Soda Lake Geothermal Plant, Nevada, USA

The Soda Lake Geothermal plant is a dual geothermal electric-generating facility situated eight miles north-west of Fallon in Nevada, the second-ranking state in terms of geothermal resources. Soda Lake I was launched in 1987 and the second part of the facility, Soda Lake II, has been in operation since 1991.

The combined capacity of Soda Lake I and Soda Lake II is almost 26.1MW. Together, they generate an average output of 8MW, which was achieved for the first time in 2008. In winter, the facility generates approximately 14MW of power. This is reduced to 4MW during the summer.

Owned and operated by Magma Energy, the Soda Lake Geothermal Plant was recently refurbished to contribute an additional 1MW of power to the net output.

Soda Lake Geothermal Plant expansion

An expansion programme to meet the plant's design capacity is currently under way. By March 2010, it will be expanded to generate 16MW of net power. As part of the phase I expansion, two new production wells will be drilled and the surface piping and equipment will be upgraded.

A flow test of the first production well 45A-33 was successfully completed on 6 Jan 2010. The well, drilled in June 2009, demonstrated a continuous flow of 1,200gpm at 385°F. It will generate 3MW of net power on completion. More power generation units will be added to the facility to reach its design capacity of 23MW.

Geothermal plant make-up

The Soda Lake facility is spread over a land area of 2,071ha. Four production wells and four injections wells supply geothermal fluid to the plant. Both Soda Lake I and Soda Lake II are binary cycle power plants with an installed design capacity of 5.1MW and 18MW respectively.

Binary cycle technology enables the plants to use cooler reservoirs that stop excess gas release. It allows usage of a higher number of reservoirs, resulting in greater efficiency and lower cost.

A water-cooled condensing system is installed in Soda Lake I, and Soda Lake II is equipped with an air-cooled condensing system. To carry the generated power, a 60kV line is provided from the entrance of the plant.

Geothermal process

The plant is supplied with hot fluid from geothermal reservoirs. Heat is transferred via a heat exchanger to a separate pipe that carries fluids of lower boiling temperature. The fluids, which consist of isobutene or isopentane, are vaporised to generate power for the turbines. Pressure of the expanding vapour drives the turbines, which then powers the generators. Following this process, the geothermal fluid is cooled and returned to the reservoirs.

Nevada power grid network

The power generated from the Soda Lake plant is carried to an electrical substation, which redistributes it to the local electrical grid. Transmission lines, including 120kV, 230kV and 345kV, run in close proximity to the Soda lake operation. The area is also served by a regional railroad line that goes southwards.

All the generated power is purchased by NV Energy, a Sierra Pacific Resources subsidiary, located in Reno, Nevada. The company was acquired by Magma Energy Corporation in October 2008.

Power market in Nevada

Nevada is the fastest growing state in US in relation to electricity consumption. In 2005, the state consumed 32,501 million kilowatts of electricity. It currently ranks 34 in the US for electricity consumption.

The power market in Nevada is traditional and regulated. Many high-voltage transmission lines run across the stage to bring power to California. The state derives approximately 7% of electricity from geothermal power plants.

Currently, Nevada has 16 geothermal plants that together generate approximately 318MW of power.

A legislation passed by Nevada's state government has mandated that all power manufacturers increase their output of renewable energy from 8% to 20% by 2015.

Nevada ranks second in the US in terms of geothermal potential. Less than 5% of Nevada's geothermal resources are consumed by the Churchill County, which uses no more than 10% of the geothermal power generated.