Precooling the highly perishable fruits and vegetables from California’s desert valleys is a large block load of refrigeration that coincides with maximum air conditioning. Harvest season daytime highs of 100 to 115 F (38 to 46° C) are typical between early morning lows of 70 to 90 F (21 to 32° C). Pulp temperature of fruits fully exposed to clear sky will vary through an even wider range due to solar heating and night sky subcooling by radiation.

Picking in the relatively cool thermal sink of night air and black sky from midnight to sunrise can allow precooler input temperatures normally 20 F (11° C) cooler than for daytime harvest. The 40% reduction in cooling load and the five hour earlier daily start-up of compressors can provide substantial energy savings and time-of-use (TOU) benefits for precooler operators. An energy efficiency ratio (EER) of 14 for cantaloupe was indicated.

Mobile illumination apparatus attached to picker aids such as platforms, belt loaders or special carts and using fluorescent lamps powered by attached portable generators have been highly successful and cost effective. Ennancement of product quality and reduction of thermal stress on workers are additional benefits of increasing economic consequence. The technology is described.

Units: Dual