Data center real estate investment trust QTS Realty Trust Inc. signed a 10-year agreement to purchase renewable energy to meet the expected electricity requirements of its data centers in Chicago and Piscataway, N.J.

The deal, signed alongside Citigroup Energy Inc. and Calpine Energy Solutions LLC, brings to three the number of data centers in the REIT's portfolio that use 100% renewable energy, including its facility in Irving, Texas.

As part of the deal, QTS bought environmental attributes equal to 100% of the expected power consumption of the data centers from Rio Bravo Wind in Starr County, Texas, which is owned by Rio Bravo Windpower LLC.

The company also purchased an equivalent amount of financial energy from the Radford's Run Wind Farm in Macon County, Ill., which is owned by E.ON Climate and Renewables North America LLC.