Solar trackers are systems that help positioning of solar panels at an angle absolute to the sun. A solar tracker is commonly used to position a solar panel which is perpendicular to the sun’s ray at the same time, and place as telescopes so that they can determine the direction of sun in a correct manner. Solar trackers adjust the direction of the solar panels according to the movement of the sun. This paper discusses the standard process of how solar tracking applications operates along with an in-depth understanding about the two major types of solar tracking application i.e. single axis and dual axis along with tracking systems, tracking components and tracking control algorithm

Solar trackers are systems that help positioning of solar panels at an angle absolute to the sun. A solar tracker is commonly used to position a solar panel which is perpendicular to the sun’s ray at the same time, and place as telescopes so that they can determine the direction of sun in a correct manner. Solar trackers adjust the direction of the solar panels according to the movement of the sun. This paper discusses the standard process of how solar tracking applications operates along with an in-depth understanding about the two major types of solar tracking application i.e. single axis and dual axis along with tracking systems, tracking components and tracking control algorithms.

What are solar tracking applications?

Solar tracker is a device used to align photovoltaic panels, lenses, reflectors or other optical devices toward the sun. Since the sun’s position in the sky cannot remain the same due to the time of day, trackers helps align the collection system to maximize energy production.

It holds several major factors determining the use of trackers including the amount of direct solar irradiation, cost to install and maintain the trackers, feed-in-tariffs in the region where the system is deployed, and the solar technology being used.

Solar tracking application hold two major categories mainly named single axis and dual axis.

Single axis
Solar trackers can deliver a horizontal or a vertical axis. The horizontal axis completely depends on the region as it can only work in tropical region where the sun has a high temperature in the noon time, but the days are short. Whereas, the vertical axis is used in high latitude where the sun temperature is in control, and the time period of day is long. This type of tracker is generally used with parabolic and linear Fresnel mirror designs in concentrated solar power applications.

Dual axis
Dual axis consists of horizontal and vertical axis both, therefore they can easily detect the sun’s apparent motion virtually across the world. Concentrated solar power applications with dual axis include dish systems and solar power towers. Dual tracking plays a crucial role in solar tower applications due to angle errors resulting from long distance between the mirror and the central receiver located in the tower structure.

Many traditional solar PV applications prefers two axis trackers to place the solar panels exact perpendicular from the where the sunlight is falling. This efficiently maximizes the total power output by keeping the panels in direct sunlight for the maximum number of hours per day.

Tracker Components

• Sun tracking algorithm: This algorithm calculates the zenith angles and solar azimuth of the sun. Moreover, these angles are used to position the solar panel or reflector to point toward the sun. There are a few major algorithms which are purely designed on the mathematics which is based on the astronomical references while others mainly prefer real-time light-intensity readings.
• Positioning system: The positioning system holds a functionality to move the panel or reflector toward the sun at the optimum angles. Some positioning system are hydraulic and some are electrical. Electrical systems utilize frequency drives, encoders, or linear actuators to monitor the current position of the panel and move to desired positions.
• Drive mechanism: The drive mechanism majorly include linear drives, linear actuators, hydraulic cylinders, worm gears, threaded spindles, swivel drives, and planetary gears.
• Sensing devices: Pyronometers are needed to study the light intensity for the trackers that use keeps the requirement of light-intensity. Ambient condition monitoring for pressure, temperature, and humidity may also be required to optimize power output and efficiency.
• Control unit: The control unit operates the sun tracking algorithm and coordinates the movement of the positioning system.

Tracker Control Algorithms

Tracker control algorithms is a concept which is designed typically to incorporate a control strategy that is a hybrid between open-loop and closed loop control. The open-loop component functions on the demand when the sun is obscured to terminate clouds, eliminating or distorting the feedback signals.

Whereas, the closed-loop component operates errors that result from calibration, variability in installation, encoder mounting, and assembly. Closed loop systems track the sun by relying on a set of lenses or sensors with a limited field of view, directed at the sun, and are fully illuminated by sunlight at all times. As the sun is on the movement, it begins to shade one or more sensors. The system detects and activates actuators and motors to move the device back into a position where all sensors are once again equally illuminated.

Tracking system

Active tracking
Active tracking is concept generally used in motors, actuators, and gears to place the solar tracker so that it is positioned exact perpendicular to the sunlight. Trackers that are used in sensor to track the sun position inputs data into the controller which results to drive the actuators and motors to position the tracker in a correct manner. Depending on the location, solar maps notifies the users about the sun direction according to the time throughout the day. There are also trackers that uses solar maps, but trackers that use solar map do not necessarily hold a requirement of sensors input to track the sun. During the sunny weather, the sensor might not come in use to track the sun, however, during the cloudy weather, the information from the solar map would be used and it becomes a compulsory need for the users. Solar panels can produce energy during cloudy climate.

Passive trackers
Passive trackers are generally been used to compress gas to move the tracker. Depending on the position of sunlight on the gas containers contrasts in gas pressure is created, moving the tracker until it gets to an equilibrium position. The user can be lucky preferring passive tracker as its tracking system does not demand for a demand. But passive trackers are more likely vulnerable to wind gusts, and slow in response in comparison to active tracking.

Photovoltaic Cell
Photovoltaic cells is a concept when a combined solar panels are created and can be used to detect light intensity. It produces the maximum voltage when the sun is positioned perpendicular to the cells. As the angle between the cell and the sunray drops down, the voltage also decreases. At points, when the cells are placed parallel with the sunlight, it will generate a minimum voltage.

Benefits of Solar Tracking applications

High Precision Sun Tracking Algorithm
Following the NREL Solar Position Algorithm for Solar Radiation Applications Technical Report, positioning with +/-0.005° accuracy using the MicroLogix platform can be achieved.

Calculated Angles
The derived angles can be applied in solutions using hydraulic or electrical positioning methods.

High Quality, Industrial Hardened Components
Controllers which are built to industry standards lowers installation and maintenance cost over “black box” controllers specifically for strident industrial applications.

Off-the-Shelf (OTS) Components
The OTS components are supported across the globe with the help of network of industry technical distributors, systems integrators, and specialists. OTS components reduce time to market for the OEM and meet end user goals for global support.

Future prospects
The generation where solar electricity is considered as a necessity is one of the few low-carbon energy technologies with the potential to escalate at a very large scale. The market has witnessed a rapid growth in installed solar generating capacity; costing, advancements in technology, and performance. Further developments in the solar industry are needed to enable a dramatic increase in solar penetration at socially acceptable costs.