Solar Tracker Optimizer

STO is a system that tests and optimizes the tracking accuracy of single-axis solar trackers.

It accurately monitors second by second the inclination of PV modules, analytically calculates the deviation from the optimal tilt, and generates the tilt-correction parameters delivering optimized alignment and maximized energy production.


  • Suitable for all types of single-axis solar trackers
  • Battery-powered
  • Optimal tilt curve calculated also in uneven ground conditions
  • Easy clamp-on installation
  • Automatic calculation of the production loss (Kw/h) generated by the error detected with respect to the optimal tilt curve implementable

Maximizing energy production from single-axis solar trackers

The optimal angle is calculated by STO itself through a combined set of algorithms:

(i) the ephemeris algorithm, which calculates the position of the sun on the basis of time and local GPS coordinates

(ii) the shadowing algorithm, which calculates the mutual shadowing generated by adjacent trackers

(iii) the ground tilt algorithm, which calculates the mutual mismatch due to the East-West tilt of ground in any possible ground configuration.

Optimal inclination, grow revenues

Very often the tracking accuracy of mono-axial systems is lower than expected. Minor undetected mismatches between the actual and the optimal tilt curve can easily cause the Performance Ratio to drop below the contracted value, resulting in financial penalties and in lost annual revenues ranging from tens of thousands of Euro for a 5 MW installation, up to several million Euro for a GW plant.
STO has been conceived for delivering accurate insight on the tracking accuracy of such systems, and for optimizing their operating parameters during the phases of field test and of plant operation.


Testing and operation optimization of single-axis solar PV plants during the phases of field test and of operations.

STO has been tested and used by

Enel Green Power in the Finis Terrae (Chile, 160 MhW), Ituverava (Brazil, 254 MhW), and Villanueva (Mexico, 754 MhW) power plants, delivering an average annual production increase between 2% and 5%.

STO is a sunto proprietary technology. Patent pending.

STO is mainly composed by three types of hardware units:

  • STO/a, thought to be completely autonomous and to be installed on the tracker you want to monitor without needing any wiring
    connection, measures the current tilt of the tracker table, calculates the optimal angle, and logs the measured data in a “csv” file stored in the internal micro SD card.
    The device can be configured via Wi-Fi using the customized STO APP or simply connecting it to another device able to
    manage a browser.
    In the web page generated by STO/a it is possible to read or to change the current setting, or simply download the stored data.
  • STO/b works like the STO/a unit and furthermore it generates two cool contacts to control the tracker motion according to the optimal calculated curve.
  • The 10.1′ industrial tablet, complete with cable, battery charger, STO configuration APP, and user and installation manual.

The system is delivered in a wheeled waterproof box  containing No. 8 STO/a units, No. 2 STO/b units, No.1 industrial tablet, and complements and spare parts (No. 24 clamps, No. 3 spare battery chargers with cables, No. 1 universal travel adapter, No. 1 multiplug, No. 2 spare micro-SD cards, No. 6 complementary micro-SD cards adapters, No. 1 screwdriver, and No. 2 mini-USB cables).

The dimensions of the waterproof box are 595 x 475 x H 270 mm and its weight is 16.5 Kg.

STO/a unit specifications

Weight0,5 Kg
Dimensions190 x 80 x 63 mm
International ProtectionIP 65
Power supply0.5 W Max, battery supplied
Battery specifications2200 mAh, 11 V, 200 g, 3 cells (8.1 Wh/each)
Autonomy3 weeks in monitoring mode
Measuring error0.3 degree

STO/b unit specifications

Weight0.5 Kg
Dimensions190 x 80 x 63 mm
International ProtectionIP 65
Power supply0.5 W Max, battery supplied
Battery specifications2200 mAh, 11 V, 200 g, 3 cells (8.1 Wh/each)
  • 2 days in correction mode (device always on)
  • 3 weeks in monitoring mode
Measuring error0.3 degree
Detachable cool switch cable length6 m
Cool contacts resistance> 1 GOhm when open; < 0.5 Ohm when shorted
Cool contacts current strength 0.5 A max

10.1' Industrial tablet specifications

Weight1 Kg
International ProtectionIP 65
Power supply100-240 V AC; 5 V, 3 A DC
Autonomy8 hours
Full charging time4 hours
Battery capacity10.5 Ah @3.8 V
Radio power25 mW
Radio range300 m in open air
Max occupation band0.6% (duty cycle radio on/off)
Typical occupation band0.03% (duty cycle radio on/off)
Compliance to standardsETSI EN 301-489-1 V1.9.2 (2011-09)


DescriptionItem CodeQuantity
Solar Tracker Optimizer. Supplied in a wheeled waterproof box containing No.8 STO/a units, No. 2 STO/b units, No. 1 industrial tablet, complements, spare parts, and User GuideSTO1-BRD