| Popis: |
Photosynthetically active radiation (PAR) is a key parameter for modelling the photosynthetic behaviour of plants in response to sunlight and, subsequently, for determining crop yield. Separating PAR into direct and diffuse components is of significance to agrivoltaic systems, which combine solar energy conversion and agricultural farming on the same portion of land. Placing photovoltaic on agricultural land results in varying shading conditions throughout the day and seasons, producing a higher contribution of incident diffuse PAR to the crops beneath the system in these shaded regions. Additionally, photosynthesis is more efficient under conditions of diffuse PAR than direct PAR per unit of total PAR. This work introduces a new separation model for PAR, which is able to accurately estimate diffuse PAR from the global one. The model modifies the YANG2 model, by adding four new predictors: the optical thickness of PAR, vapour pressure deficit, aerosol optical depth, and albedo of PAR. The proposed model has been calibrated, tested, and validated at three sites in Sweden with latitudes above 58° N, obtaining R2 exceeding 0.91 and nRMSE less than 17%. Compared to YANG2, which was previously found to be a high-performance model, the new model is superior by up to 1% both in R2 and nRMSE. Additionally, an analysis of the seasonal trends and variation of the different PAR components is provided to alleviate the dearth of PAR studies in high-latitude regions. |
