|One of three 459-foot tall towers at the Ivanpah Solar Electric Generating System. Photo Courtesy of Bechtel Corp.|
By Members of the Bechtel project management and Six Sigma team
Building the world’s largest concentrating solar facility – and one that is the first of its kind – requires nothing less than innovation at every step. While the 377 MW Ivanpah Solar Electric Generating System (ISEGS) falls squarely into a sweet spot of complexity and scale, one can never overlook the processes and tools needed to manage a project of this kind.
From building a first of a kind automated assembly line to erecting three 450-foot power towers, Bechtel had the opportunity to apply its expertise to what has become a unique facility. Developed by Solar Partners – NRG Energy, Google and BrightSource Energy – the ISEGS is a concentrating solar power (CSP) facility built in the Mojave Desert that will nearly double the amount of commercial solar thermal electricity produced in the U.S.
To ensure customer satisfaction and predictability of outcome throughout this multi-year project, Bechtel turned to Six Sigma. Six Sigma is Bechtel’s chosen methodology for improving quality and performance.
Bechtel is one of the few engineering, procurement, and construction (EPC) companies that use Six Sigma to deliver big projects to its customers. The company has been using it for over a decade and has trained thousands of technical and professional employees on Six Sigma tools. Those who have completed the most robust training achieve advanced level certifications.
Developing a Business Case for Ivanpah
Six Sigma works best on projects that have a lot of repetition or first of a kind elements. Ivanpah is an ideal candidate. Consider that the project includes assembling and installing software-controlled heliostats or mirrors – 173,500 of them. The heliostats, each the size of a garage door, consist of two mirrors mounted on a post that tracks the sun throughout the day to direct sunlight to boilers or solar receiver steam generators (SRSG). The sunlight heats water inside the boilers to create superheated steam, which then generates electricity. There are three boilers on the project, each weighing 2,200 tons. Each boiler sits on top of a 339-foot power tower for a total height of 450 feet – that’s one and a half times taller than the Statue of Liberty.
There was no standard template for the Ivanpah project. Heliostats had been installed at one of BrightSource’s pilot projects, but nothing at this scale. All the processes of assembly, transporting and installing the heliostats had to be developed from scratch. To boot, the heliostats had to be installed on existing rolling terrain to avoid and minimize the need to grade or level at the project site, further adding to Bechtel’s challenges.
The kind of complexity embedded in the Ivanpah project was a good fit for the Six Sigma approach. By using Six Sigma to address design, procurement, and construction challenges, Bechtel was able to develop new processes that helped us meet performance goals and execute successfully, while simultaneously building trust and credibility with our customer.
Working with the Customer to Define Process Improvements
Bechtel’s engineering and construction teams joined with engineering and construction experts from BrightSource to form a Six Sigma team. Keeping in mind the needs of the customer in addition to cost and schedule, the team identified five areas that needed process improvements: material handling; heliostat assembly; field transportation; solar field installation; and power tower erection. In each of these areas, the team found new or more efficient ways that drove better performance and better results.
As one might imagine, managing materials for a project this size is quite complicated. Bechtel was tasked with handling 42 million total heliostat components, including 22 million rivets, more than 7,500 tons of steel; 2,000 kilometers of cable; and more than 36,000 cubic yards of concrete.
The original plan called for a 19-acre area to hold heliostats, pylons and other solar field equipment, in addition to the erection and operation of the assembly equipment. When the area was reduced from 19 to 14 acres in an effort to reduce the project footprint, the team had to use modeling tools to make sure all the materials came in and out without any hiccups.
The team developed models to map how heliostat containers were moved throughout the site. With the data from the models and feedback from traffic and logistics stakeholders, the team redesigned the area to allow for stacking of the heliostat containers. Choosing specialized yard equipment meant containers could be moved more easily in the smaller space provided.
Heliostat Assembly Building
Outside of the solar fields and power towers, Ivanpah’s Heliostat Assembly Building (HAB) has been a main site attraction. While one might find an assembly line at a manufacturing facility, chances are you won’t see one on a solar site. But Ivanpah’s HAB was state-of-the-art and featured robotics designed by BrightSource to lift the mirrors from a stack to the pad bonding area, where special pads were put on the backs of the mirrors in preparation for installation. Visiting the HAB was like looking inside a watch; parts moved in place, one after another, perfectly timed and in sequence. The beauty of its efficiency was in the simplicity of the design. But, it wasn’t always planned that way.
