BrightSource's Heliostat Technology Solar Thermal Energy Project Concentrated Solar Power
 

BrightSource’s Heliostat Technology

by Alyssa Cauble

The Ivanpah Solar project just celebrated installation of the 100,000th heliostat, but what, you may ask, is a heliostat?  The word ‘heliostat’ comes from the Greek words helios (sun) and stat (stationary), meaning a device that tracks the sun from a stationary point. In order to harness the energy of the sun, we must first capture its sunlight, which is called “flux.”

Most concentrated solar technologies use mirrors to focus flux, and there is a wide range of heliostat designs used across the industry. BrightSource has developed several versions of the flat-pane heliostat and continues to improve the design and functionality of the flux-reflecting device. Our heliostats are made of specially designed mirrors to withstand desert heat and winds while tracking and reflecting the sun’s rays onto the boiler atop the power tower to create high temperature steam.  

In 2007, our first heliostats were built for the 6MW Solar Energy Development Center (SEDC). The SEDC’s heliostats are single-pane and have a reflective area of 78 square feet. Each mirror is connected to a dual-axis tracking system, allowing the mirror to move on the pylon 360 degrees for optimal reflection. The team at the SEDC produced 15-20 heliostats each day for the demonstration facility and after five months of work, the team installed more than 1,600 heliostats in the SEDC solar field.

In preparation for the construction of a 29MWth solar-to-steam facility for Chevron’s Coalinga oil field in California in 2009, the team improved upon the initial design and placed two separate mirrors on a single frame, doubling the reflective surface of each heliostat for a total of 155 square feet. The heliostat production facility in Coalinga included an assembly line and increased the output to 32 heliostats per day for the 3,822 total heliostats in the Coalinga solar field.

Our work at the SEDC and Coalinga were largely in preparation for our Ivanpah project.  The 377MW Ivanpah Facility requires many, many more heliostats; 173,500 to be exact. With the new two-panel design, nearly 350,000 mirrors would need to be assembled and installed quickly. To meet the challenge, the team further refined the heliostat design and assembly line in 2010 to increase efficiency. The result was a 163 square feet reflective surface, an improved tracking system and an even more elaborate, efficient assembly line for rapid manufacturing. As Ivanpah nears completion, the team continues to produce over 500 completed heliostats each day – more than one heliostat every 90 seconds.  

Further improvements are coming in 2013. In June 2012, BrightSource announced the award of a grant to automate the heliostat assembly process. The Flexible Assembly Solar Technology (FAST) system will reduce the cost and construction time for heliostat production by streamlining the assembly and installation processes directly on the solar field, eliminating the need for temporary and costly assembly lines.  Improved heliostat production comes just in time for the 500MW Rio Mesa and 500MW Sonoran West projects, due to begin construction in 2013 and 2014, respectively.