water pumping windmill

7/28/2019 Water Pumping Windmill

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WATER PUMPING WINDMILL

One of the classical applications of wind energy is water pumping. Wind pumps are found

economically competitive with these options, even at areas of moderate wind. Direct water

pumping windmills are characterized by the old west style of a multiblade, horizontal axisdesign set over top of the well. Water pumping requires a high torque to start the pump and

this is supplied by the multiblade design. A water pumping windmill pumps water from

wells, ponds, and bore wells for drinking, minor irrigation, salt farming, fish farming, etc.

Available windmill are of two types, namely direct drive and gear type. A windpump is a

windmill used for pumping water, either as a source of fresh water from wells, or for draining

low-lying areas of land. Once a common fixture on farms in semi-arid areas, windpumps are

still used today where electric power is not available or too expensive.


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The most commonly used windmill has a horizontal axis rotor of 35.5 m diameter, with 12

24 blades mounted on the top of a 1020 m high mild steel tower. The rotor is coupled with a

reciprocating pump of 50150 mm diameter through a connecting rod. Such windmills start

lifting water when wind speed approaches 810 kilometres (km) per hour. Normally,

a windmill is capable of pumping water in the range of 1000 to 8000 litres per hour,

depending on the wind speed, the depth of water table, and the type of windmill. Windmills

are capable of pumping water from depths of 60 m. Water - pumping windmills have an

advantage in that no fuel is required for their operation, and thus they can be installed in

remote windy areas where other conventional means of water pumping are not feasible.

However, water - pumping windmills have limitations too. They can be operated

satisfactorily only in medium wind regimes (1218 km per hour). Further, special care is

needed at the time of site selection as the sites should be free from obstacles such as buildings

and trees in the surrounding areas. The cost of the system being high, many individual users

do not find them affordable.

Wind velocity for water pumping

Force Strength km/h Effect

0 Calm 0-1 Smoke rises vertically

1 Light air 1-5 Smoke drifts slowly2 Light breeze 6-11 Wind felt on face; leaves rustle

3 Gentle breeze 12-19 Twigs move; light flag unfurls

4 Moderate breeze 20-29 Dust and paper blown about; small branches move

5 Fresh breeze 30-39 Wavelets on inland water; small trees move

6 Strong breeze 40-50 Large branches sway; umbrellas turn inside out

7 Near gale 51-61 Whole trees sway; difficult to walk against wind

8 Gale 62-74 Twigs break off trees; walking very hard

9 Strong gale 75-87 Chimney pots, roof tiles and branches blown down

10 Storm 88-101 Widespread damage to buildings

11 Violent Storm 102-117 Widespread damage to buildings

12 Hurricane Over 119 Devastation

Force 2 - 3 orLight breeze and gentle breeze Wind speed range applicable for wind umps

Force 4 - 5 or Moderate and fresh breeze - Wind speed range applicable for electricitygeneration


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Wind pumps can broadly be classified as mechanical systems and electrical systems. In

mechanical wind pumps, the shaft power developed by the rotor is directly used to drive the

pump. On the other hand, in electrical wind pumps, wind energy is first converted to

electricity, which is then used to energize the pump. Mechanical wind pumps can further be

categorized as systems with positive displacement and roto-dynamic pumps. Various types of

pumps like the screw pump, piston pump, centrifugal pump, regenerative pump and

compressor pump are being used in mechanical wind pumping option.

Wind powered piston pumps

Positive displacement piston pumps are used in most of the commercial wind pumps. The

system consists of a high solidity multi-vane wind rotor, drive shaft, crank, connecting rodand a reciprocating pump. Rotary motion of the windmill rotor is translated to reciprocating

motion of the connecting rod by the crank. The connecting rod operates the pumps piston up

and down through the cylinder during its strokes. Two check valves, both opening upwards,

are fitted on the piston and the bottom of the pump. These valves allow the flow only in

upward direction. When the connecting rod drives the piston in the upward direction, the

piston valve is closed and thus the water column above the piston is lifted up, until it is

delivered out through the discharge line. At the same time, suction is created below the

piston, which causes the suction valve to open and thus fresh water from the well enter intothe space below. During the downward stroke, the piston valve is opened and the suction


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valve is closed. The water collected below the piston thus enters into the space above,

through the piston valve. These cycles are repeated resulting in pulsating sinusoidal water

discharge from the system. The volume of water discharged during one delivery stroke is

given by the product of inner area of the cylinder and the height through which the water

column is displaced during a stroke.

Wind powered piston pump

Thus, if d is the inner diameter of the pump cylinder and s is the stroke length (distance

between the extreme lower and upper positions of the piston) then, theoretically the volume

of water pumped per discharge stroke is given by

From the figure, we can see that


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Pumping capacities as influenced by the diameter of the cylinder and blade diameter of

the windmill

Multiblade windmills traditionally pump water by directly operating a pump cylinder with a

drive rod. The pump cylinder is submerged in the well attached to the end of the delivery

pipe. It is a very simple pump similar to a hand-operated bicycle pump. The drive rod is

operated directly by the windmill rotor through the drive gearing which translates the rotating

motion to the up and down reciprocating motion.

