Greenwire: Wind power developers have long relied on complex tax-equity financing to bring most of their projects to market, but that system, once hailed as innovative, has collapsed over the last year, leaving the wind sector flailing for the cash it needs to make generation projects a reality. This is how it worked: Large financial institutions like AIG, Wachovia, J.P. Morgan, Wells Fargo, Lehman Brothers and others would buy federal tax benefits from renewable energy startups that did not …