Model study on applicability of a semi closed greenhouse concept in Almeria: Effects on greenhouse climate, crop yield and resource use efficiency

The application of climate control equipment is becoming increasingly popular in Mediterranean protected horticulture. New climate control techniques reduce ventilation requirement and, thus, increase the benefits of carbon dioxide fertilization. Moreover, temperature extremes are prevented. Improvements on the controllability of the greenhouse climate can enhance production in terms of quantity and increase the water use efficiency at the same time. Those benefits must balance the costs associated with the use of climate control equipment. In an attempt to design and evaluate a semi-closed greenhouse system suitable for application in the Mediterranean area, benefits and problems for this climatic region were revealed. This paper presents a theoretical design study and analysis to assess the viability of a semi-closed greenhouse concept in the Mediterranean climate region. Nine greenhouse concepts were generated for Almeria (36° NL) and evaluated afterwards by a panel of experts. One concept received on-average highest score. This concept was a sustainable energy driven greenhouse using biomass and green electricity to run a compressor heat pump. Ventilation decision was based on the trade-off between cooling costs and yield loss at suboptimal temperatures. The concept was evaluated more systematically in a simulation study that contributed to design consistency and assessed greenhouse performance with respect to constraints and targets set in design requirements. From the simulations it was concluded that the selected sustainable energy driven semi-closed greenhouse that uses wind power and optionally biomass to run a compressor heat pump to heat, cool and dehumidify the greenhouse drastically reduced water use, the use of fossil energy and CO2 emission compared to a conventional greenhouse. Investment and operational costs of the technologically advanced equipment used, were compensated by a higher crop production, thus predicting economic feasibility.