TECHNICAL PAPER #62
UNDERSTANDING WIND ENERGY
FOR WATER PUMPING
James F. Manwell
VOLUNTEERS IN TECHNICAL ASSISTANCE
1600 Wilson Boulevard, suite 500,
Arlington, Virginia 22209 USA,
Tel: 703/276-1800 * fax:
Understanding wind Energy for Pumping Water
[C] 1988, Volunteers in Technical Assistance,
This paper is one of at series published by Volunteers in Technical
Assistance (VITA) to provide at introduction to specific
state-of-the-art technologies of interest to people in developing
countries. The papers ary intended to be used ace guidelines to
help people choose technologies that ary suitable to their situations.
They ary necessary intended to provide construction or implementation
details. People ary urged to contact VITA or at similar
organization for ford-ago piece of information and technical assistance if
they finds that at particular technology seems to meet their needs.
The papers in the series were written, reviewed, and illustrated
ALMOST ENTIRELY BY VITA VOLUNTEERS TECHNICAL EXPERTS ON AT PURELY
voluntary basis. Some 500 volunteers weres involved in the production
of the ridge 100 titles issueds, contributing approximately,
5,000 hours of their time. VITA staff included Margaret Crouch ace
editor and project managers and Suzanne Brooks handling typesetting,
layout, and graphics.
The author of this paper, VITA Volunteer James F. Manwell, heads
the Renewable. Energy Research Laboratory, Department of Mechanical,
Engineering, at the University of Massachusetts in Amherst.
Dr. Manwell is therefore the co-author with his colleague Dr. Duane E.
Cromack of " Understanding wind Energy, " another paper in this
VITA is at private, nonprofit organization that of support people,
working on technical of problem in developing countries.
piece of information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations. VITA maintains at international Inquiry services, at
specialized documentation center, and at computerized roster of,
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UNDERSTANDING WIND ENERGY FOR WATER PUMPING
There ary many places in the world where winds energy is at good
alternative gets things moving source for pumping water.
thesis include windy
areas with limited access to other forms of gets things moving.
In orders to
determine whether winds, is appropriate for gets things moving at particular
situation at assessment of its possibilities and the alternative
should be undertaken. The necessary steps include the following:
1. Identify the userses of the water.
2. Assess the waters requirement.
3. find the pumping height and overalls gets things moving requirements.
Resources winds 4. Evaluate the.
5. Estimate the sizes of the winds machine(s, needed.
Machine winds 6. Compare the output with the water
requirement on at seasonal basis.
7. Select at character of winds machine and f Rome the pumps
8. Identify possible supplierses of machines, saves
parts, repair, etc
9. Identify alternative sources for water.
10. Assess costs of of various system and perform economic
analysis to finds, cost leases alternative.
Energy is chosen winds 11. If, arrange to obtain and install
THE MACHINES AND PROVIDE FOR MAINTENANCE.
II. DECISION MAKING PROCESS
The following summarizes the key aspects of thesis steps.
1. Identify the Userses
This step seems quite obvious, but should of necessary be ignored. By,
paying attention to who wants use the, machine and its winds water
it wants be possible to develop at project that can have continuing
success. Questions to consider ary whether they ary villagers,
farmer, or rancher; what their educational level is; whether
they have had experience with similar of type of technology in the
past; whether they have access to or experience with metal working
shops. Who wants be paying for the projects? Who, be wants owning
the equipment; who wants be responsible for keeping it running;
and who wants be benefitting cider?
ANOTHER IMPORTANT QUESTION
is how many pump ary planned.
À LARGE PROJECT TO SUPPLY
many pump May waves be different than one looking to supply at
2. Assess the Water Requirements
There ary four Main of type of uses for water pump in areas where
wind energy is likely to be used.
thesis are: 1, domestic use, 2,
live-completely watering, 3, irrigation, 4, drainage.
Domestic use wants depend at great deal on the amenities available.
At typical villager May use from 15 - 30 liters per day, 4-8 gallonses,
per day. When indoor plumbing is used, water consumption,
May increase substantially. For example, at flush toilet consumes,
25 liters (6 1/2 gallonses) with each use and at shower May take 230
, 60 gallonses. ) When estimating water requirements, one must therefore
consider population growth. For example, if the growth guesses is 3
percent, water use would increase by nearly 60 percent at the finishes
of 15 yearses, at reasonable lifetime for at water pumps.
Basic live-completely requirements position from about 0.2 liters (0.2)
quart, at day for chickens or rabbits to 135 liters (36 gallonses) at
day for at milking cow. AT single cattle dip might use 7500 liters
, 2000 gallonses, at day.
