Design and Engineering Proof-of-Concept of a Robotic Variable-Height Vertical Farming System for Energy-Efficient Canopy Lighting

This paper presents the design and engineering proof-of-concept evaluation of a robotic variable-height, four-level vertical farming system that mechanically advances plant rows daily through compartments of increasing height, so that the luminaire-to-canopy distance is matched to the crop development stage. One prototype robotic system and one fixed-height multi-shelf reference system were built and operated in parallel in a single shared room, from a common nutrient reservoir, over one 32-day production cycle; the study was therefore an engineering demonstration rather than an independently replicated agronomic experiment. Engineering outcomes were measured directly. Relative to the fixed-height system, the robotic architecture maintained a target mature-canopy set-point of 200 µmol m−2 s−1 while reducing installed lighting power from 780 to 650 W and daily non-HVAC electrical energy by 13.8% (12.94 vs. 15.02 kWh d−1), and it delivered 41.7% greater cumulative canopy-level light (355.4 vs. 250.8 mol m−2), corresponding to about 70% more canopy photon delivery per unit of lighting electricity; the single-cycle energy intensity fell from 41.2 to 27.6 kWh kg−1 fresh biomass (a value derived from the descriptive biomass and therefore indicative rather than generalisable). The energy required for the mechanical row transfers was ≈0.0027 kWh d−1 (≈0.02% of daily consumption), with the actuators fully de-energised between transfers. Crop growth and quality were recorded as secondary biological validation: fresh biomass and market quality traits were numerically comparable-to-higher in the robotic system during the single cycle, but because cumulative light differed between systems and no independent replication was performed, these observations are descriptive and are not interpreted as a demonstrated agronomic effect. The results demonstrate the mechanical and operational feasibility of growth-stage-matched luminaire positioning and its measured lighting energy benefit; multi-cycle, independently replicated trials are required for agronomic generalisation.