Journal of Energy
Volume 2016 (2016), Article ID 5082678, 14 pages
http://dx.doi.org/10.1155/2016/5082678

Research Article

Modelling of Sudan’s Energy Supply, Transformation, and Demand

Ali A. Rabah, Hassan B. Nimer, Kamal R. Doud, and Quosay A. Ahmed

Energy Research Centre, Faculty of Engineering, University of Khartoum, P.O. Box 321, Khartoum, Sudan

Received 27 March 2016; Accepted 12 June 2016

Academic Editor: Ciro Aprea

Copyright © 2016 Ali A. Rabah et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The study aimed to develop energy flow diagram (Sankey diagram) of Sudan for the base year 2014. The developed Sankey diagram is the first of its kind in Sudan. The available energy balance for the base year 2012 is a simple line draw and did not count the energy supply by private and mixed sectors such as sugar and oil industries and marine and civil aviation. The private and mixed sectors account for about 7% of the national grid electric power. Four energy modules are developed: resources, transformation, demand, and export and import modules. The data are obtained from relevant Sudanese ministries and directorates and Sudan Central Bank. “e!Sankey 4 pro” software is used to develop the Sankey diagram. The main primary types of energy in Sudan are oil, hydro, biomass, and renewable energy. Sudan has a surplus of gasoline, petroleum coke, and biomass and deficit in electric power, gasoil, jet oil, and LPG. The surplus of gasoline is exported; however, the petroleum coke is kept as reserve. The deficit is covered by import. The overall useful energy is 76% and the loss is 24%. The useful energy is distributed among residential (38%), transportation (33%), industry (12%), services (16%), and agriculture (1%) sectors.

1. Introduction

Figure 1 shows the energy Sankey diagram of USA as an example. The Sankey diagram is an important tool to visualize the energy balance for a system or a country or a region. The Sankey diagram depicts the energy flows from supply to demand taking into account transformation. Sankey diagram was developed over 100 years ago by the Irish engineer Riall Sankey to analyze the thermal efficiency of steam engines. Since then, it has been widely used. Besides visualization, Sankey diagram is a vital tool to identify sources of inefficiency and potential saving in the energy system.

Figure 1: Sankey diagram of USA. Source: [5]. Data is based on DOE/EIA-0035(2015-03), March 2014. If this information or a reproduction of it is used, credit must be given to the Lawrence Livermore National Laboratory and the Department of Energy, under whose auspices the work was performed. Distributed electricity represents only retail electricity sales and does not include self-generation. EIA reports consumption of renewable resources (i.e., hydro, wind, geothermal, and solar) for electricity in BTU-equivalent values by assuming a typical fossil fuel plant “heat rate.” The efficiency of electricity production is calculated as the total retail electricity delivered divided by the primary energy input into electricity generation. End-use efficiency is estimated as 65% for the residential and commercial sectors, 80% for industrial sector, and 21% for the transportation sector. Totals may not equal sum of components due to independent rounding. LLNL-MI-410527.

For the preparation of Sankey diagram for a country, four modules are needed. The first is the demand module, which contains the details of the demand for end-use energy (both primary and secondary fuel) for the residential, services, industrial, agricultural, and transportation sectors [1]. The demand for each sector from primary and secondary energy is defined. For example, the demand of residential sector is electricity, oil products, and biomass for lighting, cooking, and HVAC. The second module is the transformation module. It consists of all energy transformation processes, such as electricity generation, oil refining, and charcoal conversion. In these modules, the energy is divided into useful energy and lost energy. The useful energy is then distributed to demand sectors. The third module deals with the available resources. The main energy sources are coal, crude oil, natural gas, hydroelectricity, biomass, nuclear energy, and renewable energy such as solar, wind, and geothermal energy. The fourth module deals with energy import and export. There exist a number of models used to develop the energy supply and demand modules. Prominent energy models include MARKAL, LEAP, ENERGY 2020, MAPLE C, NEMS, and MAED. Details on these models and their implementation can be found in a number of published studies [2–4].

This study is aimed at providing Sankey diagram for Sudan for base year 2014. What is available now in Sudan is energy balance for 2012 [7] (cf. Table 1). However, the available energy balance data did count only the energy produced by public sectors. The energy produced by private and mixed sectors is not counted. These include the electric energy produced by oil refineries and sugar factories which constitute a significant share of Sudan energy mix. It also did not count for bagasse and bioethanol. Likewise, it does not count the petroleum associated gas (AG) and renewable energy, in particular photovoltaic energy. The most difficult part of this work is the data quality check. There exist a number of reports on Sudan’s energy status. These reports include conflicting data, double counts, and inconsistent units. The authors have extensively verified the data from their original sources. Data on renewable energy status in Sudan is scarce as well. Extensive search including field survey was made to collect data on this area. Data on the demand side is not well documented as well and hence enormous effort was exerted to collect the data from their original sources. The main contribution of this work is to make proper documentation of Sudan energy data on both supply and demand side. The other contribution is to produce Sudan’s energy flow diagram for the first time.

Table 1: Sudan energy balance 2012 [6].