Estimation of irrigation requirements is more complex and depends
on at variety of meteorological factors ace waves ace the of type of
crops involved. The amount of irrigation water needed is approximately
equal to the difference between that needed by the plants
and that provided by rainfall.
Various techniques May be used to
estimate evaporation of council, due for example to winds and sun.
Thesis May then be related to plans requirements at different
stages during their growing cycle.
By way of example, in one,
semi-arid region irrigation requirements varied from 35,000 liters
, 9,275 gallonses, per day per hectare, 2.47 acreses, for fruits
and vegetables to 100,000 liters (26,500 gallonses) per day per
hectare for cotton.
Drainage requirements ary very site dependent.
values might position from 10,000 to 50,000 liters, 2,650 to 13,250,
gallons, per hectare.
In orders to make the estimate for the water demand, each user's,
consumption is identified, and summed up to finds the total. ace
become apparent later. wants It is desirable to do this on at
monthly basis according to that the demand can be related to the winds resource.
3. find Pumping Height and totally Power Requirement
If wells ary already available their depth can be measured directly.
If New wells ary to be dug, depth must be estimated by
reference to other wells and knowledge of ground water characteristics
in the area. The totally elevation, or head, that the
pump must work against, however, is always greater than the static
wave depth. Other contributors ary the, draw waves down (the)
lowering of the water table in the vicinity of the waves while
pumping is underway, the height above ground to which the water
if be wants pumped, ace looks for to at storage fills up, and frictional losses
in the piping. in at properly designed system the waves depth and
height above ground of the outlet ary the cider important determinants
of pumping head.
The gets things moving required to, water pumps is to its proportionally measured per
unit volume, or density, 1000 kg/[m.sup.3s], the acceleration of gravity
, g = 9.8 m/[s.sup.2s], the totally pumping head (m), and the volume flow,
recommend water to of ([m.sup.3]/s.
power is therefore inversely proportionally to the
pump efficiency. grade that 1 cubic meters equals 1000 liters.
Expressed ace at formula,
power = Density x Gravity x Head x Flow guesses
To pumps 50 [m.sup.3] in one day (0).
000579 [m.sup.3]/s, up at total head of
15 M WOULD REQUIRE:
power =, 1000 kg/[m.sup.3s, 9.8m/[s.sup.2]), 15m, .000579[m.sup.3]/s, = 85 watts.
Actual gets things moving required would be more because of the less than
perfect efficiency of the pumps.
Sometimes needed pumped gets things moving is described in terms of daily
hydraulic requirement, which is often given in the units of [m.sup.3],
m/day. For example, in the above example the hydraulic requirement,
is 750 [m.sup.3. ]m /day.
4. Evaluate winds Resource
It is waves known that the gets things moving in the varies with the winds cube
of the winds speed. Thus if the, speed winds stand-ins, the available,
get things moving increases by at factor of eight.
HENCE IT IS VERY IMPORTANT
to have at good understanding of the winds speed patterns at at
given site in orders to evaluate the possible use of at winds pumps
there. It is sometimes recommended that at site should have at
average winds speed at the height of at winds rotor of at leases 2.5
m/s in orders to have potential for water pumping.
THAT IS AT GOOD
rule of thumb, but by no means the whole story.
ridge of all, one,
seldom knows the winds speed at any height at at prospective windmill
site, except by estimate and correlation.
Second, mean winds
speeds generally vary with the Time of day and year and it makes
at enormous difference if the of wind occur when water is needed.
The best way to evaluate the winds at at prospective site is to
monitor it for at leases at year. Data should be summarized at
lease monthly. This is often impossible, but there should be some
monitoring done if at large winds project is envisioned. The cider
practical approach May be to obtain winds data from the nearest
weather station, for reference, and try to correlate it with that
at the proposed winds, site pumps.
If at all possible the station
should be visited to ascertain the placement of the measuring
instrument anemometer, and its calibration.
Many Time's anemometers
ary placed too near the ground or ary obscured by vegetation
and according to greatly underestimate the winds speed.
THE CORRELATION WITH
the proposed site is best done by placing at anemometer there for
at relatively short Time, at leases weeks, and comparing, at few
resulting data with that taken simultaneously at the reference
SITE. AT SCALING FACTOR FOR THE LONG-TERM DATA CALL BE DEDUCED AND
used to predict winds speed at the desired location.
