Clean tech investment has rebounded after two quartals of free fall, according to a report by Cleantech Group LLC. The 2Q09 total is up 12 percent from the previous quarter, although down 44 percent from the same period a year ago. The average round size in 2Q09 was $12.9 million, up from $12.3 million 1Q09. Venture capital investments in solar technology are on the lowest level in three years.