Demand sectors
Power
Oil
Biomass
Total

ktoe
%
ktoe
%
ktoe
%
ktoe
%

Residential
401
54.3
298
7.9
3088
62.2
3911
40.0

Transportation

2994
79.2

3073
31.4

Services
181
24.5
43
1.1
1303
26.2
1579
16.1

Industry
120
16.3
400
10.6
575
11.6
1133
11.6

Agriculture
36
4.9
43
1.1

85
0.9

Total
738
100
3778
100
4966
100
9781
100

Share of energy supply
7.5

38.6

50.8

100.0

2. Methodology

2.1. Data Collection

The energy supply, demand, and transformation data are obtained from the following reports:

(1)Annual report of Sudan Central Bank.(2)Annual reports from the Ministry of Oil and Gas [6, 7].(3)Annual report from the Directorate of Agriculture and Forestry [8].(4)Annual report from Sudanese thermal power generation corporation [9].

The collected data is further subjected to quality check for completeness, avoiding double counting and uncertainty assessment.

2.1.1. Completeness

The available reports on electric power generation in Sudan account only for power produced by the public sector. The power generation of private and mixed sectors is not counted by the published reports. For example, the power generation of petroleum refineries and sugar factory, as mixed sectors, is not accounted for in Sudan energy balance for 2012 [6]. This data gap is filled using field survey. There also exists no inventory of standby generators countrywide.

2.1.2. Avoiding Double Counting

Some data duplicate is found in the available literature. For example, ORC produced Naphtha which is used as feedstock to KRC to produce gasoline and other products; hence, it is double counted in Sudan energy balance for 2012 and the reports of Central Bank and the Ministry of Oil and Gas. The reports of ORC and KRC refineries are considered rather than Sudan Central Bank’s reports.

2.1.3. Uncertainty Assessment

There is a lack of proper documentation of bagasse, animal waste, and agriculture waste. However, there are data of production of sugar, cereals, crops, cotton, and count of animals. The waste is estimated from production data. For example, bagasse is estimated from sugar production. The sugar recovery is taken as 9% of the crushed sugar cane and the bagasse is taken as 39.5% of the crushed sugar cane. The estimated bagasse is cross-checked by field survey of the sugar plants and it is found that the assumptions are accurate within 5% for all sugar factories. Similarly, the animal dung is estimated from animal count. The dung production is taken as 10.95, 1.83, 1.83, and 5.48 tons/animal/head for cows, sheep, goats, and camels, respectively [10]. The dung that is potential for energy use is taken as 10%. The agricultural waste is estimated using harvest index (HI) [11]. The harvest index for cereals, oil crops, and cotton is taken as 0.4, 0.52, and 0.16, respectively. The residue is calculated as amount of products multiplied by . The other challenge is that the portion of agriculture residue used as fuel is unknown as the residue is shared by many applications such as animal feed, building material, and pulp and paper industry. This is on the one hand. On the other hand, the residue is mostly left in the farm as a fertilizer or burned during land preparation. Under this circumstance, the ratio of agriculture waste accepted by Sudan energy balance 2012 was considered.

2.2. Energy Modelling

Although there exist a number of energy modelling software programs such Long Range Energy Alternative Planning Systems (LEAP), in this work, a simple Excel worksheet is used for energy modelling. The energy framework for development of Sankey diagram consists of four modules [1].

(1)Energy resource module: this module takes account of all the primary fuel such as petroleum, coal, natural gas, uranium, biomass, and renewable energy (cf. Figure 2).(2)Transformation module: the transformation module handles data on the conversion of primary fuel into secondary fuel such as power generation and conversion of crude oil in the refinery to secondary fuels.(3)Demand module: the demand module contains the details regarding the end-use energy demand for both primary and secondary fuel. The consumption sectors include agriculture, industry, services, residential, and transportation sectors (cf. Figure 3).(4)Import and export module: this module deals with energy import and export. The energy import and export are normally in the end-use form such as electricity and secondary fuel oil.

Figure 2: Primary energy resources.

Figure 3: Energy demand by sector.

The data generated by the four modules for the base year 2014 is used to develop the energy Sankey diagram for Sudan. The software “e!Sankey 4 pro” was used. e!Sankey is widely used software for the development of Sankey diagrams for a country or a region.

3. Results and Discussion

The main sources of primary energy in Sudan are oil, hydroelectricity, biomass, and renewable energy. Coal, natural gas, and uranium are nonexistent in Sudan. The main transformation and conversion processes are electric power generation, oil refinery, and wood-to-charcoal conversion.

3.1. Electric Energy Supply and Demand

3.1.1. Hydroelectric Power

Table 2 shows the hydroelectric power generation plants in Sudan. The installed capacity, nominal capacity (MW), expected GWh, and year of establishment are given. The planned and under-construction hydroelectric power plants are also given. The total installed and potential hydroelectric power in Sudan is 4176 MW; the installed capacity is 1585 MW (38%).

Table 2: Hydroelectric power plant (operational, under construction, and planned).

