The National Grid Corporation of the Philippines (NGCP) has officially welcomed the upcoming Terra Solar Power Project, recognizing it as a major step forward for the country's renewable energy ambitions. However, the grid operator simultaneously issued a stark warning about the potential operational challenges that such a large-scale, intermittent power source could pose to the stability of the national transmission system.
A Massive Boost for Clean Energy
The Terra Solar Power Project represents a significant infusion of clean power into the Philippine energy mix. With a total generation capacity of 2,500 Megawatts (MW), it stands as one of the country's largest solar ventures. Crucially, the project will be supported by a substantial 1,125MW battery energy storage system (BESS), designed to store excess energy and sustain output for approximately four hours when solar generation dips.
Under a Power Supply Agreement, 850MW of Terra Solar's output will be supplied directly to MERALCO, primarily during daytime hours. The remaining 1,650MW will be injected into the grid via the Wholesale Electricity Spot Market (WESM). As a variable renewable energy (VRE) source, the project operates on a "must-dispatch" basis as mandated by Republic Act 9513, which grants priority to renewables in the dispatch schedule.
The Grid Stability Challenge
While celebrating the addition of new supply, NGCP emphasized that not all renewable technologies are created equal. The corporation pointed out that solar and wind power are, by nature, variable and intermittent. This characteristic can lead to fluctuations in system frequency and voltage if not meticulously managed.
"Any new power source introduced into the system will help keep supply stable. However... some technologies are, by nature, variable or supply intermittently, and therefore need to be handled more carefully," NGCP stated. The grid operator cautioned that unmanaged variability could potentially lead to under-frequency load shedding or rotating power interruptions in some areas.
This concern was recently illustrated by a voltage fluctuation incident in parts of North Luzon, which NGCP attributed to unstable output from renewable energy sources in the region. The incident forced the grid operator to take immediate mitigating actions to prevent wider disturbances.
The Critical Role of Fast-Acting Support
NGCP highlighted the operational reality of solar variability, citing experience from the San Marcelino Solar Farm in Zambales. There, brief cloud cover can cause short-term solar output to swing by as much as 300MW. Conventional power plants like coal have limited ability to respond quickly to such sudden changes due to their longer ramping times.
This is where battery energy storage systems (BESS) become indispensable. NGCP identified BESS as a "fast-acting resource" critical for providing rapid support to maintain frequency stability as solar penetration increases. The Terra Solar project's integrated BESS is a key component in addressing this very challenge.
A Call for Progressive Policy and Balanced Resources
Looking ahead, NGCP reiterated its call to the Department of Energy (DOE) for more incisive and progressive policies governing the entry of variable renewable energy into the grid. The company stressed that grid stability must be the primary consideration.
NGCP advocates that the entry of bulk VRE projects like Terra Solar must be complemented by a balanced mix of dependable baseload power and fast-ramping energy resources. This combination is essential to ensure a stable and reliable power supply for the entire country, paving the way for a sustainable energy transition without compromising grid integrity.
The corporation also reminded all generation companies that all required facilities, as determined in system impact studies, must be fully complied with on the plant side to ensure seamless and stable integration into the national transmission network.
