In the experiments, the average dew yield from the
artiﬁcial-cooling collectors for the 14 events is 0.23 mm/
night. This is far smaller than the artiﬁcial cooling potential
of the six frozen bricks, which is equivalent to 1.3 mm/
night. This indicates that most of the heat sink from the
cooling source is wasted. With what power and at what
time the artiﬁcial cooling should be applied to enhance dew
formation more efﬁciently at a low cost of energy
consumption is an interesting issue to be further explored.
To examine artiﬁcial-cooling-enhanced dew collection,
dew collecting experiments were performed over a month
(April–May) in a coastal area of South Australia, with four
collectors of two materials (aluminium and Teﬂon). The
results show that artiﬁcial cooling enhances dew formation
nearly 45% for the Teﬂon collectors, while the enhance-
ment is over 150% for the aluminium collectors. The
enhancement magnitude is dependent on meteorological
conditions, increasing with speciﬁc humidity for both the
Teﬂon and aluminium collectors, and with vapour pressure
deﬁcit for the aluminium collector. In addition to
increasing the dew formation duration and heat loss rate
from the collector surface, the two mechanisms which
contributes to dew formation enhancement for both
aluminium and Teﬂon collectors, artiﬁcial cooling also
increases the aluminium surface emissivity through dew
formation that would not otherwise occur.
Without artiﬁcial cooling, the Teﬂon collector is on
average 120% more efﬁcient than the aluminium collector
over the whole dew collection period. While with artiﬁcial
cooling, the Teﬂon collector is only 20% more efﬁcient
than the aluminium collector over the same period. The
difference between the two artiﬁcial cooling collectors
becomes more signiﬁcant when the air is of a low speciﬁc
humidity (,6.5 g/kg), and/or of a high vapour pressure
deﬁcit (.0.8 hPa). The results also show that radiative
cooling still contributes to dew formation on the artiﬁcial
cooling collectors. But the material type becomes less
important owing to that the high emissivity of dew water
compensates for the low surface emissivity. These results
provide useful information for designing collecting devices
or roofs to enhance dew formation in urban environments.
Julie Guerin, Amanda Treijs, Tess Stevens, and Chuanyu Zhu
assisted in some data collection. Craig T. Simmons and Erick
Bestland provided valuable comments in preparing the
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