Salinity gradient solar ponds - Solar Energy Sciences and Engineering Applications - page 216

GLOSSARY

Density gradient: The variation with depth of the density of the
saline solution in a salt water solar pond
(see 'salinity gradient').
Lower Convective Zone (LCZ): The bottom zone which is generally about
or Storage Zone 1 to 1.5 m thick and has near-saturated brine
stores the incoming solar radiation in the form
of heat.
Organic Rankine Cycle engine: A heat engine based on the Rankine Cycle and
using a low boiling point organic working fluid
that can be used to generate electricity from low
temperature heat (less than 100 ◦ C) as supplied
by a solar pond.

Non-Convective Zone (NCZ) The central zone, in a vertical direction,

or Gradient zone: in a salt water solar pond in which there is

a salinity gradient.

Salinity gradient: The variation in salinity with depth used in

a salt-water solar pond to create a density gradient
that suppresses convection currents. In such a solar
pond salinity is near saturation at the bottom
of the pond and rises to near fresh water level
in the top layer. Salt water solar ponds are also
commonly called 'salinity gradient solar ponds'.

Solar pond: A large-area collector of solar energy in the form

of a shallow pond that stores heat for use for
practical purposes. Designs include salt-water
ponds, gel ponds, and ponds with covers. Incoming
solar radiation is stored in the lower layer of the
pond by suppressing the convection currents in the
layer above that would otherwise lead to heat loss
to the surroundings.

Utilisation coefficient (of a solar pond) on average for a given period

or thermal efficiency: is the total thermal output delivered to

an application divided by the cumulative solar
radiation incident upon the pond's surface over
that period. Normally the period chosen to assess
thermal efficiency would be a full year, after
the solar pond had warmed up to its operating
temperature range.

Upper Convective Zone (UCZ) The upper layer of a salt water solar pond

or Top layer or Surface zone: (also called the 'upper convective zone') comprising

low salinity or fresh water that is continually added
to the pond and removed at an overflow to take
away salt that diffuses to the surface from the layers
beneath. The top layer which is about 20 to 30 cm
thick has very low and uniform salinity.