The original design of the HAB consisted of one building that contained both the pad bonding equipment and the assembly line equipment and only one exit area at one end of the building. This design posed significant risk of congestion.
The Six Sigma team got an inside view of a mock-up assembly testing facility where they could conduct time and motion studies. The results of the studies enabled them to redesign the building using efficiencies that would enable craft to assemble 500 heliostats per day, or 1.7 a minute.
The redesign included separating the facility into two distinct areas: One set of smaller buildings for pad bonding and a larger building for heliostat assembly that had multiple exits. The separation of the buildings with additional exits meant less congestion and maximum efficiency.
In order for 173,500 heliostats to be installed on schedule, 500 of them would need to be transported to the solar field every day for two years. Based on the scale of the project, this equaled roughly 35,000 miles of travel required to move the heliostats.
To solve the puzzle, the Six Sigma team analyzed various transportation models to uncover the most efficient routes – from the time the heliostats left the HAB to the time they reached the point of installation. The team designed a transportation management system with a number of crane, tractor and trailer combinations needed to sustain the required installation rate. The processes were then institutionalized within the execution plan for the solar field.
HELIOSTAT AND SOLAR FIELD INSTALLATION
Once the team figured out the best way to transport materials and assemble the heliostats, they needed to evaluate the solar field installation. This process involved analyzing how holes were augured to pylon insertion, and finally, to heliostat installation.
When working on a project this size and the company has strong relationships with vendors, Bechtel had the flexibility of redesigning installation equipment to best suit the needs of the project and customer. For example, the team contacted a vendor to redesign excavators so that auguring and pylon insertions could be done without changing attachments on the machinery. The team also chose leading edge excavator machines that were fuel efficient and had the ability to reach 25 feet to auger holes and install pylons. By changing the design of the equipment, craft were able to better protect the Mojave Desert landscape during installation by reducing impact to the desert environment.
The efficiencies created in the heliostat and solar field installation process enabled craft to reach and exceed the 500 heliostat-a-day goal. At peak, craft installed heliostats at a rate of 600-750 per day. Additionally, a GPS system was utilized on each auger and pylon excavator that reduced the required survey manpower and provided quick and accurate installations to the required tolerances.
Craft Participation in the Six Sigma Process
The success of the Six Sigma team also depended on craft input. The craft provided the team with invaluable feedback with regards to work flow, cycle times, equipment functionality and challenges with pylon installation. By being a part of the process, the craft became more invested in the success of the project and the desire to continuously improve the process.
The Six Sigma philosophy of “continuous improvement” also carried over into their daily work. Craft would have competitions to see which teams could insert the most pylons or build and install the most heliostats in a day according to project specifications. These competitions created a tremendous sense of team spirit and pride in their work. Craft participation in the Six Sigma process was critical and led to discretionary effort that strengthened customer satisfaction throughout the build. The same enthusiasm, effort, and can-do attitude they displayed at the beginning of construction continues on the project today.
Power Tower Erection and Boiler Lift
Another first-of-a-kind challenge on Ivanpah was the erection of the 339-foot steel power towers and the lift of three 2,200-ton boilers. Construction experts recommended building the tower and lifting the boilers in pieces. The team created multiple assembly areas around the tower foundation where craft could begin work on the next section immediately after finishing the first.
|One of the towers and heliostats of the Ivanpah project. Courtesy: Bechtel.|
The lower portion of the tower was built on the tower foundation, while the upper portion was preassembled on the ground and lifted into place. Building pieces on the ground was safer for the craft, and the repetition of the modular approach enabled the workers to perfect the process, saving time along the way.
With the tremendous weight of the boilers and their original size of 50 feet x 50 feet x 120 feet, craft built ten 90-ton structures in a common area and then lifted the sections with a special 450-foot tower crane. Only 22 of these cranes existed in the world, and Ivanpah had three of them. By making lifts at maximum weight, the number of lifts was reduced, saving time and maximizing productivity. After the team successfully erected the first tower, they improved the processes and institutionalized lessons learned for the other two, which are complete.
Andy Gillespie, Bechtel project manager of the Ivanpah Solar Electric Generating System, along with members of the Bechtel/Ivanpah Six Sigma team, Mark Wagner, Kimberly Johnson, Terry Copeland, and Kathi Kirschenheiter, contributed to this article.
Power Engineering and Bechtel will be hosting an #Ivanpahchat on Twitter Nov. 5 from 10a-11a Central (11a-12p Eastern). Be sure to follow @pwrengineering for more details!
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