Results from modelling the Nigerian energy system are presented below from 2015–2065 with the model period running until 2070 to account for end-game optimization issues at the end of the model period which are typical of bottom-up optimization models. Out of the twelve model runs, three runs produced a generation shortfall, deploying the model’s backstop. This backstop is included as a very expensive technology with unconstrained capacity that the model can deploy if it is unable to meet demand in any scenario to keep the model from failing. Table 4 shows the runs with backstops and the size of the shortfall in TWh. To contextualise these figures, the current (2022) electricity demand is 81 TWh and is expected to rise to 919 TWh in 2065 (Allington et al., 2021). This shortfall is additional to the shortfall met by diesel generation and is due to emissions constraints in NDC scenarios.
Table 4. Generation shortfall in model runs.
|
BAU
|
Least Cost
|
UNDC
|
CNDC
|
Improvement to 2030
|
OK
|
OK
|
OK
|
OK
|
Improvement to 2050
|
OK
|
OK
|
14 TWh
|
OK
|
BAU/No Improvement
|
OK
|
OK
|
2,314 TWh
|
1,381 TWh
|
Across scenarios, the generation results presented below show that increased plant availability decreases the use of diesel generators. Increased availability also reduces total system costs and emissions; however, the pace of the improvement (to 2030 versus 2050) has a much smaller impact on both costs and emissions.
However, in the near term it is possible for Nigeria to meet its NDCs with little or no change to its generation mix if plant availability is improved.
4.1 Generation
Business-As-Usual
As Figure 3 shows, capacity is dominated by CCGTs in the model runs with plant improvement to 2030 and 2050. SCGTs, which are the current dominant form of turbine, are phased out after 2040 in all scenarios. In the scenarios with improvement in plant availability, diesel generation is phased out once plants reach full availability. Without improvement, diesel remains an important part of the generation mix (30-50% of generation) throughout the model period.
Hydropower does not come close to its technical potential of 64.3 TWh of annual generation, and peaks at 15 TWh of generation from in 2030. Decentralised PV takes over 4% of generation in 2050 in all scenarios and capacity peaks in 2062 with 22.875 GW installed across model runs.
As no investment in EE is allowed in BAU, variation in the total amount of electricity generated is due to the mix of on/off grid generation — scenarios with high amounts of diesel need to generate less as less energy is lost to the low T&D efficiency.
Least Cost
The least cost generation mix, shown in Figure 4, also includes high amounts of natural gas which is largely made up of CCGTs with SCGT capacity declining after 2025. Biomass also plays a significant role from 2035 onwards and ultimately makes up for 27% of power generated in 2065 in most runs. Coal enters the generation mix after 2025 and remains a stable part of the generation mix until the end of the model period.
The renewable energy mix includes similar amounts of hydropower to the BAU scenario. Onshore wind also plays a small role in the generation mix with utility-scale PV supplying 10% of power generated in 2050 across most model runs.
Diesel generation varies significantly across model runs with higher rates of diesel in runs without availability improvement. Greater variation in the generation mixes and investment in EE mean that diesel generation is lower in Least Cost model runs than in the BAU runs. As was seen in the BAU model, in runs with availability improvement diesel generation is phased out before plant availability reaches target levels.
UNDC
Only one UNDC run, the run with 2030 improvement, could successfully meet demand without surpassing emissions targets. In all other runs, the model’s backstop kicked in indicating that no technologies available would be able to meet demand given the constraints on the model. The results for these “failed” runs are presented but the backstops are indicated, and the power generated by backstops is assumed to come from diesel self-generation.
CCGTs remain an important part of the generation mix in the UNDC model runs with SCGTs playing smaller role and disappearing from the mix after 2040. Coal is the only other centralized fossil resource in the model runs but coal generation is roughly half of what it was in the Least Cost runs.
The model invests aggressively in nuclear from 2029 onwards and this makes up 16% of generation in 2050 across runs. Hydropower hits its investment limit in 2054. On-grid solar hits its production limit in 2040 and wind hits its limit in 2050. Off-grid PV is largely absent across model runs until 2050 where it supplies 4-5% of electricity generated.
Even in scenarios without improvement, diesel generation makes up less of the annual power generated in UNDC model runs than in Least Cost or BAU runs.
CNDC
Only two CNDC runs were able to run without backstops — the runs with availability improvement to 2050 and 2030. It is likely that more of the CNDC runs were successful than the UNDC runs (despite the lower emissions limit) due to the forced investment early in the model period in off-grid renewable energy which lessens the on-grid load.
As per scenario constraints and NDC targets, SCGTs phase out of generation by 2030 but CCGTs generate throughout the model period. As seen in Figure 6 coal does enter the generation mix in 2030 but at half the level observed in UNDC runs. As was observed in UNDC model runs, nuclear is deployed to the fullest extent permitted as are wind and solar.
Across all models runs, the level of diesel generation is slightly below the corresponding run’s generation in the UNDC by an average of 3%.
4.2 Emissions and NDC Targets
As shown in Figure 7, the BAU model run without availability improvement has the highest emissions overall, followed by the Least Cost run without availability improvement. The UNDC and CNDC model runs have the lowest total emissions over the model period, even when energy generated by the backstop is assumed to be generated by diesel generators.
Across all scenarios, runs with no availability improvement have consistently higher emissions – an average of 45% above those with improvement across scenarios. There are also smaller differences in emissions between runs with 2030 improvement versus runs with 2050 improvement. A slower rate of plant improvement increases total emissions by an average of 2% over the model period.
