US Renewables Group and Carlyle/Riverstone to Provide Growth Capital to ThermaSource, a Geothermal Engineering and Consulting Firm

Santa Rosa, CA – US Renewables Group, LLC ("USRG"), Riverstone Holdings LLC ("Riverstone") and The Carlyle Group announced today that they will provide growth capital to ThermaSource, a Santa Rosa, California-based provider of drilling, engineering and consulting services to the geothermal energy sector. Funds will come from USRG and Carlyle/Riverstone Renewable Energy Infrastructure Fund ("CRREIF") and be used to acquire new and reconditioned drilling rigs. US Renewables Group and Carlyle/Riverstone are making their investment through their affiliate GRR Holdco, LP, an owner of geothermal drilling rigs. Financial details were not disclosed.

"We are enthusiastic about the opportunity to partner with two proponents of geothermal energy, USRG and Riverstone," said Lou Capuano, Chief Executive Officer of ThermaSource. "With their support, ThermaSource will have the resources required to meet the critical needs of an expanding market for geothermal drilling and consulting."

"The opportunity to partner with ThermaSource was one of the attractions in acquiring and restarting the 55 megawatt Bottle Rock geothermal power project in the Geysers," said Tom King, Managing Director of USRG Management Company, LLC. "ThermaSource has been the premier drilling services company serving the geothermal sector. Their experience and expertise will help accelerate the expansion of geothermal energy."

"We are excited to back Lou and his ThermaSource team," said Stephen Schaefer, Managing Director of Riverstone. "We expect great opportunities in the next several years in the geothermal industry and believe that ThermaSource will be at the center of much of that growth."

About ThermaSource
ThermaSource LLC ("ThermaSource") provides the geothermal industry with engineering, project management and consulting services. ThermaSource also provides drilling rigs with experienced crews. The company was founded in Santa Rosa, CA in 1980 by Louis E. Capuano, jr. ThermaSource has been an important contributor to the industry for the past 26 years, having worked on many international projects including several in Canada, Japan and Indonesia as well as geothermal projects in all of the western states. For more information, visit www.thermasource.com.

About US Renewables Group
US Renewables Group, LLC ("USRG") is a company organized to manage a series of private equity funds (including USRG Power and Biofuels Fund I, LP and USRG Power and Biofuels Fund II, LP) that acquire, develop and operate renewable energy and clean fuel assets. To date, the firm has committed over $150 million covering more than 12 investments representing a range of renewable power and fuels sectors including geothermal, biomass, land fill methane, ethanol and biodiesel. USRG has offices in Los Angeles and New York. For more information, visit www.usrenewablesgroup.com.