Reuters: Ireland’s Mainstream Renewable Power bought three wind farms in Illinois and plans to spend $1.7 billion to ramp capacity up to 787-megawatts by 2013, marking its first investment in the United States. The company, which is also developing smaller wind-power projects in Canada, plans to raise about half the capital needed through tax-equity financing, under which banks bankroll renewable energy projects and win tax breaks. [ID:nN10463042] Investors get a generous tax credit for …