Number
Name
Year
Capacity

Installed
Nominal
Production

MW
MW
GWh

Operational plant

1
Merowe Dam
2009
1250
1240
5580

2
Roseires Dam
1966
280
270
1050

5
Sennar Dam
1962
15
12
49

3
Jebel Aulia Dam
2003
30
19
55

4
Khasm El Girba Dam
1964
10
10
15

Subtotal A

1585
1551
6749

Under-construction plant

5
Upper Atbra and Sitat
2015
323
320
834

6
Sennar upgrading
2015
11
13.7
66

Planned plant

7
Shereik

420

2103

8
Kajbar

360

1799

9
Sabaloka

205

866

10
Dal Low

648

2185

11
Dagash

312

1349

12
Mograt

312

1214

Subtotal B

2257

9515

Total (A + B)

384

16264

Available power%

38

39

3.1.2. Thermal Electric Power Generation

Table 3 shows the installed, under-construction, and planned thermal power plants. The installed power is 1400 MW and the under-construction and planned power are 405 MW and 600 MW, respectively. The installed thermal power generation is about 46% of the total installed public power generation (hydro + thermal). One important point in thermal generation is its diversity in prime movers and fuels sources. The prime movers in thermal generation include steam turbine (ST), gas turbine (GT), combined cycle of gas turbine (CCGT), and internal combustion (IC) engines. IC engines are used in remote areas that are not covered by the national grid. The fuels used include gasoil (GO), diesel (blend of gasoil and gasoline), heavy fuel oil (HFO) also called furnace and number 6 fuel oil, heavy coker gasoil (HCGO), crude oil, petroleum coke, and liquefied petroleum gas (LPG). Diversity is a merit; however, the use of gasoil in steam turbine is the weak point of thermal generation sector in Sudan. Gasoil is competitive oil as it is used by transportation and agriculture sectors, in addition to its high cost relative to heavy fuel oil and petroleum coke. But it seems that the use of gasoil in ST and GT generation is an issue of “energy security” rather than economic factors; otherwise, the use of gasoil is not a common practice in ST and GT power generation. Table 4 shows the electric power generation in Sudan in the period from 2002 to 2014. The hydroelectric power share increased from 42% in 2002 to more than 75% in 2014. This is mainly due to the inception of Merowe Dam in 2009. The imported electric power from Ethiopia increased to 469 GWh (4%) in 2014.

Table 3: Thermal power plant.

Number
Thermal power plant
Year
Prime mover
Fuel
Capacity

Installed
Nominal
Available

MW
MW
GWh

Operational thermal power plants

1
Shahid Mahmoud Sharief 1 + 2 ST
1984
ST
HCGO
60
28
212

2
Shahid Mahmoud Sharief 3 + 4 ST
1994
ST
HFO + HCGO
120
110
840

3
Shahid Mahmoud Sharief 5 + 6 ST
2011
ST
HFO
200
190
1408

4
Shahid Mahmoud Sharief 1 + 2 GT
1992
GT
GO
50
34
265

5
Garri1: CCGT
2003
CCGT
GO + LPG
180
170
1346

6
Garri2: CCGT
2003
CCGT
GO + LPG
180
170
1346

7
Garri4: ST
2010
ST
Pet coke
110
100
675

8
Kusti
2013
ST
Crude oil
500
470
3590

9
Diesel generation

IC
Diesel

Available thermal power A
1400
1272
9682

Under-construction and planned thermal power plant

9
Al Fula
2016
ST
AG/NG
405
381
2908

10
Red Sea
2016
ST
Coal
600
534
4079

Planned thermal power cycle B
1005
915
6987

Total (A + B)
2405
2187
16669

ST: steam turbine.

HCGO: heavy coker gas oil (heavy gasoil).

HFO: heavy fuel oil (equivalent to number 6 fuel oil).

GT: gas turbine.

GO: gasoil.

CCGT: combined cycle gas turbine.

AG: petroleum associated gas; NA: natural gas.

Table 4: Electric power profile (GWh).

Year
Hydro
Steam turbine
Gas turbine
Diesel
Combined
Import
Production
Hydro%
Import%

2014
8914
1400
0
202
864
469
11848
75
4

2013
8317
1205
0
183
582
320
10607
78
3

2012
6619
1484
5
182
1145
74
9509
70
1

2011
6452
1631
1
161
210
0
8455
76
0

2010
6199
473
14
192
620
0
7499
83
0

2009
3236
887
94
309
1847
0
6372
51
0

2008
1466
1106
152
442
2340
0
5506
27
0

2007
1457
1057
371
140
1997
0
5021
29
0

2006
1368
1108
501
353
1192
0
4521
30
0

2005
1239
1047
319
385
1135
0
4125
30
0

2004
1107
1037
1256
349
0
0
3749
30
0

2003
1163
1168
210
328
0
0
3354
35
0

2002
1287
116
381
310
0
0
3094
42
0

3.2. Private and Mixed Sectors Power Generation

There exist a number of private and mixed industries that produce their own power consumption. The major industries are as follows:

(1)Oil refineries.(2)Oil fields production facilities.(3)Sugar industry.(4)Cement industry.(5)Sea port and civil aviation.(6)Others.

The power production by these sectors is not accounted for in Sudan energy balance 2012.

3.2.1. Oil Refinery

Table 5 shows the installed power of oil refinery and oil fields. The total installed power by oil industry is about 38 MW. A large portion of KRC refinery power generation is from waste heat and low grade fuel such as vent gas and oil slope (slurry). The electric power produced by oil industry is about 1% of the national grid electric power (the hydro and thermal power generation).

Table 5: Oil industry thermal power generation plant.

