Results and Discussion
Structural improvement of fog collectors: The
measurements of water production presented in Table 1
resulted in a high degree of distinction between the SFC
on the one hand and the new designs on the other hand.
All values are subject to a high standard deviation due to
recurring periods of fog free days. Still, the measurements
indicate up to sixfold higher maxima of water production
of the Eiffel compared to the SFC, although both
collectors cover the same collection frame of
8m x 4m = 32m² and nearly the same amount of space.
The difference in mean values between Eiffel and SFC is
even more pronounced than in the maxima; over the
measurement period the Eiffel produced ten times the
amount of the SFC at the same location. The
interpretation of these patterns is the effect of the
diagonal strips installed between the two main layers.
These strips allow for fog collection even at fog events
with wind directions that hit the collector sideways. With
Table 1: Results of water production
measurements of tested fog collectors;
mean, maximum and minimum value with
standard deviation (measurement period in
brackets).
mean 28.7 L/d
max 598.7 L/d
min 0.0 L/d
std dev. 82.4 L/d
mean 281.2 L/d
max 2,651.6 L/d
min 0.0 L/d
std dev. 487.1 L/d
mean 62.7 L/d
max 200.0 L/d
min 0.0 L/d
std dev. 52.2 L/d
mean 28.6 L/d
max 94.2 L/d
min 0.0 L/d
std dev. 24.1 L/d
SFC
(19.09.07-13.01.08)
Eiffel
(19.09.07-13.01.08)
Harp
(21.10.07-13.01.08)
Diagonal Harp
(20.10.07-13.01.08)
regard to the Harp collectors the data shows lower maxima but the mean values were similar or
higher in comparison to the SFC – even though both of them expose a considerably smaller
collection frame (4m x 2m = 8m² in case of the Harp collector and the same dimensions
diagonally cut in half 4m x 2m x 0.5 = 4m² in case of the Diagonal Harp). Although the Harp
designs showed the best surface-water yield ratio, in the interest of simplicity, reproducibility and
robustness, we favour the Eiffel collector. Considering the limited space with optimum conditions
for fog harvesting even at locations with high fog abundance, the achievements in fog harvesting
efficiency might open another door into a broader field of application.
Tree collectors: Taking into account the ratio of drip collecting surface and amount of collected
water, the ceramic channel with tubes showed the best results. The stone channel let too much
water seep into the ground which thus never arrived in the collection buckets. The funnel system had the disadvantage that the tubes at the bottom of the
funnel were blocked by material falling off from the
trees. Since dust and falling leaves also affect the
channels on the long run, it is recommendable to use a
channel with a higher brim and a screen at the tube
inlets (Lummerich 2008)