17 research outputs found
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Harvesting condensed atmospheric vapour as dew water can be an alternative or
complementary potable water resource in specific arid or insular areas. Such
radiation-cooled condensing devices use already existing flat surfaces (roofs)
or innovative structures with more complex shapes to enhance the dew yield. The
Computational Fluid Dynamic - CFD - software PHOENICS has been programmed and
applied to such radiation cooled condensers. For this purpose, the sky
radiation is previously integrated and averaged for each structure. The
radiative balance is then included in the CFD simulation tool to compare the
efficiency of the different structures under various meteorological parameters,
for complex or simple shapes and at various scales. It has been used to precise
different structures before construction. (1) a 7.32 m^2 funnel shape was
studied; a 30 degree tilted angle (60 degree cone half-angle) was computed to
be the best compromise for funnel cooling. Compared to a 1 m^2 flat condenser,
the cooling efficiency was expected to be improved by 40%. Seventeen months
measurements in outdoor tests presented a 138 % increased dew yield as compared
to the 1 m^2 flat condenser. (2) The simulation results for 5 various condenser
shapes were also compared with experimental measurement on corresponding pilots
systems: 0.16 m^2 flat planar condenser, 1 m^2 and 30 degree tilted planar
condenser, 30 m^2 and 30 degree tilted planar condenser, 255 m^2 multi ridges,
a preliminary construction of a large scale dew plant being implemented in the
Kutch area (Gujarat, India)
Fog and Dew Collection Projects in Croatia
The present paper discusses the fog and dew water collection in Croatia.
Zavizan, the highest meteorological station in Croatia(1594m) is chosen for
collecting of fog water with a standard fog collector (SFC). The highest daily
collection rate was 27.8 L / m2. The highest daily collection rate in days
without rain was 19.1 l/m2. Dew is also a noticeable source of water,
especially during the drier summer season. Dew condensers in Croatia have been
installed on the Adriatic coast (Zadar) and islands Vis and Bisevo. We report
and discuss the data collected since 2003. In the small Bisevo island, a
special roof has been designed to improve the formation and collection of dew
on a house. Data from April 2005 will be presented and discussed.Comment: accessible sur
http://balwois.mpl.ird.fr/balwois/administration/full_paper/ffp-587.pd
Source water, phenology and growth of two tropical dry forest tree species growing on shallow karst soils
Seasonally dry tropical forests are dominated by deciduous and evergreen tree species with a wide range of leaf phenology. We hypothesized that Piscidia piscipula is able to extend leaf senescence until later in the dry season due to deeper and more reliable water sources than Gymnopodium floribundum, which loses leaves earlier in the dry season. Physiological performance was assessed as timing of leaf production and loss, growth, leaf water potential, depth of water uptake determined by stable isotopes, and leaf stable isotopic composition of carbon (δ¹³C) and oxygen (δ¹⁸O). P. piscipula took water primarily from shallow sources, whereas G. floribundum took water from shallow and deep sources. The greatest variation in water sources occurred during the onset of the dry season, when G. floribundum was shedding old leaves and growing new leaves, but P. piscipula maintained its leaves from the previous wet season. P. piscipula showed greater relative growth rate, greater leaf expansion rates, and more negative predawn and midday water potentials than G. floribundum. P. piscipula also exhibited greater leaf organic δ¹³C and lower δ¹⁸O values, indicating that the decrease in photosynthetic carbon isotope discrimination was associated with greater stomatal conductance and greater photosynthesis. Our results indicate that the contrasting early and late dry season leaf loss phenology of these two species is not simply determined by rooting depth, but rather a more complicated suite of characteristics based on opportunistic use of dynamic water sources, maximizing carbon gain, and maintenance of water potential during the dry season
Roofs as dew collectors: III. Special Polyethylene foil on a school in Sayara (NW India)
International audienc
Dew Water Physical and Chemical Characteristics in Tropical Climate (French Polynesia).
International audienc
Collecting dew as a water source on small islands: the dew equipment for water project in Bis˘evo (Croatia)
In many regions and geographical settings, dew water collection can serve as a water source, supplementing rain and fog water collection. This is particularly useful when precipitation is low or lacking, especially in remote areas and islands in the dry season. A project called Dew Equipment for Water (DEW) was initiated for a 15.1 m2 roof in the island of Biševo (Croatia), equipped with commercial plastic cover selected for its superior dew collection properties. Measurements of both rain and dew water will be performed over several years and data will be correlated with meteorological data collected in situ. Preliminary measurements during the period 21 April–21 October 2005 showed that dew water contributed significantly, 26% of the total collected water
Comparison of Various Radiation-cooled Dew Condensers by Computational Fluid Dynamic
International audienc