Thanks to the policy of supporting the development of renewable energy sources, incentives and reducing the cost of technologies, the share of renewable energy sources in Kazakhstan has increased significantly. Thus, according to the Ministry of Energy of the Republic of Kazakhstan, according to the results of the first half of 2024, the share of renewable energy in electricity generation reached 6.5% with an installed capacity of 2.9 GW of renewable energy (WPP – 1.4 GW, SPP – 1.2 GW, sHPP – 0.27 GW).

According to the Energy Balance of the Republic of Kazakhstan, by 2035 (Order of the Ministry of Energy of the Republic of Kazakhstan No. 44 dated 30.01.2023), the total installed capacity of WPP and SPP is planned to increase to 7.5 GW, including wind WPP up to 5.3 GW and SPP up to 2.2 GW. In addition, this balance does not take into account about 3.5 GW of WPP and 0.4 GW of SPP, planned for sale in accordance with the Auction Plan for 2024-2027 (Order of the Ministry of Energy No. 187 dated 23.05.2023), as well as such large projects as ACWA Power – 1 GW WPP, CPIH – 1 GW WPP, WPP Masdar – 1 GW, Shelek WPP – 1 GW.

It is well known that renewable energy is a variable source of generation that is not fully amenable to dispatching, with a characteristic forecasting error, therefore, the integration of a large volume of renewable energy into the energy system can lead to certain restrictions associated with insufficient network capacity and maneuverability of traditional power plants. In this case, with excessive generation in the power system, the principle of maintaining its stable operation (balance of consumption and generation at each moment of time) forces the system operator to limit the generation of renewable energy sources and accept less wind or solar energy than the resource allows.

Curtailment means a forced reduction in the volume of wind or solar energy generation to a value lower than is potentially available at the moment.

Thus, the successful integration of a large volume of renewable energy into the energy system is associated with the need to introduce institutional changes, introduce market incentive mechanisms, transform the network topology, increase its capacity and flexibility, the structure of traditional generating capacities with an emphasis on the development of maneuverable sources, and improve operational activities. In case of delay in the implementation of these changes, renewable energy restrictions can reach significant volumes.

Limiting renewable energy generation has a direct impact on the attractiveness of the project, and when concluding a take-or-pay contract, consumers will be forced to pay for ungenerated electricity.

International experience shows that in a number of countries with high rates of renewable energy development, with an increase in the share of electricity from renewable energy sources, the share of restrictions on their generation also increases (Figure 1.)

Thus, the share of restrictions on WPP/SPP generation in the future, with a degree of RES penetration of 30%, can reach 6-7%.

In this article, Energy System Research LLP has estimated the expected volume of renewable energy restrictions for 2030 – 2035, taking into account the indicators of the Energy Balance of the Republic of Kazakhstan until 2035, the main indicators of which are presented in the table below (Table 1).

To determine the possible scope of WPP/SPP restrictions, a model was created that allows an analysis of hourly load coverage by power plants, taking into account:

-      configurations of the load diagram of each area,

-      variable nature of renewable energy sources,

-      regulatory capabilities of existing and prospective traditional power plants for 2030-2035,

-      throughput of weak sections,

-      the mode of operation of energy storage systems (ESS).

The simulation results were used in carrying out research on the operation of the power system, as well as in coordinating the projects of Mirny WPP, Acwa Power WPP, Shelek WPP, etc.

The main assumptions made in the model are presented below.

Generation

Analysis of the maneuverability characteristics of existing power plants showed a wide range in the rate of power gain and discharge in %/min of installed capacity (Table 2). 

Significant variation in characteristics is due to equipment wear or involvement in the regulation of base power plants.

The values of the accepted maneuverable characteristics of promising power plants in % of Rinst and the rates of power gain/decrease in %Rinst/min are shown in the table below by type (Table 3).

Load

Configuration of the prospective load diagram was adopted on the basis of the 2021 reporting diagram. The results of the analysis of extremes and derivatives of hourly load data for 2021 are presented in the table below (Table 4).

The graph of the total load of consumers of the North-South and Western zone ICS is characterized by a daytime and evening peak:

-      daytime peak load (Astana time) - 10:00 – 13:00 for the North-South ICS, 11:00 - 15:00 for the Western zone

-      evening peak load (Astana time) – 18:00 - 22:00 for the North-South ICS, 20:00 - 23:00 for the Western zone

The number of hours of use of the maximum load T _max is 7060 hours for the North-South ICS and 6970 hours for the Western zone.

 Renewable energy generation profile

The hourly profile of renewable energy generation was calculated using specialized PVSyst software – for SPP, WindPRO – for WPP, according to historical data on the watercourse – for sHPP.

Interstate flow rates

Analysis of the work of the National Grid of Kazakhstan showed that the unbalances were in the range of ± 1000 MW and were covered by the exchange flows of power with the energy systems of neighboring states. However, taking into account contractual obligations on interstate flow rates in the amount of ± 150 MW from RF and ±50 MW from CA, the export/import range has been adopted in the amount of ± 150 MW for further extension.

 The topology of the electrical network

At the 2030 stage, in order to unite the Western Zone with the North-South ICS of Kazakhstan, it is planned to construct an intersystem 500 kV overhead line Karabatan-Ulke, which will ensure the exchange flows of power of the Western Zone from North-South ICS.

 Taking into account the planned unification, modeling of the coverage of the prospective load for 2030 and 2035 was performed for National Grid of Kazakhstan including Northern, Southern and Western zones, taking into account the limited capacity in:

-      North-South transit (L-5300, L-5320, L-5400).

-      Beineu-MAEK area (L-2075, L-2085)

-      Inder - Right Bank area (L-2540).

Hourly coverage schedules for 2030 and 2035 for 7 days of each season are shown in the figure below (Figure 2).