Number
Oil industry power plant
Year
Prime mover
Fuel
kW

1
KRC (2 12 MW)
1999
ST
FG + bunker
24000

2
KRC (2 12 MW)
2006
GT
FG + bunker
12000

3
ORC 50 Hz
1999
IC
Diesel
250

4
ORC 60 Hz
1999
IC
Diesel
500

5
Heglig oil field 1
na
IC
Diesel
25.5

6
Heglig oil field 2
na
IC
Diesel
11.5

7
Neem oil field
na
IC
Diesel
11.2

8
Canar oil field
na
IC
Diesel
0.8

9
Diffra oil field
na
IC
Diesel
3.9

10
Other (mainly the power for the oil pipeline)
na
IC
Diesel
1000

Total
37803

FG: fuel gas mainly CH₄.

Since 2014, it has become standby generator as the refinery is connected to national grid of 50 Hz.

3.2.2. Sugar Industry

Sudan ranks high in sugar production among African countries. Sugar industry produces its own power consumption from bagasse, a byproduct of sugar cane. The installed sugar capacity is about 1.0 Mt of sugar/year. Table 6 shows the installed capacity of electric power plants in sugar factory. The installed capacity is about 190 MW, which is about 6% of the national grid electric power. However, the available capacity is 96 MW as the White Nile sugar factory is working at low capacity. Bagasse is sufficient to produce electric power for 210 days/year including cane crushing season of 180 days/year. Besides electric power, the factories also produce their own process heat for sugar cane mills, heating, and evaporation and crystallization process. The potential for high power generation in sugar plant is feasible. If cogeneration is installed, the process heat load will be reduced as the sugar mills and shredders will be electric driven rather than steam driven which in turn saves steam for power generation.

Table 6: Sugar industry power plant [12].

Number
Factory

Sugar capacity
Bagasse
Power plant

Year
Installed
Current

kton
kton
kton
ktoe
MW
D/Y
GWh

1
Kenana
1981
300
307.6
1350
580
20
210
326

2
Sennar
1976
70
73.1
321
138
6.5
210
33

3
Assalaya
1980
70
65.4
287
123
6.5
210
33

4
Guneid
1962
70
73.1
321
138
6.0
210
30

5
New Halfa
1966
70
59.5
261
112
6.0
210
30

6
White Nile
2012
450
73.4
322
138
(104) 6.0
210
33

Total

980
652.1
2862
1230
(190) 96

485

Bagasse sugar ratio: 4.4.

The design capacity of power plant is 104 MW.

Personnel contact.

3.2.3. Standby Power Generation

All public utility services such as hospitals, universities, municipals, city water, and commercial buildings have their own standby IC electric power generators. However, there is lack of inventory data on standby generators countrywide. In this work, a field survey was made and about 100 standby IC generators with name plate capacity of about 1.2 kW with diesel as fuel source have been established. However, due to lack of information on the operation hours of the standby power generation, it is excluded in the present study. Besides services, air aviation and sea port also rely heavily on off-grid generation.

3.2.4. Photovoltaic

Table 7 shows the solar radiation in a number of Sudanese cities. The average sunshine duration is about 9 h. Most of the solar installation in Sudan is photovoltaic cell. The total installed capacity is about 2 MW. About 50% of the installed capacity is by telecommunication industry. All remote off-grid antennas and satellites are solar driven.

Table 7: Solar radiation and sunshine duration in Sudan [13].

Station
Mean temperature
Sunshine duration
Solar radiation

C
h
MJ/m²/day

Port Sudan
28.4
9.0
20.87

Shambat
29.7
9.9
22.82

Wadi Medani
28.4
9.8
22.84

ElFashir
25.8
9.6
22.80

Abu Na’ama
28.8
8.8
21.90

Ghazala Gawazat
27.2
9.3
21.72

Dongala
27.2
10.5
24.06

Toker
28.8
7.3
17.60

Zalingi
24.5
8.8
22.98

Babanusa
28.2
8.9
21.30

Kadugli
27.5
8.5
21.30

3.2.5. Summary of Power Supply and Demand

Table 8 shows the power supply by various power producers and consumption by various sectors. The hydropower represents the biggest share of about 70% despite the fact that the installed capacity is about 54% of the total installed power capacity. This is due to the high outage associated with thermal power generation. The power demand by various sectors is also given. The residential sector has the biggest share of demand followed by the service sector.

Table 8: Electric power supply and consumption in base year 2014.

Power supply (ktoe)
Power demand by sectors (ktoe)
Total

Hydro
Thermal
IC
Import
PV
Residential
Industrial
Agriculture
Service
Trans.

Public sector
767
677
17
40
0
534
151
52
283
0
1019

Oil industry

54

0
0
0
29
0
0
0
29

Sugar industry

61

0
0
0
61
0
0
0
61

Renewable

0

0
0.4
0
0
0
0.4
0
0

Total
767
285
17
40
0
534
240
52
283
0
1109

%
69.11
25.65
1.57
3.63
0.03
48.12
21.68
4.67
25.53
0.00
100.00

PV: photovoltaic.

3.3. Oil Supply and Demand

Table 9 shows Sudan’s oil production in the last 3 years, after the separation of South Sudan. The portion of export is given as well. Besides oil production, a significant amount of associated gas (AG) is also produced. However, the AG is not utilized; it is flared. The historical and projected daily flared amount is about 15–17 MMSCFD from 2006 up to 2030 [14]. For this work, the minimum is considered (15 MMSCFD). Sudan has four oil refineries with a total installed capacity of 143.7 thousand BPD (cf. Tables 9 and 10). However, three of these refineries are out of service representing about 20% of the total installed refinery capacity.

