National Grid Corp. of the Philippines (NGCP) cautioned that a heavy reliance on intermittent power sources may pose operational challenges to grid stability even as it welcomed the Terra Solar Power Project as a significant addition to the country’s energy mix.
The 2,500-megawatt Terra Solar facility includes a 1,125-MW battery energy storage system capable of sustaining output for four hours.
NGCP said in a statement solar generation could cause fluctuations in system frequency and voltage that could lead to under-frequency load shedding or rotating power interruptions if not properly managed.
The transmission operator noted that while any new power source helps keep supply stable, variable renewable energy sources like wind and solar should be handled more carefully than other technologies.
The company said that operational considerations must be managed on both the transmission side and the generating plant side to mitigate inherent fluctuations.
A recent voltage fluctuation incident in North Luzon underscored these concerns after unstable output from local renewable energy sources forced NGCP to take mitigating actions.
Experience at the San Marcelino Solar Farm in Zambales showed that brief cloud cover can cause short-term solar variability of up to 300 MW.
The company said that while such variability could be managed with fast-acting resources, conventional generation like coal power plants has limited capability to respond quickly due to longer ramping times. Battery energy storage systems play a critical role in providing rapid support to maintain frequency stability as solar penetration increases.
Terra Solar will supply 850 MW to Meralco through a power supply agreement primarily during the daytime, while the remaining 1,650 MW will be injected into the grid via the Wholesale Electricity Spot Market. As a variable renewable energy source, the project operates on a must-dispatch basis under Republic Act 9513, which mandates priority scheduling for dispatch into the transmission grid.
NGCP reiterated its call to the Department of Energy for more progressive policies on the entry of variable renewable energy that focus on grid stability.
The company said the entry of bulk renewable power should be complemented by dependable baseload and fast-ramping energy resources to ensure a reliable power supply.
The Philippines continues to transition toward a cleaner energy mix, but the cost of maintaining grid reliability remains a factor for power consumers.
