Global wind power installation investments are expected to expand from $11.8 billion last year to $48.5 billion by 2015, according to an annual study released last month by Clean Edge Inc, an American research and strategic marketing firm based in San Francisco. The study further predicts that overall, global clean energy revenues will grow from $40 billion in 2005 to $167 billion by 2015. Also noted in the study is that venture capital investors poured $917 million into more than 80 private energy related companies last year, a dollar increase of 28% from 2004. "It's clear that clean energy is becoming a critical and lucrative factor in the global economy," says Ron Pernick of Clean Edge. The study goes on to report that clean-tech stocks in general are doing well and that a number of clean-energy stalwarts are trading at or near their 52-week highs. "Suddenly, so-called alternative energy technologies are looking pretty mainstream," it says. The study, "Clean Energy Trends 2006," examines factors that influence clean energy market growth and tracks key trends. The report has been published since 2002.