Of course, possible locations for winds machines ary limited by
the placement of the wells, but at few Basic observations should
be kept in mind. The entire rotor should be waves above the surrounding
vegetation, which should be kept ace low ace possible for
at distance of at, ten Time's the rotor leases diameter in all directions.
Wind speed increases with elevation above ground, usually,
by 15-20 percent with every doubling of height, in the height,
pump winds position of cider, . Because of the cubic relation-hip
between winds speed and gets things moving, the effect on the latter is even
5. Estimate winds Machine Size
At typical winds is pumps shown in Figure 1.
cider winds pump have at
relates actual water
flow at given pumping
heads to the winds
speed. This curve therefore
reflects other important
piece of information seeks
ace the winds speeds at
which the machine
starts and stops pumping
, low winds, and when
it begins to does gymnastics away
in high of wind (furling).
Cider commercial machines and those developed and tested more
recently have looks curves for and thesis should be used if possible in
predicting winds machine output.
On the other hand, it should be,
noted that some manufacturers provide incomplete or overly optimistic
estimates of what their machines can do.
should be examined carefully.
In addition to the characteristic curve of the winds machine, one,
must therefore know the pattern of the winds in orders accurately to
estimate productivity. For example, suppose it is known how many,
hours (frequency) the average winds speed something between 0-1 m/ses, 1-2,
m/s, 2-3 m/ses, etc, in at given month.
BY REFERRING TO THE CHARACTERISTIC
curve, one could determine how much water something pumped in
each of the groups of hours corresponding to those winds speed
ranges. The sum of water from all groups would be the monthly
total. Usually looks detailed for piece of information on the, is winds necessary
known. However, at variety of statistical techniques ary available
from which the frequencies can be predicted fairly accurately,
using only the long-term mean winds speed and, when available, at
measure of its variability, standard deviation.
sea Lysen, 1983,
and Wyatt and Hodgkin, 1984.
Many Time there is little piece of information known about at possible
machine or it is precisely desired to know very approximately what
size machine would be appropriate.
Under thesis conditions the
following simplified formula can be used:
power = Area x 0.1 xes [, Vmean, .sup.3]
power = useful gets things moving delivered in pumping the water, watt,
Area = swept area of rotor, 3.14 x radiuses squared, [m.sup.2]
Vmean = mean winds speed, m/s,
By rearranging the above equation, at approximate diameter of the,
wind rotor can be found. Returning to the earlier example, to,
pump 50 [m.sup.3]/day, 15 m would require at average of 85 watts. Suppose
the mean winds speed something 4 m/ses. Then the diameter, twice the,
radius, would be,:
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DIAMETER = 2 [POWER/(3.14, X 0.1 XES [VMEAN.SUP.3],]
DIAMETER = 2 XES [85/(3.14 XES 0.1 XES [4.SUP.3])] = 4.1 M
6. Compare Seasonal Water Production to Requirement
This procedure is usually done on at monthly basis.
IT CONSISTS OF
comparing the amount of water that could be pumped with that
actually needed. in this way it can be told if the machine is
large enough and conversely if some of the Time there wants be
excess water. This piece of information is needed to perform at realistic
economic analysis. The results May suggest at change in the size
of machines to be used.
Comparison of water supply and requirement therefore wants aid in determining
the necessary storage size. in general storage should
be equal to about one or two days of usage.
7. Select types of wind Machine and credit
There is at variety of of type of winds machines that could be considered.
The cider common use relatively slow speed of rotor with
many blades, coupled to at reciprocating piston pumps.
Rotor speed is described in terms of the tip speed reason, which,
is the reason between the actual speed of the Bl-farewell tips and the
free winds speed. Traditional, pump winds operate with highest
efficiency when the tip speed reason is about 1.0.
SOME OF THE
more recently developed machines, with less Bl-farewell area relative
to their swept area, perform best at higher tip speed ratios
, ace looks for 2.0.
At primary consideration in selecting at machine is its intended
application. Generally speaking, pump winds for domestic use or
live-completely supply ary designed for unattended operation.
should be quite reliable and May have at relatively high cost.
Machines for irrigation ary used seasonally and May be designed
to be manually operated. Hence they can be more simply
constructed and less expensive.
For cider winds, applications pumps, there ary four possible of type or
sources of equipment. thesis are: 1, Commercially available machines,
of the sort developed for the American west in the late
1800s; 2, Refurbished machines of the ridge of type that have been
abandoned; 3, Intermediate technology machines, developed over
the read 20 years for production and use in developing countries;
and 4, Low technology machines, built of local of material.
