Venture firm Battery Ventures has made two personnel moves to beef up its clean technology investment effort.

Battery, which has offices in both Silicon Valley and Boston, made the two moves in its Silicon Valley office — the latest sign that Silicon Valley has become a leading center for clean tech investments.

First, it has hired David Dreessen, most recently with San Francisco’s Nth Power, to join its Menlo Park office in the valley.

In his seven years with Nth Power, Dreessen worked on 16 clean technology investments, including Evergreen Solar and Northern Power.

Second, Battery promoted Menlo Park-based Jason Matlof to “partner.” Matlof joined Battery in early 2005 as a venture partner, and is involved with portfolio companies Advent Solar and Agito Networks.

Battery has also invested in Lion Cells, a lithium ion battery company.