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The potential of wind electricity generation in Bangladesh
RenewableEnergyVol. 1, No. 5/6, pp. 855-857, 1991 Printed in Great Britain.
0960-1481/91 $3.00+.00 Pergamon Press plc
TECHNICAL NOTE The potential of wind electricity generation in Bangladesh M . SARKAR* a n d M . HUSSAIN Department of Physics and Renewable Energy Research Centre, University of Dhaka, Dhaka 1000, Bangladesh
(Received 17 April 1990; accepted 27 June 1990) Abstract--The hourly wind speed data of the coastal station Chittagong have been collected for the years 1978-81. From the hourly average wind speed, the hourly and monthly energy outputs were computed for three commercial machines (22 kW, 16 kW and 4 kW) having different cut-in wind speed. The 22 kW machine was found to produce higher energy output per m: than the other two for our energy regime. The hourly and monthly energy variation of the 22 kW machine was studied and the cost per kWh of energy produced by this machine was obtained. Considering the wind speed distribution of Bangladesh, it appears that a wind machine in combination with a conventional diesel back up system will be economiclaly viable for electricity generation in the off-shore islands but not in inland locations.
INTRODUCTION Bangladesh is one of the highly energy deficient countries in the world. The per capita commercial energy consumption in Bangladesh in 1981 was 35 KgOE [1] which is pretty low even compared to that of neighbouring India (158 KgOE) and Pakistan (I 79 KgOE). By 1985, electricity consumption grew to 41 KgOE in Bangladesh but the disparity increased further. Electricity which is only 10% of the commercial energy and 2% of the total energy consumed is being produced here in different ways : hydro-electricity and electricity generated using natural gas are the main sources in the eastern zone and in the western region oil burning generators are used. In some islands such as Kutubdia Sandwip etc. electricity is produced using small diesel generators (I0-100 kW). For one such station, it has been found [2] that the fuel cost per kWh of electricity supplied is Tk.8.92 in 1982 which is much higher than the national average fuel cost of Tk.0.83 in the same year. In this work an attempt has been made to study the possibility of harnassing wind energy for electricity production in Bangladesh. An earlier study on wind speed and wind energy availability in Bangladesh [3] showed that in the western region almost all meteorological stations have an average annual wind speed of around 4 km/h except the station Jessore and Faridpur where the average speed recorded in 8 km/h. In the eastern side, the average speed is a little bit higher with the exception of (i) the inland station Dhaka Airport where the speed is much above average and (ii) the coastal station Chittagong where the highest average speed (I3 km/h) has been recorded. It is reported [4] that the average speed of Sagar Islands in India which is near to Bangladesh is 19 km/h. During a brief survey with a hand anemometer, a coastal area of Bangladesh (Char Jabbar) again showed high wind speeds. So far as we know, there is no hourly wind speed data of off-shore island coasts. But our guess is that the wind speed in those areas should be at least equal to that of Chittagong and might approach that for Sagar Islands. An annual average wind speed of 13 km/h which has been
recorded in Chittagong might be useful in generating electricity economically under Bangladesh conditions. In this paper, taking the data of Chittagong to be representative of coastal areas we would like to show how much energy one can get from three different types of wind generators having cut-in wind speeds of 2, 3.5 and 4.5 m/s. The cost of the energy produced by the machine which gives the maximum energy output was then calculated and compared with that of the diesel generators. DATA COLLECTION AND RESULTS For the station Chittagong, the Meteorological Department of Bangladesh collects hourly wind speed data with the help of a vertical-axis cup anemometer. The data for the period 1978-80 were collected manually from the log-book. These were then averaged over three years to get the hourly, monthly and annual speeds. Suposing that the wind machine has a tower height of 60 ft the wind speed corresponding to this height was computed from measurements made at a lower height of 10 m using the formula
* Present address : IRST, 38050 Povo, Trento, Italy. 855
v, - \ h , /
The value of ct was taken from the literature [5]. Mani and Mooley [4] made a systemic study of ct over different parts of India. From that work, one can guess that for Chittagong, the average value of ~ might be 0.3. In that case the overall energy output will be 20% higher. We have chosen to make a rather conservative estimate of the energy output with lower ~t and possibly a lower wind speed. The characteristics of three machines (22 kW, 16 kW, 1 kW) as found from the literature [6--8] are shown in Table 1. Taking the average output energy for wind speeds in between the cut-in and rated values to be linear, a straight line fit was drawn. Corresponding to each hourly average speed for a month the energy output for that particular hour was determined from that fit. All the hourly energy outputs were added up to get the daily output which is again multiplied by the total number of days of a month to get the monthly energy
856
Technical Note Table 1. The characteristics of three machines found from the literature [6-8]
Name
Country
Aeroman (22 kW) W 16 (16 kW) Enertech (4 kW)
Holland Australia U.S.A.
