The U.S. Department of Energy on Dec. 12 put out for comment a draft environmental impact statement on a 720-mile transmission line that would allow wind generation from Oklahoma into the Tennessee Valley Authority system.
DOE said in a notice to be published in the Dec. 17 Federal Register that will will hold a 90-day public comment period on this draft EIS, with 15 public hearings to be held in January and February at sites along the power line route.
In June 2010, the Department of Energy (DOE), acting through the Southwestern Power Administration and the Western Area Power Administration, both power marketing administrations within DOE, issued a Request for Proposals (RFP) for new or upgraded transmission line projects. In response to the RFP, Clean Line Energy Partners LLC of Houston, Texas, the parent company of Plains and Eastern Clean Line LLC and Plains & Eastern Clean Line Oklahoma LLC, submitted a proposal to DOE for the Plains & Eastern Clean Line Project.
Clean Line’s stated objectives for development of this project include:
- Improving public access to renewable energy at a competitive cost by facilitating the transfer of available wind energy in the Oklahoma and Texas Panhandle regions to areas with increasing demands.
- Providing an efficient and reliable interconnection between the Southwest Power Pool (SPP) and TVA that facilitates the transfer of 3,500 MW of wind-generated electricity and is consistent with applicable transmission system plans.
- Assisting in satisfying the growing customer demand for renewable energy.
TVA’s purpose and need for agency action is to respond to Clean Line’s request to interconnect the project to the TVA transmission system. In response to the interconnection request, TVA conducted studies that indicate certain upgrades are needed to the TVA transmission system to maintain system reliability. TVA therefore has the additional purpose and need of making the upgrades to its transmission system that would be necessary to interconnect with the project while maintaining reliable service to its customers.
Clean Line expects that future wind energy generation facilities would connect to the AC collection system by way of a number of possible configurations. The applicant based a 40-mile radius on preliminary studies of engineering constraints and wind resource data, industry knowledge, and economic feasibility. These configurations could range in size from a direct tap, a bus ring, or even a small substation (about 2 to 5 acres in size) with transformer and switching equipment. The type and size of these AC connections is unknown at this time; the final design of these facilities would depend on a number of factors including their location, the number of connections, and the nameplate capacity and voltage of generation facilities.
The applicant has identified a specific route for its 600-kV high voltage direct current (HVDC) transmission line from the Oklahoma Panhandle Region to interconnect with TVA’s electrical system in western Tennessee. The alternating current (AC) collection system is located within Region 1 for this project, within a 40-mile radius centered on the Oklahoma Converter Station Siting Area including Cimarron, Beaver, Texas, Ochiltree, Hansford, and Sherman counties. To facilitate efficient interconnection of wind generated electricity, it is expected that the applicant would construct four to six AC collection transmission lines of up to 345 kV from the Oklahoma converter station to points in the Oklahoma and Texas Panhandle regions. The location of the AC collection system routes will be driven by future wind energy development.
Converter station in Arkansas added due to input in EIS process
“During the scoping period, DOE received comments from stakeholders in Arkansas who were concerned that the state would endure impacts from the Project without receiving any of the benefits (e.g., ability to accept increased amounts of renewable energy, tax revenues from property and ad valorum taxes associated with new facilities, and increased number of jobs),” the draft EIS noted. “Based on these comments, DOE requested that Clean Line evaluate the feasibility of an alternative that would add a converter station in Arkansas. The Arkansas converter station would be an intermediate converter station; it would not replace the Oklahoma or Tennessee converter stations. Based on the Applicant’s feasibility evaluation, an Arkansas converter station could be sited in either Pope or Conway County, Arkansas. This alternative converter station would be similar to the Oklahoma and Tennessee converter stations except that it would likely require a smaller land area, encompassing approximately 40 to 50 acres. Based on preliminary design and studies, it would be capable of interconnecting 500MW. With the implementation of this alternative, the delivery capability of the Project would be increased to 4,000MW.”
The last segment of the line is in Region 7, which begins south of Marked Tree, in Poinsett County, Arkansas, and continues east and southeast, across the Mississippi River and into Tipton and Shelby counties in Tennessee, for approximately 43 miles, ending near the Tipton-Shelby county line south of Tipton, Tennessee. The project, as proposed, includes construction and operations and maintenance of a converter station in either Shelby or Tipton County to enable injection of up to 3,500 MW into the Shelby Substation.
TVA completed its Interconnection System Impact Study to determine whether any upgrades (or modifications) to its transmission system would be necessary to protect grid reliability while accommodating Clean Line’s request for interconnection at 3,500 MW. TVA’s Interconnection System Impact Study has identified connected actions as necessary to enable the injection of 3,500 MW from the Plains & Eastern Clean Line:
- upgrades to existing infrastructure; and
- construction of a new 500-kV transmission line, approximately 37 miles long, in western Tennessee, including necessary modifications to existing substations on the terminal ends of the new line.
The total length of existing transmission lines that could require some degree of upgrade is approximately 350 miles; most of these lines are located in central and western Tennessee. The detailed identification of the necessary upgrades to each transmission line and construction of a new transmission line is the subject of an interconnection facilities study begun by TVA in 2014 and anticipated to be completed in mid-2016.