California's aggressive renewable portfolio standard requires utilities to obtain 33% of their energy from renewable resources by 2020. Although the state has great renewable energy potential, transmission constraints do exist, making the task of meeting the mandate difficult.
Enter the Sunrise Powerlink, a 117-mile, 500 kV transmission line that is being developed by San Diego Gas & Electric (SDG&E) to carry power from Imperial County west to San Diego. According to SDG&E, experts have identified the Imperial Valley/Baja Norte regions of California as having huge renewable energy potential.
Studies conducted by California's Renewable Energy Transmission Initiative (RETI) estimate that the area has the potential to produce up to 12 GW of renewable energy – 6.5 GW of solar power, 3.5 GW of wind power and 2 GW of geothermal.
‘If you look at the various studies that have been done on Imperial County, the eastern part of San Diego County and northern Baja, this region is considered a mega region for renewable energy,’ says SDG&E's Jennifer Ramp, adding that the utility has signed several power purchase agreements (PPAs) for projects that will connect to the transmission line.
The Sunrise Powerlink, which will have a capacity of 1 GW, was approved by the California Public Utilities Commission (CPUC) in December 2008, by the U.S. Bureau of Land Management in January 2009 and by the U.S. Forest Service in July 2010. Construction began in fall 2010, and the project is almost complete, with an in-service date expected for this summer. Cost estimates for the line are almost $1.9 billion.
‘There was a four-year regulatory review process with over 75 public hearings. The [environmental impact statement/environmental impact report] was more than 11,000 pages – the largest in California history,’ Ramp explains.
SDG&E implemented more than 350 environmental-mitigation measures, which required almost 1,000 separate tasks, including protections for 10 special status-species.
‘Some of the requirements created unprecedented challenges for our construction team, such as vegetation clearing limitations, bird nests impacting construction and no-fly zones, narrow flying corridors, and extensive stormwater pollution prevention plans,’ she explains.
The utility needed to train more than 400 environmental professionals from 11 different companies to monitor air quality; fire safety; and biological, cultural and visual impacts. More than 140 of these professionals are deployed every day to ensure compliance in all areas, she adds.
Hindsight is 20/20, and Ramp says that SDG&E would have conducted a better up-front assessment in order to understand all the environmental-mitigation requirements and their associated effects on construction.
In order to reduce the number of access roads that had to be built in certain areas, SDG&E used helicopters to deliver more than half of the 436 towers being installed for the project. The utility purchased an Erickson Air-Crane, which transported individual segments of the transmission towers to various locations.
‘It's really an amazing process to watch an air crane arrive at a fly yard, pick up a massive piece of a tower with a long line and then fly it out into this area and place it precisely on the four points,’ says Ramp. ‘That takes a lot of skill.’
Last year, however, there were two minor accidents – which occurred within days of each other – involving the helicopter. One incident occurred when a tower section being carried by the air crane fell approximately 200 feet. No injuries were reported, according to SDG&E, and an investigation found that a short circuit in the wires that control the hooks holding the helicopter's payload was the cause.
A couple of days later, a similar accident took place when three of the helicopter's hooks released unexpectedly while carrying a tower section. The structure was lowered to the ground while hanging from the fourth hook. In this case, the tower tipped over, but no injuries were reported.
The project has also faced opposition from environmental groups and others concerned with the aesthetics of overhead transmission lines.
‘There have been communities that have raised concern over the project, and we've worked with those communities,’ says Ramp. ‘When you look at any major infrastructure project, you're going to have opposition – it could be aesthetics; it could be traffic impacts.’
A portion of the transmission line that runs through the community of Alpine, Calif., will be built underground. This 6.2-mile section is almost complete. Ramp says that Alpine Boulevard, a main street in the town, will be ‘better than when we started.’
‘SDG&E opened up a public affairs office in downtown Alpine to deal with the concerns of the community and to work with local residents on various traffic-impact concerns, as well as streetscape improvements,’ says Ramp.
Renewable energy developers represent one group that has no objections to SDG&E's transmission project. Without the Sunrise Powerlink, John Calaway, director of wind energy development for Pattern Energy, says the company may not have been able to pursue its 300 MW Ocotillo wind project because of a lack of high-voltage transmission capacity in California.
Pattern Energy will sell the power from its wind project to SDG&E through a 20-year power purchase agreement (PPA), which was approved by the CPUC in January. The company has been developing the project for about three years and expects construction to begin this summer.
The Ocotillo project is expected to be complete by end of the year, but not without opposition similar to what the Sunrise Powerlink project faced, Calaway says.
‘We certainly anticipate having legal challenges, and we're very well prepared to defend the integrity of our project, just like Sunrise Powerlink has,’ he notes.
SDG&E has also signed a 25-year PPA to purchase 200 MW of energy from the Mount Signal solar project in Imperial County. The first 100 MW of energy from the photovoltaic facility is expected to be online by mid-2013, with project completion slated for late 2013.
As of February, SDG&E has signed contracts for 600 MW of renewable energy projects that will link to the new transmission line.
There is no doubt that the Sunrise Powerlink is important for renewable energy projects, such as Pattern's Ocotillo wind project, says Calaway. But he adds that renewable energy projects are also important to the transmission project.
‘In order for the Sunrise Powerlink to actually accomplish its goals, the Ocotillo wind project is very important and fundamental to utilizing it for the purpose that it was built for,’ he says.
Photo credit: San Diego Gas and Electric