Power of the Sun

When completed, the Ivanpah Solar Electric Generating System (ISEGS) in California’s Mojave Desert will look striking and reduce carbon dioxide (CO₂) emissions by more than 400,000 tons per year. The ISEGS innovations will also provide much-needed power during the peak hours of the day to more than 140,000 homes in California.

ISEGS is currently the largest solar plant under construction in the world. It is a 392-MW gross solar complex using more than 300,000 garage-door-size mirrors to focus the power of the sun on solar receivers atop power towers. The solar receivers are like traditional boilers, turned inside out. The project is located about five miles from the California-Nevada border on federal land managed by the Bureau of Land Management.

BrightSource Energy designed the proprietary solar thermal energy system, which generates power the same way as traditional power plants — by creating high-temperature steam to turn a turbine. However, instead of using fossil fuels or nuclear power to create the steam, the system uses the sun’s energy.

The ISEGS complex is comprised of three separate plants to be built in phases between 2010 and 2013, and will use BrightSource Energy’s Luz Power Tower solar thermal technology. The Ivanpah facility is the first BrightSource solar power plant to utilize this type of technology.

Partnering for a unique grade control technology solution

Bechtel, the San Francisco-based engineering, construction, and procurement firm, is responsible for managing the construction process of the ISEGS project. The firm has more than 2,000 employees working on the site.

“I worked with grade control technology in the past and felt comfortable soliciting input early in the process to see if there might be an efficient GPS machine control solution for building the solar fields,” states Mark Wagner, lead area superintendent with Bechtel. “We were looking at the precision placement of 173,500 pylons scattered over 3,600 acres, so traditional staking would be incredibly time consuming and very costly.”

It was clear that the ISEGS project would be more than a typical machine control system project, so Dave George, commercial manager-worldwide with Trimble brought in the local Trimble dealer and appropriate product and machine experts from within Trimble, including personnel from the U.S., New Zealand, and Holland. The project required a highly customized solution.

The three parties — Bechtel, Trimble, and the local Trimble dealer, Cashman Equipment Company — determined that an excavator-mounted vibratory hammer could work if the Trimble technology and custom attachment could work together. They travelled to vibratory hammer manufacturer, Hercules Machinery Company (HMC), headquarters in Fort Wayne, Indiana, to create a custom vibratory hammer that could be mounted to a long reach excavator, with the ability to traverse the ephemeral washes of the site and still meet the tight tolerances required for the pylon insertion.

Trimble experts recognized that determining the exact location points for the pylons with the machine — not with surveyors — was the most effective solution … a solution that was found in an unconventional source.

Reducing environmental impact is a priority

“We were looking at 173,500 holes that needed to be drilled and the same number of pylons that needed to be inserted,” Wagner says. “The rigs had to have the accuracy of a surveyor’s rod AND the ability to collect the pylon’s ‘as-built’ data.” The answer came from Trimble, who had experience with Trimble HYDROpro Construction Software, a software package for specialized waterway and coastal construction tasks that require precise point positioning.

HYDROpro Construction’s pile feature is used for precise pile positioning applications for bridge and wharf construction. Trimble engineers were able to modify this powerful construction software for use on the Mojave Desert site where water is scarce and the average annual rainfall is less than five inches.