In 2005, American venture capitalists invested more than $1.6 billion in clean tech.  According to the trade group Cleantech Venture Network, this is a 35 percent increase over 2004.  The cleantech field includes technologies related to water purification, air quality, nanotechnology, alternative fuels, manufacturing, recycling and renewable energy.

Rising energy prices and the increased demand for clean and renewable energy sources such as wind, solar, biomass, biofuels and hydrogen fuel cells are driving this newfound investment dynamo.  Clean Edge Inc. figures that the global market for these energy sources were around $40 billion last year and should grow to $167 billion by 2015.

Whereas past investement in clean tech have had rather dismal returns, the market demand and new technologies are changing the investment potential.

"The need for technologies that help sustain the world's growing population without causing more damage to the environment will only increase with time," said Jack Harrington, general partner, Advanced Technology Ventures, a bi-coastal venture capital firm. ATV has recently sponsored a competition called the California Clean Tech Open, a business plan competition that supports ATV's goal of furthering innovation in the clean tech industry. Winners will be awarded more than $500,000 in cash and service prizes at a Sept. 29 event in San Francisco. ATV is behind this competition in an effort to attract entrepreneurs and encourag innovation in the clean technology market.