Business Green: Back in the mid-1990s, Rob Harmon wanted to develop wind farms. Like other aspiring developers, he identified promising locations and then talked to local utilities about buying the power. He encountered a common response. “They told me they’d pay me what they paid for commodity electricity,” Harmon recalls. The commodity price for electricity was often determined by coal plants. Unlike new wind farms, these plants had often paid off their capital costs years ago. They also …