Table 9: Oil production.

Year
Oil production
Export

MMBPD
(000 tonnes) BPD

2014
42.4
11,093

2013
45.1
15,837

2012
37.4
7,210

Table 10: Sudan refineries.

Number
Refinery
Capacity (000 tonnes) BPD

Installed
Available

1
Khartoum Refinery Corporation (KRC)
100
100

2
Port Sudan Refinery Corporation (PRC)
21.7
0

3
Obeid Refinery Corporation (ORC)
15
15

4
Concorp Refinery
10
0

5
Abu Gabra Refinery
2
0

Total capacity
143.7
115

Tables 11–17 show the fuel oil of ORC, KRC, import, total supply, total demand and supply and demand balance, and thermal power generation oil consumption, respectively. The main products include fuel oil, gasoil, kerosene, gasoline (Mogas), LPG, jet fuel, and petroleum coke. The surplus of benzene is for export. Sudan has surplus in some fuel oil and deficit in others. It has surplus in crude oil, gasoline, and pet coke. The surplus of crude and gasoline is for export while the surplus of pet coke is kept as reserve. The deficit of gasoil, LPG, and aviation is met from import. One of the causes of deficit in gasoil is its competitiveness. Gasoil is used by power generation, transportation, and agriculture sectors. As energy conservation measure fuel shift of gasoil is recommended for power generation and agriculture sector and gasoil is to be limited to transportation sector, heavy fuel oil is recommended for thermal power generation and total electrification of agricultural sector via using electric water pump for irrigation system rather than IC motors.

Table 11: ORC oil products (ton/year) [6].

Year
Fuel oil
Gasoil
Kerosene
Naphtha
Total
ktoe

2010
361641.00
134446.00
38011.00
26981.00
405

2011
385330.00
141606.00
40405.00
27299.00
414

2012
385352.00
140899.00
41439.00
24245.00
148

2013
307604.00
114010.00
30937.00
19070.00
328

2014
339663.00
126600.00
32510.00
24547.36
312

Table 12: KRC products (ton/year) [6].

Year
Crude
Fuel oil
Gasoil
Kerosene
Benzene
LPG
Jet fuel
HCGO
Pet coke
Total
ktoe

2010
4265128
0
1860390
0
1241909
327413
133616
379768
322032
4379

2011
3854381
0
1651867
0
1150216
311840
133882
321413
285163
3964

2012
3738191
0
1655445
0
1099800
319690
117924
277230
268102
3850

2013
3403239
0
1515564
0
1009741
289363
79438
253612
255521
3501

2014
3405113
0
1379208
0
1067914
321453
107074
293368
236096
3573

Table 13: Fuel import (ton/year) [6].

Year
Gasoil
LPG
Aviation
Total

Ton
ktoe

2010
337864
37760
136538
540

2011
653661
92282
150459
945

2012
628063
114013
109110
899

2013
898842
195335
82674
1244

2014
1159119
132903
66593
1427

Table 14: Sudan fuel demand/consumption (ton) [6].

Year
Fuel oil
Gasoil
Kerosene
Benzene
LPG
AV
Pet coke
Diesel
Total

2010
555290
2380175
3018
824232
398347
235344
340858
26131
4763395

2011
531991
2358366
3497
838924
231382
289474
211637
22384
4487655

2012
348063
2544450
3119
901671
374968
223797
265292
19887
4681247

2013
337800
2475863
4270
918269
357588
190060
189236
31088
4504174

2014
290696
2616231
3744
895420
397251
144718
245672
27913
4621645

Table 15: Supply and demand balance (000 tonnes) [6].

Year
Fuel oil
Gasoil
Kerosene
Benzene
LPG
Naphtha
AV
H. coker GO
Pet coke
Diesel

2010

2011

2012

2013

2014

Table 16: Fuel demand for thermal electric power base year 2014 [9].

Fuel
Fuel oil
Benzene
H. coker GO
Pet coke
Diesel
Total

tonne
222844
240981
162581
14899
33916
425

ktoe
214
258
156
11
38
677

Table 17: Oil supply and demand in 2014.

Item

ktoe
%
Share%

Crude oil production

6067
79.89

Associated gas

100
1.32

Gasoil

1206
15.88

Aviation

71
0.93

LPG

150
1.98

Subtotal A

7594
100.00

Flared AG

100
5.93
1.32

Crude export

1587
94.07
20.90

Subtotal B: export + loss
1687

Subtotal C = A − B
5907

Refinery conversion + distribution + emission

30
3.19

Benzene export

165
17.82

Power production

677
73.13

KRC + ORC (internal consumption for power generation)

54
5.85

Subtotal D = C − oil used in power generation
926

100.00
12.19

Residential

398
8.00

Transportation

3935
79.00

Service

50
1.00

Industry

548
11.00

Agric.

50
1.00

Fuel for consumption by sectors
4981

65.59

Total by sectors
5907

100.00
100.00

Service includes public buildings, school, universities, hospitals, municipals, and so forth.

