WASH Cluster – Groundwater Pumping
GWP
Groundwater Pumping
Session 2
Mechanised Pumps
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WASH Cluster – Groundwater Pumping
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Pump classification
Positive
displacement
Rotodynamic
Centrifugal
Axial flow
Submersible
Surface mounted
Positive rotary
e.g helical rotor
Reciprocating
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Power sources
They may be driven by:
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Electricity from the national grid,
Diesel engine for direct drive
Diesel engine for electricity generation
Photovoltaic system
Wind-powered pumps
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Motorised Pumps
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Pumps are machines designed to
add energy to fluids. They typically
do this by using a rotating element
to push a fluid in one direction.
Rotodynamic pumps generate flow
by using one of three actions:
radial flow, mixed flow, and axial
flow.
These classifications do not rate
the performance quality of the
pump, they are merely groupings
based upon the pump’s action.
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Motorised Pumps (Radial Flow)
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Radial flow pumps are centrifugal
pumps in which the pressure is
developed wholly by centrifugal
force.
Radial flow pumps consist a
rotating impeller and stationary
casing (volute or solid). The
impeller produces liquid velocity
and the casing forces the liquid to
discharge from the pump
converting velocity to pressure.
Centrifugal pumps to produce
continuous flows at high pressure.
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Motorised Pumps (Axial Flow)
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In mixed flow pumps, the pressure
is developed partly by centrifugal
force and partly by the lift of the
vanes of the impeller on the liquid.
Axial flow centrifugal pumps
develop pressure by the propelling
or lifting action of the vanes of the
impeller on the liquid.
An axial flow essentially consists
of a propeller in a pipe. The
propeller can be driven directly by
a sealed motor in the pipe or
mounted to the pipe from the
outside by a drive shaft that
pierces the pipe.
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WASH Cluster – Groundwater Pumping
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Submersible Pumps
 Centrifugal Pumps are rotodynamic
pumps, which convert mechanical energy into
hydraulic energy by centripetal force on the
liquid. A rotating impeller increases the velocity
of the fluid. The vanes in the casing of the
pump then convert this amplified velocity into a
rise in pressure. The pumps usually have
multiple impellers. The selection of the correct
size of the pump for its intended duty point is
important. Energy is wasted if the pumps are
operated far away from the optimal running
point.
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Submersible Pumps
The main parts of a submersible pump are:
 Electric motor hermetically enclosed in a
stainless steel sleeve,
 Pump body either a centrifugal pump or a
positive displacement pump
 Rising main of GI or stainless steel pipes
connected with sockets or PVC-HI hose. If a
hose is used, the motor with connected pump
body has to be hung from the top of the well by
a stainless steel cable,
 Electrical cable for connecting the motor to the
starting panel (power source),
 Starting panel
 Various sizes of submersible pumps are
available, which can be installed in casings of
Ø3”, 4”, 6”, 8”, 10” and 12”.
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Positive displacement pump
Progressive cavity pumps
• Water moves by trapping a fixed amount of fluid and
forcing that trapped volume into the discharge pipe.
• Pump is a single helix rotor inserted into a double helix
stator.
• This forms pockets of water which are lifted from the
bottom to the top
• Produces a constant flow
• Small diameter pumps for boreholes are considerably
more efficient than centrifugal pumps.
• Progressive cavity pumps have high starting torque
which is important if using solar systems
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WASH Cluster – Groundwater Pumping
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AC mains power
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Mains electricity is normally supplied as single phase current at
either 220 Volt and 50 Hz frequency (Europe, Africa, Asia) or at
110V and 60Hz (America). For high power connections over 10KW
nearly always 3-phase power is supplied at a voltage of 380V.
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Electric motors are generally available
from the smallest size of 100-200W.
They run on a fixed speed depending
on the frequency (1500rpm at 50 Hz or
1800rpm at 60Hz). Energy efficiency is
between 75% for small motors to 90%
for bigger size motors.