Blade material
Rated power (kW)
Rated wind speed (m/s)
Fibre glass Fibre glass Wood
22 16 4
8.5 8.0 10.7
Blade diameter No. of (m) blades II.0 12.0 6.0
2 3 3
output. Table 2 shows such energy output per m 2 for different months of the year for the three machines. DISCUSSION From Table 2, it is found that the energy output per unit blade area (kWh/m 2) is highest for the 22 kW machine. From the hourly energy values for the same machine (Fig. I), it is found that for the months from April to August, most of the time, the output is above 5 kW and peaks at around 3 p.m. o f local time. Small, cottage industries which run during the day time could be very profitably powered by a wind generator as energy storage requirement would be minimum and investment on batteries would not be high. Wind power can also be used for water storage pumping or lighting in the earlier hours of night during the above months with similar advantage. Late at night, power required for lighting, is small in developing countries and a large battery bank is not necessary. Storage batteries are costly and a wind machine with small storage batteries tends to become less costly. It is also evident that for the period from October to February and also for some hours in the months of March and September, the energy output is practically zero. So a stand alone wind machine cannot be used as a power generating unit. It must be coupled with an auxiliary device, say a conventional diesel generator which should be used only for the lean period. From a cost analysis (shown in the appendix), it is clear that the cost per k w h energy produced by the above 22 kW machine (Tk.1.68) is much less than that o f a small diesel burning system. If it is assumed that 40% of the energy produced over the year is available for utilization, even then Table 2. Monthly energy output (kWh/m 2) for the wind machines Month
22 kW
16 kW
4 kW
January February March April May June July August September October November December
19 23 25 60 60 93 108 99 23 4 0 3
8 11 18 40 42 55 62 56 21 6 3 5
5 7 7 18 15 29 36 29 5 0 0 0
Total
517
327
151
Cut in Furling speed speed (m/s) (m/s) 3.5 2.0 4.5
24 -18.0
Output
Price
220/380 volts $38,000 240 volts -230 volts --
the energy produced by the wind generator remains cheaper than the fuel cost per kWh of energy supplied (Tk.8.29). In the western zone o f Bangladesh where electricity is generated by burning oil, the wind speed is reported [3] to be low. So a wind machine has no importance in those areas. In the eastern side, hydro-electricity and natural gas burning systems are two sources of electricity. Wind speeds in some of the places in this zone, especially in the coastal belt are sufficient to run a windmill for few months of the year. But the cost per kWh energy produced by a wind mill will be more costly than the existing centrally generated electricity in the main land. So one can say that normal grid line will not be benefited by feeding in power from machines. Our off-shore islands are expected to have sufficiently good wind speeds to run a wind machine cost effectively. At present, in some of those areas, electricity is produced by diesel generators and normal grid lines cannot be extended to those places. Wind generators with a diesel back up system will be most suitable for the off-shore islands. The points that emerge out of this study are: (1) wind generators in combination with diesel systems should be suitable for off-shore islands, (2) normal grid lines will not be benefited by feeding in power from wind generators, (3) meteorological stations should be established in seaside locations in the islands to record the hourly wind speed in order to obtain better information on the energy availability and (4) as a pilot project, a small wind generator may be setup in one of the islands at a suitable location to study with a good accuracy the energy production and its cost.
