CAGAYAN DE ORO CITY – A Mindanao-based consortium unsolicited proposal to rehabilitate, operate and maintain the Agus-Pulangi Hydropower Complex (APHC) will be using proven technology and management systems previously used in the grid by the National Power Corporation (Napocor).
The Greenergy Renewables Group Inc. (GRGI) submitted the unsolicited proposal dubbed Energy Storage Project (ESP) to the Public-Private Partnership Center last September. GRGI proposes establishing a mass-based owned Special Purpose Vehicle (SPV) entity to implement the long-sought rehabilitation of the ageing power complex that served as the backbone of the Mindanao power grid.
Lake Lanao offers significant energy storage via its vast water volume (over 1 billion cubic meters usable) and elevation, primarily serving the Agus-Pulangi hydropower system, but its potential is linked to managing water levels for both power and ecological/community needs, allowing integration with solar for grid stability, acting as a large natural battery for Mindanao’s renewables.
Lake Lanao acts as a massive natural reservoir for the Agus River system, storing potential energy in its water volume, which is released through dams to generate electricity. It holds a significant “allowable disposable volume” of about 1 billion cubic meters, with water level fluctuations managed between 698.15 to 701.65 meters above sea level (masl) to balance power needs with flood prevention and ecology.
The lake’s hydropower plants (part of the Agus-Pulangi complex) provide baseload and peaking power, crucial for Mindanao’s grid, though sensitive to dry seasons.
Moving forward, most significant perhaps is how its storage capacity is vital for integrating intermittent renewables like solar, as excess daytime solar power can reduce hydro load, conserving water for peak evening demand.
“Lake Lanao is our biggest natural battery storage facility,” said Engr. Cerael C. Donggay, President & CEO of GRGI. “When I was still the Napocor’s Vice President for Mindanao, we used our two 200MW power barges as the battery charger of Lake Lanao. These two operate during the daytime, allowing Lake Lanao to restore its water levels. During peak hours in the evening, the stored energy was released to meet the increased water demand.”
Lake Lanao acts as a vast natural reservoir, but its storage potential translates into the generating capacity (MW) of the hydropower plants it serves, not a fixed GWh figure, though its role is critical for Mindanao’s energy.
In comparison, the largest operational Battery Energy Storage Systems (BESS) in the Philippines today are San Miguel Corporation’s (SMC) network, with its various sites contributing to a total of 1,000 MWH, and Citicore’s integrated agrovoltaic/BESS system in Batangas (320 MWh) recently coming online, with SMC’s large scale deployments pioneering the grid.
What GRGI proposes to do is replace the electricity previously provided by the power barges with floating solar farms in Lake Lanao, a system already being used in Thailand, South Korea, and other Asian countries.
Proof of Concept
The state-run Electricity Generating Authority of Thailand (EGAT) 1,000 MW Hydro-Floating Solar Hybrid (Hydro-FSP) plan started with five pilot dams: Sirindhorn (45MW), Srinakarin, Ratchaprapha, Bhumibol, and Ubol Ratana, integrating solar with hydropower for stable, renewable energy, creating the world’s largest hydro-floating solar system at Sirindhorn Dam as the initial success, with more phases planned across other dams like Vajiralongkorn to build out the total capacity.
Floating solar is an emerging technology where solar panels are mounted on floating structures and placed on natural or man-made water bodies. The electricity generated is then transmitted to electrical equipment on shore via underwater cables. Existing transmission systems in hydropower facilities can be utilized to store and distribute the electricity generated from the floating solar arrays. At some large hydropower plants, covering just three to four percent of the reservoir with floating solar could double the capacity of the plant.
Combining hydropower and solar power outputs can help manage periods of low water availability by using solar capacity first, and drawing on hydropower at night or during peak demand, according to a market report on floating solar produced by the World Bank Group and the Solar Energy Research Institute of Singapore (SERIS) Titled Where Sun Meets Water: Floating Solar Market Report. The study noted that in reservoirs, floating solar panels can drastically reduce evaporation by limiting air circulation and intercepting sunlight before it hits the water’s surface. The reduction of sunlight also helps prevent algae blooms, which pollute water and raises treatment costs.
The technology is making inroads in Singapore and archipelagos like Indonesia and the Philippines, which have vast coastlines and numerous inland bodies of water. Apart from Thailand, there is also interest in the technology from other countries which have invested heavily in hydropower such as Lao PDR which operates 46 hydropower stations.
While floating solar panels cost more to install compared to ground-mounted systems, they are a better long-term investment as they are up to 16 percent more efficient as the cooling effect of the water helps reduce thermal losses and extends their lifespan. Apart from saving land for agricultural or other uses, floating solar arrays can also convert underutilized bodies of water such as ponds or lakes into revenue-generating operations.
More recently, South Korea switched on a major 47.2 MW floating solar farm on the Imha Dam, creating a powerful hybrid system with the dam’s hydropower for stable, 24/7 renewable energy, solving land scarcity issues, boosting efficiency via water’s cooling effect, and offering a model for integrating solar and hydro, with profits shared with local residents. This project uses existing infrastructure (dam, transmission lines), providing clean power for thousands and reducing evaporation.
Imha Dam already hosts a 50 MW hydropower plant, and the combined setup allows the complex to send floating solar power to the grid during daylight hours and switch to hydropower generation overnight to maintain steady output.
By combining solar and hydro, South Korea has created a flexible system that stabilizes energy supply even during cloudy periods. Hydropower can instantly ramp up when the sun dips, ensuring consistent output and reducing reliance on fossil fuels.
Vast potential
The installation of floating solar arrays only started in 2007 with just over 100 projects worldwide according to the US’ National Renewable Energy Laboratory (NREL). Out of these, 73 of the largest projects are in Japan. Hence, it is a relatively new renewable energy source.
However, the industry has grown more than a hundred-fold in less than four years. From a worldwide installed capacity of 10 MW at the end of 2014, the number had risen to 1.1 gigawatts (GW) by September 2018, according to the Where Sun Meets Water report.
The report estimates the global potential of floating solar, even under conservative assumptions, to be 400 GW – roughly the total capacity of all solar photovoltaic installations worldwide at the end of 2017.
The global cumulative installed floating solar capacity reached an estimated 5.9 GW by the end of 2023, with some sources citing over 7.8 GW operational as of early 2024. Market growth in 2024 and 2025 is expected to push the total capacity to around 8 GW.
The sector is expected to grow at a compound annual growth rate (CAGR) of over 27%. The global capacity is projected to reach between 50 GW and 75 GW by 2030.
The Asia-Pacific (APAC) region is the primary driver of growth, with China, India, Japan, South Korea, and Thailand being major markets. China hosts some of the world’s largest floating solar installations, including a 320 MW project in Shandong province.
