Energy-Aware Spatial Uniformity Assessment in a Container Farm Using a 27 Node Wireless Sensor Network

Abstract

Cooling is a major energy demand in container farms, but a suitable room-average temperature does not necessarily indicate spatially uniform growing conditions. This study examined whether air-conditioning energy consumption was associated with microclimate uniformity in a 10-ft container farm. Seven days of temperature, relative-humidity, and actuator-energy data were collected at 10-min intervals using a wireless sensor network deployed at three vertical levels. A total of 27 indoor sensor nodes were installed, but three nodes became non-operational during the observation period, leaving 24 valid nodes for spatial analysis. Spatial uniformity was quantified using vertical thermal and humidity gradients, spatial temperature standard deviation, and temperature range, while three-dimensional inverse distance weighting was used to visualize the spatial distributions. The AC consumed 28.37 kWh, representing 47.8% of the monitored actuator energy. However, the spatial temperature standard deviation remained nearly unchanged between AC OFF and ON conditions at 1.205 and 1.197 °C, while the temperature range increased from 4.539 to 4.680 °C. The vertical thermal gradient was also higher during AC ON periods. Daily AC energy showed negligible correlations with spatial temperature dispersion. These results indicate that greater AC energy consumption was not consistently associated with improved spatial uniformity. Improving air circulation and redistribution should therefore be investigated as a more relevant engineering intervention.