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Sihwa Lake Tidal Power Plant turns national embarrassment into global model

Published: 12 Dec. 2025, 07:00

The Sihwa Lake Tidal Power Plant in Ansan, Gyeonggi [K-WATER]

At the Sihwa Lake Tidal Power Plant in Ansan, Gyeonggi, on Nov. 27, gates opened with the ebbing tide, sending water surging from the lake into the sea. Inside the central control room, employees of the Korea Water Resources Corporation (K-water) closely monitored water level changes between the two bodies of water, separated by a seawall.

"We lower the Sihwa Lake water level as much as possible, then use the difference in elevation between the sea and the lake during high tide to generate electricity twice a day. Each day, seawater equivalent to nearly half the lake’s capacity flows in and out," said Lee Dong-hee, head of operations at the plant.

On one wall of the control room, the lunar calendar date — Oct. 8 — was prominently displayed. “We have to follow the lunar calendar to track the tides. When the full moon rises, tidal ranges are at their largest and power generation is most efficient,” Lee explained, highlighting the reversal of fortunes the plant delivered to what had once been considered one of Korea’s worst national projects.

From failed project to global model

The Sihwa Lake Tidal Power Plant is Korea’s only tidal power facility and was completed in 2011 as part of an effort to improve the lake’s water quality. Once dubbed the “lake of death,” it suffered severe pollution after a seawall was built to block ocean water in a bid to secure water for agriculture and industry. As the lake stagnated, fish died in large numbers and a foul odor permeated.

The government eventually abandoned its freshwater conversion plan and, in 1997, reopened the lake to the sea. It invested 600 billion won ($409 million) to build what is now the world’s largest tidal power plant, taking advantage of a tidal range as high as 7.8 meters (15.6 feet) — ideal for such energy generation.

The Sihwa Lake Tidal Power Plant in Ansan, Gyeonggi [K-WATER]

The Sihwa Lake Tidal Power Plant in Ansan, Gyeonggi, seen polluted soon after construction in 1994 [K-WATER]

Today, the facility generates 552 gigawatt-hours annually, enough power for roughly 500,000 people — equivalent to the entire population of Siheung. Using AI, the plant calculates daily changes in tidal levels to maximize electricity production, drawing international interest as a benchmark model.

The tidal exchange also helped restore the lake’s water quality to levels seen before the seawall’s construction. The lake’s chemical oxygen demand, a measure of water pollution, dropped from 17.4 milligrams per liter in 1997 to 2.2 milligrams per liter in 2021. As the ecosystem recovered, Sihwa Lake became a key stopover for migratory birds. The number of natural monuments — which in Korea include animals — observed in the area more than doubled from seven species in 2005 to 18 in 2020.

Samsung's 10 years of renewable energy

Tidal power and other water-based renewables are drawing attention from businesses. K-water signed a power purchase agreement with Samsung Electronics last year to supply all electricity generated by the Sihwa plant to the company over a 10-year period through 2033.

The Sihwa Lake Tidal Power Plant control room in Ansan, Gyeonggi [K-WATER]

The Sihwa Lake Tidal Power Plant in Ansan, Gyeonggi [K-WATER]

“This isn’t a direct power transmission but a virtual agreement,” said Koh Ji-hun, head of K-water’s Energy Convergence Business Division. “But we do receive monthly settlement payments based on the plant’s output. The fixed price ensures stable revenue from electricity generation.”

Samsung’s decision to secure a decade’s worth of power in advance comes amid growing pressure from global partners like Google and Apple to meet the RE100 goal — sourcing 100 percent of electricity from renewable energy.

According to the Carbon Disclosure Project’s 2024 annual report, Samsung and SK hynix have achieved RE100 compliance at overseas sites at rates of 97 percent and 100 percent, respectively, but remain at just 12 percent domestically.

K-water plans to expand the Sihwa plant from 10 to 14 generators and is considering building a new tidal power plant in Saemangeum, North Jeolla. “By 2030, we aim to continuously develop water-based energy equivalent to 10 nuclear power plants — 10 gigawatts — and lead the country’s energy transition while helping companies strengthen their global competitiveness,” said K-water President Yun Seog-dae.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY CHON KWON-PIL [[email protected]]