A NOVEL METHOD OF GENERATING

HYDROELECTRIC POWER USING A

LARGE COLLAPSIBLE BLADDER

Dr Uday Prashant

BASIC CONCEPTSMy discovery involves two basic concepts

1) Flow induced collapse in collapsible

tubes

2) Fluid structure interactions in flexible

tubes

This combinations leads to development of

novel hydroelctric turbine which functions at

very low heads and low flow conditions

efficiently

• With conventional turbine technology it is

practically impossible to extract power from

such low energy density flows –

head 1 -2 m range,

flow rate 0.3 – 0.4 litre/ sec

velocity 1 -3 m/sec.

Power in 1- 4 w & efficiency 60 – 95 %

Actually even lower flow conditions it is

possible to generate power with this method

but I lacked proper instrumentation to do so

• High head: 100-m and above- Pelton wheel require low

flow rates; 10 -30 cubic m/sec

• Medium head: 30 - 100 m; Francis require moderate

flow rates 30 -70 cubic m/sec

• Low head: 2 - 30 m; requires large flow rates. 50 – 100

cubic m/sec

• For Pico power project :- A 1 kW scheme could acquire

its energy from 200 m head with a flow rate of 1 litre/sec

or 2 m head with a flow rate of 100 l/sec

. With current technology either of them must be

large i.e high energy density flows are required for

operation conventional turbines efficiently

Basic principle of all turbines

• The power extraction from fluid arises from

turning the flow of jets.

• The fixed blades are stators and rotating

blades are rotors.

• The change in momentum of jets

causes reaction on rotatory blades and

transfers energy to shaft.

V= Absolute velocity of fluid

Vr= Relative velocity of fluid

Vw= Whirl velocity

Va= Axial velocity of flow

u = Velocity of the moving blades

m = V A (Area of blades)

In low energy density flows in

hydrokinetic turbines are but

they are inefficient and

dependant upon velocity of

water which is limited under

natural conditions

What if we have turbine which will

do away with these jets & vanes

or blades and operates by

entirely different mechanism

then we can produce energy at

even at low flow and head

conditions which was previously

not possible.

Specific Speeds

• More specific speed – lower efficiency and

increases cost

• Large heads---- large reserviors/dams–

submerge large areas of lands--- possible only in

mountain areas which act as natural reserviors,

• Large flows--- disturb entire course of river flow---

---- very costly ---lot of civil work required--- long

term can cause earthquakes

Ultra Low Head Turbines

Zero Head floating Hydrokinetic devices

work like wind mill – low efficiency

Novel turbine –Novel principle

• The flow is instantaneously reduced. Steady

continuous flow is converted to unsteady

pulsatile flow by collapsible bladder

• There is large negative pressure “WAVE”

generated travelling at speed of sound in

water.

• This pressure wave interacts with specially

designed flexible tubes with elastic supports and

transmits energy.

Advantages

• It works at very low Heads 1 – 2 m

• It works at very low flows also – viable even at such

low flows 250 ml/sec

• It works in lower velocities 1 -3 m/sec of flow

• It is very cost effective/ economically viable

. No concept of specific speed, works in wide flow

conditions

Advantages

• It can be used in small streams also.

• Doesn’t require complex civil engineering work

• Can be installed in few days of time.

• It is environmentally friendly (fish friendly)

• It is mobile and can also be easily shifted and installed in

other locations with similar flow conditions

Schematic diagram of novel

pulsatile flow generator

Working Principle

• Bladder collapses because of Venturi effect, or application of

Bernoulis Principle

• FSI or waterhammer effect causes the cycle to repeat and

converts kinetic energy of water to pressure wave which is inturn

converted to motion of pipes

Formulae

• From Joukowsky equation”

dp = d * c * dv

dp is pressure surge developed during the water hammer

c is velocity of sound in water

dv is change in velocity which is same as

V = (2gH)1/2 as after collapse velocity is zero & H is height of baldder from

ground.

• The pressure energy acts on entire surface of the u and straight

tube and ther force acting on it is given by

• F = P * A

• A = 2* pi * r2 + 2*pi*H

• If f is the frequency; s is amplitude of ocillations then power

generated per second is proportion to P * A * f * s

•

Vertical Height fixed at 1.8 m from bladder to lower end of

distal straight tube of diameter 12 mm. Spring constant

38 kg/m

Volume of flow in

l/sec

Frequency

no/min Amplitue in cm

Force in Kg

Newton

Power

avialable Power in watts

Hydraulic efficiency

%

0.18. 136 3 1 kg 3.1w 0.76w 24

0.2 128 8.5 1.085 3.6w 1.2w 35

0.222 114 9 1.125 3.9w 1.8w 45

0.227 115 8 1.150 4w 3w 75

0.25 112 10. 12. 4.4w 3.9w 89

0.3 106 10.5 12.50 5.3w 4.77w 90

When Flow rate is fixed at 250 ml/sec and height is varied the power

and efficiency.

