Like a sunflower, solar PV panels track the sun

Written By Tony Boniface, PE

On February 15, 2016

At a Glance:

Solar trackers come in two basic designs: single and dual-axis. Both types alter the orientation of a solar array to face toward the sun throughout the day—for maximum solar exposure. Solar trackers are often a good solution when an application needs to increase energy production without exceeding local interconnection power limits.

The benefits of a tracker solar system: on and off the grid

Tracking solar arrays are a beautiful thing to behold; like sunflowers, they optimize their energy absorption by following the path of the sun throughout the day.

Trackers come in two basic designs: single and dual-axis. The latter type maintains the perfect perpendicular orientation of the solar array to the sun throughout the day – for maximum solar exposure. The focus of this article is the dual-axis tracker. With their optimized solar gain, dual-axis tracking arrays can harvest up to 45% more energy than a non-tracking, fixed solar array of the same size. The following image shows graphically the effect tracking has over a fixed array of the same size.

The gains in energy that can be obtained with a tracker (over fixed arrays) are most significant at higher latitudes and in the summertime.

(General) Advantages of a tracker

There are a number of factors to consider:

  • Cost is considerably less than a fixed array that produces the same amount of energy per year.
  • Makes the most of itsembodied energy. (The amount of material in a tracker system is comparable to that of a fixed array of the same wattage. Creating up to 45% more energy for this invested embodied energy, a tracker leverages that latent energy substantially better.)
  • Leverages resources — the size of system electrical components are smaller than those of a fixed array of the same energy production capacity.
  • For off-grid systems, battery size can be reduced for a given average energy load.
  • Eliminates the need to manually adjust the array orientation.
  • Eliminates the need to sweep snow from panels as the tracker will dump the snow load when orienting to the early morning sun. Furthermore, snow and ice will melt sooner on a tracker as it is always facing the sun.
  • Trackers produce energy both earlier and later in the day than do fixed arrays. This is beneficial for both grid-tied systems as well as off-grid systems.
ground-mounted solar system

(General) Disadvantages of a tracker:

  • Trackers are kinetic, mechanical systems which have parts that wear. While a well designed tracker minimizes the need for regular maintenance and component replacement, fixed arrays (with no moving parts)have no such issues.
  • It should be taken into consideration that a tracker will present a greater viewshed issue than a correspondingly larger fixed array set at a low angle.

The specific advantages of a tracker depend on whether it is grid-tied or off-grid

Grid-tie advantage #1:

Often net-metered grid interconnection points are power limited by the utility. When up against these power limits with array size, trackers allow increasing energy production capacity without exceeding the interconnection power limits.

Grid-tie advantage #2:

In general, electrical grids regulate better with steadier power delivery. A tracker does this by delivering more energy to the grid without increasing the peak power of the array as would be required of a fixed array that is comparable in energy production to a tracking array.

Grid-tie advantage #3:

Grids are often faced with their peak power demand towards the end of the day. Trackers, unlike fixed arrays, continue producing close to maximum power late in the day thereby coinciding with grid peak power demand.

Grid-tie advantage #4:

A tracker provides a better capacity factor.  A higher capacity factor is of great value to utility operators and even off-grid system owners.

While these advantages don’t necessarily benefit the system owner, they are valuable to grid operators which will only help to gain greater acceptance of grid-connected solar systems.

Where the advantages of a tracker really shine are in off-grid systems

Off-grid advantage #1:

Off-grid power systems rely on a battery bank to provide power when the solar array is not producing as much as the load is drawing. A solar array that follows the sun allows more power to be available directly from the array both earlier and later in the day. This has the advantageous effect of reducing battery cycling and battery size.

Off-grid advantage #2:

Off-grid systems, particularly for powering homes, have a steady energy appetite as daily home energy needs persist throughout the day and year, often increasing in winter. The availability of solar energy varies over the course of the year, thus it is necessary that the orientation of an off-grid array be adjustable in order to maximize solar gain.

Often manually adjusted pole-mounted arrays are used for this purpose, and while not a difficult task, the adjustment does require two people and the use of a wrench and ladder.

At best the energy gain of a manually adjustable array over an optimally oriented fixed array is at most only 15%. A tracker, in contrast, automatically adjusts every ten minutes to the absolute perfect orientation and harvests much more energy than either a fixed or manually adjustable array.

Off-grid advantage #3:

Since wintertime solar array production is already compromised by fewer daylight hours, it is important to make the most of the sunshine when it is available. Keeping solar arrays snow-free is therefore very important. While fixed arrays need to be swept off,   trackers dump snow automatically each day.

Dual-axis trackers present many advantages over fixed and manually adjustable arrays.

Because they depend on moving parts and must work reliably for many decades, choosing a quality tracker and experienced installation company is key to making a good buying decision.

To discuss a tracker for your particular energy needs, contact us today!

Tony Boniface

About the Author

In 1996, Tony Boniface founded Independent Power Systems in Bozeman, Montana to provide off-grid power solutions using solar, small wind, and energy storage for homes, water pumping, and other remote applications. He was instrumental in educating the state utility, the Montana Power Company, on the virtues of solar energy and was ultimately awarded the installation of the first grid-connected solar system in the state, as well as the country.  Tony holds a BSEE from the University of Massachusetts and is a licensed Professional Engineer and Master Electrician.

1 Comment

  1. Arlys mills

    I saw a video of a solar collecter with blades like a windmill that could fold into one blade when not in use. During the day it would follow the path of tne sun. I believe it was im use im Germany
    It had a small footprint.

    Reply

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