Energy provider: In 2002, California established a Renewable Portfolio Standard (RPS) requiring electric utilities in the state to increase procurement of eligible renewable energy resources to achieve a target of 20 percent of their annual retail sales by the year 2010. That was increased in 2008 to 33% by 2020, by then governor, Arnold Schwarzenegger. Governor Jerry Brown raised the bar again in 2011. His bill included three‐stage compliance period with utilities producing 33 percent of their electricity from renewables by 2020, including 20 percent by December 31, 2013, 25 percent by December 31, 2016, and finally 33 percent by December 31, 2020.
As a result, one of the largest solar projects in California was launched. The 170-megawatt Centinela Solar Energy project is one of largest of its kind in California. Located in Imperial County, in far Southern California, the plant is being built on approximately 2,000 acres. The plant will use photovoltaic (PV) technology to convert sunlight into electricity, enough to power between 60,000 and 82,500 homes.
PJ Umphres, Equipment Representative, Underground Sales, Ontario, California, has been instrumental in supplying the equipment needed to make this project possible. One of Umphres specialties is supplying equipment necessary for the installation of the hundreds of miles of underground power cable that are required to make such a facility operational. He said, “When you think of solar energy, the last you thing you think about is cabling. But, ultimately, you have to be able to get the power from the panel arrays to the transformers and off to the utility. So it takes a considerable amount of power cable to accomplish.” Umphres works with cable installation tools and equipment manufacturer Condux International, from Mankato, Minnesota, to specify the appropriate pullers and accessories for the project.
According Centinela Solar Energy, LLC, all of the electricity generated by the plant will be eligible for use by California electric utilities to satisfy obligations under the State’s RPS program. The project is expected to create 360 jobs during peak construction and 5-7 permanent jobs while generating more than $30 million in local tax revenue over the life of the project.
Solar power harnessed through the use. PV power systems convert sunlight into electricity. The PV arrays convert solar radiation into direct current (DC) electricity. The direct current from the PV array is collected at an inverter and converted to alternating current (AC). AC electricity is consistent with the current flowing through the electrical grid. Electricity flowing from the inverter is conducted to a step‐up transformer before being conveyed to the transmission and distribution system.
In order to get the electricity from the solar array to the electric utility, hundred of miles of cable is being installed at an extremely efficient pace by electrical construction crews utilizing hydraulic underground cable pulling equipment from cable installation equipment manufacturer Condux International, from Mankato, MN.
Fluor Construction, a Fortune 500 company with offices throughout world, is the prime contractor for the Centinela Solar Project and has been subcontracted for much of the field installation work to local contractors with experience in solar array construction.
On the Job
For the Centinela Solar Project, work ranges from installing the solar panel arrays to the infrastructure necessary to get the power from the array to the overhead lines and onto San Diego Gas & Electric. Much of that work includes the installation of hundreds of miles of aluminum and copper conductor to carry the electricity.
Working in the desert in the summer can be a daunting and something that contractors do not take lightly. According Umphres, safety is a top priority on the job site. He said, “During the summer temperatures can run between 110 and 120 degrees every day. The contractors on site employ several fulltime safety individuals. They also have fulltime water people on site everyday, as well as, people dedicated to erecting shade structures for crewmembers.
“There are countless water coolers full of ice and water. There are safety meetings every morning to review safety procedures and the importance of staying hydrated. The contractors monitor the water intake of their employees and if anyone starts to feel ill they are taken to the safety trailer to cool down and are sent home rest.”
The array is being built a “block” at a time, approximately 220-acre sections. In addition to installing the solar panels, crews are direct burying power cable to transfer the electricity. To transfer the direct current electricity from the array to the inverters, trenches are dug from the array to a skid, a prewired building containing 12 inverters for that particular block.
Trenches average 4 feet wide by 3 feet deep. Up to six individual 500 MCM aluminum cables are installed at one time at lengths up to 450 feet. To keep the cables from twisting during installation, crews attach the individual cables to a spreader bar and pull directly from a reel truck. To pull the cables crews are utilizing a Condux APS75 Hydraulic Puller.
Condux Cable Pulling Specialist, Joel Westphal said, “The APS75 provides up to 7,500 lbs. of continuous pulling power and is well suited for the installation of the power cables on the Centinela Solar Project. The puller lets users view pulling forces, distance pulled, and hydraulic pressures in real time. It also utilizes a tension limiter, which adds safety for the operators, as well as, protects from over-pulling of the cable. The operators can record pulling operations, as well, and download through a USB port.”
For a typical run, the reel truck is positioned within the array of panels, after the trench is opened. With the puller stationed near the skid, the winch cable is paid out the length of the run to the reel truck. At his point, the cables are connected to the spreader bar and then to the 3/8-inch diameter winch line and pullback can begin. The crews working on the project have perfected the process, making it a model of efficiency and production.
Once cables are installed from the array to the inverters, a line out to the pole is also direct buried. A smaller 19-inch wide by 3-foot deep trench is dug up to 1,000 feet in length. These cables are also pulled into place using the hydraulic puller.
Umphres said, “The workers we have here are amazingly hard workers and they move at an unbelievable pace. They run the pullers almost constantly. They have had up to three pullers running at the same time pulling cable, eight hours a day, for almost nine months.” Estimates for the entire project, put the total amount of cable installed at over 500 miles.
Umphres estimates that installed cables in over 360 trenches, will total over 500 miles of electric cable when the project is complete. Five blocks are currently online and producing power. The remaining sections of the project are expected to complete and online by mid-2014.