It Is Necessary to Reduce Output of Renewable Energy

10:13:16 AM | 19/4/2021

The National Load Dispatch Center of Vietnam (EVN NLDC) said that during the Lunar New Year (the period when the demand for electricity decreased to the lowest in the year), it had to reduce nearly 8,000 MW of renewable power, including about 3,500 MW of rooftop solar power.

According to this center, electricity is a special commodity, produced and supplied on the principle of aggregate demand equaling aggregate supply. If this principle cannot be maintained, the national power system will face dangerous incidents causing widespread power outages, even disintegration of the whole system.

However, the Covid-19 pandemic has made the demand for electricity consumption in Vietnam decrease nationwide. The electricity consumption of the country increases by an average of about 10% annually, but it only increased 2.45% in 2020. In the first months of 2021, the electricity consumption has only increased approximately 4.0% over the same period in 2020.

At the same time, there is a huge gap in electricity demand between the hours of the day (the difference between noon and evening can be up to about 6,000-8,000 MW), between working days and holidays (around 4,000-6,000 MW).

Currently, the proportion of renewable energy supplied to the system is high, accounting for approximately 23.5%. However, because the power generation capacity depends entirely on the immediate primary energy, which changes frequently and is difficult to predict, the guarantee of supply and demand is still heavily dependent on traditional sources. Despite operating more flexibly, currently, hydropower sources only account for about 20% of the system capacity.

In particular, during peak hours (in the evening every day), the power supply depends entirely on traditional sources because at this time, all solar power sources (contributing about 12,000-13,000 MW) are not able to operate and generate electricity. In addition, there are times when power generation sources in the Central/Southern regions cannot generate maximum power due to the constraints of the 110/220 kV transmission grid and the 500 kV connection from the Central to the North.

Therefore, the daily mobilization of power sources should be properly calculated, the source structure must ensure redundancy to meet not only changes in power consumption, but also with the fluctuations of the renewable energy sources with the rate varying by thousands of megawatts in seconds.

Therefore, according to the National Load Dispatch Center, the reduction of generating renewable energy in recent time and at the present is required to ensure the safe and stable operation of the electricity system.

In order to exploit renewable energy as much as possible, the National Load Dispatch Center has worked with domestic and international organizations to research and evaluate the level of renewable energy absorption according to actual conditions in Vietnam. The results show that in a very short time, the absorption capacity of the national electricity system may reach 55% as during the Lunar New Year.

However, in long-term operation, to ensure the correct and sufficient compliance with the requirement such as the Inter-reservoir operation procedures issued by the Prime Minister, the existing electricity purchase and sale contracts in effect, the standard technique requirements for grid operation, this proportion will be much lower.

The National Load Dispatch Center has proposed to continue coordinating in shifting the rush hour of small hydropower sources. Currently, the capacity of absorbing renewable energy sources in the Central and the South has been increased by more than 1,000 MW due to shifting the time of generation of small hydropower sources from 9:30 am-1:30 pm to 6:00 am-8:00 am; at the same time, scheduling the optimal operation of the diagram of generating traditional power sources (coal, gas, hydropower); including flexible and timely cessation of gas-fired power sources; accepting to mobilize oil resources into afternoon peaks to meet the load demand, although this can lead to an increase in system costs.

Relevant units calculate and propose the grid works needing to accelerate progress in order to increase the ability to release the capacity of renewable energy sources; actively participating in research projects on battery energy storage systems to change supply as well as ensure stability for a backup power system.

A0 said although the reduction in generating renewable energy had been improved, it still had to continue to do so. In particular, according to this center, during the Lunar New Year (the period when the demand for electricity is lowest in the year), there were times when it was necessary to reduce nearly 8,000 MW of solar and wind power, including 3,500 MW of rooftop solar power.

In the coming time, the phenomenon of oversupply and overload of the grid causing the reduction of renewable energy is expected to continue to appear, as in the period of July-September (the North enters the main season of floods of hydroelectric lakes), the reduced electricity output will be about 180 million kWh/month, in the October-December period (wind power sources are fully operational as planned, while the Central and the South are in flood season), the amount of reduction is likely to reach 350-400 million kWh/month.

Source: Vietnam Business Forum