U.S. billionaire Bill Gates joined Warren Buffett on his Shenzhen trip Tuesday. The pair were accompanied by BYD CEO Wang Chuanfu, and visited four BYD factories in Shenzhen and Huizhou in Guangdong Province.

The main purpose of the trip is for charity, but vigorous development in the new energy industry has also drawn the attention of the two billionaires. Warren Buffett told the waiting media, he's satisfied with his investment in BYD. This trip is his first to the company's headquarters, since Berkshire-Hathaway controlled holding company MidAmerican Energy purchased a stake in BYD.