Solar Power Vocab: Single & Dual Axis Solar Trackers

single axis solar tracker photo
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With the increase in commercial scale solar power plants in the past year, it seems appropriate to explain a bit of terminology that those people only familiar with home and portable applications don't have to contend with, but can really boost power output. I'm talking about solar trackers, in their single and dual axis varieties. Renewable Energy World has a thorough description of them, including the market dynamics currently at work, but this is the back of the napkin version:Efficiency Boosts of 27-40% Possible With Trackers
In the broadest sense solar trackers move the solar panel so that it is position as close to optimum as possible in relation to the angle of the sun, across seasons and time of day. Compared to just laying a panel flat, correct positioning can boost the panels output by up to 15%, but by using a motorized tracker gains of between 27-40% can be achieved.

As the post title indicates there are two types: Single and Dual Axis. Single axis trackers move on one axis over the course of the day, following the sun; doing so can boost output by about one-third. Dual axis trackers on the other hand move both east and west but also vertically; this can increase output by 35-40% as compared to a flat panel.

Single Axis Trackers Generally Cheaper, Lower Maintenance
REW describes the advantage of single-axis trackers:

Single-axis tracking is one of the most straightforward ways to improve the potential performance and economics of a commercial solar installation. By using relatively simple equipment, considerably more performance can be expected. Tracking system manufacturer RayTracker, for example, says its systems have been proven to improve energy yield over fixed angle modules by up to 23% and over flat modules by 38%.
Manufacturers of the simpler, single-axis devices have claimed that the additional net energy yield delivered by a dual-axis system over a single-axis system is frequently lost as a result of additional installation, permitting and on-going maintenance costs. And, such systems are at greater risk of failure, having more moving parts than a single-axis tracker. Furthermore, single-axis trackers tend to have a lower profile, sometimes half the height of dual-axis trackers, and are therefore more likely to receive planning permits.

Want the full scoop? Check out: Solar Trackers: Facing the Sun
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