Microclimate Prediction for Dynamic Greenhouse Climate Control

Abstract

<jats:p>Greenhouse energy-saving and biocide reduction can be achieved through dynamic greenhouse climate control with computerized model-based regimes. This can be optimized when next to greenhouse macroclimate (i.e., the aerial environment) also, the crop microclimate is predicted. The aim of this article was to design and apply a simple deterministic microclimate model for dynamic greenhouse climate control concepts. The model calculates crop temperature and latent heat of evaporation in different vertical levels of a dense canopy of potted plants. The model was validated with data attained from experiments on dynamic or nondynamic (regular) controlled greenhouse cultivation. Crop temperature was with a 95% confidence interval of 2 °C or 2.4 °C for sunlit or shaded leaves, respectively, accurately predicted in a simple greenhouse with predefined climate set points. With a more dynamic greenhouse control also including assimilation lighting and screens, the prediction quality decreased but still had a 95% confidence interval of crop temperature prediction of 3.8 °C for sunlit leaves. Simulations showed that controlling greenhouse temperature according to the predicted crop temperature rather than according to the air temperature can save energy. Energy-saving is highest during winter and 12% energy saving was attained during January under Danish climate conditions.</jats:p>

Nutrient Cycling in Aquaponics Systems

“…The reality, however, is that the evapotranspiration of the crop (ET c ) in greenhousebased aquaponics systems is highly dependent on multiple factors such as physical climate and biological variables. ET c is calculated per area of the ground surface covered by the crop and is calculated for different levels in the canopy (z) by integrating irradiative net fluxes, boundary layer resistance, stomata resistance and the vapour pressure deficit , in the canopy (Körner et al 2007) using the Penman-Monteith equation. This equation, nevertheless, only calculates the water flux through the crop.…”

The Influence of Day and Night Temperature Fluctuations on Growth and Flowering of Annual Bedding Plants and Greenhouse Heating Cost Predictions

“…In temperate climates, high-energy inputs can be required to maintain a desirable greenhouse temperature, making fuel for heating one of the largest floriculture production expenses (Bartok, 2001). Greenhouse growers can reduce energy consumption by managing the greenhouse environment with dynamic temperature control (DTC) strategies (Körner et al, 2007;Lund et al, 2006). In DTC, in contrast to static temperature control, heating set points are lowered during periods when the greenhouse energy loss factor is high (e.g., outside temperature and incoming solar radiation are low) and increased when the energy loss factor is low (Körner et al, 2004).…”

Aquaponics Systems Modelling

“…This is an ongoing issue in greenhouse modelling, as microclimate variables, such as the central leaf temperature, are highly variable and dependent on many parameters and variables. One version of a leaf temperature model used in a crop canopy for crop temperature (T c ) integrated over vertical layers (z) by Körner et al (2007) integrating absorbed irradiative net fluxes (R n,a , Wm À2 ), boundary layer and stomata resistances (r b and r s , respectively, sm À1 ) and vapour pressure deficit at the leaf surface (VPD s , Pa) in the canopy is shown here, i.e.…”