Solar Tracking in Australia
If you are considering buying a solar tracker, you should find out what is the cost and the seasonal gain of a solar tracker as opposed to the cost and seasonal gain of an extra panel. We recommend doing your sums first or employing a professional solar system designer to do them for you.
The gain from having a solar tracker is largely dependent upon latitude and climate.
Maximum gain is to be expected in summer at the greatest latitude. You would get more than 100% gain from a tracker on the north or south pole in mid summer as opposed to a fixed solar array at that location. In mainland Australia the greatest gain would be in Tasmania.
Overcast days are as important a consideration as latitude. Solar modules still work in overcast situations, but at a reduced rate as the module is operating mostly from diffused sunlight instead rather than direct sunlight. In extreme cases of heavy cloud cover, the solar module can cease to function completely, but this occurs rarely. As a result, you may expect up to 36% gain in Launceston in January compared against a fixed array tilted at the best angle for January whilst in Hobart you may expect 34% gain in the same conditions, because Launceston has less cloud cover than Hobart.
The sun rises south of east and sets south of west in the summer months in the southern hemisphere if you live between the equator and a latitude of 24 degrees south. Therefore, if you have a fixed solar array pointing due north, the sun shines on the back of the array in the early morning and in the evening. If you live south of 24 degrees latitude then this does not apply. These are the times of the day when the sun is least intense. Assuming cloudless skies, you may expect 1% or 2% of your daily solar energy for each half hour at these times whereas you may expect 7% to 8% of your daily solar energy for each half hour around midday. Conversely the sun rises north of east and sets north of west in the winter months which means that the sun will be shining on the front of a fixed solar module all day. You may expect a 15% gain of a tracker over a fixed array set at the best angle for the month of June in Hobart, and a 10.5% gain in Launceston. Therefore you would probably consider buying an extra solar module instead of buying a tracker, depending on gain compared to cost.
In Sydney you may expect a 30% gain in summer and a 10.9% gain in winter. In Rockhampton you may expect a 30% gain in summer and a 6% gain in winter. North of Rockhampton an extra variable is added that makes things more confusing because in summer the sun is to the south all day long whereas in winter the sun is still to the north.
In the tropics, the sunlight hours remain much the same regardless of the season whereas in Hobart the daytime goes for slightly more than 15 hours in December to less than 9 hours in June. In Hobart you may have greater need for the extra solar energy in winter when you get the least gain from a solar tracker.
An important consideration for the advantage of solar trackers is the type of loads that you wish to operate. Refrigeration, space cooling and to some extent water pumping may be considered as summer type loads as you would expect these devices to use more power over the summer months. Lighting, assuming you don't use electric lights in the daytime and possibly entertainment may be considered as winter type loads as you would be more likely to use artificial lighting and spend less time outdoors.
Another consideration for solar trackers is how reliable they are. According to Murphy's Law, wherever moving parts are added the chances of something going wrong are increased. In case of failure, unless the solar tracker stops in the midday position, a fixed solar array would become much more efficient.
Lastly it is also important to note that solar trackers are more prone to storm damage than fixed arrays. A large solar array is like a sail ready to fly off when the wind gets underneath it. It would be a real shame for an expensive setup to be destroyed because it is more prone to storm damage.