Long distances from grid to the pump
site require high investment in the
power line.
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Internal combustion engines
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Petrol engines are less common because the
highly flammable fuel is difficult to handle and they
are not as reliable and efficient as diesel.
Diesel engines for stationary applications run at
about 1,200 to 1,400 rpm and their efficiency is
about 30% (i.e. the fuel consumption is about 200300 g/kWh or 0.25 – 0.4 lt/kWh).
Engines require regular maintenance, which
necessitates often a full-time operator. And the
logistics to ensure that enough fuel and lubricants
are always available need to be sorted out.
Diesel fuel is more expensive than electricity from
the grid.
Diesel generators are used in places without
connection to the power grid or as emergency
power-supply if the grid fails. These generators are
widely used for not only emergency power, but also
many have a secondary function for providing back
up power to utility grids.
Diesel Generator (Skat)
Petrol Generator (Briggs and Strat
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Pump selection to meet demand
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When water is pumped to a higher
elevation the pumping effort is the total
head plus the friction head loss in the
pipeline. The friction head loss for a
given flow rate can be calculated for any
chosen pipe diameter. Smaller pipes
create higher losses than bigger pipes
because the water speed is greater. The
pump has to be chosen that is able to
produce the required flow and pressure.
The daily water demand in a community
area will vary during the year due to
seasonal pattern of the climate, the
work situation, cultural or religious
occasions
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Pump power
Pw = Qρgh
Where:
Pw= Water power
Q = flow rate of water (m3/s)
ρ= density of water (≈1000kg/m3)
g = 9.8m/s2
h = operating pressure head
Required input power = Pw/η
Where η = overall efficiency
WASH Cluster – Groundwater Pumping
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Sizing a pump
1. Draw system curve for range of flows,
including the required flow (use table given as
handout)
2. Select a pump which matches the duty
required and obtain the characteristic curves
3. Superimpose the two curves to find the
operating point
4. Check it gives you the required flow rate
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Adjusting your pump
Ideally the operating pump will correspond
as closely as possible to the required flow
rate. Otherwise you can alter the speed of
the pump to achieve this but:
Flow – varies with speed
Head – varies with (speed)2
Power – varies with (speed)3
So varying the speed will greatly increase
the power demand.
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• Appendix 1 – Solar powered pump sizing
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Sphere standards: max 500 people/handpump – assume need to use max
Daily necessary is 15 l/person and say head is 30m.
Step
Calculate the peak daily
hydraulic output (in
kWh)
Formula
Ehyd = QxH/367
Example
Number of people = 800
Ehyd = peak daily hydraulic energy output
(kWh/d)
Daily demand = 40l/cap
Q = output required
(m3/d)
H = total pumped head (m)
Estimate the subsystem η = the efficiency of conversion of
efficiency = η
electricity to hydraulic output (wire-towater). Consult the manufacturer's
documentation or technical studies.
Head = 27 m
Q = 800x0.04 = 32 m3/d
Ehyd = 32x27/367= 2.35 kWh/d
η = 0.5
Good: 50-70% - Bad: 20-30%
Calculate the daily l
energy demand
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Ehyd eff = Ehyd/η
Ehyd eff = 2.35/0.5 = 4.71 kWh/d
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WASH Cluster – Groundwater Pumping
Calculate the daily
irradiation per square
metre
Look up the mean extra-terrestrial
radiation in the map above for the
location, given on the map, and finally
reduce by a 20% margin of safety
(safety factor = 0.8)
Edaily/m2 = Irrrad x Safety factor
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Location = Ethiopia
Latitude = 15o
Irradiation: ~5.5 kWh/m2
Edaily/m2 = 5.5 x 0.8 =
4.4kWh/m2
Calculate
approximate peak
watt rating
Ppeak = Ehyd eff/Edaily/m2 x1,000W/m2
Calculate the number
of modules
Choose a module (Wp per unit)
Module: Wp = 55 Wp/unit
Modules = Ppeak / Wp (round up the
answer to an integer number)
No’s = 1,070 / 55 = 19.46
Panel : $500 each (x20) Pump: $1,000
Total = $11,000 without tank
Cost (approximate)
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Ppeak = 4.71 / 4.4 x1,000
= 1,070 Wp
Round Up No’s = 20
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WASH Cluster – Groundwater Pumping
Solar
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• One slide explaining PVs
• A photovoltaic module is a packaged
interconnected assembly of photovoltaic cells,
also known as solar cells. Current is created
when light falls onto the active surface.
