wind energy in sudan

Wind energy in Sudan

Abdeen Mustafa Omer

ERI, PO Box 4032, Khartoum, Sudan

Received 11 November 1998; accepted 18 January 1999

Abstract

Wind data for 70 stations in Sudan have been analysed. Yearly wind speeds map wasdrawn. Results suggest that wind power would be more pro®tably used for local and small-scale applications. # 1999 Elsevier Science Ltd. All rights reserved.

1. Introduction

The use of wind as a source of power has a long history. Man has been familiarwith the use of wind mills and pumps; sailing ships were, in the past, the mostsigni®cant example of its technical utilization.

The early form of wind machines had sails attached at right angles to avertically mounted shaft. This form is reported to be in use in Japan and Chinafrom 2000 B.C. The horizontal axis wind mills were developed in Europe in the12th century (Holland and Britain), and they were widely used for corn grindingand water pumping. With the development of the internal combustion engines andre®nement of the steam engines, and because of the availability of the inexpensivepetrol, a technical advancement ensued which suppressed wind energy technologyand inhibited its further development. However, during the last decade interesthas been refocused on natural renewable energy sources due to the increasingprices and foreseeable exhaustion of presently used commercial energy sources.Particularly in areas of low population density where the implementation of acentral power system would be uneconomical, the decentralized utilization of windenergy can provide a substantial contribution to development [1].

Many designs of wind machines have been suggested and built. The horizontalaxis type is the only one which has been built in large numbers. The vertical axis

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machines have generally been considered ine�cient, but a recent design (1975) hasreceived considerable attention (the variable geometry vertical axis wind machine)[2].

To distinguish between di�erent designs of wind machines the tip speed ratio(m) can be used, which is de®ned as the rates of blade speed to the undisturbedwind speed. If the application is for pumping water, by using a reciprocal pumpdirectly connected to the wind machine, a high starting torque and low rationalspeed are required. For this reason a small value would be suggested and tosatisfy this the wind rotor has a large number of blades. If the wind machine isfor generating electricity then a low starting torque and high speed are necessary.Therefore a high value should be selected (say 8±10); such a wind machine willhave 2 or 3 blades (sometimes one blade) [3].

The use of the wind machine is divided into two; one is the use of small-scalewind machines for water pumping or electricity generation, and the other is theuse of large-scale wind machines for generating electricity (big wind machines orwind farms) [4]. However, the wind machine can be useful to both developed ordeveloping countries. It provides power which can be used for pumping water,electricity generation or any other task.

The amount of power extracted from the wind depends generally on the designof the wind rotor. Di�erent theories were used to achieve a good design [3].

2. Wind energy potential in Sudan

Before making an estimate of wind energy potential of Sudan, it is necessary tosummarize the most important feature of the power available for the wind.

The theoretical maximum amount of energy that could be extracted was ®rstcalculated by Betz [21] for a horizontal axis wind machine and comes out to be59.3% [5] of the total energy from the wind. This is known as Betz e�ciency.Applying Betz's e�ciency factor to the derived formula of the power available inthe wind [5], the theoretical maximum power that can be extracted from the windis:

P � �16=27� � �1=2� � @a� A� V 3 �1�where @a is air density (kgmÿ3), the density of the air depends on the temperatureand on the altitude above seal level. For Sudan it is 1.15 kgmÿ3 [6]; A is the totalfrontal area of the wind machine rotor (m2) and V is undisturbed wind speed(msÿ1).

In practice, the wind machine power will be lost because of the aerodynamiclosses of the rotor.

The e�ect of height in relation to the site of a small wind machine can be verysigni®cant. Within the atmospheric boundary layer the velocity pro®le [7] indicatesthe following form:

A.M. Omer / Renewable Energy 19 (2000) 399±411400

�V1=V2� � �h1=h2�n �2�where V2 is the known wind speed measured at height h2; h1 is the height at whichthe wind speed is to be estimated; n is the exponent related to the surfaceroughness and determined from measurements at the di�erent heights. Values of(1/7) to (1/6) are commonly used for the exponent n.

The wind data given by Meteorological Department O�ce is usually quoted atstandard height of 10 m.

2.1. Sudan climate

The climate of Sudan is temperate [14]. There is a season of heavy rain frommid June to the end of September. During the rest of the year there is no rain.The season through the year may be divided as follows: December±March is theperiod of the dry season or winter season; April±June is the advancing monsoonperiod; and October±November is the retiring monsoon period.