APPENDIX The cost per kWh of energy produced by the 22 kW machine has been calculated under the following assumptions [7] : (1) the life time of the machine (t) was assumed to be 20 years, (2) the interest rate (r) and inflation rate (0 were taken to be 15% and 12% respectively, (3) operation, maintenance and repair cost (Corer) was considered to be 25% of the annual cost of the machine (machine price/life time), (4) scrap value S was taken to be 10% of the machine price and civil work and (5) investment (I) includes the machine price plus its 20% for the civil work and other connections. The present value o f costs (PVC) is [7] 1-1 +i-]
[-
[1+i'¥]
['l+i]'
pvc =/+ CompLex_i] × i_1- l ~ r ) J - S / ~ r J
For the 22 kW machine, the price [6] is taken to be US$38000 and the cost of civil work (20% of the price) = $7600. Therefore investment I = $45600, C,,mr= $(38000/20) X0.25 = 5;475.00 and S = $ (45600 x 0.10) = $4560.00 where r = 0.15 and i = 0.12. Using all these values in the above equation
Technical Note
857
APRIL
FEBRUARY
JUNE
20-
/2
I v
I/
:) in I-20
:
I
"~
.~.,. I
OCTOBER
AUGUST
I
1
DECEMBER
._I
< Io I--
0-20
I0-20 20-20
I
I
0-20
10-20
I
20-20
,/
I
I
0-20
10-20
I
20-20
TIME ( IN GMT) Fig. 1. Hourly energy output (kW/m 2) for the wind machine Aeroman (22 kW) over the different months of the year.
PVC = $50151.00. From Table 2 the annual output of 22 kW machine is 517 × [(D/2) 2] kWh = 49132 kWh where D is the diameter of the blade. So the total output in 20 years = (49132x20) kWh. Therefore, the cost per kWh = $50151/49132 × 20 = $0.051 = Tk.68 (1 US$ = Tk.33.00). Even if only 40% of the total output is available for consumption the cost per kWh power supplied would be Tk.4.20.
REFERENCES 1. M. Hussain, Energy 12, 369 (1987). 2. B, Hezeltine, A report from Centre for Policy Research,
Dhaka University, Dhaka, Bangladesh, 1983 (unpublished). 3. M. Hussain, S. Alam, K. A. Reza and M. Sarkar, Energy Conversion and Management 26, 321 (1986). 4. A. Mani and D. A. Mooley, WindEnergy Data oflndia. Allied Publications, New Delhi, India (1983). 5. R. H. B. Exell, S. Thavapalachendran and P. Mukhia, AIT Research Report No. 1489, Published by the Renewable Energy Research Information Centre, Bangkok, Thailand. 6. G. Furlan, N. A. Mancini and A. A. M. Sayigh, Non Conventional Energy Sources, p. 713, World Scientific Publications, Singapore (1985). 7. S. M. Habli, M. A. S. Hamdan, B. A. Jurdan and Adnan O. Zaid, Solar Energy 38, 59 (1987). 8. Private communications. Wind Technology, P.O. Box 716 Wodonga 3690, Australia.
0960-1481/91 $3.00+.00 Pergamon Press plc
TECHNICAL NOTE The potential of wind electricity generation in Bangladesh M . SARKAR* a n d M . HUSSAIN Department of Physics and Renewable Energy Research Centre, University of Dhaka, Dhaka 1000, Bangladesh
(Received 17 April 1990; accepted 27 June 1990) Abstract--The hourly wind speed data of the coastal station Chittagong have been collected for the years 1978-81. From the hourly average wind speed, the hourly and monthly energy outputs were computed for three commercial machines (22 kW, 16 kW and 4 kW) having different cut-in wind speed. The 22 kW machine was found to produce higher energy output per m: than the other two for our energy regime. The hourly and monthly energy variation of the 22 kW machine was studied and the cost per kWh of energy produced by this machine was obtained. Considering the wind speed distribution of Bangladesh, it appears that a wind machine in combination with a conventional diesel back up system will be economiclaly viable for electricity generation in the off-shore islands but not in inland locations.
