Solar photovoltaic products, wind power, biofuels, and fuel cells collectively experienced a 40% growth in revenues in 2007, according to a new report from Clean Edge, Inc. Global revenues for the four clean energy markets increased from $55 billion in 2006 to $77.3 billion in 2007. And although the fuel cell and distributed hydrogen market remains relatively immature, with revenues of $1.5 billion in 2007, the three other renewable markets each exceeded $20 billion in revenue. Of the four energy markets, wind power earned the highest revenue, at $30.1 billion. In terms of production, the biofuels industry produced 13 billion gallons of ethanol throughout the world, as well as 2 billion gallons of biodiesel, while solar photovoltaic system installations fell just short of 3,000 megawatts.