Solar Tracking

Like all things mechatronic, solar tracking is hard to describe.  If we consider the actual motion, it’s two degrees of freedom and both motions are rotary.  The problem is to rotate a flat rectangular panel both about it’s midline, which is azimuth tracking, and rotate it about its baseline, which is elevation.

And the two motions are essentially simultaneous.  Yes, we only see the azimuth motion because it is the daily motion of the panel.  But the angle of elevation has to be mechanically available at the same time so that the annual change of the sun’s angle to the earth can be adjusted.  You could probably get by with this one by going out and mechanically adjusting it 4 times a year, and it would work fine.  It’s just an extra hassle, and if you’re going to bother doing tracking it might as well be good tracking.

Here’s the reason tracking is so important.  The National Renewable Energy Lab says that dual axis tracking can add up to 36% to the energy harvest of photovoltaic panels.  That’s a big number.  It’s a bigger number than anything that is in the lab dealing with the fundamental efficiency of the energy conversion process.

Because tracking the sun has such a big impact on energy harvest, it gets attention.  There are about 20 companies and tracking systems around the world.  There are all kinds of interesting solutions to the mechanical problem.  There ought to be a prize for the best design.  Some of them are really wild.  But all of them have one thing in common.  They all move arrays of panels instead of one panel at a time.

There are two main areas of solar tracking, concentrating solar and photovoltaic panels.  Concentrating solar systems are generally arrays of mirrors that focus the sun’s energy on a target area to produce high temperatures that generate steam and turn a generator.  Large arrays of mirrors all pointed at the same spot require constant adjustment and very high precision in order to get the sun’s energy concentrated on the right spot.

In photovoltaic systems, the panels convert light to electricity directly and need to be perpendicular to the sun.  But accuracy of  +/- 1 degree is acceptable.  So in one sense, it’s not as difficult.  But 2 axes of rotation is a difficult motion problem to solve.  So there are a lot of solutions out there.

I spent some time working on this and there are several really simple solutions that are possible.  And in the process of researching all the possible solutions, we found a wide range of mechanical systems that are available.

Solid Tech Inc. is in the process of developing a cost effective solution that does 2 axis solar track on a single solar panel.  This approach serves commercial flat roof installations and residential applications increasing the total energy harvest and reducing the payback period for the system including the cost of tracking.

Stay tuned for more details.