Hydropower
Hydropower
potential in the
agricultural sector
by Ian de Jager
Hydropower is blossoming anew especially in the Western Cape.
H
ydropower is again blooming and is just in the beginning of its cycle and there is huge scope still to be developed
or upgraded, writes SABI Western Cape chairman Ian de Jager, whose engineering firm I&F Engineering has
recently constructed some exciting large scale hydropower projects for renewable energy and green energy
conscious farms and enterprises.
Background
energy to clients.
Hydropower
can
only
be
developed at specific sites. You
need a flow of water, but more
importantly you need a head
or elevation in the flow – from a
dam or mountain down to a lower
elevation: this we call the “head”
which will become the pressure we
require before the turbine inlet.
Hydropower can be developed
from any river where changes in
elevation like a rapid or waterfall
is present. Even a dam can present
hydropower potential where a
certain head is available. The
flow rate of the water and the
head will then determine the
power (kW) that can be generated
and the flow duration will deliver
the energy (kWh). The power
generated depends on flow and
head or pressure.
Thus power
P = ρQgH
ρ = density of water,
Q = flow in m³/s,
g = gravity constant,
H = head or pressure in metre H 2 O
The energy from a hydropower
plant can be either used directly
on the farm to supplement the
energy drawn from Eskom to
reduce costs or it can be fed into
the National Grid to be used
anywhere in South Africa where
Eskom or a municipality delivers
Due to our climate, in the Western
Cape we have a different situation
than in the rest of the country.
When it rains in the winter – the
farmers do not irrigate much as
the soil is wet and the vegetation
is in the rest phase. In the summer
our farmers tend to need irrigation
and the rain is very sporadic.
This also means that when ample
water is available for hydropower
generation – less energy is
required on the farm.
Banking energy and turbines
Luckily, Eskom appraised the
situation and gave the farmers
the opportunity to bank energy in
the grid over a year period to be
used in the summer months. So
the problem was solved. This also
gives farmers in the Western Cape
the opportunity to generate power
in the High Demand periods from
June to August when energy is
more than double the cost as in
the other (summer) months. The
banking of energy is based on
the value of the energy (kWh)
and because you are banking at
high value, you can utilise nearly
double the energy in the summer.
Turbines are developed for the
specific head and flow. For different
head ranges there are different
types of turbines developed for
I&F Engineering recently completed the 2.3 MWatt Hydropower plant at L’Ormarins, a well-known wine and thorougbred horse farm.
The pipeline winds down the Hottentots Holland Mountains, the turbine building houses two Pelton turbines.
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SABI | APRIL / MAY 2017