A Modelling Approach to Assess the Impact of Agrivoltaics on Water Use Efficiency and Alfalfa Biomass Growth

Simulations for the Aotearoa New Zealand Livestock Sector

Abstract

Agrivoltaics presents a promising solution to addressing the dual challenges of food and energy security. This study explores how different agrivoltaic configurations affect water use efficiency (WUE) and alfalfa biomass growth in the Canterbury region of Aotearoa New Zealand. Using advanced modelling tools, the research evaluated low-, medium-, and high-density setups for both fixed-tilt and single-axis tracking systems. The results reveal that agrivoltaic systems can moderately improve WUE relative to open-field conditions, primarily through reductions in evapotranspiration driven by suppressed soil evaporation under partial shading. Across the configurations assessed, WUE increased by approximately 4 to 9%, with low-density single-axis tracking systems exhibiting the most favourable balance between water savings and biomass production. While total above-ground biomass declined with increasing panel density, reductions were generally limited to approximately 15 to 25% relative to the control. Shoot biomass was more sensitive to shading than leaf biomass, which showed comparatively smaller reductions, highlighting potential implications for grazing-oriented production systems. For livestock grazing systems where leaf material is prioritized, these configurations may remain suitable under moderate shading conditions, whereas the implications of reduced shoot biomass for forage-harvesting systems require further evaluation. The findings suggest that carefully designed low-density agrivoltaic systems can enhance water-use performance while maintaining acceptable levels of agricultural productivity. Further research incorporating field validation and farmer-specific management objectives is recommended to refine system designs and support practical adoption.