NUMERICAL ANALYSIS OF ROTATION STEP AND TRACKING STRATEGY IN FLAT-PLATE SOLAR COLLECTORS: THERMAL PERFORMANCE AND COST-EFFECTIVENESS

Abstract

This study presents a numerical analysis of Sun-tracking strategies for flat-plate solar collectors, with emphasis on the influence of discrete rotation step size and control strategy on thermal performance. Two distinct control approaches were examined: absolute Sun tracking (aSAT), which continuously aligns the collector with the solar position, and relative Sun tracking (rSAT), which performs incremental angular adjustments. A total of sixteen configurations were simulated, combining both tracking strategies with eight discrete rotation step angles ψ = {1°, 2°, 5°, 10°, 15°, 30°, 45°, 90°}. Simulations were conducted using EnergyPlus 9.6 coupled with a custom Python interface, allowing one-minute resolution control of collector orientation. This framework enabled a detailed assessment of the effect of actuator precision on incident solar radiation and useful thermal gain. A temperature-dependent efficiency model, based on the Hottel–Whillier formulation, was implemented to account for heat losses as a function of ambient temperature and irradiance. Results demonstrate that increasing the rotation step ψ leads to a nonlinear decrease in collected energy, with energy losses reaching approximately 9% when ψ increases from 1° to 90°. The optimal balance between performance and mechanical simplicity was found for ψ = 10–15°, where the system retained over 90% of the energy yield of a continuously tracking collector. Absolute tracking (aSAT) achieved up to 17% higher daily energy gain compared to relative tracking (rSAT), especially for fine rotation steps. Although economic aspects were not included, the results provide clear design guidance for optimizing Suntracking mechanisms in flat-plate solar thermal systems. The developed numerical framework may support further experimental validation and the integration of tracking algorithms in low-energy and near-zero-energy buildings (nZEBs) under varying climatic conditions.