Last Sunday’s sudden power outage, which lasted for more than five hours, brought back unpleasant memories of the lengthy power cuts during the economic crisis in 2022. The public, who endured more power cuts in the following days until the system was properly restored, was further taken aback by the bizarre news that the emergency was caused by a monkey.
While it was true that a monkey hitting the transmission line at the Panadura Grid Substation was the initial trigger, there were more to the story, involving a lot of technical details, which, when unravelled later, served as an eye-opener on the stability of the nation’s power generation and transmission systems.
Sunny Sunday effect
The risk of system failure on Sundays and holidays, when power consumption is lower compared to other days of the week—when factories, business establishments, schools, and public institutions are in full swing — has been a talking point among power sector officials for some time now. Ceylon Electricity Board (CEB) Engineers’ Union Editor Buddhika Wijayawardena said that the vulnerability of the system has been a point of internal discussion from at least November 2024.
The risk has mainly stemmed from the surge of solar-based renewable energy – an intermittent power source – into the national grid, weakening the officials’ control over the system. Even though all this came as new knowledge for the common man on the street in hindsight, CEB officials had navigated through similar risky situations on several occasions in the past few months, avoiding power failures.
However, during last Sunday’s “monkey accident,” which led to a chain reaction of power station tripping, including at the Norochcholai Coal Power Plant, and the auto-disconnection of rooftop solar, their attempts to stabilise the system proved futile, and the country experienced a blackout. The Public Utilities Commission has now begun an investigation into the incident, and it is better to wait for its report before drawing any conclusion.
Wijayawardena said that solar contribution to the grid had been higher on February 9 as it was a sunny day, but demand had dropped to about 890MW, whereas about 1,400MW is generated at noon on a normal day.
“Similarly, demand had dropped to 790MW on Sunday, February 2, and to 769 MW on September 22, 2024, a day after the Presidential Election where a curfew was in place, but we managed to balance supply and demand. In January, solar energy generation did not reach a peak due to rain. Again in March, we predict that demand for power at noon will increase somewhat as people switch on fans and air conditioners as hot weather sets in,” he said.
Solar influx
According to the Long-Term Generation Expansion Plan (LTGEP), the CEB had only planned to connect 160MW from rooftop solar in 2024 and 150 MW each for 2025 and 2026. However, by the end of 2024, 600MW had been added to the grid from rooftop solar – a 33 percent increase compared to the total expected by the end of 2026 and a 44 percent increase compared to 2023.
“The attractive price of Rs. 37 paid for solar power contributed to this sudden surge. (This rate was later brought down to about Rs. 26.50.) While we can be happy about the higher solar energy contribution as it reduces the dependency on thermal energy – such as furnace oil (unit cost: Rs. 45-50) and diesel (unit cost: Rs. 80-85) – and saves foreign exchange spent on coal and oil imports, its intermittent nature and the lack of infrastructure and technology to store and monitor that energy have created a problematic situation,” Wijayawardena told the Sunday Observer.
He said that the capacity of the current solar power connections, installed both on the ground and rooftop, has surpassed 1,600MW, which is one-fourth of the total capacity of power plants in Sri Lanka. Yet, in the absence of enough solar batteries, the grid largely depends on hydro, coal and oil to meet the peak demand at night, which can be as high as 2,700 MW. At the same time, the stability of the grid has weakened to dangerous levels in the day-time due to high absorption of solar energy.
“The problem with rooftop solar is that the CEB cannot monitor real-time data on power generation. As of now, we only make predictions for each day. Since the CEB has no access to or control over rooftop solar, restoring the system after a failure also proved challenging. We need to go for a smart grid system, which includes smart metres and grid automation and control, to be able to see real-time data and better match supply with demand, but that is a large investment, which can only be realised gradually. We have started a pilot project of installing 50,000 smart metres in the Dehiwala-Mount Lavinia area,” he added.
CEB Spokesperson Dhammika Wimalaratne told the Sunday Observer that the recent incident would not change the current policy of promoting green energy, and that the targets of meeting 70 percent of the country’s power demand through renewable energy by 2030 and achieving carbon neutrality in power generation by 2050 remain intact.
“We will connect more renewable energy, but will take measures to invest in a stronger grid. Balancing supply and demand has been challenging as solar generation is not visible to the National System Control Centre. A disturbance like this can happen at any moment, but a blackout could have been avoided had we got more inertia to absorb such changes. All these corrective measures will be taken by the CEB in time to come,” he said.
Energy storage
The authorities have paid attention to developing Grid-Scale Battery Energy Storage Systems (BESS) to capture surplus power from solar when supply outpaces demand. Rapidly absorbing or releasing energy to maintain steady voltage and frequency, the BESS helps in grid stabilisation and prevents blackouts during disturbances.
In November 2024, the Asian Development Bank (ADB) had approved a USD 200 million loan to upgrade the power sector infrastructure (USD 150 million for the CEB and USD 50 million for Lanka Electricity Company), and a 100MW/100MWh BESS will be installed as part of it. Another 5MW/10MWh BESS has been planned for 2025 under a Korean Grant. According to the LTGEP 2023-2042, plans have been made to incorporate a cumulative battery storage capacity of 1,125 MW into the network by 2030.
“Moreover, homeowners with solar panels can be encouraged to install batteries and supply solar power to the grid in the evening. For that, an attractive price should be paid for the power supplied in the evening. Such a system is in place in countries like Australia, the USA and Germany,” Wijayawardena said.
Pumped hydro storage development is another strategy the power authorities have considered for energy shifting and frequency regulation. It is a hydroelectric facility that stores electricity by pumping water uphill to a higher reservoir during periods of low energy demand, then releases that water through turbines to generate electricity when demand is high. Wijayawardena said plans have been made to integrate a 600MW Pumped Storage Power Plant by 2034, adding that accelerating this long-term project may be required in the present context.
Demand shifting
Observing that the system’s stability can be maintained without an issue if demand does not drop below 1,000 MW, Wijayawardena proposed offering incentives for industries and commercial establishments to operate on Sundays. The LTGEP has paid attention to introduce a Time of Use (TOU) cost-reflective tariff to encourage customers to shift their night loads to daytime.
Another option to maintain grid stability is interconnection with neighbouring countries such as India. “This proposal enables the country to sell its excess solar energy produced during the daytime to another country. Many countries that rely heavily on renewable energy have opted for grid interconnection with countries which have more stable grids. However, the Government will have to tread carefully on this proposal, weighing its pluses and minuses for the economy, security and national interests,” the Union representative said.
Asoka Abeygunawardena, an expert in Renewable Energy, said that Sri Lanka had experienced country-wide blackouts six times since 2013, including the last Sunday’s incident. He criticised the CEB officials for failing to ensure the protection of the grid.
“When the ambitious ‘Soorya Bala Sangramaya’ project was launched in 2015, there were targets of installing one million rooftop solar panels and newly integrating 1,000MW of solar power to the grid by 2025. The officials, who were aware of these plans, should have been prepared in advance to handle this situation by improving the renewable energy storage facilities. They had 10 years to do so, but had been idling till even a monkey can cause an island-wide blackout,” he said.
Asked about the delay in implementing the measures to absorb renewable energy, the CEB spokesperson cited a lack of funds as the main constraint, adding that some of the projects had to be held over due to the economic crisis. However, he assured that the CEB would speed up efforts to maintain a secure, reliable, and sustainable power system.
(Graph credits to Buddhika Wijayawardena)
