Energy/Industrial: Ivanpah Solar Electric Generating Station

Photo courtesy of Bechtel

Three 450-ft-tall 'power towers' contain boilers to create steam.

Photo courtesy of Bechtel

The project includes 173,500 heliostats that track the sun's movements.

The largest solar power generating project of its kind in the world, Ivanpah uses emerging technology to produce electricity through 173,500 heliostats connected to a dual-axis tracking system, allowing the mirrors to move on a pylon 360° for optimal reflection. In turn, the sun's rays are directed onto boilers sitting atop three 450-ft-tall towers to create steam.

Creating 30% of all solar thermal energy in the U.S., Ivanpah outputs 377 MW to power 140,000 California homes annually, eliminating the need to create 400,000 metric tons of carbon dioxide each year.

The installation contains 42 million heliostat components, including 22-million rivets, 7,500-plus tons of steel, 1,200 miles of cable and 36,000-plus cu yd of concrete. The project generated more than 2,700 construction and supply-chain jobs in 17 states.

"The quantity and weight of the components was massive and challenging," one awards judge says. "Building it right the first time really worked well."

Following component manufacture, the heliostats were assembled on site at a first-of-a-kind hangar-size facility. A robotic arm moved the garage-door-size mirrors down the assembly line, where workers attached motors for the tracking system. At peak construction, the team assembled 800 heliostats daily. The job required exact precision and attention to detail. Installation was aided by a custom transportation system.

Additional construction firsts tested the team's commitment to maintaining the schedule, field collaboration, safety and quality. Designed to withstand desert heat and winds, the towers were assembled in sections and in multiple areas. Each boiler was separated into 10 sections, which were then lifted into place with heavy-duty cranes.

As installed, the heliostats were within +/-10 centimeters of the identified depth. There was only 15 cm of leeway.

The team also placed a tuned mass damper on the 2,200-ton boilers and towers; these act as 110-ton counterweights so that each tower has less than 2 ft of sway. Throughout, contractors emphasized safety, resulting in zero lost-time incidents.

During construction, the designer improved the heliostat configuration from a single pane with a reflective area of 78 sq ft to two separate mirrors on a single frame, doubling the reflective surface of each to 163 sq ft. An improved tracking system and assembly line also enhanced the original strategy, resulting in greater efficiency.

Committed to minimum disturbance to the desert, the team limited grading, efficiently augered holes and installed pylons and minimized concrete foundations.

The safety of native tortoises was ensured. At one point, the federal government shut down the operation temporarily to relocate the threatened species.

Key Players

Contractor/Lead Engineer Bechtel Power Corp.

Owner NRG Energy Inc.

Design BrightSource

Boiler Engineer Riley Power

Subcontractors Siemens Energy; Conedrive; Gestamp Renewables; Prospect Steel; TEAM Industries; Las Vegas Paving; Elemental Energy