After years of lofty promises, Wall Street believes the renewable energy industry can produce a payoff. In just a few years, investors have gone from zero to billions in the amount of money they’re pumping into renewable-energy companies and environmentally friendly projects. Tax-equity funds and specialty financial tools like “green bonds” and yieldcos have become increasingly popular. And investments in the renewable-energy companies that benefit from these financial tools have far outperformed those in oil-and-gas drilling and coal mining since the start of 2013, according to Bloomberg New Energy Finance, a research arm of Bloomberg LP. Analysts, bankers and investors at the Renewable Energy Finance Forum in New York this week were ebullient. Many see the sector as past a tipping point: Skepticism has melted among the financial brokers of the energy world, and they have started to fund the renewable-power sector as a legitimate upcoming rival to fossil […]