Building BIG solar safetly

Fluor Corporation faced everything from high temperatures to snakes and scorpions on the construction site of the Centinela solar project—one of the largest solar projects completed in the U.S. in 2014—in California's Imperial Valley. But it a

By Paul MacDonald

When Fluor Corporation representatives got together with the construction managers and contractors on the Centinela solar project for daily meetings, they always met first thing in the morning at 6 a.m. Even then, it was already warm, and the temperature would continue to climb during the day, sometimes reaching 120 degrees on the site, which sits just on the California side of the U.S. Mexico border, about 90 miles east of San Diego.

The climate was only one of the challenges that Fluor and its subcontractors had to deal with on the 170-MW Centinela Solar Energy Facility, one of the largest solar projects completed in the U.S. in 2014.

In 2012, LS Power, the owner of the project, completed financing and authorized construction of the $700 million project, built near the small town of El Centro, California. Sited on more than 1,600 acres of private land, Centinela utilizes solar PV technology and sells its entire output to San Diego Gas & Electric under long-term power sales agreements.

Fluor Corporation was engaged to engineer, procure, and construct the project and also provides operation and maintenance services for the next five years, now that it is completed. Fluor was awarded both the 125-MW Phase 1 and the 45-MW Phase 2 of the Centinela project. The company provided the engineering and procurement services for the lump-sum project from its southern California operations center, in suburban Los Angeles.

The successful completion of the large Centinela project is the result of a long-standing relationship and effective coordination between LS Power and Fluor, said Matt McSorley, president of Fluor's Power business. "We are especially proud of the project team's exemplary health, safety, and environmental record."

Fluor completed the project safely, working more than 700,000 construction hours with no lost-time accidents.

The Centinela facility is the second major solar plant that Fluor has designed and built for LS Power. In November 2013, Fluor completed the 125-megawatt Arlington Valley Solar Energy II facility in Maricopa County, Arizona, near Phoenix.

Fluor Corporation's Luisa Tahfur, the company's project manager on the massive Centinela project, said both the Arlington Valley and Centinela projects were originally supposed to proceed in tandem, but Centinela was re-scheduled by about six months.

Once things were in place though, Tahfur and the Fluor team-and their contractors-hit the California desert floor running.

"We had some of the same people on the Arlington Valley and Centinela projects on the engineering side, but Centinela really had its own, separate construction team," noted Tahfur.

There was some civil work required on the site. "We basically took it from dirt and fully prepped it for the solar project," said Tahfur. "Some of the areas had to be excavated and backfilled to compact them in preparation for the array fields. We were fortunate in that we had one of the larger civil contractors in California do the work, which definitely helped." Granite Construction was the civil contactor on the project.

The nearest town to the project, El Centro, served as a source of local labor for the project. "We had a lot of interface with El Centro, and they were interested in helping the Centinela project out," said Tahfur.

"With such a large project-170 MW and literally hundreds of thousands of solar panels-planning and organization was key," said Tahfur.

"We definitely needed to envision how we were going to sequence the work and the array fields in a way that would not impact the receiving of materials." They opted to essentially divide the project in two, with Highway 98 running through the middle of the site. "We had to be mindful of the highway location for a few reasons, for safety, for traffic, and for logistics," she said.

"In terms of receiving materials, we had limited laydown space for materials. LS Power wanted to make maximum use of the site, and we supported them on that. Basically, we were installing materials as we were receiving them-so the sequencing of the work was very critical."

This just-in-time approach meant that installation moved along quickly, and delivered materials didn't sit on the site for long. Three days was the maximum length of time materials would be on site prior to installation.

At the daily 6 a.m. meetings, Tahfur and the Fluor group would review what was going that particular day, and they also looked ahead, with a particular focus on what was scheduled over the next two weeks. Keeping this timeline front and center worked well in keeping the project on track, said Tahfur.

They had worked with the civil contractor, Granite Construction, and the electrical contractor, Contra Costa Electric, part of the EMCOR Group of companies, on previous projects. California-based Jacobsson Engineering Construction was also involved in the project. "We were very fortunate in that we had a good team of people and contractors working on the project."

Tahfur noted that there is usually a pattern for construction of solar projects; they start out slowly, then build momentum until they hit a steady production level of erecting support structures and putting panels in place.

"That is very typical of solar projects," she said. "But with Centinela, because we had the benefit of working on its sister project, Arlington Valley, we started out quickly. The ramp up on a solar project normally takes a while. But the project was divided into 11 blocks, and we were finishing blocks pretty close to two to three weeks ahead of time, and we kept that momentum for about 75 percent of the project." Essentially, they were able to use the Arlington Valley project as a template for how to build Centinela.

Tahfur noted that there was a strong focus on safety and quality control throughout the project.

They were also able to stay flexible, to meet changing needs on what areas could be built at any one point. "Sometimes we could not start with specific blocks until set dates with permitting, and that leveled out the schedule later on." She reports that the quality of the union labor on the project was high, which also helped.

A key to the overall success was the planning-having the right resources, the right contractors, and being very focused on the schedule.

"We learned from the contractors we had on the project-they had a unique way of sequencing the work and the arrays. We were all learning from each other, and the end result was very positive. In my 25 years of construction experience, the team we had on Centinela was the most cohesive I've ever worked with."

	The construction team installed a total of more than 875,000 Yingli photovoltaic panels mounted on a single-axis tracking system on the 1,600-acre site. The tracking systems for Centinela were supplied by Array Technologies.