INTRODUCTION Bangladesh is one of the highly energy deficient countries in the world. The per capita commercial energy consumption in Bangladesh in 1981 was 35 KgOE [1] which is pretty low even compared to that of neighbouring India (158 KgOE) and Pakistan (I 79 KgOE). By 1985, electricity consumption grew to 41 KgOE in Bangladesh but the disparity increased further. Electricity which is only 10% of the commercial energy and 2% of the total energy consumed is being produced here in different ways : hydro-electricity and electricity generated using natural gas are the main sources in the eastern zone and in the western region oil burning generators are used. In some islands such as Kutubdia Sandwip etc. electricity is produced using small diesel generators (I0-100 kW). For one such station, it has been found [2] that the fuel cost per kWh of electricity supplied is Tk.8.92 in 1982 which is much higher than the national average fuel cost of Tk.0.83 in the same year. In this work an attempt has been made to study the possibility of harnassing wind energy for electricity production in Bangladesh. An earlier study on wind speed and wind energy availability in Bangladesh [3] showed that in the western region almost all meteorological stations have an average annual wind speed of around 4 km/h except the station Jessore and Faridpur where the average speed recorded in 8 km/h. In the eastern side, the average speed is a little bit higher with the exception of (i) the inland station Dhaka Airport where the speed is much above average and (ii) the coastal station Chittagong where the highest average speed (I3 km/h) has been recorded. It is reported [4] that the average speed of Sagar Islands in India which is near to Bangladesh is 19 km/h. During a brief survey with a hand anemometer, a coastal area of Bangladesh (Char Jabbar) again showed high wind speeds. So far as we know, there is no hourly wind speed data of off-shore island coasts. But our guess is that the wind speed in those areas should be at least equal to that of Chittagong and might approach that for Sagar Islands. An annual average wind speed of 13 km/h which has been
recorded in Chittagong might be useful in generating electricity economically under Bangladesh conditions. In this paper, taking the data of Chittagong to be representative of coastal areas we would like to show how much energy one can get from three different types of wind generators having cut-in wind speeds of 2, 3.5 and 4.5 m/s. The cost of the energy produced by the machine which gives the maximum energy output was then calculated and compared with that of the diesel generators. DATA COLLECTION AND RESULTS For the station Chittagong, the Meteorological Department of Bangladesh collects hourly wind speed data with the help of a vertical-axis cup anemometer. The data for the period 1978-80 were collected manually from the log-book. These were then averaged over three years to get the hourly, monthly and annual speeds. Suposing that the wind machine has a tower height of 60 ft the wind speed corresponding to this height was computed from measurements made at a lower height of 10 m using the formula
* Present address : IRST, 38050 Povo, Trento, Italy. 855
v, - \ h , /
The value of ct was taken from the literature [5]. Mani and Mooley [4] made a systemic study of ct over different parts of India. From that work, one can guess that for Chittagong, the average value of ~ might be 0.3. In that case the overall energy output will be 20% higher. We have chosen to make a rather conservative estimate of the energy output with lower ~t and possibly a lower wind speed. The characteristics of three machines (22 kW, 16 kW, 1 kW) as found from the literature [6--8] are shown in Table 1. Taking the average output energy for wind speeds in between the cut-in and rated values to be linear, a straight line fit was drawn. Corresponding to each hourly average speed for a month the energy output for that particular hour was determined from that fit. All the hourly energy outputs were added up to get the daily output which is again multiplied by the total number of days of a month to get the monthly energy
856
Technical Note Table 1. The characteristics of three machines found from the literature [6-8]
Name
Country
Aeroman (22 kW) W 16 (16 kW) Enertech (4 kW)
Holland Australia U.S.A.
Blade material
Rated power (kW)
Rated wind speed (m/s)
Fibre glass Fibre glass Wood
22 16 4
8.5 8.0 10.7
Blade diameter No. of (m) blades II.0 12.0 6.0
2 3 3
output. Table 2 shows such energy output per m 2 for different months of the year for the three machines. DISCUSSION From Table 2, it is found that the energy output per unit blade area (kWh/m 2) is highest for the 22 kW machine. From the hourly energy values for the same machine (Fig. I), it is found that for the months from April to August, most of the time, the output is above 5 kW and peaks at around 3 p.m. o f local time. Small, cottage industries which run during the day time could be very profitably powered by a wind generator as energy storage requirement would be minimum and investment on batteries would not be high. Wind power can also be used for water storage pumping or lighting in the earlier hours of night during the above months with similar advantage. Late at night, power required for lighting, is small in developing countries and a large battery bank is not necessary. Storage