Oil is once again approaching $100 per barrel, and that makes alternative fuel sources an attractive spot for both consumers and investors. Tesla Motors (TSLA +0.76%) is the clear way to play the electric vehicle market, and as technology improves, its business will grow. But the short-term growth may really be in natural gas fuel, where Westport Innovations (WPRT +2.62%) and Clean Energy Fuels (CLNE +0.52%) dominate. In the following video, energy analyst Travis Hoium covers why he likes these alternatives.