Outline of Research

Project Title

141b0:Development of a low-cost structure design and environment control for safe, energy-saving, and optimized greenhouse production

Project Leader

Limi Okushima

Contents

Our research and development programs are focused on a low-cost structural design and environmental control for safe, energy-saving, and optimized greenhouse production. Wind tunnel experiments and computational fluid dynamics (CFD) are used to achieve the following goals of the programs:

  • Design of greenhouse structures highly resistant to wind and snow loads with minimum frame materials, optimized light environments for crops, and low heat losses.
  • Environmental control for year-round crop production and safe working conditions for large-scale greenhouses with efficient operation of natural ventilation, fog cooling, air circulation, and insect screening.
  • Energy saving and LED supplemental lighting for greenhouse crop production.

Topics

Prediction of natural ventilation in a multi-span greenhouse using the computational fluid dynamics (CFD) technique

Objectives

Recently, rapid progress has been made in computational fluid dynamics (CFD) techniques, and CFD has been increasingly applied to research of  environment control in greenhouses. This study aimed to use CFD simulations to predict temperature distribution in a full scale, naturally ventilated multi-span greenhouse (Fig.1).

Abstract

  • This study utilized a computational fluid dynamics (CFD) program (Fluent 6, Fluent Inc.) at the Computer Center for Agriculture, Forestry and Fisheries Research, MAFF, Japan (Fig. 2).
  • CFD-simulated airflow patterns showed that the external air entered the greenhouse through roof vents located on the leeward side and traveled along the greenhouse floor towards the windward side (Fig. 3a). The CFD-simulated air temperature contours showed that the internal air temperatures on the windward side of the greenhouse were higher than those on the leeward side (Fig. 3b). These results were in good agreement with the measured results (Fig. 4).
  • CFD simulation can be a valuable tool for analyzing internal airflow and air temperature as well as evaluating designs for heating, cooling, and ventilation systems in greenhouses.

Fig. 1 Plane and vertical views of the multi-span greenhouse.Fig. 2 Supercomputer system (MAFF).Fig. 3 Computational fluid dynamics (CFD) -simulated airflow pattern (a) and air temperature contours (b) of the central vertical plane in the greenhouse.Fig.4 Horizontal distribution of measured and CFD-simulated air temperature differences inside (Tidb) and outside (Todb) the greenhouse.