9 sq-ft research model.

Visit "Applications" to see some of our experiments.

The goal was to develop a target-axis heliostat built with common construction materials and simple solar tracking electronics capable of sub-degree accuracy.

There are advantages and disadvantages of this type of autonomous heliostat design.

Advantages:

• Aiming is simple, just point the heliostat toward the target.
• Leveling is not required.
• Simple electronic design. (No encoders, microprocessors, or computers.)
• Inexpensive DC motors.
• Low parasitic power consumption. (Approximately 4 milliamps.)
• Wide power supply range (9 - 36 VDC)

Disadvantages:

• Optical sensor will not work if anything gets between it and the sun (clouds). It will start working as soon as the sun is visible again.
• Rotary actuators can be quite expensive.
• Spot drift during overcast periods (***WARNING*** this is a major safety concern with heliostats especially if they are optically actuated. If the sun goes behind the clouds or the heliostat malfunctions the focal spot will drift off target. For low solar concentrations and lighting applications this is usually not a problem, but imagine if you had 20 heliostats set up ... anything in the path of the solar spot while it is off target or is moving back to the target could get VERY HOT and possibly CATCH ON FIRE!
  Screening and blinding are two possible ways to address this problem.)

Click to play a time lapse movie of the heliostat tracking the sun for about six hours.