AN OVERVIEW OF NATURAL VENTILATION, AIRFLOW, EVAPORATIVE COOLING AND HEAT PUMP HEATING IN GREENHOUSES UNDER MILD CLIMATIC CONDITIONS
Under mild climatic conditions, less resource inputs may be required in low-technology greenhouses than high-technology under severe climatic conditions. The advanced technologies for environmental control have not been adopted in most Japanese greenhouses, which are pipe-structured and covered with plastic film. Year-round production in greenhouses is a primary concerns for increasing the efficiency and productivity of horticulture. However, Japan has disadvantages such as high temperature and humidity during the summer, and a large amount of energy for greenhouse heating that requires import of natural resources. Improvements for more sophisticated greenhouse systems to meet these requirements are needed. Ventilation is one of the most important techniques for controlling greenhouse environments, and natural ventilation systems are widely adopted. In recent years, the use of fog cooling system is increasing in greenhouses during the summer, and the use of circulation fan system is increasing in greenhouses during the winter. This paper describes the current technological status of greenhouse environment control in Japan, basis of cooling greenhouse air, characteristics and feasibility of natural ventilation in terms of temperature rise and distribution, and fog cooling under natural ventilation. Moreover, we describe recent studies on the computational fluid dynamics (CFD) approach, circulation fan systems, and heat pump systems.
Ishii, M., Okushima, L., Moriyama, H. and Sase, S. (2014). AN OVERVIEW OF NATURAL VENTILATION, AIRFLOW, EVAPORATIVE COOLING AND HEAT PUMP HEATING IN GREENHOUSES UNDER MILD CLIMATIC CONDITIONS. Acta Hortic. 1037, 493-500
greenhouse, natural ventilation, airflow, computational fluid dynamics, high pressure fog cooling, circulation fan, heat pump