Don't call it "alternative energy," Michael Liebreich, CEO of Bloomberg New Energy Finance, told the audience at the Department of Energy in Washington, DC. After having already crunched the trending numbers (and aided by dramatic graphs), he asserted that the big increase in non-fossil fuel energy investment, from $54 billion in 2004 to over $260 billion in 2012 (a trillion dollars in eight years), means you can no longer call this growing sector "alternative energy," and anyone who does is "simply out of date." It's just clean energy, period, and he's absolutely convinced that the long-term trend is clear. That's not to say it hasn't been a bumpy ride. He considers the recent big drop in investment after 2011 "growing pains...the teenage years" - not at all like the boom and bust of the 1980s - and sees the industry back in "robust health" soon. Why is Liebreich so optimistic? He thinks that solar and wind technology will continue getting cheaper and cheaper, while costs for coal and natural gas inevitably rise. As the price of electricity goes negative on sunny and windy days in more countries, this rapid transformation is beginning to happen everywhere. Even Africa, once completely ignored, has come to life and is now receiving more investment than Latin American for the first time - South Africa is actually beating out Brazil.