Working of Piston Pump


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Points to consider when selecting a windmill:

First of all, a water source is needed, knowing the volume of water to be pumped

(livestock requirements) and the lift (from water level to top of tank) if using a well, it

should be drilled first to know the lift and volume available

Some estimate of available wind must be made, preferably from site readings

select a tower height

adjust site readings to the tower height

Choose the combination of cylinder size for volume and rotor diameter for lift

Use manufacturers tables for size estimates usually best to choose the largest rotor and

smallest cylinder that will fill the need, for easy start in lighter winds and minimized

strain on the system as a rule-of-thumb, expect an average of 4 - 5 hours/day of pumping

at the specified rate for 24 kph wind unless local conditions are known

Other points:

windmill pump outlets are normally discharged into an open tank i.e. into the top of the

tank - if the outlet is to go into the bottom of the tank or rises above the well head a

packer head is installed to seal the drive rod hand pumping can be done on some

windmills in emergencies - the hand pump is part of the installation and the operating

handle is attached when needed

Wind electric pumps

In a wind electric pumping system (WEPS), a small and efficient wind electric generator

energizes a roto-dynamic pump-mostly centrifugal-to deliver water in reliable and often cost

effective way. Several industries around the world manufacture and distribute these systems

which are extensively used for supplying water in remote areas.

Wind electric pumps have some distinct advantages over the mechanical wind pumps. As the

electric power can be transmitted through cables, the wind turbine need not be installed just

above the well as in case of a mechanical pump. This gives the flexibility of installing the

turbine at a windy spot, for example at the top of a hill, where wind resource is strong. The

pump can be placed at the valley where the water source is available. As WEPS do not

require high starting torque, we can use fast running, low solidity rotors for these systems.

This improves the efficiency and reduces the constructional cost of the rotor. Further, the

output from the wind generator can be utilized for other applications like electrical lighting.


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The electrical transmission also results in lower maintenance and higher reliability. A typical

WEPS consist of a three bladed high speed rotor coupled with a permanent magnet generator.

Most of the systems have custom built low speed generators driven directly by the rotor. If

commercially available high speed generators are to be used, a gear box is required in the

drive train to step up the rotor speed. Size of commercial systems ranges from 1 kW to 10

kW. Electricity from the generator is transmitted to the pumps motor through cables which

may extend even upto 700 m.

For deep well pumping, electro submersible centrifugal pumps can be used. Electronic

controllers are used to connect and disconnect the pumps motor from the wind turbine.

These systems are highly reliable and reported to have 100 per cent availability for years,

even without any attention. Although permanent magnet generators are common for WEPS,

systems with induction generators are also available. Here, the reactive power required for

exiting the induction machines is delivered externally.

The major drawback of WEPS is its high initial cost as it additionally requires the generator,

motor and electronic control unit. In traditional wind pumps, the mechanical power available

at the rotor shaft is directly used to lift the water. Whereas, in WEPS, we transform the shaft

power into electrical form using the generator which is again converted back to mechanical

power by the pump motor. This multistage transformation of power may cause drop in

system efficiency. However, the better rotor-pump matching and flexibility and reliability of

the system justify the use of WEPS for remote applications. WEPS are economical in areas

where the annual average wind velocity is above 5 m/s.

A wind electric pumping system overcomes some of the problems with the simple wind water

pumper. This system generates electricity, which, in turn, runs an electric pump. Wind

electric pumping systems allow greater siting flexibility, higher efficiency of wind energy

conversion, increased water output, increased versatility in use of output power, and

decreased maintenance and life-cycle costs.

Water Requirements

The size of the wind turbine required for water delivery depends on the average daily volume

of water required, the total pumping head, the average wind speed, and the system efficiency.


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Theoretically the volume of water pumped per discharge stroke is given by

V = 3.14/4 * d2 * s

= 3.14/4 * 0.0572 * 0.2

V = 5.1 x 10 -4

Assume slip 0.05% and N = 50 cycles/min

Q = 5.1 x 10 -4 x 50/60 x (1 0.05)

= 4.03 x 10 -4 m3/s

Q = 0.4 l/s

Power required = g x Qm x h/ efficiency of pump

Assume, head = 20 m and efficiency = 0.7

P = 9.8 x 0.4 x 20 /0.7

P = 112 W

COST OF WATER PUMPING WINDMILLS

The cost of a water pumping windmill varies from Rs 45 000 to Rs 150 000, depending on

the type. In addition, Rs 10 000Rs 20 000 is required for the foundation, storage tank, and

the installation of the windmill. As the system involves moving parts, it requires frequent

maintenance. The repair and maintenance cost of a windmill is about Rs 2000 per year.

The Ministry of New and Renewable Energy provides a subsidy of up to 50% of the ex-

works cost of water pumping windmills, subject to ceilings of Rs 20 000, Rs 30 000, and Rs

45 000 in the case of direct drive, gear type, and AV-55 Auroville models, respectively. For

non-electrified islands, subsidy of up to 90% of the ex-works cost is provided for the above

types of windmills, subject to ceilings of Rs 30 000, Rs 45 000, and Rs 80 000, respectively.

water pumping windmill

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