PICO HYDRO FOR VILLAGE POWER
A Practical Manual for Schemes up to 5 kW in Hilly Areas
Phillip Maher and Nigel Smith
Edition 2.0 May 2001
This manual is an output from a project funded by the UK Department
for International Development (DfID) for the benefit of developing
countries. The views expressed are not necessarily those of
DfID.
Disclaimer
pmaher 31/05/01 7-8
reached at least twice the background level, then the procedure
must be repeated with a greater quantity of salt. Readings continue
to be recorded every five seconds until the conductivity has
returned to its background level. This will normally be after a
further 10 to 15 minutes. If possible select a scale on the meter
that is just sufficient for the maximum conductivity to be read.
This may mean loss of the first set of results.
The meter readings are typically given in micro Siemens (µS) which
are units of conductivity (ohms-1 x 10-6).
STEP 4:Plot a graph of changing salt
concentration against time
These readings should be plotted on squared paper as a graph of
conductivity against time. The shape of the graph allows the
results to be evaluated. A smooth curve with a peak value at least
twice the level of the background conductivity, indicates that the
procedure has been successful. If the curve is badly skewed or the
readings are uneven then the procedure will need to be
repeated.
STEP 5: Calculate the area under the curve
The area under the curve must be established in order to calculate
the flow rate. This is done either by counting the squares
underneath the curve or by summing the results using a spreadsheet.
If you count the squares then the axis scale must be taken into
account.
STEP 6: Calculate the flow rate
The equation for calculating the flow rate is as follows:
Q M k
A =
× −1
where: Q = flow rate (l/s) M = mass of salt (mg) k-1= conversion
factor (ohm-1/mg l-1) A= area under curve (s x 10-6 x
ohm-1)
The conductivity is converted into salt concentration by
multiplying by a conversion factor that takes water temperature
into account. The conversion factor, k-1 has units ohm-
1/mg l-1 and assuming a water temperature of 22°C, the value
of k-1= 2.04.
Note: The mass of salt must be converted to milligrams (grams x
103) before being used in the equation.
S i t
e
i n g
p m a h
e r 3 1
/ 0 5
/ 0 1
7
-
9
7 -
8
R e s u
l t s f
r o m
t h e
‘ s a l t
g u l p
’ m e t
h o d
o f f
l o w
m e a s
u r e m
e n t c
a n
b e
q u i c
k l y
u s i n
g
a
s p r e
a d s h
e e t .
T i m
e
C o n d
u c
t i v
i t y
C o n d
u c
t i v
i t y
T i m
e
C o n d
u c
t i v
i t y
C o n d
u c
t i v
i t y
R e a d
i n g
I n c
r e a s
e
R e a d
i n g
C h a n
g e
( s e c
o n d s
) O h
m
- 1 x
( s e c
o n d s
) O h
m
- 1 x
2 1 4
0
M e a s
u r e m
e n
t
T h u
k o ,
E a s
1 9 9
8
T i m e
:
0 a m
W a t e
r T e m
p e r a
t u r e
:
2 2 °
C
5 0 m
e
t r e s
M a s s
o f s a
l t u s
e d :
2 5 0
0 0 m
i l l i g
r a m e
s
B a c k
g r o u
n d C o
n d u c
t i v
i t y
2 9
. 2 m
S i e m
e n s
T i m e
p e
r i o d
b e t w
e e n
r e s u
l t s
5 S e c
o n
d s
C o n v
e r s
i o n F
a c t o
r k
2 . 0
4 o
/ m g
l - 1
F l o w
R a t e
= m a s
s o f s
a l t
i n m g
x f a c
t o r k
/ a r e
a u n d
e r c u
r v e
A r e a
u n d e
r c u
r v e =
T o t a
l o f c
o n d u
t i v
i t y c
h a n g
e x
t i m e
p e
r i o
d
A r e a
u n d e
r c u
r v e =
1 0 6
9 8
F l o w
R a t e
=
4 . 7
7
l i t r e
s p e r
s e c o
n
d
P o w e
r A v a
i l a
b l e =
F l o w
R a t e
x H e a
d x G
r a v
i t y
P o w e
r A v a
i l a
b l e
=
2 3 3
8 w a
t t s
b a y ,
T h u
k o ,
0 2 0
)
1000 0.15 0.39 0.81
1500 0.23 0.58 1.21
3000 0.46 1.17 2.42
Table 19-3 Additional kW per belt if Ratio is 1.95 or greater
and turbine pulley smaller than the load pulley
If the pulley ratio is 1.95 (1.95:1) or greater, then the power can
be increased by the amount shown in Table 19-3. For example, if an
SPA belt is chosen and the turbine speed is around 1500 rpm, the
power which that belt can deliver increases by 0.58 kW if the ratio
is 1.95 or more.
pmaher 31/05/01 20-1
References:
1. Harvey, A. et al. ‘Micro Hydro Design Manual,’
Intermediate Technology Publications, 1993.
2. Inversin, A. ‘Mini Grid Design Manual,’ ESMAP, World Bank,
2000.
Editorial Address
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Engineering The Nottingham Trent University Burton Street
Nottingham NG7 4BU
Tel. +44 (0) 115 848 2885 Fax: +44 (0) 115 948 6567 Email:
[email protected] Web:
http://eee.ntu.ac.uk/research/microhydro/picosite
Intermediate Technology Publications
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