Illumination of barns for dairy cattle : energy-efficiency and circadian lighting in a Swedish context

Improving energy efficiency in agriculture is key to reducing environmental impact. Lighting in animal buildings is one of the most cost‐effective energy saving measures. Lighting retrofit offers a short payback period, enhances animal welfare and production, and aligns with regulations for phasing out fluorescent lighting. The purpose of this study was to investigate the energy-saving potential of daylighting and electric lighting retrofits in dairy barns, focusing on energy efficiency and circadian lighting conditions. The study involved on-site measurements and lighting simulations of a dairy barn located in Southern Sweden. The results show that energy use reductions of 63% can be achieved with LED upgrades. Moreover, installing skylights in the roof would increase daylight autonomy from 12% to 55%, while providing higher melanopic illuminance than electric lighting. In conclusion, implementing LED lighting and daylighting strategies such as skylights can improve energy efficiency and indoor lighting quality in dairy barns.