Optimization design of reflection power gain for Venlo-type greenhouse rooftop photovoltaic system

This study addresses the limitations of conventional PV systems by proposing an innovative roof replacement design that leverages reflective power gain through roof modification. By replacing south-facing roofs with PV panels and north-facing roofs with reflective glass (RG) panels, the proposed system effectively enhances the efficiency of PV installation. The contribution is not merely the placement of RG on the north roof but a roof-integrated reflective configuration in which PV output and crop-light requirements are evaluated together. The results indicate that the RG characterized by the highest reflectivity (54.8%) and low visible-light transmittance (17.3%) (No. 6) provides the best overall system performance. In grid-connected systems, this configuration increases the system's efficiency by 2.52%, while in stand-alone setups, it improves efficiency by 3.38%. Notably, it also maintains one of the highest levels of daily PAR sum inside the greenhouse, reaching 15.97 ± 3.86 mol m−2 d−1 in grid-connected systems and 15.24 ± 3.51 mol m−2 d−1 in stand-alone systems, supporting its suitability mainly for medium and low light demanding crops under the DLI criteria used in this study, while the monthly analysis identifies winter limitations and shows that high-light-demanding crops cannot be fully supported. These findings highlight RG No. 6's superior reflective performance compared to alternatives. This system can reduce at least 0.87 tons of carbon dioxide emissions annually. The recovery period for grid connection is 0.76 years, and the recovery period for off-grid operation is 0.60 years.