Big Solar      Panels

Solar Module and Tracking Systems

On single solar module one crystalline silicon solar cell with a surface area of around 100cm by 100cm generates around 3 A of current at a voltage of 0.5 V, if exposed to full sunshine. Up to five years ago, the typical solar module made of crystalline silicon consisted of 30 to 36 solar cells connected in series with power peaking at approximately 50 V. Today solar modules with a peak power up to 300 W are readily available. Such a solar module consists of more than 100 solar cells connected in cross patterns. In case if solar module is made of thin-film materials (e.g., amorphous silicon or copper indium diselenide), complete modules are manufactured so the above mentioned step from single solar cell to a solar module is not necessary. The solar module’s top layers are transparent. The outer layer, the cover glass, protects the remaining structure bellow from the sometimes harsh environment. It also keeps out water, water vapor, and gaseous pollutants that could cause corrosion of a cell if they penetrated the module during its long outdoor use. The cover glass is usually hardened (tempered) to protect the solar module from hail or wind damage. Cover glass is glues on to the solar module with transparent adhesive. The solar module is usually covered with an anti-reflective coating. Some solar module manufacturers also etch or texture the cell surface to further reduce the reflection. The solar cells bottom layer is called the back contact and is a metal film, which in connection with the front contact forms a bridge to an external circuit. The module’s back side is usually covered with a layer of this glass. In most solar modules frame is aluminum or composite material that gives it needed stiffness so it can be mounted in various ways and locations.

As stated above, the optimal conditions for a solar module system are only present if the irradiation on the solar generator area is continuously vertical to the sun. To realize this in practice the whole solar generator area must he continuously adjusted as the sun moves throughout the day. This systems is called tracking system and they can utilize one axis (polar trackers-horizontal trackers), two axes (active trackers) or passive trackers.

One-axis tracking systems moves only at one angle. So the sun is perpendicular to the module only in one plane. The best conditions for one-axis tracking systems are obtained if the axis is parallel to the earth’s axis. To maintain accuracy these solar trackers are adjusted by hand to compensate for the seasonal ecliptic shifts that occur in autumn, winter, spring, and summer.

With two-axes tracking systems the sun is always perpendicular to the module. These types of trackers use motors to control movements by means of programmable controllers, microprocessors or GPS control devices that provide precise solar tracker movement. Programs within the control unit use a combination of solar movement algorithms that adjust rotational axis movement in orientations that constantly maintain minimal cosine angle throughout all seasons.

And lastly the rotational mechanism of a passive tracker is based on use of low-boiling compressed gases that are moved or displaced from east to west side of a solar trackers by solar heat, which converts liquid to gas, causing the solar tracker to tilt from side to side. Passive solar tracker compared to one axis or two exes tracking systems are considered to have unreliable tracking efficiency. However, they do provide better solar output performance than fixed-angle solar support platforms.