With India’s plan to install 175 GW of renewable energy by 2022 grid integration of intermittent renewable energy sources is expected to be a challenge and the Central Electricity Authority (CEA) has released a report to address the issues of balancing required by conventional power generators to accommodate renewable sources of energy.
The report analyzes generation trends, providing preliminary estimates of costs involved, and required flexibility measures. The main objective of the study is to forecast the future generation scenario for the year 2021-22 and compare it with the demand projected in the 19th Electric Power Survey (EPS) and estimate the degree of flexibility if total renewable generation is to be accommodated in the grid around the clock.
“The aim is to ensure security, reliability, and stability of electricity grids to supply affordable and reliable power to consumers while maximizing the generation of power from renewable energy sources (RES) and integration of the same into the grid,” the report said.
According to the report, in the present scenario, the installed capacity of renewables in India was 70 GW as of August 2018. Around 23.5 GW was the maximum power produced by RES during the day, which reduced to around 11.7 GW at night.
The report looked at a future date (July 1, 2021) where renewables are expected to be at their highest point ever with the generation of 108.926 GW to be integrated into the grid, at a time when the grid demand is expected to be 192,322 MW. However, the day of the lowest minimum thermal load (MTL) of 25.73 percent will be on July 27, 2021, when 108.082 MW of solar and wind generation will be integrated into the grid at 1200 hrs. The grid demand will be 181.151 MW during the integration. RES generation on July 27, 2021, varies from a minimum of 22.295 MW at 300 hrs. to 108,082 MW at 1200 hrs.
The report also studied the Indian transmission network to find limitations in the grid during the integration of renewable generation in the year 2021-22. It considered that out of the 100 GW of solar, 33 GW would be grid-connected, and the rest would be local consumption. This scenario seems unlikely because as of today, already approximately 25 GW of solar has been grid-connected so far according to the Mercom 2018 Q4 & Annual India Solar Market Update.
However, in this scenario, renewable energy sources would make up 36 percent of the total installed capacity, which would put the pressure on coal-fired plants to flex their generation to as low as 26 percent of rated capacity, which they are not designed to do according to the report.
The projected load demand per the 19th Electric Power Survey in 2021-22 is around 227.451 GW. The load flow studies for the peak as well as off-peak conditions for the day were conducted when solar and wind generation is about 108 GW. It was found that there would be no congestion in the 400 kV and above systems of the national grid.
In India, coal-fired thermal power projects operate as baseload plants and therefore it would need to provide maximum flexibility, other than demand-side measures to ease restrictions posed by large-scale renewable integration.
The report includes time of day tariff, open electricity market, demand response from high voltage industrial consumers, the supply of electricity to agriculture sector by dedicated feeders, as some of the demand-side measures to improve the flexible power scenario from the demand side. For example, if 2 GW of the agricultural load is shifted from night hours to hours of peak solar generation, the minimum thermal load of coal-fired units can be improved by 2 percent.
The report also suggests coordinated efforts from all fuel sources should be implemented to provide flexible power in the grid. It finds that with just one percent of renewable energy curtailment, the burden on other sources to provide flexible power reduces substantially. The 1 percent curtailment of RES on an annual basis would improve the minimum thermal load on coal-based capacity from 25.73 percent to 45 percent. However, it should be seen as a last resort.
“One percent renewable generation curtailment leads to loss of 2630 MU of renewable energy in the year 2021- 22. This, in turn, corresponds to a loss of ₹ 6.58 (~$ 95.66 million) in terms of monetary value of renewable energy at an average cost of ₹2.5(~$0.036)/kW”, found the report.
“Curtailment is already an issue and curtailing renewable energy in the future goes completely against India’s renewable energy targets and goals,” commented Raj Prabhu, CEO of Mercom Capital Group “Finding and implementing the right energy storage technology into the mix would be a better solution.”
Last year, Mercom reported how solar project developers continue to face curtailment issues. In states like Tamil Nadu, Andhra Pradesh, Karnataka, among others, the issue of curtailment is more challenging, falling somewhere between 10 and 25 percent.