American clean-energy companies racked up a $1.6 billion trade surplus with China in 2011. The report from the Pew Charitable Trusts contradicts the widely held belief that China has overtaken U.S. leadership in clean technologies. According to Pew's research, the U.S. solar industry held a $913 million trade surplus with China in 2011. American wind companies boasted a $146 million surplus. And U.S. energy smart technologies" - a catch-all category Pew used to survey makers of advanced batteries, light-emitting diodes and electric cars - scored a $571 million trade surplus with China. China exports to the United States items that lend themselves to mass production, such as solar cells and modules. U.S. companies sell to China items that require advanced engineering, such as electronic control systems and manufacturing equipment. The United States also sells more specialized materials used in clean-tech products, such as polysilicon for solar cells and fiberglass for wind turbine blades. Competition among clean-tech companies in China and the United States has strained relations between the two countries. American authorities have slapped import tariffs on Chinese solar panels, and the Chinese government has threatened to retaliate. And yet the Chinese and American clean-tech industries are deeply intertwined, according to the Pew report. In 2011, the latest year data were available, trade in alternative energy technologies between the two countries reached $8.5 billion.