"Is This Really Possible?" The World Is Watching... Could My Car Become a "Mobile ESS"? [Energy Odyssey] 15

III. The Dream of Electrification

Renewable Energy Expansion Makes Storage Capacity Critical
AIDCs Also Need Flexible Power Management
Can V2G Projects Move Beyond the Pilot Stage?

Editor's NoteRecent supply chain crises caused by wars in the Middle East and the government's megaprojects have made energy more important than ever. With South Korea relying on overseas sources for most of its primary energy, the country faces the difficult challenge of achieving energy security, carbon neutrality, and economic growth simultaneously. In this series, reporters covering energy sites and developments across government and industry will examine a range of current issues and explore possible solutions.

Demand for energy storage systems (ESS), which had risen as renewable energy accounted for a growing share of power generation, is poised for a resurgence in the age of artificial intelligence (AI). Electricity is produced and consumed simultaneously. An ESS stores electricity after it is generated and supplies it where needed when demand rises or supply falls short.

An ESS is a supporting system that enables the efficient use of renewable energy. The amount of power generated by solar and wind energy can vary depending on the weather and time of day. Solar power, for example, is often generated in greater quantities than needed during daylight hours, while generation falls in the evening, when demand peaks. This intermittency is considered its biggest drawback. An ESS helps bridge this gap: it stores energy when electricity use is low and supplies it when demand is high.

Yaksu Offshore Wind Power in Yeonggwang, South Jeolla Province. The 4.3-MW Yaksu Offshore Wind Power project is a pilot project launched by the Jeonnam Development Corporation, the first local public corporation to do so. It is located offshore, about 2.5 km from Baeksu-eup, Yeonggwang County. Photo by Kang Jinhyeong

ESS systems take various forms depending on how they store energy. The main types include pumped-storage hydropower, which uses the potential energy of water; compressed air energy storage, which uses the pressure energy of compressed air; and battery energy storage systems (BESS).

Demand for BESS has recently increased as AI data centers expand. In the AI era, data centers need flexible power management that can rapidly receive and supply electricity when needed, not merely a large electricity supply.

According to the Korea Trade-Investment Promotion Agency (KOTRA), U.S. data center power demand is projected to rise from 52 gigawatts (GW) last year to 115 GW in 2030. AI data centers use enormous amounts of electricity, and their power consumption can fluctuate significantly as numerous GPUs start and stop processing at the same time. ESS helps balance these fluctuations. When power consumption suddenly spikes, it rapidly supplies stored electricity; when demand falls, it stores electricity again, responding to sharp changes.

How ESS Works with a Battery System

A battery-based ESS consists primarily of a battery system, a power conversion system (PCS), a battery management system (BMS), and an energy management system (EMS).

The battery system is the core component of an ESS that stores electricity. Batteries are organized into units such as cells, modules, packs, and racks. Moving from cells to modules and from packs to racks, their physical size, weight, voltage, and energy storage capacity increase in stages. A battery ESS stores large amounts of electricity by installing multiple packs or racks in a container.

The recent expansion of lithium iron phosphate (LFP) battery factories by battery material manufacturers is also linked to the growth of ESS. LFP batteries have lower energy density and are heavier than conventional ternary batteries. However, because ESS facilities are fixed installations on land, LFP's advantages in cost competitiveness, safety, and relatively long lifespan are especially pronounced.

A BMS is installed inside the battery system. It coordinates the tens to thousands of battery cells in an ESS so that they operate as one system. If it detects abnormal voltage, current, or temperature, it enables safe operation through charging and discharging. It also estimates the remaining capacity and the battery's lifespan and performance, controls cell balancing and overcharging and over-discharging, and manages the battery to ensure safe operation.

A PCS does more than simply convert electricity; it is a device that determines the stability and efficiency of the entire power grid. Its function is to convert alternating current (AC) to direct current (DC), and vice versa. The electricity stored in and discharged from batteries is DC, while household electricity and transmission and distribution networks use AC, making power conversion essential.

While a BMS manages the internal condition of a battery, an EMS monitors the amount of electricity stored in an ESS. It serves as the software that manages the overall operation of the ESS.

ESS is also expected to play an important role in energy security. This is because ESS is essential to expanding renewable energy generation as the country transitions to a decarbonized electricity system.

Agrivoltaic solar power plant installed on farmland in Wolpyeong-eup, Yeomsan-myeon, Yeonggwang-gun, South Jeolla Province. Photo by Kang Jinhyeong.

By storing surplus electricity generated by solar and wind power, ESS can reduce reliance on imported fossil fuels. ESS is also used in AI data centers and advanced communications facilities, where it protects servers and critical national infrastructure in the event of a power grid emergency or fluctuations in electricity supply.

The government has launched the third bidding round for the central ESS contract market. The third round totals 1,180 megawatts (MW) in installed capacity, the largest volume on record and exceeding the combined 1,100 MW of the first and second rounds. The move is intended to prepare for growing renewable energy generation and data center demand.

Tensions between the United States and China are benefiting the ESS industry. Chinese LFP batteries currently account for more than 90% of the battery ESS market, but their share is expected to fall significantly under U.S. supply chain restrictions related to Prohibited Foreign Entities (PFEs). The United States has said that ESS projects beginning construction this year will be ineligible for tax credits if they use raw materials or components produced by entities or companies linked to certain countries of concern, including China, Russia, Iran, and North Korea.

Reselling Unused Electricity from a Parking Lot

A demonstration project is also underway for Vehicle to Grid (V2G), which enables electricity to be bought and sold using electric vehicles. V2G uses an electric vehicle's battery like an ESS, supplying surplus electricity back to the power grid while the vehicle is parked.

Vehicles can be charged with electricity generated during the day, and the electricity remaining in an electric vehicle can be sold back in the evening. Electric vehicles thus become more than just a means of transportation: they serve as "mobile batteries" that help stabilize the power grid and as ESS units that can move.

Revenue varies depending on the electricity market price, the time the vehicle is connected, and the amount of electricity generated. According to Herit, the virtual power plant (VPP) operator for Hyundai's ongoing V2G demonstration in Jeju, the vehicle will not discharge below the minimum battery level set by its owner. It discharges automatically only during periods when it can contribute to the power grid and prices are high. The system can also be set to ensure the vehicle has the amount of charge the customer wants by the scheduled departure time.

Lee Seonyeong, a Jeju resident participating in the demonstration project, said, "It is meaningful not only because it helps stabilize the power grid by supplying electricity when needed, but also because it contributes to the environment."

However, expanding V2G has been difficult because building infrastructure for bidirectional chargers, which differ from standard chargers, is costly, and the model of transmitting electricity and receiving payment using privately owned cars rather than power plants does not fit existing electricity market rules.

This content was produced with the assistance of AI translation services.