2.2. The source of data measurements

Data is obtained from the Sudan Meteorological Department O�ce inKhartoum. Measurements with cup anemometer coupled to chart recorder forselected stations. The annual average wind speeds were taken from these stations.Based on this data an isovent map was prepared showing the distribution of windall over the country (Fig. 1). The annual average wind speed exceeds 4 msÿ1 alongthe main Nile from Khartoum down to Halfa and south of Khartoum coveringthe Gezira area and exceeds 5 msÿ1 at the costal area along the Red Sea.

2.3. Statistical distribution for wind data

In recent years e�orts have been made to de®ne an adequate statistical modelfor describing the wind velocity duration curves to enable an approximateprediction of wind machine performance.

Most attention has been focused on the Weibull function [7], which gives agood ®t to the experimental wind data. There are some other statisticaldistributions which can be used to describe the wind speed frequency curves e.g.the normal distribution function and Reyleih function.

The general form of Weibull function is:

f�X � � eÿ�Xÿ Xu=Xo�k �3�where X, Xo, Xu, K are constants.

For Xu = 0

f�X � � eÿ�X=Xo�k �4�To express wind velocity distribution curves in function the above equation maybe written as:

A.M. Omer / Renewable Energy 19 (2000) 399±411 401

Fig. 1. Annual average wind speeds of Sudan (msÿ1).


f�V � � eÿ�V=C �k �5�where V is the mean average wind speed; C is a constant related to average(mean) wind speed; and K is the Weibull exponent, related to a certain site.

2.4. Wind power calculation

Annual mean wind speeds were derived from the original monthly mean windspeeds. Annual mean wind powers were derived from monthly mean wind speedswhich were calculated according to the following procedure: given a monthlymean wind speed, V, the maximum extractable monthly mean wind power perunit cross sectional area, P, is given by:

P � 0:3409V 3 �6�where V is in msÿ1; and P is in Wmÿ2.

The constant 0.3409 takes Betz limit into account and is derived from thefactors given by Golding [15]. This analysis procedure is similar to that reportedby Lysen [16].

3. Possible options for the use of wind energy in Sudan

3.1. Pumping water

Water is a general need in rural areas of developing countries, and, thereforemeans of water lifting are required. In a country such as Sudan, grid electricity isgenerally not available in most rural areas. Diesel fuel is expensive, and the supplycan be uncertain, especially in the rainy season. Also there are no natural oilreserves, and oil must be imported (more than 70% of the income is for importingoil) [4]. For these reasons it is important to consider the potential of alternativerenewable energy sources to provide the power source to operate the pumps.Wind power has been used in the past for water pumping, corn grinding, andprovision for power for small industries.

3.2. Water needs in rural areas

The people of Sudan, like other Africans, have the problem of a scattered ruralpopulation living in small communities (about 300±5000 in a village) [5]. Duringthe dry season, streams and shallow wells are widely scattered, and women walklong distances (about 4 km) to collect water [8]. Bullocks and camels were used tolift water by means of rope and leather buckets. Usually one or two wells wereprovided for the requirements of the entire village. But these streams and shallowwells dry out before the end of the dry season, and alternatives for providingwater such as electric pumps, diesel pumps, and wind pumps are required.


3.3. Agriculture

The available area is estimated at 84 million hectares [9] of which 32 million arebeing used, 7 million for crops, and 25 million as pasture land. The present exportearnings of the country are agricultural, and come primarily from: cotton (60%);oil seeds (20%); and gum (10%).

The high technology input in agriculture is re¯ected by many large projects, forinstance, the Gezira scheme, Rahad scheme, Kenana Sugar scheme, the GadarifMechanized Cultivation project, Jebel Marra project in Darfur, the Khashim ElGirba project, and Jonglei project.

3.4. Cattle watering

Cattle watering can be combined with irrigation. This may result in better grass,and a better quality of livestock. The average ®gure of water needs for cattle [8]are: sheep and goatsÐ4 gallons dayÿ1; cows and donkeysÐ7 gallons dayÿ1; andcamelsÐ11 gallons dayÿ1.

In [4], livestock mainly in the remote western part of Sudan totalled 14.2million cattle, 13.4 million sheep, 20.5 million goats, and 2.7 million camels.

4. Present means of water supply

4.1. Electric pumps

These pumps are satisfactory but can only be used in limited areas whereelectricity is available. The Public Electricity and Water Corporation (PEWC),part of Ministry of Energy and Mining (MEM), is the national enterpriseresponsible for the generation of the bulk distribution of electric and water inSudan. The present capacity of the national grid is about 400 mega watts [10].There is no country-wide interconnected grid system.

