Design, Control, and Performance Aspects of Semi-Closed Greenhouses

Several greenhouse energy saving technologies and management strategies have been developed in order to meet the needs for implementation of production systems with low and efficient energy use and low CO2 emissions. Towards this aim, a number of greenhouse concepts that make use of these technologies have been developed and tested, such as the closed greenhouse, the solar greenhouse, the energy-producing greenhouse, and others. The closed or semi-closed greenhouse concept is widely accepted as a concept to achieve the targets for energy saving and low CO2 emissions. A major difference of this concept to a conventional greenhouse is that climate control by window ventilation is partially or completely replaced by systems that treat the air, regulate the air exchange between inside and outside, and in few cases collect and store the excess heat load in order to be reused at a later time. A semi-closed greenhouse allows temperature, humidity, and CO2 concentration to be controlled independently, during heating as well as cooling mode function. Among others, semi-closed greenhouses offer possibilities for better control of greenhouse environment, for increasing water use efficiency by decreasing the evaporation losses via ventilation and for reducing the pesticide use by decreasing the entry of insects and fungal spores in the greenhouse through the ventilation openings. The aim of this review is to focus on the design, control, and performance aspects of semi-closed greenhouse systems which use either (a) an air treatment corridor with evaporative cooling pad connected with an air distribution system with perforated polyethylene tubes or (b) decentralized air treatment units distributed inside the greenhouse. It gives on overview of the principles of the semi-closed greenhouse, the potential energy consumption and the expected savings. Additionally, it gives insight into the climate conditions in relation to the conventional greenhouse, crop growth, water consumption, and pest control.