Articles
STUDY OF A PASSIVE SOLAR HEATING GREENHOUSE CROP GROW GUTTER
Article number
893_35
Pages
381 – 388
Language
English
Abstract
Water-filled transparent polyethylene tubes have been used as a passive solar system in greenhouses in Greece.
In this work, the performance of a passive solar heating system used to serve as a crop grow gutter is studied.
The experiments were performed during autumn and winter of 2007 in two greenhouses, located at the University of Thessaly near Volos, Greece, cultivated with a tomato crop.
One greenhouse was used for control and plants were grown in rockwool slabs located in a commercial grow gutter, while in the second greenhouse the rockwool slabs were located over the new grow gutter.
The gutter consisted of a water-filled polyethylene tube with a diameter of 0.45 m combined with two perforated tubes (diameter of
0.2 m) on the top, in a distance of 0.25 m between them, to serve as gutter-channel for drained nutrient solution collection.
The perforated tubes had holes of about
0.01 m every 0.50 m and greenhouse air was pumped to inflate the tubes and mix the greenhouse air.
Several parameters inside and outside the greenhouse were recorded in order to set up and evaluate a numerical model working as basis for further parametric studies.
The experimental results showed that the new passive solar heating grow gutter resulted in about 7 to 15% heating energy saving.
The perforated tubes air escaped with a temperature of 1 to 2°C higher than the average greenhouse air temperature, increasing locally the air temperature at plants level, indicating heat dissipation from the water-filled tubes.
The configuration of the water-filled PE tube, combined with the perforated tube is simulated using the Fluent CFD code, incorporating external User Defined Function source code for the non-trivial boundary conditions.
The experimental measurements obtained are used for model validation; while a small parametric study is performed altering the operational conditions of the proposed system in order for conclusions to be drawn and possible optimizations to be recommended.
In this work, the performance of a passive solar heating system used to serve as a crop grow gutter is studied.
The experiments were performed during autumn and winter of 2007 in two greenhouses, located at the University of Thessaly near Volos, Greece, cultivated with a tomato crop.
One greenhouse was used for control and plants were grown in rockwool slabs located in a commercial grow gutter, while in the second greenhouse the rockwool slabs were located over the new grow gutter.
The gutter consisted of a water-filled polyethylene tube with a diameter of 0.45 m combined with two perforated tubes (diameter of
0.2 m) on the top, in a distance of 0.25 m between them, to serve as gutter-channel for drained nutrient solution collection.
The perforated tubes had holes of about
0.01 m every 0.50 m and greenhouse air was pumped to inflate the tubes and mix the greenhouse air.
Several parameters inside and outside the greenhouse were recorded in order to set up and evaluate a numerical model working as basis for further parametric studies.
The experimental results showed that the new passive solar heating grow gutter resulted in about 7 to 15% heating energy saving.
The perforated tubes air escaped with a temperature of 1 to 2°C higher than the average greenhouse air temperature, increasing locally the air temperature at plants level, indicating heat dissipation from the water-filled tubes.
The configuration of the water-filled PE tube, combined with the perforated tube is simulated using the Fluent CFD code, incorporating external User Defined Function source code for the non-trivial boundary conditions.
The experimental measurements obtained are used for model validation; while a small parametric study is performed altering the operational conditions of the proposed system in order for conclusions to be drawn and possible optimizations to be recommended.
Authors
N. Katsoulas, C. Kittas, C. Fidaros, T. Bartzanas, K. Baxevanou
Keywords
CFD modelling, energy saving, hydroponic crops, perforated tube, water-filled tube
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