Industrial design and implementation of a large-scale dual-axis sun tracker with a vertical-axis-rotating-platform and multiple-row-elevation structures

Abstract A dual-axis tracked Photovoltaic (PV) system can produce up to 30% more electrical energy in a year as compared to a fixed-tilt PV system. To be economically feasible, a sun-tracker must also be accountable for the cost effectiveness, durability and long-term reliability despite the gain in electrical yield. To achieve this purpose, in this paper, we are reporting a practical industrial design of a large-scale dual-axis sun-tracker consisting of a vertical-axis-rotating-platform and multiple-row-elevation structures (VRP-MRE). The advantages of the tracker design include lower wind-load moment, high tracking precision, high repeatability and high durability. All these favourable features are attributed to the use of a large perimeter rotating platform coupled with a low-cost electro-mechanical encoder, and a torque tube mechanism that can simultaneously drive multi-row elevation movement through a shared push-pull type of linear movement. Several important characteristics of the new tracker have been studied in detail, such as the range of motion, slew rate, control system, electrical wiring, special tracking behaviour and special requirements when it is used in the equatorial region. A prototype of industrial-scale sun-tracker with a 35-m of diameter has been designed to achieve tracking resolutions of 0.111° in the azimuthal direction and 0.03° in the elevation direction. The overall measured tracking accuracy was 0.28°, and the achieved precision was 0.0111°. A total of 60 kWdc PV modules were installed on the sun-tracker. The energy consumption by the driving systems of the sun-tracker was calculated, which on average ranges from 0.40% to 0.50% of the total energy generation by the PV system.