FEATURE
Solar
pumps:
get expert
help!
By Dr Philip Olivier
V
ariable-speed drives (VSDs)
have been used in agricultural
applications for a long time.
In recent years, many farmers have
employed them with solar power to
run borehole pumps. When converting
a borehole pump to solar power, it is
far better to use standard equipment
as it is modular and relatively cheap.
This makes repairs and maintenance
easier in the long term. Frequently, it
is only a single component such as a
pump, motor, solar panel or VSD that
needs to be repaired or replaced.
Harnessing South Africa’s sunshine
There are several reasons that solar
pumps have become so popular.
The price of solar panels has
decreased by more than 70% over
the last five years or so. Furthrmore,
a solar pump is generally cheaper,
requires less maintenance and is less
labour-intensive than other types of water
pump such as a wind pump or generator. should therefore be oversized in
relation to the pump. Moreover, the
panels need to be configured to supply
the voltage and amperage required
by the VSD. An incorrectly designed
system can result in poor performance
or damaged components.
Secondly, sunshine is a more constant
factor than wind across most of South
Africa. solar panels and VSDs: getting
the ideal match If you purchase good-
quality equipment and the borehole
pump has been converted to solar
power correctly, you should have many
years of trouble-free water pumping. Unfortunately, solar pumps do not
always run at full speed, as is the case
with pumps that run off a constant
power source. The main function
of the VSD is to adjust the speed of
the pump to the available energy
from the sun; this means that when an
existing pump that worked efficiently on
Eskom power or a generator is put onto
solar power, its performance may not
meet your expectations. It is important,
therefore, to seek expert advice on the
type of water pump for your requirements.
Cautionary measures
Some energy loss takes place when
an external VSD is used to power
a borehole pump. The solar panels
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