Warren Buffett’s renewable energy empire has expanded with the purchase of three new wind-energy projects in Iowa, adding a total of 404.8 megawatt wind capacity to the eco baron’s MidAmerican Energy Holdings company portfolio.

MidAmerican plans to build 176 wind turbines in Iowa by the end of 2012, which is a combination of the recent acquisitions of RPM Access’s 103.5 megawatt wind project, the 200.1-megawatt Eclipse Wind Farm and 101.2-megawatt Morning Light project from Clipper Windpower Development Group.

Earlier in December 2011, MidAmerican agreed to buy Topaz Solar Farm, a solar power farm situated between Los Angeles and California, worth $2 billion and the second largest solar plant under construction in the world.

Then by late January 2012, Buffett – the world’s third richest man – announced the formation of a new branch focused on the development of modern renewable energy. Its four units involve solar, wind, hydro and geothermal energy.

MidAmerican’s wind generation will total at 2,284.8 megawatts with the Iowa wind projects up and running. The Topaz Solar Farm on the other hand is expected to run from 2015, and will produce enough energy to power 160,000 homes.

Once the newest projects are completed, Buffett would have invested $9 billion in solar and wind utilities, with $4 billion in wind power investment in Iowa alone.