4.2. Diesel pump units

Large and small diesel engines are being used but these su�er from a number ofproblems, e.g.:

. Unavailability of diesel fuel in most areas.

. Shortage of skilled mechanics for maintenance, and repair.

. Long distance to nearest workshops.

. Shortage of spare parts.

Because of the above mentioned problems, the use of wind pump systems inplaces where there is no electricity is preferable to using diesel pumps, especially inthe case of pumping water for drinking purposes.


4.3. Wind pumps

Work on this type of pump has been proceeding in Sudan since the 1950 s forthe purposes of pumping water, for drinking, and irrigation in remote desertareasÐGezira region, the Red Sea hills along the main Nile north or Khartoumdown to Wadi Halfa. These wind machines are of the Southern Cross types, andsu�ered from several problems [5]. None of them is now working. Ten windpumps type CWD (Holland) were installed around the Khartoum area (®ve ofthem were working until February 1991) [11,17±19].

4.4. Generation of electricity

Wind power shown in Fig. 1 indicates that Sudan possesses favourable windsparticularly in the northern parts. Wind energy is more appropriate than some ofthe other new energy sources if utilized in tasks like water pumping. With a tap ina village, people need to waste less time and energy carrying water, and cantherefore, use their time for other activities e.g. education [8].

Consideration should also be given to the potential of wind power for usesother than pumping e.g. electric power. A program of wind power for generatingelectricity as well as for pumping water appears to be attractive for ruraldevelopment, e.g. lights, radios, televisions. Wind electric generators can beutilized to meet the power requirements of isolated settlements. For a typical smallvillage of 800 people presently an installed capacity of about 35 kVA might besu�cient for domestic use [10]. The installed capacity may have to be raised withthe growth in agro-industrial activities of the village. Wind energy is found tomatch well with the demand pattern of the loads, high load during the day forillumination.

An important problem with the wind pump system is matching the power of therotor with that of the pump. In general the wind pump system consists of thefollowing items: the wind rotor; transmission; the pump.

The overall e�ciency of the system is given by the multiplication of the rotore�ciency, transmission e�ciency, and the pump e�ciency.

Overall � zRotor � zTrans� zPump

where zOverall is the overall e�ciency; zRotor is the rotor e�ciency; zTrans is thetransmission e�ciency; and zPump is the pump e�ciency.

For wind pumps, though e�ciency is important, a more suitable de®nition isthe number of gallons of water pumped per day per dollar.

5. Economics of the wind pump system

The e�ciency of the wind pump system and its ability to compete with otherpower supplies e.g. diesel pump in providing water to meet needs of a rural area,


will depend to some extent upon local conditions. Therefore, it is important to uselocal data so that a decision can be made on the basis of the cost per unit volumeof water pumped.

The most common formula used is:

CT � �A� F� P�M �=V �7�where CT is the total cost-based on initial capital cost, life, and discount rate; F isthe total fuel consumption; P is the fuel cost per liter; M is the maintenance cost;and V is the volume of water pumped.

Other sets like electric powered pumps are preferable where electricity isavailable, but in the large majority of remote areas where water pumping is ofinterest, diesel engines are the only sources of pumping. Therefore, it is sensible tocompare a diesel pump unit with a wind pump system.

5.1. The annual cost

The annual cost is the function of the capital cost which is calculated by theinterest rate and the life of the system [12].

A � �C� I� �I� 1�T �=�I� 1�Tÿ 1 �8�where A is the annual cost; C is the capital cost; I is the interest rate or discountrate; and T is the lifetime.

5.2. Maintenance

The lifetime of a wind pump or diesel pump set will be a�ected by the level ofmaintenanceÐand provision of labour, spare parts, and lubrication should bemade.

5.3. Fuel price

The steadily increasing cost of fuel is a recognised problem all over the world,and has to a large extent motivated the interest in other devices such as windmachines.

5.4. Typical ®gures

5.4.1. Wind pump systemThe cost of wind pumping systems depends mainly on the materials used in the

design. If the unit is designed by the local available skills and materials, andrelatively simple design, then the cost will be much lower than the imported one:

Capital cost (C ) =D.S 6000 f 5 mLifetime (T ) =20 years


Operation cost (Comr) =25% of the capital costPump e�ciency ( f pump) =60%Interest e�ciency (I ) =10%

5.4.2. Diesel pump set (same capacity)

Capital cost (C ) =D.S 2400Lifetime (T ) =6 yearsMaintenance cost (Cm) =10% of the capital cost [13]Interest rate (I ) =10%Fuel cost per liter for 1st year =D.S 0.8In¯ation rate of fuel cost =15%.General in¯ation rate =10%.