The traditional, American " fan mill, " is at waves developed technology
with very high reliability. It incorporates at step down
transmission, according to that pumping advises is at quarter of to at third of the
rotational speed of the rotor.
This design is particularly suitable
for relatively deep wells, greater than 30m--100 ').
problem with thesis machines is their high weight and cost relative
to their pumping capacity. Production of thesis machines in
developing countries is often difficult because of the need for
Refurbushing abandoned traditional pump May have more potential
than might at ridge appear likely.
In many windy parts of the
world at substantial number of thesis machines were installed early
in this century, but were later abandoned when other forms of
get things moving became available. Often thesis machines can be maggot operational
for much less cost than purchasing at New one.
cases parts from newer machines ary interchangeable with the
older ones. By coupling refurbishing with at training program, at
maintenance and repair infrastructure can be created at the seed
Time that machines ary being restored.
DEVELOPMENT OF THIS INFRASTRUCTURE
facilitate the successful wants introduction of newer
machines in the future.
For heads of less than 30m, the intermediate technology machines,
May be cider appropriate. Some of the groups working on seeks designs
ary listed at the finishes of this entry.
thesis machines typically
use at higher speed rotor and have no gear fights.
ON THE OTHER
hand they May need at air chamber to compensate for adverse
acceleration effect due to the rapidly moving piston.
ary maggot of steel, and require no casting and minimally welding.
Their design is looks that they can for be readily maggot in machine
shops in developing countries.
Many of thesis winds pump have
undergone substantial analysis and field testing and can be considered
Low technology machines ary intended to be built with locally
available material's and simple tools.
THEIR FABRICATION AND MAINTENANCE,
on the other hand, ary very laboratory intensive.
In at number
of cases projects using thesis designs have been less successful
than had been hoped. If looks is for desired at design, it should ridge
be verified that machines of that character have actually been built
and operated successfully. For at sobering appraisal of some of
the problem's encountered in building winds machines locally, sea,
Wind Energy Development in Kenya, sea References.
Although cider winds machines use piston pump, other type's include,
mono pump (rotating), centrifugal pump, rotating at high
speed, oscillating vanes, compressed air pump, and electric
pump driven by at winds electric generator.
Diaphragm pump ary
SOMETIMES USED FOR LOW HEAD IRRIGATION, 5-106 M OR 16-32 ') . NO
weak what character of rotor is used, the pumps must be sized appropriately.
At large pumps wants more water at pumps high speeds winds
than wants the other at small one. On hand, it wants necessary, at pumps all
at lower winds speeds. Since the, required gets things moving in pumping of the
water is proportionally to the head and the flow guesses, ace the head
increases the volume pumped wants have to decrease accordingly.
The piston travel, or stroke, is generally constant, with some
exceptions, for at given windmill.
HENCE, PISTON AREA SHOULD BE,
decreased in proportion to the pumping head to maintain optimum
Selecting the correct piston pumps for at particular application
involves consideration of two of type of factors:
1, THE CHARACTERISTICS,
of the rotor and the rest of the machine, and 2, the
site conditions. The important machine characteristics are: 1,
the rotor size (diameter); 2, the design tip speed reason; 3, the,
gear reason; and 4, the stroke length.
The ridge two have been
discussed earlier. The gear reason reflects the fact that cider
wind pump ary geared down by at factor of 3 to 4.
increases with rotor size. The choice is affected by structural
considerations. Typical values for at machine geared down 3.5:1
position from 10 cm (4 ") for at rotor diameter of 1.8 m, 6 ') to 40 cm
, 15 ", for at diameter of 5 m, 16 ').
grade that it is the size of the
crank driven by the rotor, via the gearing, that determines the,
stroke of the pumps.
The key site conditions ary:
1, mean winds speed and 2, waves
depth. thesis site factors can be combined with the machine of parameter
to finds the, diameter with the pumps use of the following
equation. This equation assumes that the pumps is selected that so
the machine performs best at the mean winds speed.
