UC Davis

Practice of intensified food production using controlled environment facilities like greenhouses is rapidly growing across the world. Due to high heating, ventilation and air conditioning (HVAC) energy demand and entailing resource input and emissions, there is increasing interest on studying alternatives to conventional technologies for this sector. Geothermal heat pumps have been studied extensively for sustainable heating applications in greenhouses, however, consequences of transitioning to these systems for both heating and cooling is unavailable in literature. This study implements a novel approach based on a dynamic coupled energy-yield simulation model to track resource input and environmental trade-offs for shifting to a stand-alone ground source heat pump (GSHP) system from a traditional boiler and fan-pad based HVAC system. The model was applied on a case study scenario for a tomato greenhouse in the Mediterranean climate of California considering two cropping cycles, one in summer and the other during winter. For producing 1 kg of tomato during the winter grow season, overall water uses in the GSHP equipped greenhouse was comparable to the conventional system, however, HVAC operating emission and cost were respectively 83% and 29% less. To produce 1 kg tomato during the summer cropping cycle, water consumption could be reduced by 69-75% and emission by 25-40% in the GSHP greenhouse compared to conventional fan-pad and boiler equipped greenhouses at an increased (2.15-2.69 times) operative cost. This study outlines a template to implement computer aided simulation for conducting cross technology comparisons between HVAC systems aligning with the food-energy-water‑carbon nexus for low-carbon and resource-conscious agricultural production.