SAN FRANCISCO - Silicon Valley venture fund CMEA Capital said on Friday it will invest an additional $100 million in alternative energy companies over the next three years.

The San Francisco-based fund, an early stage investor in many green companies including battery maker A123 Systems, biofuel firm Codexis and solar manufacturer Solyndra, has already invested in 14 alternative energy companies over the past seven years.

The alternative energy sector is finally ready to take off, CMEA Founder and Managing Director Tom Baruch said in a statement. For the first time in history, environmentally friendly methods for producing energy like solar and wind power are becoming inexpensive.

With the right financing, this sector has the potential to get our economy out of the doldrums, he added.

CMEA's portfolio company, A123, which makes lithium-ion batteries for the automotive market, had a smash-hit debut on Nasdaq on Thursday, and has a market cap over $1.9 billion.

Another of CMEA's high-profile investments is Solyndra, which is building a second factory in Fremont, CA, after it was awarded $535 million loan guarantee from the U.S. government.

In total, the firm manages seven funds representing investments over $1 billion.

(Reporting by Poornima Gupta; Editing by Richard Chang)