[PDF]Wind Pumping Handbook

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Wine-pumping Handbook;

6y: Sarah Lancashire, Jeff Kenna & Peter Fraenkel



Published by: Intermediate Technology Publications Ltd.
9 King Street
London WC2E 8HW
U.K.



Available from: Intermediate Technology Publications Ltd.
9 King Street
London WC2E 8HW
U.K.



Reproduced with permission.

Reproduction of this microfiche document in any form is subject to the same
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WINDPUMPING HANDBOOK

11 —

Sarah Lancashire, Jeff Kenna and Peter Fraenkel




WINDPUMPING HANDBOOK
Sarah Lancashire, Jeff Kenna and Peter
Fraenkel



IT Publications 1987



Preface



Windpumping is an established technology, with over one million
windpumps in use worldwide. A windpump needs no fuel, little
maintenance and it usually lasts 20 yef rs or more. Designs exist
which are suitable for small-scale local manufacture. The aim
of this handbook is to help potential users and decision makers
take advantage of the benefits that windpumps can offer.

This handbook was first written for a windpump familiarisation
seminar held in Nairobi in November 1986. The seminar was
organised and presented by I.T. Power, hosted by the Ministry of
Water Development of Kenya and funded by the Overseas Development
Administr ati on .



i



Contents



Page

Preface

List of Figures
List of Tables



1 , INTRODUCTION !

1 . 1 Purpose of this Handbook 1

1.2 Windpump technology is time-proven 2

A briaf history of windpumps

Past experience with windpump designs

1.3 The wind energy resource 5

The effect of wind speed
The effect of air density
Energy availability

How to find the amount of energy available

from the wind

1 . 4 Choices of energy resource g



2. WINDPUMP DESIGN - STATE OF THE ART 11

2.1 Principles of wind energy conversion: Lift and 11

drag

2.2 Rotor design 13

Pitch

Solidity

Tip-speed ratio

Performance coefficient

Torque

2.3 Pump types 17

2.4 Transmissions, tails and towers 21

Transmissions

Tails

Towers

2.5 The feasibility of local manufacture 23

The advantages
Criteria for success

Types of design suitable for local manufacture



3. SITE EVALUATION 25

3.1 Assessing the wind regime 25
The wind regime parameters needed
Wind measurement
Quality of wind data
Measurement options
Choosing the windpump site



ii



3.2 Assessing the water requirement 35

Water for domestic use and animals
Water for irrigation
How to find the pumping head
Borehole yield

3.3 Sizing the windpump 44

Volume-head product
Sizing the rotor
Sizing nomogram
Sizing the pump

3.4 Storage requirement 49

4. IS A WINDPUMP THE BEST OPTION? 52

4.1 The decision route 52

4.2 What are the alternatives? 54

Diesel engines
Solar pumps
Handpumps
Animal pumps

4.3 Social and institutional factors 58

Practical factors
Social factors
Institutional factors

4.4 Costing the options 61

Economic or financial assessment

Life-cycle costing

Example financial assessment

5. PROCUREMENT, INSTALLATION AND OPERATION 69

5.1 Specifying and procuring 69

5.2 Installation 70

The site

Receipt of windpump
Borehole construction
Windpump foundations

Erecting the tower and assembling the rotor
Building the storage tank and delivery pipe
Fences

