Renewable energy boomed in 2015, a year that saw fossil fuel prices plummet and ended with a historic climate agreement hammered out in Paris.In fact, investments in renewables such as wind and solar were more than double the amount spent on new coal and gas-fired power plants in 2015, according to the Renewables Global Status Report (pdf) from REN21, an international non-profit association based at the United Nations Environment Programme in Paris, France.