Rooftop photovoltaic systems can mitigate dairy barn heat stress by suppressing roof heat flux: a temporal analysis

Abstract

Integrating rooftop photovoltaic (PV) systems on barns offers renewable energy generation and potential thermal benefits for livestock. However, the temporal dynamics of PV systems in modulating barn thermal environments, particularly during critical heat stress periods, remain insufficiently quantified. The dynamic effects of PV panels on roof heat flux (q) and indoor temperature (ti) through integrated field measurements and computational modelling in a naturally ventilated dairy barn were investigated in this study. A computational model, validated by mean absolute percentage error (MAPE) values of 4% to 6% against field-measured data, quantified heat transfer dynamics. Linear mixed model analysis revealed that PV panels significantly reduced q during daytime (57.7% influence weight, p < 0.001), with the strongest reduction occurring during peak solar radiation at 11:00—13:00. This was primarily attributed to shading, photoelectric conversion, and cooling achieved in the ventilated air layer beneath. Consequently, PV panels significantly lowered ti during daytime (8.7% influence weight, p < 0.05), achieving a maximum reduction of approximately 2.3 °C during the critical afternoon heat stress period (14:00—16:00). Mediation analysis confirmed that the decrease in q fully mediated the PV effect on ti. Furthermore, PV integration reduced the duration of severe heat stress conditions, as assessed by the temperature-humidity index. These findings demonstrate that rooftop PV systems effectively mitigate peak heat load ingress and indoor temperatures in the afternoon in dairy barns, thereby reducing heat stress and cooling energy demand. Science4Impact Statement: This research provides quantified evidence to support advisory and decision-making processes for farm managers, agricultural policymakers, and PV integrators. By demonstrating that rooftop photovoltaic systems serve a dual purpose—generating clean electricity and acting as a passive cooling solution that reduces peak indoor temperatures by up to 2.3 °C during critical afternoon hours—this work directly informs investment decisions in sustainable infrastructure. The findings can incentivize technologies addressing both climate mitigation and animal welfare adaptation. Furthermore, the identified temporal pattern between heat flux and temperature enables the optimisation of active cooling systems, shifting from reactive to proactive, energy-saving barn management. The robust methodology, involving a validated computational model and advanced mediation analysis, ensures the reliability of these insights for practical application.