Passive optical sensor networks for microclimate monitoring in controlled-environment agriculture

Passive optical sensor networks offer an opportunity to observe greenhouse microclimates with high spatial resolution and minimal energy demand, yet most climate control systems still rely on a few wired point measurements. This study investigates a network of passive optical sensor nodes for microclimate monitoring in controlled-environment agriculture. Each node uses low-power photodiodes and colour channels to estimate incident radiation, canopy light environment and surrogate indicators of humidity and aerosol load, and communicates data to a wireless gateway. Networks were deployed in multi-span greenhouses producing tomatoes and leafy greens and operated over two full cropping cycles. Optical estimates of radiation and canopy conditions were calibrated against reference instruments and linked to temperature and humidity patterns. Performance was evaluated in terms of measurement error, spatial representativeness, reliability and impact on climate control decisions. Results show that passive optical networks support finer microclimate management with reduced wiring, maintenance and associated energy savings