China's growing energy security problem
China posted a surprise trade surplus of $15.3bn (£10.2bn) in February, adding to signs of recovery in the Chinese economy.
But economic growth in China depends on a large and constant source of energy to keep its factories and cities running.
Martin Adams, energy editor at the Economist Intelligence Unit in Hong Kong, says to counter the problem of having a secure energy supply China is trying to turn more to green energy, albeit on a small scale.