batteries are costly and a wind machine with small storage batteries tends to become less costly. It is also evident that for the period from October to February and also for some hours in the months of March and September, the energy output is practically zero. So a stand alone wind machine cannot be used as a power generating unit. It must be coupled with an auxiliary device, say a conventional diesel generator which should be used only for the lean period. From a cost analysis (shown in the appendix), it is clear that the cost per k w h energy produced by the above 22 kW machine (Tk.1.68) is much less than that o f a small diesel burning system. If it is assumed that 40% of the energy produced over the year is available for utilization, even then Table 2. Monthly energy output (kWh/m 2) for the wind machines Month
22 kW
16 kW
4 kW
January February March April May June July August September October November December
19 23 25 60 60 93 108 99 23 4 0 3
8 11 18 40 42 55 62 56 21 6 3 5
5 7 7 18 15 29 36 29 5 0 0 0
Total
517
327
151
Cut in Furling speed speed (m/s) (m/s) 3.5 2.0 4.5
24 -18.0
Output
Price
220/380 volts $38,000 240 volts -230 volts --
the energy produced by the wind generator remains cheaper than the fuel cost per kWh of energy supplied (Tk.8.29). In the western zone o f Bangladesh where electricity is generated by burning oil, the wind speed is reported [3] to be low. So a wind machine has no importance in those areas. In the eastern side, hydro-electricity and natural gas burning systems are two sources of electricity. Wind speeds in some of the places in this zone, especially in the coastal belt are sufficient to run a windmill for few months of the year. But the cost per kWh energy produced by a wind mill will be more costly than the existing centrally generated electricity in the main land. So one can say that normal grid line will not be benefited by feeding in power from machines. Our off-shore islands are expected to have sufficiently good wind speeds to run a wind machine cost effectively. At present, in some of those areas, electricity is produced by diesel generators and normal grid lines cannot be extended to those places. Wind generators with a diesel back up system will be most suitable for the off-shore islands. The points that emerge out of this study are: (1) wind generators in combination with diesel systems should be suitable for off-shore islands, (2) normal grid lines will not be benefited by feeding in power from wind generators, (3) meteorological stations should be established in seaside locations in the islands to record the hourly wind speed in order to obtain better information on the energy availability and (4) as a pilot project, a small wind generator may be setup in one of the islands at a suitable location to study with a good accuracy the energy production and its cost.
APPENDIX The cost per kWh of energy produced by the 22 kW machine has been calculated under the following assumptions [7] : (1) the life time of the machine (t) was assumed to be 20 years, (2) the interest rate (r) and inflation rate (0 were taken to be 15% and 12% respectively, (3) operation, maintenance and repair cost (Corer) was considered to be 25% of the annual cost of the machine (machine price/life time), (4) scrap value S was taken to be 10% of the machine price and civil work and (5) investment (I) includes the machine price plus its 20% for the civil work and other connections. The present value o f costs (PVC) is [7] 1-1 +i-]
[-
[1+i'¥]
['l+i]'
pvc =/+ CompLex_i] × i_1- l ~ r ) J - S / ~ r J
For the 22 kW machine, the price [6] is taken to be US$38000 and the cost of civil work (20% of the price) = $7600. Therefore investment I = $45600, C,,mr= $(38000/20) X0.25 = 5;475.00 and S = $ (45600 x 0.10) = $4560.00 where r = 0.15 and i = 0.12. Using all these values in the above equation
Technical Note
857
APRIL
FEBRUARY
JUNE
20-
/2
I v
I/
:) in I-20
:
I
"~
.~.,. I
OCTOBER
AUGUST
I
1
DECEMBER
._I
< Io I--
0-20
I0-20 20-20
I
I
0-20
10-20
I
20-20
,/
I
I
0-20
10-20
I
20-20
TIME ( IN GMT) Fig. 1. Hourly energy output (kW/m 2) for the wind machine Aeroman (22 kW) over the different months of the year.
PVC = $50151.00. From Table 2 the annual output of 22 kW machine is 517 × [(D/2) 2] kWh = 49132 kWh where D is the diameter of the blade. So the total output in 20 years = (49132x20) kWh. Therefore, the cost per kWh = $50151/49132 × 20 = $0.051 = Tk.68 (1 US$ = Tk.33.00). Even if only 40% of the total output is available for consumption the cost per kWh power supplied would be Tk.4.20.
REFERENCES 1. M. Hussain, Energy 12, 369 (1987). 2. B, Hezeltine, A report from Centre for Policy Research,
Dhaka University, Dhaka, Bangladesh, 1983 (unpublished). 3. M. Hussain, S. Alam, K. A. Reza and M. Sarkar, Energy Conversion and Management 26, 321 (1986). 4. A. Mani and D. A. Mooley, WindEnergy Data oflndia. Allied Publications, New Delhi, India (1983). 5. R. H. B. Exell, S. Thavapalachendran and P. Mukhia, AIT Research Report No. 1489, Published by the Renewable Energy Research Information Centre, Bangkok, Thailand. 6. G. Furlan, N. A. Mancini and A. A. M. Sayigh, Non Conventional Energy Sources, p. 713, World Scientific Publications, Singapore (1985). 7. S. M. Habli, M. A. S. Hamdan, B. A. Jurdan and Adnan O. Zaid, Solar Energy 38, 59 (1987). 8. Private communications. Wind Technology, P.O. Box 716 Wodonga 3690, Australia.