Solar panel trackers are becoming an important aspect of solar PV systems. The efficiency gains and the ability to scale down a system and save a bit of cash is compelling. It not only saves money, but time and space too. We don’t all have the luxury of having acres of land to install an array onto, so space can come at a premium.
Solar panel trackers come in two flavors, active and passive. Over the coming weeks we will be discussing each, and today we’re starting with passive thermal trackers.
Thermally operated trackers use Freon gas to change the balance of the system and move it to follow the sun. The tracker itself is a carefully balanced system with two tubes placed horizontally. Each tube contains Freon, which turns into gas at low temperature. The tubes are essentially balanced pistons attached to the tracking mechanism.
Each end of each tube is exposed at either side of the array. As the sun warms one side, the Freon warms and eventually turns to gas. This causes the balance on one side of the tube to change.
The gas needs more space than the liquid, so it pushes outwards, which pushes the piston against gears to slowly rotate the solar panels. As the panels move into position, they shade the end of the tube and the gas cools. As it cools, it turns back into liquid and balance is restored.
This process continues throughout the day until the sun goes down. There the panels remain in place until dawn the next day where the process begins again. The exposed side of the tube gets warmed and the panels rotate all the way from west to east to meet the sun.
These solar panel trackers are very simple and very reliable. The moving parts are minimal and the thermal properties of Freon is very predictable. The downsides are that they can be slow to react. The sun may have moved from the optimum angle for a while before the heat is such that the tracker moves. The process of resetting to east in the morning can take up to an hour. That can mean almost ten percent of a day’s power generation is far less than optimal.
The other disadvantage is for those living in the colder areas of the country, or who have colder winters. As the solar panel tracker is temperature dependent, it needs that warmth to operate. On colder days, it can be hard to generate that heat and the tracker remains sluggish all day.
Despite those downsides, these passive solar panel trackers are very popular. Partly because of their lower price, but also because of their simplicity. As long as the gears are kept greased and free from obstruction, the only maintenance they need is to be re-oriented four times a year for the seasonal changes. It’s this simplicity that makes them ideal for solar power.