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The Ceylon Electricity Board (CEB) has requested all rooftop solar system owners in Sri Lanka to voluntarily switch off their solar photovoltaic (PV) systems during the daytime from 9:00 AM to 3:00 PM until April 21, 2025. This request comes during the Sinhala and Tamil New Year holiday period, a time when electricity demand is very low due to the closure of factories and offices. Meanwhile, clear and sunny weather conditions have led to high generation from rooftop solar systems. This mismatch between low demand and high solar output poses a serious risk to the stability of the national power grid. The main technical issue is that too much solar power enters the grid at a time when fewer people are using electricity. To manage this imbalance, CEB is forced to shut down large power plants such as hydro and thermal units. These plants not only provide electricity but also something called “inertia,” which helps keep the frequency of the power supply stable. Solar systems, however, cannot provide this type of support. Inertia, created by the spinning mass in large generators, helps the grid resist sudden changes and avoid power failures. Without enough inertia, even small issues can cause large-scale blackouts. For example, on April 12, the demand dropped to just 1,550 MW in the morning. At the same time, solar generation increased, forcing CEB to shut down many large synchronous generators. CEB took urgent measures to manage the electricity supply and maintain grid stability. These actions helped keep the inertia support at 56%, which was enough to prevent a blackout. Without this management, inertia would have dropped to 34%, which is dangerously low. This would have made the grid extremely vulnerable to disruptions. There are more than seven million electricity users in Sri Lanka, but only about 100,000 have rooftop solar systems. Still, the impact of unstable grid conditions affects everyone. CEB emphasized that they cannot monitor or control rooftop solar systems directly, as these operate automatically based on sunlight and not according to electricity demand. This creates challenges in maintaining a balanced grid, especially during holidays when usage is very low. Currently, Sri Lanka does not have enough Battery Energy Storage Systems (BESS), water batteries, or grid-forming inverters that could help manage this situation. Until such technologies are deployed on a larger scale, the country must continue to rely on traditional large power plants to ensure the stability of the grid. To assist in this effort, CEB plans to send SMS reminders to all solar PV customers. They urge solar system owners to support this call for action to protect the grid and ensure reliable electricity for everyone during this sensitive period. The cooperation of rooftop solar users is essential to prevent blackouts and maintain a stable power supply during the New Year celebrations. |