A comparison between the costs of diesel and wind pump systems is shown inTables 1 and 2.

The energy required for lifting water can be calculated from:

E � �G�Q�H �=Mp �9�where E is energy (joules); G is speci®c gravity (msÿ2); Q is pump output (l); H ispumping head (m); and Mp is the performance e�ciency of the diesel pump set.

Table 1

Cost of diesel pump set (in Sudanese dinars)

Year Annual cost Maintenance cost Fuel cost Total cost

1986 551.06 240.00 362.48 1153.54

1987 551.06 264.00 416.85 1231.91

1988 551.06 290.40 478.38 1319.84

1989 551.06 319.44 551.28 1421.78

1990 551.06 351.38 633.98 1536.42

1991 551.06 386.32 729.07 1666.65

1992 918.80 400.20 838.43 2157.43

1993 918.80 440.22 964.20 2323.22

1994 918.80 484.24 1108.82 2311.86

1995 918.80 532.67 1275.15 2726.62

1996 918.80 585.93 1466.42 2971.15

1997 918.80 644.53 1686.38 3249.71

1998 1775.44 773.25 1939.39 4488.03

1999 1775.44 850.75 2230.23 4856.42

2000 1775.44 935.63 2564.77 5275.84


The e�ciency is derived from the water discharge by the formula:

f � �F� G�H �=�0:5� @A� V 3 � A� �10�where F is the mass ¯ow of water (Kg sÿ1); G is the speci®c gravity (G = 9.81msÿ2); H is the pumping head (m); @A is the density of air (Kg mÿ3); V is thewind speed (msÿ1); and A is the rotor area (m2).

5.5. Result of the comparison

The total annual cost of the diesel pump by the end of its lifetime (6 years) isnearly twice that expected of the wind pump system. The total annual cost by theend of the third diesel unit is more than ®ve times that expected from the windpump system. This comparison indicates that the necessary fuel and maintenanceneeded to run the diesel pump unit long-term are the main factors which governthe overall cost, and not the capital cost of the diesel pump itself. Therefore, inthe case of Sudan where the fuel is expensive, the supply is uncertain, theinfrastructure is poor, and areas are remote, the use of wind machines is the idealalternative.

6. Conclusion

1. Sudan is rich in wind; about 50% of Sudan's area is suitable for generatingelectricity (annual average wind speed more than 5 msÿ1), and 75% of Sudan'sarea is suitable for pumping water (annual average wind speed 3±5 msÿ1).

Table 2

Cost of wind pump system (in Sudanese dinars)

Year Annual cost Maintenance cost Fuel cost Total cost

1986 704.76 120.00 ± 824.76

1987 704.76 132.00 ± 836.76

1988 704.76 145.20 ± 849.96

1989 704.76 159.72 ± 464.48

1990 704.76 175.69 ± 880.45

1991 704.76 193.26 ± 898.02

1992 704.76 212.59 ± 917.35

1993 704.76 233.85 ± 938.61

1994 704.76 257.23 ± 961.99

1995 704.76 282.95 ± 987.71

1996 704.76 311.25 ± 1016.01

1997 704.76 342.37 ± 1047.13

1998 704.76 376.61 ± 1081.37

1999 704.76 414.27 ± 1119.03

2000 704.76 455.70 ± 1160.46


2. In areas where there is wind energy potential but no connection to the electricgrid, the challenge is simplicity of design, and higher e�ciency.

3. The research and development in the ®eld of wind machines should be directedtowards utilizing local skills and local available materials.

4. Local production of wind machines should be encouraged in both public andprivate organizations.

Appendix A

Annual average wind speeds, annual wind powers and number of years ofobservations for the 70 stations in Sudan at 10 m AGL [20]

Item Name ofstation

Altitude(m)

Annualmeanwindspeeds(mph)

Annualmeanwindspeeds(msÿ1)

Annualmeanwindpower(Wmÿ2)

