Sihwa Lake Tidal Power Plant is a large tidal power station currently under construction. Due to be completed in December 2010 and it will operate with a total power output capacity of 254 MW, surpassing the 240 MW Rance Tidal Power Station to become the world's largest tidal power installation.

The tidal barrage makes use of a seawall constructed in 1994 for flood mitigation and agricultural purposes. Ten 25.4 MW submerged bulb turbines are driven in an unpumped flood generation scheme; power is generated on tidal inflows only and the outflow is sluiced away. This slightly unconventional and relatively inefficient approach has been chosen to balance a complex mix of existing land use, water use, conservation, environmental and power generation considerations.

The Sihwa Lake Tidal Power Plant should provide indirect environmental benefits as well as renewable energy generation. After the seawall was built, pollution built up in the newly created Sihwa Lake reservoir, making its water useless for agriculture. In 2004, seawater was reintroduced in the hope of flushing out contamination; future inflows from the tidal barrage are envisaged as a complementary permanent solution.

Cost of the Sihwa Lake Tidal Power Plant project is being met by the South Korean Government and at present totals 313.5 billion won. Mean operating tidal range is 5.6 m (18 ft), with a spring tidal range of 7.8 m (26 ft). The working basin area is 43 km² (17 sq mi).

Sihwa Lake Tidal Power Plant
Country	South Korea
Locale	Sihwa Lake, Gyeonggi Province
Status	Under construction
Opening date	December 2010
Construction cost	₩313.5 billion
Owner(s)	Korean Water Resource Corporation
Power station
Type	Tidal barrage
Turbines	10 × 25.4 MW
Installed capacity	254 MW