Table 17 shows summary of the oil supply and demand. The total supply is 7594 ktoe (7.594 Mtoe). This oil mix consists of crude oil, AG, and imported oil (gasoil, aviation, and LPG) as shown in Table 17. The imported oils represent about 19% of the total oil mix. 9.6% of the total supply is for thermal power generation including the electric power generated by KRC and ORC. The total energy mix is distributed as follows: 65.6% demand, 20.9% export, 12.9% energy conversion loss, and 1.32% flared gas. The demand is distributed to the following sectors: industry (11%), residential (8%), service (1%), transportation (79%), and agriculture (1%).

3.4. Biomass

The types of biomass used for energy in Sudan include

(1)firewood,(2)charcoal,(3)agriculture residue,(4)bagasse,(5)bioethanol,(6)animal waste.

3.4.1. Bagasse and Ethanol

Table 18 shows the sugar produced by 6 Sudanese sugar factories. Bagasse is estimated from the produced sugar. It is taken as 39.5% of crushed sugar cane and the sugar recovery is taken as 9% of the sugar cane. Hence, the bagasse sugar ratio is 4.4-ton bagasse/ton sugar. Table 18 also shows the bioethanol production. Bioethanol is produced from molasses. All bioethanol produced is from Kenana sugar company. It should be remembered that all bioethanol is for export.

Table 18: Bagasse and bioethanol production [15].

Year
Capacity (000 tonnes/year)
Bagasse
Bioethanol

Kenana
New Halfa
Gunied
Sennar
Assalya
W Nile
Total
Mton
ktoe
(000 m³)

2002
376
85
94
78
64

697
3059
1315

2003
398
83
87
85
76

729
3200
1376

2004
428
88
87
79
74

755
3314
1425

2005
393
73
87
72
88

713
3127
1344

2006
400
85
81
81
81

728
3195
1373

2007
405
83
87
93
90

758
3326
1430

2008
402
81
85
86
91

745
3268
1405

2009
382
84
88
87
98

739
3241
1393

2010
276
57
88
77
75

574
2518
1082

2011
356
75
98
71
94

693
3040
1307
40

2012
350
66
92
77
90
6
680
2985
1283
55

2013
471
56
77
76
90
73
843
3698
1590
67

2014
308
60
73
73
65
73
652
2862
1230
70

All bioethanol is produced from Kenana sugar factory.

3.4.2. Firewood and Charcoal

Tables 19 and 20 show the firewood and charcoal, respectively, obtained from the annual report of the Directorate of Agriculture and Forestry of Sudan. It is clear that there is large data missing/gap. When these data are compared with data in the open literature, a large variation is found. Hence, these data are not considered and literature data is rather considered.

Table 19: Firewood by state in m³ [8].

Year
North
Khartoum
Central
Eastern
Kordofan
Darfur
Total

2005
4267
0
52087
31228
129324
10311
227217

2006
3547
0
37632
16038
577803
138903
773922

2007
5379
0
70113
71116
23792
29079
199479

2008
5153
770
83808
33734
278401
64868
466733

2009
3000
0
39828
15360
0
0
58188

2010
11855
0
75621
29140
127089
33056
276761

2011
6538
340
72992
34307
99828
45955
259960

2012
3410
500
49490
9753
9311
0
72464

2013
3150
0
52079
8400
6515
0
70144

2014
200
0
23757
9627
13837
52363
99784

Table 20: Charcoal by state (tons) [8].

Year
North
Khartoum
Central
Eastern
Kordofan
Darfur
Total

2005
895
0
29788
15615
5254
720
52272

2006
912
0
10479
855
13201
2219
27665

2007
1568
0
17239
507
0
1676
20990

2008
1012
158
16016
42479
11820
1015
72501

2009
0
0
310
2995
0
0
3305

2010
8556
0
10004
30545
557026
1512
607643

2011
19276
0
192198
39941
24109
70082
345606

2012
0
0
3200
9875
0
0
13075

2013
0
0
3500
5930
0
0
9430

2014
0
0
1302
155
0
0
1457

Table 21 shows firewood and charcoal production obtained from the open literature for some years as a cross-check. The data of Sudan energy balance of 2012 is adopted in this work as it is close to that given by other references.

Table 21: Estimate firewood and charcoal.

Source
Firewood
Charcoal
Total as firewood

ktoe
ktoe
ktoe

[7]
3146
878 (2926)
6072

[16]
2410
795 (2650)
5060

[17]
3944
1328 (4427)
8371

Data in brackets is firewood converted into charcoal with conversion efficiency of 33%.

The original data is given as consumption per capita.

3.4.3. Agriculture Residues

Table 22 shows the cereals, oil crops, and cotton production. The agricultural waste is estimated using harvest index (HI). The harvest index for cereals, oil crops, and cotton is taken as 0.4, 0.52, and 0.16, respectively. The agriculture waste is calculated as the amount of crop multiplied by [11]. The portion of agriculture residue used as fuel is very small as the majority is used as animal feed and building material and in pulp and paper industry, among others. On the other hand, the agriculture waste is mostly burned during land preparation for the next season. The data is cross-checked against Sudan energy balance of 2012 and is found to be consistent.

Table 22: Agriculture waste.

