|Author:||Chaibi, M. T.|
|Book Group Author:||NA|
The limited water resources in arid areas have led to the use of low-quality irrigation water in agriculture which may reduce crop yields and damage the environment. This study focused on a greenhouse concept with integrated water desalination considered for small scale applications at remote locations in areas where only saline water was available. In this greenhouse, the roof light transmission was reduced as solar radiation was absorbed by a layer of flowing water on a glass covered by a top glass. Fresh water was evaporated, condensed on the top glass and collected at the roof eaves. The study analysed the fresh water production as well as the crop growth capacity and water demand for the concept. Included are theoretical and experimental studies with a focus on the total system performance and design. The work also included perspectives on the potential for more advanced cover materials and system concepts of particular interest for further development into future applications. For the theoretical analysis simulation models with high accuracy were developed for the water desalination, the light transmission into the greenhouse, the greenhouse climate and for the crop growth and water demand. The assessment of this concept compared to conventional, single glass greenhouses includes extensive simulations and field experiments in Tunisia. Considerably less extreme climate conditions were registered in an experimental greenhouse with roof desalination compared to a conventional greenhouse. A system integrated in 50% of the roof area of a widespan greenhouse has the capacity to cover the annual demand for a low canopy crop. A similar capacity for a high canopy crop requires asymmetric roof design and desalination system in the whole roof area. Simulated yield reductions for these cases are 25 and 18% and seasonal fresh water storage was required. Lower yield reductions could be achieved with application of more light selective glass materials in the roof absorber. Here, interesting future prospects are identified for advanced glass materials with dynamic absorptance control. Economic analyses including water costs and grower revenues indicated that this greenhouse concept competes well with solar collector based technologies for water desalination.
agriculture, arid zones, climate, crop yield, desalination,economic analysis, energy balance, environmental impact, fresh water,greenhouses, growth, irrigation water, plant water relations, salinewater, simulation models, solar energy, water balance, water costs,water management, water quality, water resources, water yield, Tunisia,Maghreb, North Africa, Africa, Mediterranean Region, DevelopingCountries, Threshold Countries, Francophone Africa, arid regions,desalinization, environmental effects, glasshouses, salt water, watercomposition and quality, water resource management, Meteorology andClimate (PP500), Mathematics and Statistics (ZZ100), AgriculturalEconomics (EE110), Plant Water Relations (FF062), Plant Production(FF100), Soil Water Management (Irrigation and Drainage) (JJ800)(Revised June 2002) [formerly Soil Water Management], Energy (PP100),Water Resources (PP200)