Solar Daylighting to Offset LED Lighting in Vertical Farming: A Techno-Economic Study of Light Pipes

A team of researchers has published a detailed study on integrating solar daylighting into energy-intensive vertical farms. The system uses roof-mounted light pipes (LP)—comprising a duct and a tilting mirror within a rotating dome—to channel sunlight to the upper growing tier. Using ray-tracing software (Tonatiuh), the team modeled the optical chain, predicting it could deliver 45% to 75% of incident daylight to the crop zone. This solar input was then coupled with an AGRI-Energy model to simulate a full year of operation for a three-tier container farm in Dubai.

Comparing several strategies against a fully LED-lit benchmark, the study found that a hybrid approach is key. Operating on daylight alone reduced total farm yield by 17% and was not economically viable. However, combining solar light with supplemental LED lighting using Pulse-Width Modulation (PWM) dimming and UV-IR filtering preserved full yield while cutting specific electricity consumption to 6.32 kWh/kg—a 14% reduction. The system also delivered light at a 15-38% lower cost than a comparable optical-fiber reference.

The study concludes that while the technology is promising for reducing operational energy and carbon footprint, its widespread adoption is currently constrained by high capital expenditure (CAPEX). The electricity savings achieved are often insufficient to justify the initial investment under current economic conditions. The system's viability improves significantly in regions with high electricity prices or strong carbon pricing policies, pointing to a future where such hybrid systems could make urban agriculture more sustainable.