The details of Google’s solar thermal research

Google's heliostat 2 m x 3 m, made of glass

After a couple of years under development, Google (s GOOG) has shut down its project to design its own solar mirrors and other technology for centralized solar thermal farms. A lot of executives in the solar sector have said the idea that Google (s GOOG) could design better solar mirrors than companies in the industry was both arrogant and doomed to failure.

But, hey, it was ultimately a research project for Google, and it’s pretty fun (except for Google shareholders) that Google takes risks like this. Now it’s the job of researchers, solar execs and entrepreneurs to see if there is anything to use from Google’s solar research. Here’s what the company was working on:

  • A modular solar power tower that uses a smaller gas turbine engine, called a Brayton, for power conversion. Companies that are already working on solar power tower technology include BrightSource, eSolar and Spanish engineering giant Abengoa Solar. Google says Brayton engines do not need spray-water cooling and are in that way better suited to dry desert environments.
  • Google says it worked on cost-saving designs for the mirrors, frames, actuators, ground attachments and ways to mitigate shipping and site preparation costs. In addition Google looked to reduce the costs of installing the mirrors in the field and producing the support structures as well as the control system components.
  • Google decided the most efficient design for the mirror was a lightweight 2 m x 3 m mirror made entirely of glass, positioned at the top of the frame of the ground attachment. Google says it went with glass because it made the mirror stiff enough but also lightweight, and it made the assembly process more simple.
  • Google’s reflector itself was designed out of a glass honeycomb-style matrix sandwiched between an optical quality mirror and a sheet of structural support glass. The reflector had a slight parabolic curve to focus and concentrate reflected sunlight two to three times over a 50 meter distance. In addition the glass used for the reflector was only 2 to 3 mm thick.
  • The reflector was 2 m x 3 m for “simple and economical shipping.” Google says 8 to 10 reflectors could be loaded vertically into a reusable shipping container. Then at the installation site, vacuum lifters could be used to move the reflectors from the containers onto a heliostat frame.
  • The reflectors needed to be able to withstand 25 mph of wind and be able to orient into a stowed position in 20 minutes.
  • Google said it looked into having the reflectors concentrate sunlight at multiple towers but concluded that it was more efficient to have certain reflectors assigned to specific towers.
  • Google says it worked on software to allow the heliostats to adjust for slight movements and variations of the sun concentration.

The prototypes:

An overview view of the heliostat tech:

And videos of Google testing its heliostats with wind tunnel technology: