The construction of China's longest ultra high-voltage direct current transmission project is now underway in northwest China's Gansu Province.

Li Ming with State Grid Gansu Electric Power says this project environmentally friendly.

"The positive and negative 800-kilovolt ultra high voltage direct current transmission line connecting Jiuquan and Hunan is a green project that helps develop clean energies and control air pollution. The project, once put into operation, will have an annual transmission capacity of 48 billion kilowatt-hours and reduce Hunan's coal transportation volume by 20 million tons equal to one third of Hunan's total power consumption."

The over 2,300-kilometer-long transmission line is connecting the northwestern city of Jiuquan to Zhuzhou in south China.

It is projected to transmit 48 billion kilowatt-hours of wind and solar power to Hunan.

The line is expected to be put into operation in 2017.