Along the turquoise beaches of South Korea’s Jeju Island, hundreds of wind turbines spin as ferociously as the coastal wind. A few kilometers inland, large solar farms are hard at work converting the sun’s light into power.

During periods of high wind, the wind farm receives notices to halt its power generation. This is to prevent excess influx of power into the grid, which could potentially compromise the stability of the system and create a blackout. Consequently, hundreds of wind turbines gradually decelerate until they come to a standstill, standing eerily still amid the blustering wind.

Wind power curtailment is an increasingly contentious topic in Jeju. Curtailment, which refers to the forced shutting down of electricity generation at times of high power output, is usually implemented to prevent power oversupply and maintain grid balance. As more states and countries ramp up their renewable energy capacity, the curtailment of renewable sources is becoming increasingly common.

Earlier this year, California reached a record high in solar and wind curtailments. Subsequently, the United States Energy Information Administration published a report predicting a twofold rise in renewables curtailment in Texas by 2035. Beyond borders, countries like Australia, Japan, and China grapple with similar challenges. These data underscore the reality that the pursuit of maximizing renewable energy generation is insufficient in itself; the task of equipping the grid to adeptly manage the fluctuations in energy sources is equally important in the clean energy transition.

It is a testament to how mature and stable the energy grid is that what goes behind the power plug is often an afterthought for most people. However, beyond that power plug, the energy evolution is happening—and Jeju offers some lessons.

Located 150 miles south of the Korean peninsula, Jeju is home to around 670,000 people. It is one of the most beloved tourist destinations in the country, with a whopping 15 million visitors each year. The island is also known for its ambitious clean energy goals. Dating back to 2008, Jeju’s local government has been working on its “Carbon Free Island 2030” (CFI 2030) project, which aims to fully convert its vehicles and electricity generation to renewable sources by 2030. 

Reflecting this ambition, Jeju has rapidly expanded its renewable energy infrastructure in the past decade. In 2022, the island’s wind power capacity reached 285,440 kilowatts, a 22-fold increase since 2006. Solar added more than 500,000 kilowatts in capacity during the same period, surpassing wind power by 2017. Currently, about 18 percent of Jeju’s electricity is generated by renewable energy sources.

The expansion in renewables is necessary to meet Jeju’s goals but has brought acute disruptions to its existing energy system. 

The makeup of Jeju’s power sources is divided into three categories: central load dispatch plants using natural gas and bio-diesel, renewable energy and one-way high-voltage direct current (HVDC) lines that draw power from the Korean mainland. A handful of central dispatch power plants are designated as “must-run” generators that cannot be turned off, functioning as priority energy sources. When the energy demand increases, they are the first to be used, and when the demand runs low, they are the last to go off. 

The purpose of designating must-run plants is to ensure a steady and reliable supply of energy. Such checks and balances exist on many levels of the electrical grid, a necessary measure to support the highly-sensitive infrastructure. With must-run generators in place, renewable energy sources bear the responsibility of pausing energy production when supply runs high.

Over the past six years, the frequency of wind power curtailment has increased dramatically without a notable change in generation capacity. In 2015, there were only three cases. In 2022, that number jumped to 103, hitting a record high.

“Curtailment is inevitable in any country as renewable energy grows, due to its variability,” said Jahyun Kim, a power market and grid policy analyst at Solutions for Our Climate, a Korea-based think tank. “The difference is whether governments are willing to make fundamental changes to the energy system to try and minimize the issue.”

The curtailment’s most significant consequence is its potential to significantly stifle business enthusiasm for expanding renewable energy fleets. In Korea, wind power businesses currently do not get compensated for lost power during curtailment, causing a loss in profit. 

Deokhwan Choi, an officer at the Korea Wind Energy Industry Association, says that the fear of curtailment and other regulatory hurdles are discouraging growth in the industry. Such concern is clearly reflected in recent trends of newly built wind power facilities. 

In 2019, the capacity of newly registered wind power facilities was 1.6 gigawatts. In 2020, that number significantly dropped to around 240 megawatts. In the second quarter of 2021, there has been no new wind power registered, ringing an alarm for Jeju’s plan to reach net zero by 2030.

“While the Korean public is slowly opening up to the idea of renewables expansion, the policies around permitting and grid adaptation have yet to catch up,” Choi said. He also added that there needs to be a strong commitment from government agencies to gradually reduce fossil fuel and nuclear energy production, in order to make room for more wind and solar in the grid.

The local government, as well as KPX and the Korea Electric Power Corporation, are aware of the issue. A few of the suggested solutions are technical: building a dedicated energy storage system (ESS) and laying down additional HVDC lines. ESS functions like a giant battery for the grid and is often regarded as a necessary component for using renewable energy.

Jeju’s local government is experimenting with creating a market for excess energy during peak generation hours. The government offers companies the option to buy power at cheaper prices during the early afternoon, when oversupply typically occurs. People can also charge their electric vehicles at cheaper prices during these peak supply hours.

These proposed solutions are still in an experimental phase and there are several issues that have yet to be resolved. Building a new ESS, despite its usefulness, comes with a hefty price tag. Experts have not yet reached a consensus about how much energy storage needs to be built, which makes pinning down the exact cost difficult. 

It is also unclear who has the responsibility to build and pay for the infrastructure. Some believe the national government should initiate the project, while others argue the private sector competition would create a better product. 

Jeju’s wind curtailment issue could set an important precedent for the energy grid nationwide. While Jeju generates 18% of its power through renewable energy, South Korea as a whole only generates 7% through renewables. 

Kim said that KPX plans to initiate a pilot program for a new power market project in October. The program aims to decentralize the power system on Jeju Island, which could help reduce renewable energy curtailment. However, Kim also pointed out that the island is currently planning to build another major gas plant, which goes against its efforts for integrating renewables into the grid. “The last thing it needs is more fossil fuels,” Kim said.