Solar Turbo-generator: Anatomy of a Two-axis Mount

July 2004

A few of you may wonder what a 2-axis mount is, and why we even need it. The two-axis mount is one of the key components to making our solar generator work at optimal efficiency, so it is important to spend a little bit of time understanding how it works.

The two axes we are interested in are azimuth and elevation -- or az/el. Since the earth rotates on a pitched or inclined axis (not perpendicular to its orbit), the sun traverses the sky at varying elevations in respect to the horizon from day to day. At the winter solstice, the sun it at its lowest elevation; it's at its highest at the summer solstice.

Between these two limits, the sun's path changes in elevation slightly from day to day. In order to keep the sun's heat energy tightly focused on our heat exchanger target point, it is necessary to swing the dish east to west, as well as north to south -- thus two axes.

The actuators we are using are rated at 2,000 pounds of force, and were standard equipment for heavier satellite dishes in the 1970s and 80s. You can still find these actuators and their electronic controllers in junk yards, garage sales, etc. for next-to-nothing, so do some hunting around before buying new units.

Another option is to use hydraulic systems -- but they are a bit more complex and harder to control.

Ken Rieli