Venture capital firms poured $2.5 billion into green technology in the first quarter of 2011, according to figures from Cleantech Group reported in a news story over the weekend. That’s the second-highest quarterly figure ever for the industry after the $3 billion raised in the third quarter of 2008 and a big improvement from the $1.68 billion raised in the fourth quarter of 2010. But is the upswing in venture investment a sign of renewed investor confidence, or a sign that VCs are stepping into the breach that might otherwise be filled by the public markets? We’ve seen plenty of examples of later-stage greentech startups that have delayed IPO plans as they wait for market conditions to improve — thin-film tubular solar module maker Solyndra being the main example. Some of the biggest raises of the first quarter went to later-stage companies that might have gone to public markets in better economic times — take solar thermal startup BrightSource Energy’s $201 million Series E round, thin-film solar startup Miasole’s $106 million Series F round, and Fisker Automotive’s $150 million investment round. I’m waiting for Cleantech Group to release their official first quarter 2011 report tomorrow morning, but I’m guessing that the data will show that big later-stage rounds made up a significant portion of the quarter’s haul.