ERCAM’s Solar Trackers are composed of a set of galvanized trusses linked together end-to-end. Each truss supports an array of 4 or 5 frames and each frame holds 3 or 4 solar panels. Panels are attached to the frames with galvanized screws and clamps.
The system features a +/-55 degree E-W rotation, called primary or G1, and which tracks the sun as it moves from East to West each day. Taken by itself, this rotation is simply that of a horizontal single axis tracker.
In addition, the ERCAM dual-axis tracker also includes a mechanism that pivots the frame/panel assembly up/down (N-S axis), a movement called G2. The rotation of the frames in both axes is synchronized by a driving rod and sliders controlled by actuators, responding to the commands of the PLC.
In order to adapt to the site’s terrain, distribute its static load, and counteract wind loads, the tracker is mounted on a row of levelled (N-S) and secure pillars.
ERCAM’s solar tracking control system calculates the position of the sun, solar altitude and azimuth, as a function of date, solar time, and latitude.
It also includes a "backtracking" feature to avoid morning and afternoon shading of PV modules by neighbouring tracker rows when several trackers are installed side-by-side. This feature maximizes the performance of the installation when compared to other tracking systems which do not take into account the production loss that shading between trackers will cause.
An anemometer continuously measures wind speed, and signals the tracker to go into its stow position when high winds are detected.
BASIS of the ERCAM TRACKING SYSTEM
LOAD CALCULATION BASIS
Wind loads are calculated per the requirements of Eurocódigo 1, UNE ENV 1991-2-4.
In order to check the resistance of the different structural elements, we used the methodology outlined in Eurocódigo 3, UNE-ENV 1993-1-1 and the Spanish Structural Steel Instruction, EAE.
Aside form the minimum wind loads requirements, established for the most critical positions of the tracker, more rigorous testing has been performed including a series of different critical angles when the tracker is not in stow position (with a probability of occurrence once every 50 years) and a case where the wind load was double the one recommended by regulations.
The particular aerodynamic characteristics of each tracker were considered in all calculations
Each beam has a capacity to support 12, 15 or 16 panels and needs an approximate area (projected footprint) of 6.34 m in length and maximum 6 m in width. The tracker rows are set at a distance of 12-18 m between the axes. Energy output of 20 and 30 W/m2 can be obtained depending on the type of PV module. The tracking system works for any configuration and distance between rows, preventing shadows thus maximizing the profitability of the installation even in plants that have space limitations.
The tracker is driven by a separate hydraulic actuation system for each axis. The electrical power supply is 24/36 V DC.
The structure consists of galvanized steel and aluminium.
The control system consists of a master PLC which performs positional calculations to determine the required position. A group of slave PLCs receive this data from the master, compare it to the actual position and then, if necessary, change the position of the trackers so that the actual position is equal to the required position.
The master PLC receives the actual position of each tracker from a pair of inclinometers, allowing remote monitoring of the system.
The master PLC is compatible with a serial communication interface, e.g. Ethernet.
The system includes the following safety systems:
For an installation of 100 kw:
Daily power consumption for an installation of 100 KW: 0,32 KWh
Annual power consumption for an installation of 100 KW: 117 KWh