|Ormat binary geothermal power generation system. Click to enlarge.|
Ormat Technologies, Inc., a geothermal and recovered energy business, has signed a shared-cost Cooperative Research and Development Agreement (CRADA) with the US Department of Energy (DOE) to validate the feasibility of using geothermal power generation technology for the production of commercial electricity using hot water produced during the process of oilfield production.
The project will be conducted at the DOE Rocky Mountain Oil Test Center (RMOTC), near Casper Wyoming, and will use an Ormat Organic Rankine Cycle (ORC) power generation system to produce commercial electricity.
The test will use a commercial, air-cooled, skid-mounted standard design Ormat Organic Rankine Cycle system. Ormat will supply the ORC power unit at its own expense while the DOE will install and operate the facility for a 12-month period. Ormat and the DOE will share the total cost of the test and the study, with Ormat bearing approximately two thirds of the less than $1M total investment.
Presently there are two large unutilized sources of hot water at the RMOTC Naval Petroleum Reserve No. 3, which produces water in excess of 190°F (88°C) and at flow rates sufficient for power generation of approximately 200 kW.
The project will consist of the installation, testing and evaluation of a binary geothermal power unit in the field near these hot water sources. The ORC power unit will be interconnected into the field electrical system and the energy produced will be used by RMOTC and monitored for reliability quality.
The binary power unit brings a geothermal fluid—here, the hot water—through pipelines to heat exchangers in the Ormat Energy Converter (vaporizer and preheater). In these heat exchangers the geothermal fluid heats (preheater) and vaporizes (vaporizer) a secondary working fluid, which is typically an organic fluid with a low boiling point.
The vapors drive a turbine which powers a generator and then are condensed in a condenser. The condensed fluid is then recycled back into the heat exchangers by a pump, completing the cycle within the closed system. The cooled geothermal fluid is re-injected into the reservoir.
The Ormat ORC unit that will be used in the study is similar to the 250 kW air-cooled unit that has been producing electricity from 210°F (99°C) geothermal water for more than six years at an Austrian resort. Additionally, there are similar units in Nevada and Thailand that have been in continuous commercial operation and without overhaul, since 1984 and 1989, respectively.
A 70 kW Ormat ORC power system was also used in a project co-sponsored by the US Bureau of Reclamation, Ormat and others. This ORC unit operated for 16 years using water with temperatures as low as 154°F (68°C) to produce electricity.
Some 8,000 similar wells were identified in Texas, by Prof Richard Erdlac of the University of Texas of the Permian Basin, and the US DOE Geothermal Research Project Office. Ormat is now assessing the feasibility of utilizing some of these wells to support on site power generation by employing Ormat’s factory integrated sub-megawatt geothermal power units.