The first of nine potential geothermal powerplants being developed by Reno, Nev.-based Gradient Resources will be built by McLean, Va.-based Science Applications International Corp.’s design-build subsidiary, Benham Constructors LLC.

Construction of the 60-MW powerplant at Gradient’s Patua site, near Fernley, Nev., will begin the second quarter of this year, with commercial operation expected in the third quarter of 2017. No contract value was given to the engineering, procurement and construction contract for the estimated $270-million project. The Sacramento Municipal Utility District already has contracted for a portion of the plant’s production.

SAIC will use TAS Energy technology for the project. The modular binary-cycle plant will be SAIC’s third partnership with the Houston-based firm. Craig Hurlbert, TAS chairman and CEO, says the plant will be the largest geothermal unit ever built. Because it will be modular, it can be expanded, says J.T. Grumski, SAIC senior vice president and business unit manager.

The binary-cycle plants allow energy to be extracted from moderate-temperature water, below 400� F. Flowing through a heat exchanger, hot geothermal fluids “flash” a secondary, or binary, fluid to vapor, which then drives turbines. The U.S. Dept. of Energy says most future geothermal powerplants will be binary cycle.

Gradient, formerly Vulcan Power Co., has nine plants under development, including five 60-MW plants in northern Nevada. Gradient plans to build a six-mile power line to connect the Patua project to the existing transmission net.

AIC’s Benham group has won three geothermal plant contracts in the past six months. Earlier wins included a $22-million contract in September with U.S. Geothermal, which hired SAIC to replace an older geothermal plant in San Emido, Nev., as well as a $14-million contract with Terra-Gen Power to engineer, procure and construct a binary geothermal powerplant in Churchill County, Nev.

Grumski says there is a great deal of potential in geothermal energy because once the resources are identified, it’s a fairly economic resource with base-load, or constant, power.