• mono-crystalline silicon, multi-crystalline silicon,
and amorphous silicon. New, non-silicon types
such as cadmium telluride (CdTe) and Copper
Indium Disellenide (CIS) have recently become
available too.
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Solar
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Sizing Photovoltaic System
The mean daily water
demand and the mean daily
solar irradiation during the
least sunny month need to
be determined as the
starting point for sizing a
solar pump. The diagram
provides a quick indication
of power requirements. It
should be noted that the
result is only an estimate
and the graph should not be
used for final sizing of the
system
Session Name here
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Simplified method for sizing
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Fraenkel and Thake give a simplified method of calculating the size
of a solar system in their book Water Lifting Devices. The method
provided here is an adaptation of their method that facilitates a
‘rough and ready’ calculation of the solar array.
Sources such as the World Meteorological Organization publish
irradiation figures for the whole world. Maps that cover large areas
or whole regions can be used to make a reasonably accurate
judgement of the irradiation for a particular location.
Peter Fraenkel and Jeremy Thake, Water Lifting Devices: A
Handbook for Users and Choosers (Food and Agriculture
Organization, 2006).
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To get a fairly accurate idea of the
size and cost of a photovoltaic
array it is necessary to know at
least the following parameters:
 Water consumption per capita
per day
 Total no. of households
 Persons per household
 Total population
 Yield of water source (m3/day)
 Distance to source
 Distance from source to tank
 Static water table
 Expected dynamic water table
 Elevation from source to tank
 Total pumping head
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WASH Cluster – Groundwater Pumping
• Appendix 2 – Other types of motorised
pump
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WASH Cluster – Groundwater Pumping
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Motorised Pumps
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There are three main types of
motorised pumps that are suitable
to be installed in boreholes:
 Submersible Pumps
 Line Shaft Pumps
 Jet Pumps
The standard power sources
possible for the three pump types
mentioned above are:
 Electric AC mains
 Diesel engines
 Petrol engines her.
 Solar powered Pumps
 Wind powered Pumps
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Line Shaft Pumps
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Line Shaft Pumps have the driving element
(motor) above ground; and the pumping element
is at the bottom of the well. A “Line Shaft” is used
to connect the motor with the pumping element.
The speed of the motor is directly applied to the
pumping element by the line shaft. Gearboxes or
V-belt drives might be used for adjusting the
speed. Various motor types can be used to drive
the pumping element (diesel engine, petrol
engine, electric motor etc.).
The pumping element can vary too, but mostly
used are:
 Vertical turbine pumps similar to the
submersible pumps,
 Positive displacement unit, progressive cavity
pumps (Mono).
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Jet Pumps
A Jet Pump is an impeller-diffuser pump. About half of
the drawn water is split in the diffuser and sent back to
the well with high pressure through the pressure pipe.
At the end of the pressure pipe, the water is
accelerated through the cone shaped nozzle and
guided through the mixing chamber with high speed.
A pressure drop in the mixing chamber sucks in water
from the ejector body and intake.
The water goes up the return pipe and through the
impeller into the diffuser, where one part is sent back
to the jet nozzle and the other part is directed into the
delivery pipe.
Jet Pumps are relatively inefficient but can tolerate a
wide range of operating conditions, including abrasive
fluids such as water with high sand contents.
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