On the 18 of October, we visited lake Sihwa and its tidal powerplant, which is located along the coast of the West Sea, 60 km from the centre of Seoul. Kim Jongdeug from K-Water gave a presentation and gave a tour in the control room and the powerplant itself. He is responsible for the operation and maintanance of the Sihwa Power Plant.

The project began in 1994, with the main goal to create more land for industry and agriculture. This was executed by constructing a tidal embankment and then reclaming the area behind. This was considered a good way to expand the Metropolitan area of Seoul. This facilitated opportunities regarding the rapid urbanization of South Korea. In the beginning, Lake Sihwa was planned to be a freshwater lake. Due to the combination of still standing water and waste water dumped in the lake by industries, the water quality severely degraded. Even though measures were put in place to improve water quality, such as construction of wetlands. Eventually K-water came with the the solution; a tidal power plant. By reintroducing tidal fluctuations as inflow in the lake, water quality increased significantly (from COD 17.4 to 2.0). Since lake Shiwa was historically also made up of salt water and never became completely fresh water, this transition was no issue. Even though normally the main goal of a tidal powerplant is to be economically feasible, in this case the generation of electricity was a nice bonus. Since the tidal powerplant was constructed to improve the water quality after the reclaimed area, subsidies were needed to fund the project.

Because of the gravitational and centrifugal forces from the moon and the sun, tides are generated in the sea water. With those tidal fluctuations energy can be generated, using the differences in water head. To let the powerplant operate efficiently, a couple of environmental constraints should be met. A minimum tidal range of 5 m is required and at the tidal powerplant of Lake Sihwa this tidal range has a value of 7.8 m. There are different types of power plants, which differ in the direction(s) of tide they use to generate electricity. The powerplant of Lake Sihwa generates energy using the rising tide (one-way power generation). Generating energy using a dual-tide generator would increase the maximum amount of energy substantially, however that was not possible in this case. Since the reclaimed land behind the tidal embankment has a very low ground level, this would otherwise get in danger.

The control room is located on the opposite side of the lecture hall, with a glass wall in between. In the control room there are screens displaying the camera footage, system operation and the amount of power generation per unit. A few people were monitoring the computer screens. The green symbols on the right side display the gate conditions. Once in the three years, large maintenance is needed.

The dam generates on average 552.7 GWh per year. The energy is generated using a total of 10 generators and 8 rolling gates. To make space for this large construction excavation works have been performed up until 35 m deep. The construction brought along some challenges. For example, sometime construction had to stop because of high amounts of fog. Furthermore, the operation and maintenance phase brought its challenges. The turbines have a design with three blades, compared to alternatives that have four, to increase the number of fish that survive. However, at times things still keep stuck, like a rope from a ship. This decreases the efficiency of the powerplant.

During the last few years sustainability has become more and more important in South Korea. This was already clear from the need for the improvement of the water quality of Lake Sihwa, but there is attention for renewable energy as well. Therefore K-water has constructed some solar panels and wind mills on and around the lake. However, since there are regulations that state that the price of sea surface is related to the price of the land surface nearby, this is very expensive. Because of those high costs of placing solar panels on the water the solar park is not expanded, even though the water surface is not used for other purposes.

Does this project pave the way for others to come? Not right know in South Korea, because of the negative environmental effects during the construction fase and additionally high costs. Besides that, stakeholders in the fishing industry are often not very content with such projects, since the ecological changes resulting from the construction change the ecology and might harm the fish and mussel population. However, there are much lessons learnt from the project which can be considered for the future or abroad. For example, if it would have been clear from the start of the construction of the breakwater that the tidal powerplant would be installed, one could have opted for a dual tide generator. This way, more electricity would have been generated, but since this would endanger the reclamed land this was not performed here. For future projects, (extreme) weather conditions could be included better in the construction planning. Besides that, stability holes could be included and electric devices should be installed parallel to the waterway, for improved safety and more ease in the maintenance phase.

Altogether, the project created new land that provided extra space that was in demand because of the rapid urbanization in South Korea. First this resulted in water quality problems, but with the tidal powerplant those problems were solved and green energy is generated. We want to thank K-water once again for their time and insights in this interesting project!