Wind Energy Programme in Bangladesh :
(Paper Personated Second International
Conference on Electrical and Computer Engineering ICECE
2002, 26-28 December 2002, Dhaka, Bangladesh)
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M. Arif Hossain1, (Department of Mathematics, KUET, Khulna-9203, Bangladesh.)
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M. Zakir Hossain2, and A.K.M. Sadrul Isalm (Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh.
This paper presents a study on the wind power potential of five selected meteorological stations of Rajshahi division, in the northwest of Bangladesh. From the available observed raw wind data long term averages on monthly and annual basis have been obtained, from which probability distribution of wind speed, velocity duration curves and distribution of power in the wind are plotted. Wind roses have also been plotted for the stations. The results indicate that out of the five stations Ishwardi has higher wind potential than the others.
For this study, the data from the
commencement of the stations to 2000 is used. (For Sayedpur,
data is available only from 1991 and so it has not been
considered for this study.). Data were available for
Ishwardi since 1961, for Rajshahi 1964, for Bogra 1948,
Rangpur 1954 and Dinajpur 1948 respectively (with some
missing years). The location of the stations are : Ishwardi
24008˘ N, 89003˘ E; Rajshahi 24022˘ N, 88042˘ E; Bogra
24051˘ N, 89022˘ E, Rangpur 25044˘ N, 89014˘ E, and Dinajpur
25039˘ N, 88041˘ E.
Power is utmost important to develop and
run a country. Energy, which can produce power, sources are
limited and so we need to search for alternative sources.
Wind can play an important role in this context. A WMO
(World Meteorological Organization) report [1] reveals that
1.75·1014 kWh of wind energy is available over the entire
globe that can be utilized for betterment of human race. In
an earlier work [2] it has been found that monsoon is the
main source of the wind in the Barisal division, in the
south central part of Bangladesh. In the present work, wind
power potential of five, out of six, of the meteorological
stations of Rajshahi division, which are in the northwestern
part of Bangladesh, has been studied. The stations are at
Ishwardi, Rajshahi, Bogra, Rangpur and Dinajpur (Sayedpur
has been excluded due to shortage of data). Average monthly
wind speeds at these stations are calculated from the three
hourly data recorded. Probability distribution of wind
speed, probability of wind speed greater than a particular
speed, distribution of power in the wind, power per unit
area in the wind and power duration curves have been
enumerated. All these calculations have been made for all
the stations considered.
DATA
For the study, data has been acquired
from Bangladesh Meteorological Department (BMD). BMD has six
stations in the Rajshahi division. They record data every
three hours using 3-cup type anemometer kept at standard
height of 10 meter. In early days, due to lack of
electricity in the sites, they have recorded the data only
in daytime. Not also all these stations were commissioned in
the same year.
The collected raw data has been processed to get one year long term average at the observational hours (using only the available observations). The raw data which were in knots/hr, are transferred into m/s. With class interval of 0.25 m/s a frequency table is made (not shown). Using the frequency table probability distribution of wind speed (relative frequency), probability of wind speeds greater than a particular speed (cumulative relative frequency) and distribution of power in the wind are tabulated (not shown). The power per unit area of wind cross-section is given by P0 = 1 r u 3 . Considering air density r = 1.165 kg/m3 2 and wind speed u in m/s, we get P0 = 0.58 u3 W/m2. Let Fu is the probability distribution of wind speed u, then the distribution of power in the wind becomes P0Fu.
RESULTS AND DISCUSSION
The long term monthly averages
(from the commission date of the stations up to 2000) of
wind speed for the five meteorological stations of Rajshahi
division of Bangladesh are plotted in Fig. 1. It shows that
all of the stations experiences their respective lowest
winds through post-monsoon (October-November) to winter
(December-February). From the starting of pre-monsoon
(March-May) the speed starts to climb up and attains their
maximum by April and remains nearly constant throughout the
months from May-August, then it gradually decreases till to
October. It is also interesting to note that at the higher
latitudes the wind speeds less than that of lower latitudes.
Figure 1: Average monthly wind speeds
of the five stations of Rajshahi division.
The probability distributions of wind
speeds are plotted in Fig. 2. It indicates that Ishwardi has
wide variety of winds. On the other hand, Dinajpur has
lowest variability. The modes of the distributions are at
0.60, 1.40, 1.05, 1.20 and 0.75 for the stations Ishwardi,
Rajshahi, Bogra, Rangpur and Dinajpur respectively.
The cumulative relative frequency
against wind speed is plotted in the Fig. 3. These curves
also give the median of the distributions of Fig. 2. For
Ishwardi, Rajshahi, Bogra, Rangpur and Dinajpur, the
respective values are 1.82 m/s, 1.57 m/s, 1.29 m/s, 1.40 m/s
and 0.93 m/s.
Fig. 4 represents the distribution of theoretical
power in the wind. The respective picks are at 3.30 m/s,
2.22 m/s, 2.00 m/s, 1.82 m/s and 1.25 m/s for Ishwardi,
Rajshahi, Bogra, Rangpur and Dinajpur.
In Fig. 5 power per unit area in the wind against the
probability of wind speed greater than a particular speed is
plotted. It indicates the likelihood of obtaining particular
power levels. For example, the probability of getting 20
watt/m2 power is 14% for Ishwardi.
The wind duration curve is plotted in Fig. 6. From
these curves, it is possible to obtain the time availability
(at percentage) of wind speeds. For example, if we want to
see the availability for getting
a speed of 2.0 m/s or more, then for Ishwardi it is
about 44%, for Rajshahi 27%, for Bogra 15%, for Rangpur 16%
and for Dinajpur only 2%. Thus in Ishwardi for a wind
turbine whose cutoff speed is 2.0 m/s will in operation for
44 % time all through the year.
Wind
Speed (m/s)
Figure 3: Probability of wind speed
greater than a
particular speed u˘.
a speed of 2.0 m/s or more, then for
Ishwardi it is about 44%, for Rajshahi 27%, for Bogra 15%,
for Rangpur 16% and for Dinajpur only 2%. Thus in Ishwardi
for a wind turbine whose cutoff speed is 2.0
Figure 5: Power per unit area in the wind against the probability of wind speeds greater than a particular speed u˘.
Figure 6: Wind duration curve.
This analysis reveals that, • Monsoon is the main source of the wind in the area under consideration. • In Ishwardi, it is possible to get winds of speed 2.00 m/s or more for at least 44% time all through the year. • With the increase of latitude, maximum occurrence of wind rotates from south to east.
ACKNOWLEDGEMENT
The authors would like to thanks Mr. Md. Shibadul Islam Khan, Professional Assistant, BMD for his assistance to get the data.
REFERENCES
[1]
WMO, 1954, Energy from Wind, Tech. Note No 4,
WMO, Geneva. [2]
Hossain, M. Arif; Hossain, M. Zakir and Isalm,
A.K.M. Sadrul, “Wind Resource Assessment of
Bangladesh : Bay Belt Meteorological Stations of Barisal
Division”, BSME-ASME International Conference on Thermal
Engineering, 31 Dec 2001- 2 Jan 2002, Dhaka, Bangladesh, pp
571-576. [3] Toure, S. and Laoualy, R. (2000), “A
Theoretical Study of Wind Power in COTE D’IVOIRE using the
Weibull Distribution”, WREC2000, Elsevier Science Ltd., pp
2304-07
[4] Twidell, J. and Weir, T.(1986 ), Renewable Energy
Resources, The University Press, Cambridge, pp 204-256.
