Figure 42. VRE curtailment in SDS-Inflex and SDS-Storage cases, by region

VRE curtailment rate (%)

30

25

SDS-Inflex

20

15

10

SDS-Storage

5

0

PSH and battery energy storage resources help to reduce VRE curtailment.

Figure 43. Net load during peak demand periods in the SDS-Storage and SDS-Inflex cases

Net load (GW)

1 400

1 200

1 000

plants, which leads to significant savings of fuel and carbon costs. Minimum generation also increases in this case, which allows for more stable operation of power plants. This is captured in the reduction of operational costs in the modelling.

In addition, the peak net load of the system in 2035 reduces by 160 GW, or approximately 15% (Figure 44). This fall in peak demand reduces the need for additional investment in generation capacity and grid infrastructure, and the associated annualised investment-related benefit of this measure is calculated at approximately USD 21 billion per year.

Figure 44. Demand reduction due to smart EV charging during periods of peak demand, SDS-EV case, 2035

Net load (GW)

1 400

1 200

1 000

cost

The application of smart EV charging schemes also helps to reduce VRE curtailment in regions with very high VRE penetration, in some cases bringing curtailment levels down to international benchmarks (Figure 45). It is important to note synergy between smart EV charging and transmission infrastructure. Certain regions with very high penetration of VRE (especially the NWR) have a relatively low population and hence a low EV density. Consequently, the presence of strong grid interconnection in these regions is beneficial for linking smart EV charging resources with VRE supply, boosting overall system flexibility and reducing VRE curtailment.

Such reduction in VRE curtailment driven by system flexibility enhancements, particularly in VRE-rich regions where significant deployment is likely to occur, will be an important goal for Chinese policy makers to persevere with. Doing so will help to maintain the investability of the renewable energy sector, ensure that financing is continuously available and possibly reduce the need for government subsidies.

Figure 45. VRE curtailment in SDS-EV and SDS-Inflex cases, by region

VRE curtailment rate (%)

30

25

SDS-Inflex

20

15

10

SDS-EV

5

0

Smart EV charging can substantially reduce VRE curtailment levels at a national and regional level, helping to enhance renewable energy sector investability.

With respect to changes in power system operation, the modelling indicates that smart EV charging protocols generally shift EV charging loads to periods of VRE generation, enabling the power system to more easily meet operational requirements, particularly during periods of high stress for the power system (Figure 46).

Figure 46. Generation patterns and demand profiles during high stress periods in SDS-EV case

Note: The load shape in the SDS-EV case is distinct from the SDS-Inflex case, as the SDS-EV case allows for optimised EV charging patterns which alter the structure of demand.

Smart EV charging enables more cost-effective management of peak system load and reduces VRE curtailment levels during high-stress periods.

As VRE penetration increases in power systems, the frequency and intensity of high-magnitude ramping events increases, driven by the simultaneous decline in solar generation output and increase in electricity demand in the evening. For the SDS cases – which feature a 35% annual VRE penetration – modelling results indicate that smart EV charging becomes a relevant provider of system flexibility during these high net load ramping periods.

A detailed analysis was carried out in three steps to assess the contribution of EVs to meeting steeper ramps in the power system. First, periods of different magnitudes of net-load ramps were identified in the modelling results. These were binned into six categories depending on the steepness of the ramps in the relevant time period. Second, the contribution of individual flexibility resources to balancing the ramp was assessed. Third, all flexible resources operating on the system during the ramping event, and which could have further increased or decreased their consumption/generation to help balance the power system, were accounted for. The result indicates the degree of flexibility provided by each resource and how much flexibility remains on the system. Figure 47 demonstrates that smart EV charging measures provide a significant share of upward ramping services, which can have large impact on the efficient operation of the system, especially by reducing the need for peaking capacity.

Figure 47. Provision of upward ramping flexibility from different flexibility options before and after the introduction of EV smart charging

Notes: The upward ramps are binned into six groups of ramp severity, with the flexibility provided/remaining presented as a proportion of the maximum observed net load ramp over the modelling horizon; the “Remaining” category includes all flexible resources that are operating on the system during the ramping event that could have further increased or decreased their consumption/generation to help balance the power system.

Smart EV charging makes the most significant contribution to upward ramps, while the power system at large appears to have more than sufficient remaining flexibility from a combination of conventional power plants and storage.