SHENZHEN, China, Jan 16 (Reuters) - Solar cell maker China Sunergy Co Ltd (CSUN.O: Quote, Profile, Research) aims to spend $150 million to raise its shipment level to 500 megawatts after a few years, from an expected 160-170 megawatts this year, its chief executive said.

Nanjing-based Sunergy expects its gross margin to improve "significantly" this year as it adds more lines to produce high-efficiency cells, despite lingering supply constraints on key raw material polysilicon, Allen Wang, chief executive of Sunergy told Reuters in an interview on Wednesday.

Wang was speaking on the sidelines of a solar technology conference in the southern boomtown of Shenzhen, near Hong Kong.

Sunergy sustained losses in the third quarter of last year, hurt by a tight supply environment for polysilicon, whose prices have shot up recently as solar cell and semiconductor companies scramble to secure supplies of the key ingredient. (Reporting by Judy Hua; Editing by Anne Marie Roantree)