Vertical height

in cm

Freq of oscill

per min

Amplitude

In mm

Max Force

Per

Oscillation in

Kg

Power available in

watts

Power generated

wattsHydraulic

efficiency

30 96 1 0.1 0.1w 0.03w 0.42781

50 92 30 0.5 0.49w 0.32w 35

96 91 54 0.7 0.7w 0.41w 47

130 86 70 1 0.98w 0.67w 63.7

150 97 76 1.12 1.1w 0,8w 80

165 58 85 1.25 1.3w 1.0w 64

0

20

40

60

80

100

120

140

Fre

qu

en

cy a

nd

am

plitu

de o

f o

scilla

tio

ns

Flow rate in ml/sec

Frequency of oscillations per min

Amplitude of vibrations in mm

0

20

40

60

80

100

120

30 50 96 130 150 165

freq

uen

cy a

nd

am

plitu

de o

f o

scilla

tio

ns

Vertical height in cm

Variation of frequency with height at constant flow rate of 240 cm^3/sec

frequency of oscillatons

Amplitude of oscillations

0

10

20

30

40

50

60

70

80

90

100

0.18. 0.2 0.222 0.227 0.25 0.3

Hydraulic efficiency % as flow rate is increased and when height is fixed 180cm

Hydraulic efficiency %

When the area of tube is increased from 12 mm to 18 mm and thickness of

rubber balloon is doubled (1.5 mm) and rest of parameters held constant

following observations are noted. Height =1.5m

Vol of water

Flow in cc/sec

Freq of oscill per

min

Amplitude

In mm

Power available from

flow in watts

Power generated in watts Hydraulic efficiency in

%

0.18 136 45 2.6w 1.7w 65

0.2 128 55 3w 2.4w 80

0.22 114 65 3.2w 2.9w 92

0.23 115 55 3.3w 2.16w 65

0.25 112 70 3.6w 3.42w 93

0.3 106 80 4.4w 4.2w 95

0.33 100 85 4.9w 4.48w 92

But increasing further flow caused rupture of bladder due to the stresses and hence

my further experiments fur stopper at larger diameter than ¾ inch pipes

0

10

20

30

40

50

60

70

80

90

100

0.18 0.2 0.22 0.23 0.25 0.3 0.33

Hydraulic Efficiency of apparatus at various flow rates in liter/sec when other paramerters are constant

STEADY FLOW: CHOKING, FLOW LIMITATION AND ELASTIC

JUMPS

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

Pre

ssu

re in

mm

Hg

-ve

Time in sec

Pressure recorded distal to collapsible bladder when all conditions constant

Theory of Waterhammer

• The bladder once collapsed must remain in same state under ordinary conditions.

• But due to flexible ‘U’ tube with elastic supports it comes out of collapse state and extracts energy by water hammer effect.

• Water hammer effect is when velocity of flow changes too rapidly (t< 4L/C where L is length of tube and C is velocity of sound in water (1200m/sec))

Types of Coupling

• The most significant mechanism is the

junction coupling, others are

Poisson and

friction coupling

• Wiggert D.C, Tijsseling, A. S (2001)- Junction coupling is

taken place due to unsupported discrete points of the

piping systems such as unrestrained

valves, junctions, closed ends, pumps, etc.

• MOC (Method of Charecteristics) and FEM (Finite

Element Method) are used to solve structural equations.

A.S. Tijsseling; A.G.T.J. Heinsbroek; THE INFLUENCE OF BEND MOTION ON WATERHAMMER

PRESSURES AND PIPE STRESSESProceedings of the 3rd ASME/JSME Joint Fluids Engineering

Conference July 18-23, 1999, San Francisco, California

A hydraulic ram or impulse pump is a device which uses the energy of

falling water to lift a lesser amount of water to a higher elevation than the

source but never used for power generation.

Conclusions

• Novel technological innovations may solve some of basic

limitations inherent in current hydro electric turbine

designs

• My model is in pilot stages and needs considerable

refinement and in large scale has to be rigorously tested.

• Lastly if similar technological principles were used in

design of gas turbine then results may be more

significant and have far reaching impact

When something is new, they say

"it's not true".

When its truth becomes

obvious, they say "it's not

important".

When its importance cannot be

denied, they reason, "it's not new".

William James

Thank You