Vertical farming offers crop production in stacked layers under controlled climate and lighting. While this setup enables consistent yields, it also drives energy costs for artificial illumination. A daylighting approach using roof mounted light pipes can channel sunlight down to the top growing layer, potentially lowering electricity use without sacrificing yield. Here we translate a techno economic study into practical takeaways for modern grow rooms.
The following sections explain how rooftop daylighting works in a three tier container farm, what was compared, and what the findings mean for farmers and engineers aiming to cut energy costs while keeping yields high.
How roof daylighting with light pipes works in vertical farming
The daylighting system uses a straight light duct to collect sun light from the roof and a rotating dome housing an aluminum coated mirror that tilts to steer light toward the upper tier. This light pipe delivers a portion of the sun light from the collector to the target growing zone. The overall optical efficiency can vary with the sun position and weather, typically in the 45 to 75 percent range.
In a three tier vertical farm, the upper tier receives daylight while the lower tiers rely more on artificial lighting. Daylight can reduce the required LED input but can also alter light quality and distribution. The concept is to combine daylighting with LED to balance gains and demand.
Study design and what was compared
The study modeled the optical chain with ray tracing to estimate photon delivery to the crop zone and to quantify solar gains. The model outputs fed into a dynamic energy model to run year round simulations for a city with abundant sun. The analysis compared a daylight only strategy against a fully LED baseline and several hybrid options.
Strategies included daylight only, on/off supplementation, PWM dimming, UV IR filtering, variable transmittance glazing, and simple glazing. The optical efficiency of the light pipe depended on sun position, measured between 45 and 75 percent.
Key findings for yield, energy, and economics
Daylight only operation reduced the total three tier yield by about 17 percent and was not economically viable despite electricity savings in the 27 to 29 percent range.
Hybrid daylight plus LED strategies kept yields comparable to the LED benchmark while cutting electricity use. PWM dimming with UV IR filtering delivered the lowest specific energy consumption, about 6.32 kWh per kilogram, roughly 14 percent below the LED baseline.
Compared to an optical fiber reference under identical daylight, the light pipe system offered a 15 to 38 percent lower light cost, highlighting a potential operational advantage when electricity prices are high or carbon costs are included.
If you work in agriculture, consider a small pilot to test daylighting with light pipes in your climate. A staged trial helps balance CAPEX and energy savings and can guide you toward an optimal hybrid lighting strategy for your crops.