of eco-friendly tidal power generation technology.
Through the research and analysis of marine quality, conceptual design and environmental technology, the government has devised a basic plan for establishing a 1,320 MW tidal power plant at Incheon Bay. The facility is expected to be commissioned in 2017.
In addition, another proposed development at Garolim Bay has completed a feasibility study and basic design for a 520 MW tidal power plant.
There have been some delays to the approval of these projects due to concerns raised by some municipal corporations and environmental organisations about potential environmental impacts. Further studies and designs are being undertaken to ensure that the proposed development has a minimal impact on the marine environment, improves the surrounding coastal ecosystems and meets the requirements of the renewable portfolio standard (RPS).