Numberof years ofobservation

1. Halaib 52.00 11.33 5.07 49.43 10.002. Wadi Halfa 190.00 10.33 4.622 37.48 4.003. Station 6 470.00 10.17 4.548 35.69 10.004. Port Sudan 5.00 11.25 5.032 48.36 10.005. Abu Hamed 315.00 10.67 4.771 41.22 6.006. Dongola 225.00 10.50 4.697 39.32 10.007. Gebeit 795.00 9.00 4.026 24.76 10.008. Karima 250.00 10.42 4.659 38.39 10.009. Toker 20.00 9.08 4.063 25.45 9.0010. Aqiq N.A. 9.25 4.138 26.88 10.0011. Atbara 345.00 9.42 4.212 28.36 10.0012. Derudeb 510.00 9.00 4.026 24.76 10.0013. Hudeiba 350.00 9.00 4.026 24.76 10.0014. Shendi 360.00 9.00 4.026 24.76 9.0015. Aroma 430.00 N.A. N.A. N.A. N.A.16. Wadi Seidna 385.00 9.90 4.436 33.12 10.0017. Shambat 380.00 N.A. N.A. N.A. N.A.18. Khartoum 380.00 10.00 4.473 33.96 10.0019. Kassal 500.00 9.00 4.026 24.76 10.0020. Jebel Aulia 380.00 10.08 4.510 34.82 10.0021. Halfa El Gedida 450.00 9.17 4.100 26.16 10.0022. Abu Quta 390.00 9.83 4.399 32.29 9.0023. El Showak 510.00 9.17 4.100 26.16 10.0024. Wad Madani 405.00 10.00 4.473 33.96 10.0025. Medina Block 405.00 10.25 4.585 36.58 7.00


26. Kutum 1160.00 7.83 3.504 16.33 10.0027. El Gadarif 600.00 8.92 3.988 24.08 10.0028. Ed Dueim 380.00 9.00 4.026 24.76 10.0029. Wad El Huri N.A. N.A. N.A. N.A. N.A.30. El Fasher 733.00 7.67 3.429 15.31 10.0031. Sennar 420.00 7.00 3.131 11.65 10.0032. Doka N.A. 6.83 3.057 10.84 10.0033. El Geneina 805.00 6.83 3.057 10.84 10.0034. Kosti 380.00 9.00 4.026 24.76 10.0035. El Obeid 570.00 7.58 3.392 14.81 10.0036. Dankog 965.00 7.00 3.131 11.65 6.0037. Umm Benein 435.00 7.00 3.131 11.65 10.0038. Nierteti N.A. 7.00 3.131 11.65 10.0039. Zalingei 900.00 6.00 2.684 7.34 10.0040. Murundu N.A. 6.00 2.684 7.34 10.0041. Abu Na,ama 445.00 N.A. N.A. N.A. N.A.42. El Nahud 565.00 8.83 3.951 23.41 10.0043. Derisa N.A. 6.00 2.684 7.34 6.0044. Kas N.A. 6.00 2.684 7.34 10.0045. Garsila N.A. 6.00 2.684 7.34 10.0046. Nyala 655.00 5.75 2.572 6.46 10.0047. Mukgur N.A. 6.08 2.721 7.65 10.0048. Rashed 885.00 6.42 2.870 8.97 10.0049. Ed Damazin 470.00 10.00 4.473 33.96 10.0050. Er Renk 380.00 6.25 2.796 8.29 10.0051. Ghazala Gawazat 480.00 6.75 3.019 10.45 10.0052. Babanusa 543.00 6.17 2.758 7.96 6.0053. Kadugli 501.00 5.92 2.647 7.03 10.0054. Kurmuk 690.00 6.25 2.796 8.29 8.0055. Malakal 387.00 6.25 2.796 8.29 10.0056. Bentiu 390.00 6.08 2.721 7.65 10.0057. Aweil 415.00 6.00 2.684 7.34 10.0058. Nasir 400.00 8.00 3.578 17.39 10.0059. Raga 545.00 6.00 2.684 7.34 10.0060. Gambeila 450.00 6.00 2.684 7.34 17.0061. Akobo 400.00 N.A. N.A. N.A. N.A.62. Wau 435.00 3.83 1.715 1.91 10.0063. Tonj 430.00 5.67 2.535 6.18 10.0064. Rumbek 420.00 6.00 2.684 7.34 10.0065. Bor 420.00 6.00 2.684 7.34 10.0066. Maridi 750.00 6.00 2.684 7.34 10.0067. Juba 460.00 3.42 1.528 1.35 10.0068. Yambio 650.00 6.00 2.684 7.34 8.0069. Torit 625.00 6.42 2.870 8.97 7.0070. Yei 830.00 6.25 2.796 8.29 10.00


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wind energy in sudan

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