From Motor Efficiency to Loss Localization: A Phased, Field-Measurable Methodology for Evaluating Significant Energy Uses in Feed Mills

In the feed industry, energy efficiency is typically assessed using aggregate consumption indicators (kWh/t) or the efficiency of the electric motor in isolation, which makes it impossible to pinpoint where energy is lost along the conversion chain. This study formalizes a three-phase methodology that breaks down the useful electrical efficiency of each Significant Energy Use (SEU) into its successive stages—motor, transmission, and process—based on field-measurable variables, linking electrical conversion with the useful power model of each machine. The process efficiency of hammer mills is normalized using the Swiss Institute of Feed Technology (SFT) reference index; this constitutes a load-sensitive performance ratio, not an absolute thermodynamic efficiency. Its demonstration at the “Piensos Cienfuegos” plant (Cuba), using data from a 2015 industrial campaign, yielded overall efficiencies of 72% for the bucket elevator—conditional on the adopted nominal throughput and nameplate power factor, with a plausible range of 43–89% under coupled systematic-bias scenarios—26–28% for the hammer mills—despite motors operating at 90–92% efficiency—and 17.3% for the screw conveyor (24.7% at the processing stage). Grinding efficiency fell from 31.1% to 9.7% as the throughput of Mill III was reduced from 16 to 5 t/h, corresponding to an increase in normalized shaft-specific energy consumption from 3.50 to 11.2 kWh/t. The expanded measurement uncertainty was 11.8% (k=2), and systematic sources of uncertainty were quantified through a sensitivity analysis. The scope of this work is diagnostic: no retrofit or operational intervention was implemented at the plant, and consequently no before–after energy savings are measured or claimed. The reported efficiencies characterize the baseline condition and identify where intervention would be effective.