Large banks, including Morgan Stanley and Citigroup, are making major investments in wind farms because a change in federal renewable energy subsidies is providing investors returns of up to 15 percent, the Wall Street Journal reports. The surge in investment has been spurred in part by a new U.S. government policy, which now allows wind farm developers to receive 30 percent of the cost of the 
project upfront in cash, rather than receiving tax credits spread out over the life of the wind farm. Analysts said the new policy could mean that investment in wind farms will be $10 billion through 2010 — three times the amount initially projected by federal officials. The new investment could mean the installation in the next several years of 15 gigawatts of new wind power, half of the entire U.S. wind power capacity today. One limit to growth in wind power will be the ability of developers to sell the power, which costs more than electricity generated by coal-fired utilities. Officials say that setting state and federal requirements mandating renewable energy production could help overcome the higher cost of wind power.