By Jeremy Page 

BEIJING--North Korea almost doubled its electricity exports to China last year despite its own chronic power shortages, drawing in more revenue as other sources of income were shut off by international sanctions.

At the same time, China has been helping to boost North Korea's power supplies by building two new joint-venture hydropower plants on the Yalu River that forms their common border, according to notices on Chinese government and procurement websites.

United Nations sanctions on North Korea don't ban electricity trade. Beijing already operates at least four joint venture hydropower plants with Pyongyang, power from which is usually split between the countries, with the bulk going to China.

But the balance shifted dramatically last year, when North Korea's power-trade surplus with China grew to $10.8 million from $2.6 million in 2016, Chinese customs figures show.

China's imports of North Korean power rose 91% to 319,681 megawatt-hours, or $11 million, the highest since relevant records began in 2000, the customs figures show. Chinese electricity exports to North Korea dropped around 96% to 942 megawatt-hours, or $132,000, the lowest since 2005.

That means that North Korea earned more hard currency but had less power for its people, potentially exacerbating shortages that regular visitors say have caused increasingly severe brownouts in recent months.

The two new plants, to be completed in 2019, will "benefit both China and North Korea," said a notice posted last year on the local government website of Ji'an, a Chinese border city. In January, a tender was issued online for work on transmission lines, to be done by October.

Local and central government officials declined to comment.

The trade data and construction work show how Beijing continues to support Pyongyang in key ways even as it steps up enforcement of U.N. sanctions on its border, leading to a steep decline in overall bilateral trade last year.

North Korea's electricity supplies are closely watched by the U.S. and other countries as they try to gauge the impact of sanctions that they hope will prompt its leader, Kim Jong Un, to give ground ahead of or during his planned talks with U.S. President Donald Trump in May.

Beijing has also been alarmed by Mr. Kim's nuclear and missile tests since 2016, but is wary that collapse of his regime through economic crisis or U.S. military action could bring U.S. troops up to the Chinese border, trigger a flood of refugees into northeast China and create a unified, democratic, pro-Western Korea.

When a ban on joint ventures with North Korea was added to U.N. sanctions in September, China negotiated inclusion of a line saying the provision wouldn't apply to existing China-North Korea hydroelectric power infrastructure projects.

No other country officially trades electricity with North Korea, according to U.N. trade data. And while Beijing has sharply reduced its exports of refined oil products to North Korea in recent months--and says it strictly enforces U.N. sanctions--it still provides large quantities of crude oil that aren't included in customs figures, U.S. officials say.

North Korea, which appears in nighttime satellite photos as shrouded almost entirely in darkness, can ill afford to lose the power from its joint-venture plants with China.

Regular visitors to North Korea say power supplies improved in recent years, but brownouts have become more regular--with as little as three hours of electricity daily in some areas--since U.N. bans on coal and other major North Korean exports were introduced last year.

As those sanctions bite, Pyongyang may be "looking into any ways it can find to boost revenues, including selling electricity that it might otherwise find a way to use locally," said David von Hippel, a senior associate at the Nautilus Institute for Security and Sustainability.

North Korea's deteriorating economy and creaky national grid mean that "it may have power that it can't use locally or send to other areas of the country, and thus can sell to China," said Mr. von Hippel, who has studied North Korea's electricity infrastructure.

China's energy links to North Korea are also controversial because some U.S. and allied officials say that Pyongyang diverts supplies away from ordinary people and toward its military and to its nuclear program.

China protects its joint-venture hydropower plants with North Korea "under the argument that energy supply benefits ordinary people," said Curtis Melvin, a researcher at the U.S.-Korea Institute at Johns Hopkins SAIS.

"It does, but it also supports the military industry which has a number of important factories concentrated in Jagang Province," which covers the area adjoining the two new plants. Mr. Melvin said China's priority was likely to secure power supplies for its own northeast, but that assisting North Korea was also a motive.

Since 2012, official Chinese media have reported on plans to link North Korea to China's national grid by building a 66 kilovolt transmission line from the Chinese border city of Hunchun to the North Korean port of Rason, where many Chinese companies have invested in recent years.

Local authorities in the northeastern province of Jilin said in 2016 they were pressing ahead with that plan, but haven't provided any further information and the company in charge, Northeastern Electrical Grid Co. Ltd., didn't respond to requests for comment.

North Korea's power consumption and generating capacity have plummeted since the Soviet Union's collapse in 1991 ended all assistance from Moscow.

The International Energy Agency estimates that North Korean electricity consumption peaked at 1,247 kilowatt-hours per capita in 1990 and dropped to 460 kilowatt-hours per capita by 2015--around 4% of the level in the South.

North Korea is now thought to get around 70% of its electricity from hydropower, experts say. One significant source is the joint venture China-Korea Hydropower Company, established in 1955.

The company's joint-venture plants include one of North Korea's largest power sources, the giant Sup'ung Dam, which was completed by the Japanese in the early 1940s, bombed in the 1950-53 Korean War and later refurbished with Chinese help.

China-Korea Hydropower Company operates three other plants built on the Yalu River between the 1960s and 1980s, according to Chinese researchers.

The company is also responsible for the new Wangjianglou and Changchuan hydropower plants, which are being built on the Yalu River with combined investment of 1.1 billion yuan ($174 million), according to Chinese government websites. Company officials couldn't be reached for comment.

Xiao Xiao in Beijing contributed to this article

Write to Jeremy Page at jeremy.page@wsj.com

(END) Dow Jones Newswires

March 16, 2018 22:29 ET (02:29 GMT)