Track Rack FAQ

Track Rack Frequently Asked Questions

1)  Will Track Racks work in the Southern Hemisphere?

Our standard tracking racks (with the exception of the UTR020) are designed for use in the northern hemisphere.  This is due to the location of the “wake-up” fin on the underside of the west-side canister.  We can make a southern hemisphere version of any of our racks for no additional charge.  This option needs to be specified at the time of the order.

2)  Do Track Racks work in cold weather?

Zomeworks passive tracking is a thermal process that works by shifting a mass of refrigerant from one side of the rack to the other.  This process works very well throughout a temperature range far greater than what is found outdoors.  However, in extremely cold temperatures (<-10°F /-23°C) the oil used to dampen / stabilize the motion of the rack can become viscous enough to inhibit tracking.  In these situations, the rack can be fixed in south-facing position for the duration of the coldest weather.

Additionally, our new damping cylinder (featured on the UTRF-090/120/168) can be easily adjusted to work in a much wider range of temperature and wind conditions.

3)  Can racks be supplied with powder coat and/or stainless hardware for coastal locations?

Zomeworks tracking and fixed racks can be supplied with stainless steel bearings and hardware for an additional cost.  We do not offer powder coating as an option.

4)  What is the difference between single-axis and dual-axis trackers?

A single-axis tracker can be thought of as doing its best to follow the sun rotating on a single axle.  Because the apparent movement of the sun is due to the Earth rotating on its polar axis, in theory only one axis is required to match to movement of the sun.  In practice, in order to easily adjust for both different latitudes and for the changing declination of the sun (higher in summer, lower in winter), a design compromise is made to integrate the tilt of the modules with the tilt of the axle.  This design yields a few percent in performance, but offers the benefits of good performance, simplicity and lower maintenance.

Dual-axis trackers can come in several different configurations, but typically use a combination of azimuth/elevation axes.  By design, these type of trackers have a very wide range of motion and can gain a few percent in performance over single-axis type trackers.  The drawback is the complexity of the tracking mechanism (motors, controllers, sensors, gears, bearings), maintenance and cost.

5)  How much space do I need between trackers?  Can I arrange them diagonally?

Trackers are best arranged in N-S running rows.  The spacing mostly depends on: the height of the tracker and the latitude of the installation.  Other factors include the slope of the land and the maximum tilt angles the array will be adjusted to.  Trackers properly spaced N-S can avoid shading completely.

When running trackers W-E, extra distance is required to avoid casting shadows in the morning and evening of certain times of year.  We recommend 4-5 times the width of the rack as a general guideline.  Installing trackers diagonally is not recommended because of the potential to cast large shadows during productive times of day.  Zomeworks can help with spacing calculations.

6)  How much wind are the trackers designed to withstand?

Trackers are designed to withstand maximum wind gusts of 90-mph, 3 second duration, exposure-C as described in the ASCE 7-05 building code.

If severe weather is anticipated, we recommend that trackers be tied down using ratchet straps (or similar) to prevent damage.

In regard to daily operation, trackers resist wind gusts quite well up to around 20 mph and above that start to get blown “off-course”.  Trackers will compensate against steady winds and will quickly reacquire their position when winds die down sufficiently.  As a rule of thumb, if wind power is a good option for your location, a fixed rack might be a better choice.