Year
Sorghum
Millet
Wheat
Groundnut
Sesame
Sun flower
Cotton
Total residue

HI [11]

0.4
0.4
0.4
0.52
0.52
0.52
0.16

kton/year
Mton
ktoe

2002
4.394
578
247
990
274
4
72
2.79
2105

2003
2.825
581
330
550
122
18
86
2.46
1852

2004
4.69
769
398
790
399
7
66
3.21
2418

2005
266
280
364
520
277
12
86
2.56
1932

2006
4327
675
416
555
400
44
75
9.44
7117

2007
4.999
796
669
564
242
73
61
3.34
2516

2008
3.869
721
587
716
350
100
24
3.17
2389

2009
4.197
637
641
942
318
247
31
3.48
2620

2010
2.63
471
403
549
248
46
12
2.16
1624

2011
4.605
634
292
1.185
363
124
14
1.92
1445

2012
1.883
378
324
1.032
187
92
55
1.60
1208

2013
4.524
1.09
265
1.767
562
86
25
1.14
857

2014
2.249
359
193
963
205
56
31
2.12
1600

3.4.4. Animal Waste

Sudan is rich with cows, sheep, goats, and camels, besides donkeys, horses, and chickens. Table 23 shows the animal counts. The animal dung is estimated from average dung production per head. The dung is generally used for biogas production. The dung available for biogas production is estimated by many researchers as 10% [16]. Currently, there are no reports for biogas production in Sudan. There is some biogas production in the 1980s; however, with the inception of crude oil production, biogas production was abandoned nationwide. Hence, the animal waste is not considered in the energy balance for the base year 2014 as there was no information or rates of use in the energy sector. Table 24 shows summary of biomass supply and demand.

Table 23: Animal waste.

Year
Cows
Sheep
Goats
Camels
Dung

Dung production (tons/year/head) [10]

10.95
1.83
1.83
5.48
Mton
ktoe

Million head

2002
39.479
48.136
41.485
3.343
61
25690

2003
39.667
48.44
42.03
3.503
62
25878

2004
39.76
48.91
42.179
3.519
62
25971

2005
40.468
49.797
42.526
3.908
63
26479

2006
40.994
50.39
42.756
4.078
64
26821

2007
41.138
50.651
42.938
4.238
64
26958

2008
41.426
51.067
43.104
4.46
65
27185

2009
41.563
51.555
43.27
4.56
65
27321

2010
41.761
52.079
43.441
4.623
66
27479

2011
29.618
39.296
30.649
4.715
48
19986

2012
29.84
39.483
30.837
4.751
48
20124

2013
30.01
39.568
30.984
4.773
48
20225

2014
30.191
39.846
31.029
4.792
49
20337

Table 24: Biomass supply and demand.

Supply
ktoe
%
Demand
ktoe
%

Firewood
3146
28.68
Residential
3553
32.39

Charcoal
2925 (965)
26.66
Services
1496
13.64

Agricultural residue
1600
14.58
Industry
662
6.03

Bagasse
1230
11.21
Transport
0
0.00

Bioethanol
36
0.33
Agriculture
0
0.00

Animal waste
2034
18.54
Electric power
1230
11.21

Charcoal conversion loss
1960
17.87

Export
36
0.33

Not utilized
2034
18.54

Total
10971
100

10971
100.00

Data in brackets is firewood converted into charcoal with conversion efficiency of 33%.

Animal waste is not considered as there is no record for animal waste utilization in the base year 2014.

All bioethanol is exported.

Animal waste is not utilized.

3.5. Sankey Diagram

Sudan Sankey diagram has been developed using the energy supply, transformation, and demand data obtained for the base year 2014 (cf. Figure 4). The Sankey diagram gives a detailed flow pattern indicating the proportional consumption of primary and secondary energy in different energy demand sectors. It also shows the energy loss during transformation and conversion. The main features of the Sankey diagram are as follows:

(1)Primary energy: Sudan’s primary energy consists of oil (39%), biomass (56%), hydroelectricity (5%), and a very small portion of solar energy (photovoltaic). Besides primary energy, Sudan imports 1427 ktoe of fuel oils (gasoil + aviation + LPG) and 40 ktoe of electricity from the neighbouring country of Ethiopia. The import is about 7% of Sudan’s energy mix. However, natural gas, coal, nuclear energy, and other renewable energy sources are nonexistent in the country’s primary energy mix, despite the huge potential of solar, wind, and geothermal energy. The high proportion of biomass is due to the large population located in rural areas (70% rural population). They have no access to national grid electricity, fuel gas, and kerosene and therefore are absolutely biomass dependent in meeting their demand for cooking, heating, and lighting.(2)Transformation and conversion: the transformation processes in Sudan’s energy balance are power generation (hydro, oil, and bagasse), refinery of crude oil to secondary fuels, and conversion of wood to charcoal. The transformation and conversion and other losses are about 25% of the end-use energy. These losses are thermodynamic loss and energy management loss. It is worth highlighting two examples of energy management loss:

(a)Lack of cogeneration in sugar industry: the potential electric power generation in sugar industry is double the present level if cogeneration in the sugar industry is introduced [12]. Cogeneration is the standard practice in sugar industry worldwide. Lack of cogeneration made the sugar industry in Sudan burn bagasse inefficiently; otherwise bagasse poses serious hazard to factory safety.(b)Flaring of AG: about 15 MMSCFD or 100 ktoe (1.7% of the oil supply) is attributed to flaring of AG. In the oil fields, a significant amount of AG is produced. AG produced is, however, not utilized; it is rather flared. The study conducted by [14] indicated that AG is useful primary energy and if utilized in power generation it can drive steam turbine power plant of 80 MW or can be utilized to produce LPG of annual value of $40 M/year.