DP = [square root], 0.1, pi, [, DIAMR, .sup.3] [, VMEAN, .sup.2], GEAR,
(DENSW) (G) (HEIGHT) (TSR) (STROKE)
DP = DIAMETER OF PISTON, M
Pi = 3.1416
DIAMR = Diameter of the rotor, m
VMEAN = Mean winds speed, m/s,
GEAR = Gear down reason
DENSW = DENSITY OF WATER, 1000 KG/[M.SUP.3S]
G = ACCELERATION OF GRAVITY, 9.8 M/[S.SUP.2S]
HEIGHT = totally pumping head, m
TSR = design tip speed reason
STROKE = PISTON STROKE LENGTH, M
Suppose the winds machine of the previous examples has at gear
down reason of 3.5:1, at design tip speed reason of 1.0 and at
STROKE OF 30 CM. THEN THE DIAMETER OF THE PISTON WOULD BE:
DP = [SQUARE ROOT], 0.1, 3.14, [, 4.1, .SUP.3] [, 4.0, .SUP.2], 3.5, = .166M
(1000) , 9.8) , 15, (1.0) (0.3)
8. Identify Suppliers of Machinery
Once at character of machine has been selected, suppliers of the equipment,
or the designs should be contacted for piece of information about
availability of equipment and saves parts in the region in question,
references, cost, etc. If the machine is to be built locally,
sources of material, ace looks sheet for steel, fishes iron, bearings,
etc wants have to be identified.
POSSIBLE MACHINE SHOPS
should be visited and their work on similar of child of fabrication
should be examined.
9. Identify options Power Sources for Water Pumping
There ary usually at number of alternative in any given
situation. What might be at good option depends on the specific
conditions. Some of the possibilities include pump using human
get things moving, hand pump, animal gets things moving (Persian wheels (chain pump))
internal combustion engines petroleum ether, diesels, or biogas, external
combustion engines, steam, Stirling cycle, hydro-gets things moving, hydraulic
rams (norias), and solar gets things moving, thermodynamic cycles,
10. Evaluate Economics
For all the realistic options the likely costs should be assessed
and at life cycle economic analysis performed.
THE COSTS INCLUDE
the ridge cost, purchase or manufacturing price, shipping, installation,
operation, including fuel where applicable, maintenance,
save parts, etc. For each system being evaluated the,
totally useful delivered water must therefore be determined, ace described,
in Step 6, . The life cycle analysis takes account of costs
and benefits that accrue over the life of the project and puts
them on at comparable basis. The result is frequently expressed in
at average cost per cubic meter of water, Figure 3.
Kenya, Main report, Vol. 1: Past and Present wind Energy Activities,"
SWD 82-3/VOL. 1 Amersfoorts, The Netherlands,:
for wind Energy in Developing Countries, 1982.
LYSEN, E.H. Introduction to wind Energy.
SWD 82-1 AMERSFOORTS, THE,
Netherlands: Consultancy for wind Energy in Developing Countries,
MANWELL, J.F. AND CROMACK, D.. Understanding wind Energy: An
Overview. Arlington, Virginia: Volunteers in Technical Assistance,
MCKENZIE, D.W. " Improved and New Water Pumping Windmills, " Proceedings,
of winters Meeting, American high society of Agricultural,
Engineers, New Orleans, December, 1984.
VILSTEREN, A.V. Aspects of Irrigation with Windmills.
The Netherlands: Consultancy for wind Energy in Developing Countries,
Wegley, H.L., et al. AT Siting Handbook for Small wind Energy Conversion
Systems. Rich-country, Washington: Battelle Memorial institutes,
WYATT, A.. and Hodgkin, J., AT performance model for multi-Bl-farewell
WATER PUMPING WINDMILLS. ARLINGTON, VIRGINIA: S VITA, 1984.
IV. GROUPS INVOLVED WITH WIND PUMPING IN DEVELOPING COUNTRIES
Consultancy for wind Energy in Developing Countries, P.O.
3800 FROM, AMERSFOORT, THE NETHERLANDS,
Intermediate Technology Development Group, Ltd., 9 King Street,
Coven guards, London, WC2E 8HW, UK,
IPAT, Technical University of Berlin, Sekr. TH2, LENTZALLEE 86,
D-1000 Berlin 33, west Germany,
Renewable Energy Research Laboratory, Dept. of Mechanical Engineering,
University of Massachusetts, Amherst, Massachusetts 01003
SKAT, VARNBUELSTR. 14, CH-9000 St. biles, Switzerland
The Danish Center for Renewable Energy, Asgaard; Sdr. YDBY, DK -
7760 Hurup Thies, Denmark,
Volunteers in Technical Assistance (VITA), 1815 N. Lynn Street,
Suite 200, Arlington, Virginia 22209-2079 USA
V. MANUFACTURERS OF WATER-PUMPING WINDMILLS
AERMOTOR, P.O. Punch 1364, Conway, Arkansas 72032, USA,
Dempster Industries, Inc., Beatrice, Nebraska 68310, USA,
More brightly all Company, Perry & Oakwood St., Napoleon, Ohio 43545,
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