NEW YORK - Trina Solar Ltd said on Wednesday it had extended by five years its contract to buy polysilicon from GCL-Poly Energy Holdings Ltd through 2021

Trina, which began receiving polysilicon from GCL-Poly's unit Jiangsu Zhongneng Polysilicon Technology Development Co in 2008, will take delivery of enough of the material to manufacture 8,500 MW of solar modules over the 13 years of the contract.

Prices for polysilicon, the key material used to turn sunlight into electricity in most solar cells, have tumbled sharply in the past year from more than $300 per kilogram to about $60 as growth in the renewable energy sector slowed.

Under the contract extension, Trina said it would take shipments of polysilicon and wafers at pre-determined shipment volumes and prices. The agreement also contains a price adjustment clause that offers a market-linked price formula, although it did not disclose details.

Trina will begin taking deliveries of polysilicon wafers, the thinly sliced layers of the processed material, from GCL-Poly in 2010, supplementing the output from its own manufacturing lines, the company said.

Shares in Trina rose 1 percent to $32.20 in premarket trade.

(Reporting by Matt Daily, editing by Dave Zimmerman)