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 coastal reservoir to fresh water. However, 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.
The tidal power plant facility:
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.
10 Turbine / Generator units; Runner diameter 7.5 m; Turbine Output 25.4 MW; Generator Output 26.8 MVA; Rated speed 64.3 rpm; Rated head 5.82 m; Rated discharge 482.1 m³/s; Rated voltage 10.2 kV; Rated current 1515 A; Annual energy production ~ 550 GWh.
Sihwa embankment, Ansan City, Gyeonggi-do, Korea
The construction of the Sihwa tidal barrage power plant (TBPP) was completed in 2011 and its operation started in August.
In 2014 a 75m high observatory was constructed at the Sihwa TBPP, which has attracted over 1 million visitors since its opening.
To date, the Sihwa TBPP is the largest and most expensive tidal installation in the world, with an installed capacity of 254MW. According to IREN, the site cost $298m to build in 2011. The cost per kilowatt hour (kWh) of the plant is worked out by multiplying the construction cost and the capacity. As such, it has been estimated that Sihwa cost $117 per kWh, while it produces electricity at $0.02 per kWh. It is formed of 10 generators, which produce a total energy capacity of over 550GWh annually.
After the seawall was built, pollution built up in the newly created Sihwa Lake reservoir, making its water useless for agriculture. In 1997, seawater was reintroduced in the hope of flushing out contamination; inflows from the tidal barrage are envisaged as a complementary permanent solution. This plan was abandoned in 2001 until the TBPP was initiated in 2004. The tidal power station is providing indirect environmental benefits as well as renewable energy generation. During commissioning of the project a diffusion of pollutants to the sea was expected. To reduce this effect a gradual increase in power generation was implemented as part of commissioning procedures.