Mining the Sky - Assembly And Alignment

Laser Tracker Critical in the Alignment/Assembly Phase

In the production phase, Molari verifies the mirrors are tilted at the correct angle, and rechecks the flatness of each 4’ x 4’ facet. She explains, “Assembly has to be conducted onsite due to the size of the components. The flattening of the mirrors has to be accurate to plus or minus .002”. These tolerances make it impossible to use tools or jigs to build this light structure rigid enough to hold the mirrors. The mechanics of this project are a marvel to me. From the beginning, we have assisted in verifying integrity of their design-to-assembly process.

“The Leica AT901 is my go-to metrology tool for this type of challenging work,” said Molari. “I know I can measure and achieve a solution for any dimensional control issue such as inspecting the cant of each mirror, analyzing that data, then comparing the measurement with a neighboring facet to ensure we induce the correct angle. The work environment was taxing in these remote sites. The laser tracker was on the ground, and I had to use a scissor lift to access the ten-foot tall assembly. Wind, sand, and very high temperatures were often present during these inspection jobs. The robust construction and thermal stability of the tracker renders it very reliable in these circumstances.”

The laser tracker integrates a unique PowerLock feature that proved to be indispensable for this project. This active vision technology automatically locks onto any moving reflective target, without user intervention, as soon as it is within view of the sensor. If a line of sight is obstructed by a co-worker or a part of an assembly, the AIFM instantly re-establishes a broken laser beam and starts measuring the moving target. “You can focus on measuring a part without worrying about a broken laser beam,” said Molari. “When working outdoors, PowerLock is even more helpful as it is extremely difficult to see a laser spot in the sunshine or in the shade. There were many obstructions during assembly as you are working through trusses and mirror structures. When there was no direct line of site to a point we wanted to measure, I used the wireless Leica T-Probe to get at those hard to reach areas. You must have an agile toolset in the field.”

Sensing the Mainstream Potential

The Crescent Dunes Solar project has the potential to kick the alternative energy door wide open. At the construction site, there is a sense of excitement as heliostat arrays are erected one by one. Overall, the project’s benefits are palpable from reducing reliance on fossil fuels and lowering greenhouse gas emissions, to a stable, flexible electricity to improve grid reliability.  Other bonuses for the local economy are new green jobs, and additional tax revenue. On a recent visit to Tonopah, town representatives awarded SolarReserve’s staff with commemorative “Mining the Sky” coffee cups to show their support for the area’s largest asset.

Gary Raczka also visualizes the possibilities, “Solar has been around a long time, but what differentiates our product is its improved efficiency with very high quality optics and thermal storage. Some of our utility customers want power 24/7, as opposed to another that only wants help through the peak loads. Depending on their power requirements, we can design storage tanks and size the generators to serve our customer’s needs. Secondary, but very important, is our very aggressive internal cost targets have spawned innovation to reduce the cost of heliostats.

“As production ramps up on heliostats and other components, the price comes down. In the future, we will be able to produce electricity per kilowatt less expensively. If we modernize our nation’s energy grid to leverage new energy technologies, a solar power plant on 100 square miles in the desert could possibly power most of the United States with a proper distribution system.”