When emissions are plotted over time, as shown in Figure 8, most scenarios have consistent emissions (within 100 MT CO2e of each other) until 2034 where results begin to diverge more dramatically. In the period of 2030–2035 the Least Cost run without availability improvement surpasses the annual emissions of the BAU scenarios with improvement. In 2065, all Least Cost runs have annual emissions higher than the two BAU model runs with availability improvement. This difference between the LC and BAU scenarios is likely due to the deployment of biomass in the Least Cost runs after 2035.
Despite these changes, later in the model period all Least Cost runs with availability improvement are able to hit the 2030 UNDC target, as shown in Figure 9. The BAU run with full plant availability in 2030 also remains below the emissions threshold. Notably, no viable model runs without availability improvements can hit the NDC targets. The CNDC model runs without improvement are able to hit the targets, but these results are qualified by the fact that these savings early in the model period are likely reflective of insufficient investment, as scenarios are not able to meet demand later in the model period.
4.3 System Costs
Figure 10 shows the total discounted system costs from 2022–2065 across scenarios and model runs. Runs with backstops activated do not have costs shown as the high cost of the backstop technologies skews the costs in the run. Costs include all CAPEX, fuel costs, operational costs, costs of improved energy efficiency, and T&D expansion costs. Notably, the costs of improved plant performance are not included.
As expected, the Least Cost scenarios have the lowest discounted total system costs when compared with the relevant corresponding runs of other scenarios. The cheapest scenario overall is the Least Cost run with availability improvement to 2030 – at USD 149 billion – as this scenario has the least constrictive constraints.
Across scenarios, system costs decrease by an average of 45% as plant availability improves gradually to 2050. This equates to average savings of USD 138 billion over the modelling period. The difference between runs with improvement to 2030 versus 2050 is much lower – a slower rate of improvement only raises system costs by an average of 14%.
4.5 Flexibility
Across scenarios, increased available capacity reduced loss of load. The BAU run without availability improvement had the highest loss of load in 2040, with 41% of demand not met. The three other runs without improvement had the next highest losses as shown in Table 5.
Table 5. Key flexibility metrics.
|
Loss of load (% of demand)
|
Insufficient reserves
(% of reserve)
|
Peak net load (GW)
|
Available Dispatchable Capacity (GW)
|
BAU with Improvement to 2030
|
0.04
|
7.402
|
48.54
|
51.58
|
BAU with Improvement to 2050
|
3.39
|
31.15
|
48.70
|
40.93
|
BAU with No Improvement
|
41.05
|
99.63
|
48.99
|
21.75
|
LC with Improvement to 2030
|
0
|
0
|
40.65
|
49.24
|
LC with Improvement to 2050
|
0.07
|
7.801
|
38.25
|
41.46
|
LC with No Improvement
|
10.72
|
68.14
|
37.46
|
24.72
|
UNDC with Improvement to 2030
|
1.00
|
14.35
|
35.12
|
36.41
|
UNDC with Improvement to 2050
|
3.15
|
20.06
|
34.13
|
31.07
|
UNDC with No Improvement
|
15.53
|
89.07
|
34.56
|
20.69
|
CNDC with Improvement to 2030
|
0.83
|
13.31
|
35.23
|
43.62
|
CNDC with Improvement to 2050
|
3.53
|
20.21
|
34.52
|
36.30
|
CNDC with No Improvement
|
9.53
|
52.38
|
31.72
|
24.82
|
Entries in red indicate instances where the peak net load is greater than the available dispatchable capacity, leading to loss of load.
Some loss of load comes from ramp rate limitations in the modelled generation mix, but most of the losses appear to be caused by a lack of capacity. This can be seen in Figures 11 and 12 which present load curves for the first week of the analysis in 2040. These curves show that demand sharply increases each afternoon (between 16:00 and 18:00) and that dispatchable generation is at first able to ramp fast enough to match the demand curve. However, as the capacity is exhausted and the generation curve plateaus, energy supply is unable to keep up with demand.
This inadequacy can also be seen in Table 5 which shows key flexibility indicators, including the peak net load for the year and available capacity. The peak net load is the demand less the amount of VRE generation, and the available dispatchable capacity is the capacity that can be used to meet the remaining demand. This net load is 10 to 20 GW more than the available capacity in some scenarios.
In all scenarios other than BAU, the annual lost load in FlexTool is greater than the diesel generation in the OSeMOSYS modelling by 2–10 TWh. This indicates that the OSeMOSYS modelling does slightly underestimate the supply gap filled by self-generation. Despite this difference, the results from the two models are broadly consistent – improved availability does improve the system adequacy (as shown in the FlexTool results) and reduces the reliance on diesel generation, building a more resilient system.
Likely due to the cap on VRE, there was minimal curtailment across runs. The CNDC run had the highest curtailment with 0.3 to 0.7% of VRE curtailed. Given this VRE limit and use of natural gas in all scenarios, the inertia across scenarios is also not an issue, with zero instances of insufficient inertia in any scenario.
Broadly, the results of the flexibility analysis support the OSeMOSYS modelling in stressing the importance of improved availability for system reliability. The NDC runs with full plant availability in 2030 have some loss of load in the analysis which would need to be met by diesel or increased on-grid investments not accounted for in the OSeMOSYS modelling. This indicates that improved availability is unlikely to resolve all flexibility issues on its own, and therefore greater investment in storage or sector coupling (which are outside the scope of this study) may be needed to fully optimize the system. Future work could explore this dynamic.