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The use of solar energy as an energy source is essential to reduce greenhouse gas emissions. In a photovoltaic system, the use of a sun tracker can produce up to 40% more energy than a fixed system. However, it is important, especially in temperate climates, to have an effective control strategy that can adapt the movement of the solar tracker for all weather conditions. This work presents a new control strategy for a dual-axis sun tracker based on a radiometric cube with four photodiode sensors on its East, West, South and Zenith faces. The optimal direction that maximises the irradiance received by the sun tracker can be determined through the mathematical expression of the irradiances on the four faces of the cube, considering an isotropic model for the diffuse luminance of the sky. This new control strategy adjusts the movement of the solar tracker to an optimal position in all weather conditions. The proposed control strategy provides a 40.5% gain in energy output on a cloudy day compared to the standard chronometric sun tracking strategy. For periods of clear and highly variable sky, the difference between the two strategies is only 0.15% and 1%.

In order to design, manage and optimize the performance of a photovoltaic (PV) installation and establish a precise power production estimation, irradiance on the plane of array (POA) in relation with the geometrical characteristics of the PV modules installation occupies a high importance. This study focuses on the development of an estimation model of the POA irradiance for a photovoltaic installation equipped with flat reflectors. The model includes solar irradiance components (global, direct and diffuse), geometrical parameters and geographical characteristics of the PV installation. Experimental validations have been performed with measurements taken at the SIRTA Observatory (48.7°N, 2.2°E) in Palaiseau, France, for the period starting from June 2017 to June 2018. Results show mean absolute errors (relative to the mean) of 6% and 7% for an installation without and with planar reflector. Finally, we present several geometrical optimization strategies of the PV-reflector installation relying on two major variables: the reflector's length (LR) compared to the length of the PV module (LPV) and the tilt angle adjustment frequency (monthly, seasonally, fixed) of the system (for both PV and the reflectors). The objective of such optimization is to discuss about a reasonable configuration to achieve a maximum POA irradiance. Results show that the length of the mirrors highly affects the efficiency and performances of the PV-Reflector system and the annual gain increased from 8.5% to 28.7% when going from LR = LPV/2 to LR = 2 × LPV compared to a monthly-optimized installation without mirrors. As for the adjustment frequency, we show that a monthly-varied architecture is the most advantageous option with a 28.2 and 31.6% increasing in annual gain compared to a seasonal varied or fixed ones, respectively.