The fact that the different parties were learning from each other on the project suggests that they were trying out new approaches, to make the project as efficient and effective as possible.

An advantage for Fluor is that the project is only a few hours' drive from one of their major offices in Orange County. "It was an opportunity for our engineering and procurement people to get out to the site and see first-hand how the project came together and how their efforts contributed to the overall success of the project," said Tahfur.

Fluor and project owner LS Power had to be mindful of security; the back fence of the Centinela project sits on the border with Mexico. "We were able to manage that with our relationship with the local sheriff and law enforcement people, and that helped with them being able to patrol the project effectively. We were fortunate in that our relationship with the local authorities was excellent."

Four months prior to starting work, Fluor had sent kind of an "advance team" into El Centro to meet with local authorities and share details of the project's construction and related matters. They participated in a community fair about three months before the project started. That kind of outreach was important to the success and acceptance of the project in the community, said Tahfur.

Overall, perhaps the biggest challenge with the Centinela project was the high temperatures. "When you have temperatures of 120 degrees, you have to be even more careful about safety, that there is lots of water available, and that people working on the project are taking the appropriate breaks," she explained.

To help manage working in the high temperatures, they sometimes started construction early in the morning, when it was cooler, and finished at 3:30 in the afternoon.

Another challenge was the number of snakes and scorpions, which are just part of a desert environment. Workers had to be careful where they were working and stepping.

There were burrowing owl nests on the site, and work had to be scheduled around the nesting times of the owls. "We could not disturb them-so we would not move into an area with a nest until the nesting cycle was over. Sometimes we needed to stop work in an area with owls and be nimble enough to re-sequence what we were doing to start work in a nearby area. It wasn't always easy, but we were able to make a quick recovery from those work stoppages."

Fluor is proud of the safety record on the site-zero accidents and zero incidents, a significant accomplishment considering there were 450 workers on the site at peak.

A solar project of this size has a lot of parts, and there were a number of supporting parties on the project.

The financing was structured with two tranches, combining longterm institutional financing led by Prudential Capital Group with shorter-term bank financing led by Sovereign Bank, N.A. and four other Joint Lead Arrangers: Union Bank, N.A., Rabobank Nederland, Canadian Imperial Bank of Commerce, and NordLB.

Law firm Chadbourne & Parke represented LS Power in connection with the construction financing.

The construction team installed a total of more than 875,000 Yingli 200 MW dc YGE-U Series photovoltaic panels mounted on a single-axis tracking system on the 1,600-acre site.

The tracking system for Centinela was supplied by Array Technologies. The company's single-axis DuraTrack HZ Solar tracking system was used on the project.

Specifically engineered for large-scale applications, the YGE-U 72 Cell Series solar modules contain DuPont Tedlar PVF film-based backsheets to ensure superior all-weather performance and long-term durability.

Given Centinela's size and significance, it was imperative to Fluor Corporation to be able to guarantee system performance. Yingli engineers worked closely with Fluor to develop a project-specific performance guarantee based on highly accurate energy forecasts and module performance projections tested against real-life field conditions.

Bonfiglioli USA, a Kentucky-based subsidiary of the Bonfiglioli Group, and a leader in supplying cutting edge utility-scale power conversion system solutions, supplied its utility-scale RPS Station systems for Centinela. The fully integrated 2 MVA power platform includes two of its 1MVA modular inverter systems enclosed inside a precast concrete container and a 2 MVA medium-voltage step-up transformer.

Bentek Solar, a leading designer and manufacturer of PV products connecting PV panels for commercial and utility-scale marketplaces, supplied 170 MW of 1000VDC ungrounded string combiners and cable harnesses for Centinela.

Power facility developments are not new to the owner of Centinela, LS Power. The company is involved in both power generation and transmission and has a proven track record of successful development activities, operations management, and commercial execution. LS Power has been involved in the development, construction, or operations of over 25,000 MW of power generation in the U.S.

The new Centinela facility is sending power to the service territory of San Diego Gas & Electric across the relatively new Sunrise Powerlink, a 120-mile, 500-kilovolt transmission line that was designed to tap into the vast renewable resources of southern California's Imperial Valley. The new power line is expected to carry up to 1,000 MW of electricity and provides the many renewable energy facilities in the Imperial Valley with a clear distribution path to the San Diego market.

Renewable energy deliveries over Sunrise Powerlink will assist SDG&E and the State of California in reaching their renewable energy goals, says the utility.

"Renewables are the lynchpin of SDG&E's commitment to becoming the quintessential utility of the future," said Jessie J. Knight Jr., CEO of SDG&E. "We are accessing large amounts of environmentally-friendly power and developing infrastructure and smart technology to bring it to our communities."

The project will help SDG&E meet California's mandate to procure 33 percent of its power from renewable resources by 2020.

This area of California is said to be ideal for producing solar power due to abundant desert sunlight. Centinela will generate emissions-free energy without the use of water, an important consideration in the arid desert of the Pacific Southwest.

In addition to producing clean electricity, the solar project represents a huge economic investment in Imperial County.

"This is great news for the Imperial Valley," said Tim Kelley, CEO of the Imperial Valley Economic Development Corporation. "Renewable energy has the potential to become one of the pillars of the local economy with the Sunrise Powerlink to bring it to market. This vital infrastructure project is a win-win for the Imperial Valley and San Diego and will help our region become a national leader in renewable energy development."