In another sign of the turbulence affecting cleantech, global clean technology venture investment dropped to $1.6 billion in the second quarter, down 14 percent from the previous quarter and 25 percent from the $2.1 billion invested a year ago, according to the San Francisco-based Cleantech Group.

The group's preliminary report noted that the number of deals was 155, compared with 197 in the first quarter of this year. Many of those were for follow-on rounds of funding, a sign that early-stage startups may be having a harder time raising funding.

"Despite headwinds facing the sector and global economic instability, we continue to observe top tier funds such as Khosla Ventures, Kleiner Perkins, NEA, and others actively investing into cleantech," said Cleantech Group CEO Sheeraz Haji. "While some may be ducking 'cleantech' as a label in North America, growth in technologies addressing resource and challenges remains strong and both corporate and investor interest remains high."

Solar, transportation and continued to lead the sector based on the amount of money invested.

In North America, California led the way with $831 million in investments, followed by Massachusetts with $157 million, and Texas with $57 million.

There were nine IPOs in the quarter, but all of them took place in China. The largest IPO was for solar thermal water heater manufacturer Solareast, which made its debut on the Shanghai Stock Exchange. Oakland, Calif.-based BrightSource Energy withdrew its IPO this spring.