Korea Demonstrates DC Distribution System on an Island

The energy efficiency of a Korean island’s power system improves by more than 10% with a DC distribution system while maintaining reliability.

Source: Jintae Cho, Juyong Kim · T&D WORLD · | March 2, 2021

The island of Seogeochado where the project is based.

At the 1893 Chicago World’s Fair—held in celebration of the 400th anniversary of Columbus' discovery of the American continent—as U.S. President Cleveland pressed a button, 250,000 light bulbs lit up the fair. The electricity used for this memorable event was an alternating current (AC) invented by Tesla, and Edison's direct current (DC) has gone downhill ever since. In the 20th century, electricity generation was dominated by coal, gas and hydropower using rotating turbines. The electricity was generated with AC because electrical power could be transmitted over longer distances with lower losses.

Now, in the 21st century, photovoltaic power generation, hydrogen fuel cells and the representative renewable energy sources generate DC. In addition, most electronic appliances like refrigerators and washing machines use DC. Cell phones and lithium-ion batteries in electric vehicles (EVs), with 18.7 million U.S supplies expected by 2030, also use DC.

As the current power system adopts AC transmission as the standard, DC electricity generated from solar power, wind power and fuel cells is converted into AC, which is then converted back to DC through AC-DC converters installed in the home and mobile devices. Even under the assumption the conversion efficiency of each stage is on the high end at 90%, Korea Electric Power Corp. (KEPCO) estimates a power loss of approximately 30% occurs after undergoing three stages of conversion and reconversion.

DC Distribution System

To reduce the power loss that occurs during the conversion process, a DC system is proactively introduced by internet data centers (IDCs), which consume considerable power. In 2008, Lawrence Berkeley National Laboratory demonstrated a DC distribution system has the potential of using 28% less energy than the typical AC system. In Korea, a DC-based telecom data center also demonstrated a 13.2% improvement in efficiency with the implementation of a DC distribution system.