Abstract
Since the Great East Japan Earthquake in 2011, the production and sales of cucumber, the main vegetable product in coastal southern Iwate, have decreased, thereby requiring the development of technology for the reconstruction of this region. As this region has few snowfall days and a relatively long sunshine duration in winter, using multi-layered thermal curtains (insulation curtains) as the inner covering material of greenhouses could be effective to save fuel consumption and increase the farmers’profit. However, the optimal opening/closing timings tendency of the different insulation curtains to minimize fuel consumption remain unknown. This study presents a simplified model to calculate fuel consumption using heat balance and transfer equations and applies the model to combinations of greenhouse orientation and insulation curtain type to identify optimum opening/closing timings. Results show that (1) daily fuel consumption fluctuations could be captured, while heating start and end times tended to be earlier and later, respectively, than measured values; (2) the opening and closing timings for insulation curtains made of materials with a high heat transmission coefficient tended to be early and delayed, respectively; and (3) the opposite tendency was observed for insulation curtains made of materials with a high solar transmittance. The findings of this study are expected to contribute to energy savings by minimizing the heating fuel consumption needed for vegetable production in this region.
