(Westport Innovations story updated for Senate stall on energy, Westport earnings results)VANCOUVER, B.C. ( TheStreet) -- Wind and solar stocks may get most of the trading attention from alternative energy investors, but natural-gas vehicle stock plays are attracting interest from high profile investors who are in the alternative energy story for the long run. Westport Innovations ( WPRT) is one example of a natural gas vehicle play that has lined up some notable institutions among its major shareholders. The biggest bet on Westport Innovations occurred in the first quarter, when it was revealed by Soros Fund Management, the hedge fund group of famed investor George Soros, that it had taken a stake of near-5% in Westport shares, to become the natural-gas vehicle stock's largest shareholder. The latest quarterly filings made by Soros and other closely watched investors, like John Paulson of Paulson & Co. and Warren Buffett of Berkshire Hathaway ( BRK.B), were revealed last week. There were plenty of energy plays from among this cadre of billionaire investors, but the Soros first quarter bet on Westport was the only stand-out bet on alternative energy. Paulson's first quarter moves showed a bulking up in shares of oil and mining companies, like XTO Energy ( XTO) and NovaGold Resources ( NG), which is nothing new for the hedge fund manager. Soros, too, has major stakes in mining companies like NovaGold and oil giants like Brazil's Petrobras ( PBR) which he was increasing in the most recent quarter. Warren Buffett, while supporting operating subsidiary MidAmerican Energy's move into wind energy, also has the distinction of being a major shareholder in Nalco ( NLC), the manufacturer of the toxic chemical dispersant that has become a point of controversy in BP's ( BP) efforts to clean up the oil spill in the Gulf of Mexico. Alternative energy stocks are notoriously volatile investments, and so it's no surprise that long-term investors have often shied away from these stocks. It can be argued that in the short history of the alternative energy sector, the stocks have done more for short-term trader profits than they have for the planet. Retail investors, hoping to make their fortunes in the next great energy solution, have been failed by these high-flying, quick to crash investments, too.