(3)Demand: 74% of the total energy demand is useful energy and 26% is loss. 49% of the total loss is due to low efficiency of conversion from wood to charcoal (charcoal conversion efficiency is 33%). The useful energy is distributed among the various demand sectors: agriculture (1%), service (16%), industry (12%), residential (39%), and transportation (32%) sectors.

Figure 4: Sankey diagram for Sudan. The data used is energy data for the year 2014. The data does not include private power generation. The renewable energy includes only solar photo voltaic power; the other types of energy, such as wind and geothermal, are not included. The hydro power and biomass energy are made as main categories in energy balance. The power generation efficiency and fuel conversion loss and emissions in the refinery are considered. All units are in ktoe (ton of oil equivalent).

The developed Sankey diagram is the first of its type in Sudan. The main differences between the present and previous energy balance are the following:

(1)The previous energy balance is presented in simple line draw diagram rather than a professional Sankey diagram as all lines representing different flows are of the same size.(2)The energy balance accounts only for power produced by public sectors. For example, the electric power produced by the refinery and sugar factory is not accounted for in the overall balance. Likewise, renewable energy though small is not accounted for as well.

4. Conclusion

The study provides important information on Sudan’s energy sector covering supply and demand sides as well as conversion, distribution, and transmission. For the supply detailed data on electric power generation, oil production and conversion, biomass sources and conversion, and renewable energy was given. Energy import and export were also reported. On the demand side, detailed data of different sectors is reported. The work provided energy flow diagram (Sankey diagram) for the first time. Sankey diagram is an important piece of information for decision-makers. It can be used to develop strategies and identify potential saving, opportunities, and mitigation measures. The weak point of Sudan’s energy status is solar energy despite the high intensity of solar radiation and long sunshine hours across the country.

Competing Interests

The authors declare that there are no competing interests regarding the publication of this paper.

Acknowledgments

The authors acknowledge the research grant by the Ministry of Higher Education and Scientific Research of Sudan.

References

A. Kumar, Subramanyam, and V. R. Kabir, Development of Energy, Emission and Water Flow Sankey Diagrams for the Province of Alberta Through Modeling. University of Alberta, Department of Mechanical Engineering, Department of Energy, Government of Alberta, Alberta, Canada, 2011.

IRG, “Energy Planning and Development of Carbon Mitigation Strategies-Using the MARKAL Family of Models,” International Resource Group, Washington, DC, USA, 2010.

M. A. Jaccard, Estimating the Effect of the Canadian Government's 2006-2007 Greenhouse Gas Policies, C. D. Howe Institute, Toronto, Canada, 2007.

O. Bahn, L. Barreto, B. Büeler, and S. Kypreos, “A multi-regional MARKAL-MACRO model to study an international market of CO₂ emission permits: a detailed analysis of a burden sharing strategy among the Netherlands, Sweden and Switzerland,” PSI Technical Paper, Paul Scherrer Institut (PSI), Villigen, Switzerland, 1998.

Quadrennial Technology Review, An Assessment of Energy Technologies and Research Opportunity, Department of Energy, Washington, DC, USA, 2015, http://energy.gov/sites/prod/files/2015/09/f26/Quadrennial-Technology-Review-2015_0.pdf.

MOF, Study of Causes of Demand Increase on Oil Product and Options and Strategy of Subsidy Removal, Ministry of Finance, Khartoum, Sudan, 2014.

AEC, “Sudan energy status,” in Proceedings of the 10th Arab Energy Conference, Energy and Arab Corporation, Abudabi, UAE, 2014.

Directorate of Agriculture and Forestry (DAF), Annual Report, Directorate of Agriculture and Forestry (DAF), Khartoum, Sudan, 2014.

NEC, Executive Summary for Year 2014, National Thermal Electricity Corporation, Khartoum, Sudan, 2014.

M. Niamir, Report on Animal Husbandry among the Ngok Dinka of the Sudan-Integrated Rural, Sudan and Harvard Institute for International Elation, Khartoum, Sudan, 1982.

V. Smil, “Crop residues: agriculture's largest harvest,” BioScience, vol. 49, no. 4, pp. 299–308, 1999.

A. A. Rabah, “Future of sugar industry in Sudan,” Sudanese Engineering Journal, vol. 5, no. 3, pp. 60–64, 2013.

A. M. Omer, “Energy, environment, and sustainable development in Sudan,” IIOAB Journal, vol. 2, no. 1, pp. 31–44, 2011.

W. Abdelhamid, Flared gas uilization [M.S. thesis], Chemical Engineering, University of Khartoum, Khartoum, Sudan, 2013.

M. Bashir, B. M. Elhassan, and A. A. Rabah, “Assessment of standby evaporator as an energy conservation measure: case of sudanese sugar industry,” Sugar Tech, vol. 13, no. 3, pp. 179–184, 2011.

A. M. Omer, “The environmental and economical advantages of agricultural wastes for sustainability development in Sudan,” Journal of Brewing and Distilling, vol. 1, no. 1, pp. 1–10, 2010.

G. E. Ali, Studies on Consumption of Forest Products in the Sudan—Woodfuel Consumption in the Household Sector, Energy Research Institute, Khartoum, Sudan, 1994.