5.3 Maintenance and repair 74

5.4 Safety ' 75

BIBLIOGRAPHY 76
GLOSSARY 77



iii



List of Figures



Page



1. Horizontal-axis, multi-bladed windmill 2

2. Three-bladed horizontal-axis windmill 3

3. Schematic diagram of Savonius rotor 3

4 . Panamones 4

5. Schematic diagram of Darrieus wind turbine 4

6. Global annual average wind speeds 6

7. Approximate shaft energy output of a windpump

rotor for various wind speeds 8

8. A boat propelled by the drag force of the wind 11

9. A boat propelled by the lift force of the wind 11

10. The relative sizes of lift and drag forces for

blunt and streamlined objects 12

11. Generation of lift by an aerofoil 12

12. Schematic diagram showing angle of pitch of a

rotor blade 13

13. Change of blade pitch with radius 13

14. Typical torque versus tip-speed ratio and

performance coefficient versus tip-speed

ratio curves for rotors of varying solidity 16

15. Schematic diagram to illustrate the effect on

windpump operation time of the high starting

torque 17

16. Schematic diagram of a reciprocating positive

displacement pump (piston pump) 19

17. Schematic diagram of a rotary positive displacement

pump (progressive cavity or 'Mono' pump) 19

18. Typical head, flow and efficiency curves for

positive displacement pumps 20

19. Schematic diagrams showing the furling action of a

wind rotor in strong winds (bird's eye views) 22



iv



20. Schematic diagram showing approximate wind

acceleration factors over a hill 27

21. Sea breezes 28

22. Flow chart outlining the steps to be taken when

processing wind data 31

23. Area of turbulence around a building 33

24. Area of turbulence around trees 33

25. Effect of ground friction on wind profile 34

26. Wind profile changes over trees, etc. 34

27. Schematic diagram to show selection of tower

heights to achieve even wind speeds across

the whole rotor 35

28. Soil moisture quantities 38

29. Rate of crop growth as a function of soil

moisture content 39

30. Schematic diagram showing pumping head 41

31. Flow chart outlining the steps necessary to

size a windpump 45

32. Windpump rotor sizing nomogram 47

33. Typical charts for pump sizing by b^ad and

average wind speed 49

34. Cost of water storage depends on the volume 50

35. Steps required to choose the most appropriate

water pumping technology 53

3b. Typical fuel consumptions for small diesel

engines 55

37. Number of handpumps required as a function of

water requirement 57

38. Number of oxen required as a function of water

requirement 58

39. Flow chart showing the steps to be taken in

financial assessment 65



v



List of Tables



Page

1. Altitude correction factors for air density 7

2. Countries known to be manufacturing windpumps

in 1986 10

3. Coefficients for the effect on wind speed of

different ground roughnesses 26

4. Daily water requirement of farm animals 36

5. Population increase for various annual growth

rates 37

6. Typical irrigation water requirements for

Bangladesh and Thailand 40

7. Headloss in metres per 100m of pipe length for

various flow rates and diameters. 43

8. Discount factors for various discount rates and

numbers of years (zero inflation) 63

9 . Discount factors for recurrent costs which have

to be paid annually over a number of years,

for various discount rates (zero inflation) 63

10. Advantages and disadvantages of various

construction methods for storage tanks 73



vi



CHAPTER 1: INTRODUCTION



1.1 Purpose of this Handbook



Water for people, animals and crop irrigation is an essential
need in every country. Frequently this water has to be pumped
from the ground; the pumping requires energy. In rural araas
this energy has traditionally been provided by people operating
hand pumps or animal pumps. Where mechanized power is available
it is most commonly an internal combustion engine burning petrol
or diesel oil. Recently there has been a growing interest in the
new technology of solar-powered water pumps and a revival of
interest in windpumps.

There are many good windpump designs, both traditional and modern
lighter weight ones, currently available. These machines have
high performance and good reliability. The purpose of this
Handbook is to provide decision-makers and potential users of
windpumps with the basic information on present-day:

• windpump technology

• economics

• sizing to meet domestic or irrigation demand

• procurement

• installation

• maintenance.

It has been assumed throughout the Handbook that the reader is
familiar with the basic concepts and units of energy, power,
flow, density, etc. A comprehensive bibliography is appended for
those readers who wish to study windpumps in greater depth.



1



1.2 Windpump technology is time-pr oven



A brief history of windpumps

The ancient Egyptians used wind power 5000 years ago to propel
boats. It is uncertain when wind power was first used on land to
power rotating machinery but it is estimated to be about 2000
years ago. Historical records show that windmills definitely
existed in 200 BC in the area now known as eastern Iran and
western Afghanistan. This area receives constant winds from the
steppes of Central Asia during and after harvest time each year,
called the "Wind of a Hundred Days". The Chinese have used
windmills for low lift paddy irrigation for many centuries.

About 1000 years ago horizontal-axis sail windmills were being
used around the Mediterranean. By the 12th century windmills had
reached northern Europe. They became an important part of the
industry of both Britain and the Netherlands in the centuries
that followed. In Britain they were mostly used for milling
grain; in the Netherlands many were used for dewatering
polderland.

By the 18th century windmills were one of the highest forms of
technology. They could produce 30-40 kW of power (which is about
the same as the power of a small motor car). With the advent of
steam power and later the internal combustion engine in Europe,
the incentive to develop windmills disappeared. Instead,
windmill development continued in the USA. In the mid 19th
century settlers were moving into the Great Plains where there
was a shortage of fuel and transport was difficult. With the
need for water and the steady, regular wind across the Great
Plains, windmills were an ideal technology. By the 1880 's the
familiar all-steel American multi-bladed farm windpump had
evolved. It looked not much different from many that are still
in production today.



Past experience which has led to the adoption of present-day
windpump designs

Most modern efficient windpumps
are horizontal axis, multi-bladed
f""j ( see Figure 1 ) . Other designs
J^; have been tried in the past and
LJ have proved less satisfactory for
water pumping. They are briefly
described below:



Figure 1 :

Multi-bladed
horizontal-axis
windmi 11 ( side
view)




2




Figure 2:



Three -b laded
horizontal-axis
windmill
(side view)



2- or 3- bladed horizontal-axis
windmills are used for
electricity generation. They are
not suitable for water pumping
directly because

1 . they cannot produce enough
torque to start a piston
pump working; and

2. they rotate too quickly to
directly drive a recip-
rocating pump. These wind
turbines are also more
difficult to manufacture
owing to the precision
engineering needed.

However they could be used
indirectly for water pumping by
generating electricity and using
this to drive electric pumps.
This option is expensive but may
be suitable for some locations or
when a large amount of power is
needed.



Savonius rotors are turned by the
drag force of the wind mostly,
rather than the lift force. They
are therefore inefficient and
turn very slowly. (See Sections
1.3 and 2.1 for explanations of
drag and lift forces).




Figure 3: Schematic diagram
of Savonius rotor
(side view)




3




Panamones are turned entirely by
the drag force of the wind. They
suffer the same disadvantages as
Savonius rotors.




Figure 4:



Panamones
(plan views)




Cross flow or Darrieus wind
turbines are attracting some
attention at present. However
they are unsuitable for water
pumping because they cannot
normally self-start. Even if
they are modified to enable them
to self -start they cannot produce
sufficient torque to start a
pump. They are difficult to
protect from storm damage and
have not yet been manufactured
more cheaply than horizontal-axis
rotors .



Figure 5: Schematic diagram of
Darrieus wind
turbine (side view)



The remainder of this Handbook concentrates on multi-bladed
horizontal-axis windpumps as the only practical, commercially-
available technology for water pumping at this time.



4



1.3 The wind energy resource



Many areas of the world are sufficiently windy for windpumps to
be a realistic option for pumping water. Figure 6 shows a
contour map of the average annual wind speeds for tt.e world
(Reference 1). It must be remembered that, in general, the basic
requirement foi wind tc be a reasonable option for water pumping
is that the average wind speed in the most critical month (i.e.
the month where the demand for water is greatest in relation to
the wind energy available) is greater than 2.5 m/s (6 mph or 5
knots). The wind will vary from day to day and month to month.
It is important that there is sufficient wind available
throughout the period when water is needed. If the water is for
irrigation it may be needed for only a few months, but if the
water is for domestic consumption, there must be sufficient wind
all year. It is advantageous to have reliable windspeed data for
at least a year to decide firstly whether a windpump is a
possible option, and secondly what size of windpump to use, and
how much water storage is needed.

This section briefly explains how to determine the energy
available from the wind if the wind speed is known. Section 3.1
will explain how, where and how often to measure wind speeds.



The effect of wind speed

'he power in the wind, and therefore its energy, is proportional
to the cube of the wind velocity. This means that as the wind
speed increases, the power available increases much faster. For
example, in very light winds there is about 10 W/m 2 whilst in
hurricane-level winds there is about 40,000 W/m 2 . This extreme
variability of the wind power strongly influences most aspects of
system design, construction, siting, use and economy. In
comparison, the solar energy resource is much less variable,
there being about 100 W/m 2 in weak sunshine and 1000 W/m 2 in the
strongest sunshine.



The equation describing the power in the wind is:



Power




1/2


X


in W







Density of air
in kg/m 3



x



Cross-sectional area
in m 2



(Velocity)
in m/s



The effect of air density

The density of the air affects the energy available to a very
much lesser extent than the wind velocity. However it should not
be ignored. The density of uhe air is affected by:



5




Figure 6: Global annual average wind speeds. (Redrawn from World
Meteorological Society data in WMO Technical Note on
Wind Energy. Reference 1)
Note - Very large local variations occur in wind
speeds. This map should not be used for
windpump siting. It is included to give a
general indication only.



1 . altitude

2 . temperature

3. atmospheric pressure.

The effects of temperature and atmospheric pressure are very
small compared with altitude and may therefore be ignored.
Allowance should be made for altitude, however. For example at
an altitude of 1000 metres tha energy available from the wind at
a given wind speed is reduced by 11%.

Table 1 gives the altitude correction factors which should be
applied to the air density in order to calculate the available
wind energy. Air density at sea level is l^kg/m 3 . Figure 7
shows the same information graphically on an energy-versus-wind
speed graph.



Altitude in metres
above sea level





1000


2000


3000


Air density

correction

factor


1.00


0.89


0.78


0.69



Table 1: Altitude correction factors for air density



Example: To find the air density at 2000 m



Air density
at 2000 m



Air density
at sea level



Correction
factor



Air density
at 2000 m



1.2 x 0.78
0.94 kg/m 3



However, the wind tends to blow at higher speeds at higher
altitudes. This often more than compensates for the loss due to
reduced air density.



Energy availability

Only part of the energy in the wind is available for use. To
extract all the energy would require bringing the wind to rest
which is impossible. The available energy is extracted by
slowing down the wind and using some of its kinetic energy. The
maximum amount of energy that can, even in theory, be physically
extracted from the wind is 59.3% of the total available. In
practice wind rotors are not perfectly efficient. Good ones will
be able to extract 25-40% of the total kinetic energy.



7



To find the amount of energy available from the wind

The graph in figure 7 may be used to find out the amount of
energy that is obtainable from the wind by a well -designed
windpump in a typical wind regime.




MEAN WIND SPEED (m/s)



Figure 7: Approximate hydraulic energy output of a
windpumn rotor for various wind speeds



8



On the horizontal wind speed axis, choose the average wind speed
for the locality in which you are interested. (Note: methods of
measuring the average wind speed are described in Section 3.1).
Move vertically up the graph until you reach the curve. The
width of the curve is due to variation with altitude. This
vai xation is small compared with uncertainty in windspeed. Now
move across to the vertical axis to obtain the power extractable
>>>