'Water batteries' for the Philippines? 5 things to know

It is adding solar and wind power at a pace that could eventually transform the electricity system, while at the same time confronting one of the oldest problems in power generation: What happens when the sun stops shining and the wind stops blowing?

It is called pumped-storage hydropower, sometimes described as a giant “water battery.” Instead of storing electricity inside chemicals, it stores energy by moving water uphill.

The concept is simple: Use excess electricity — ideally from solar or wind — to pump water from a lower reservoir to a higher one. When electricity is needed, release the water downhill through turbines and generate power.

The Philippine tourism authority, for example, describes Iligan City alone as having 24 waterfalls, reinforcing the country's unusually high concentration of waterfalls.

Aliwagwag Falls in Cateel, Davao Oriental, is regarded as the highest waterfall in the country, standing at roughly 340 meters with over 130 cascading tiers.

Limunsudan Falls in Iligan, Mindanao, measures about 270 meters (870 feet) high and is known as a grand, two-tiered drop.

The iconic Maria Cristina Falls, also located in Iligan City, stands at 98 meters (322 feet) high, and is famous as the primary source of hydroelectric power for the region.

Tinuy-an Falls in Bislig, Surigao del Sur, is 55 meters (180 feet) high and spans 95 meters wide, often called the "Niagara Falls of the Philippines".

That's not to mention the 421 principal rivers recognised across the country, grouped into 18 major river basins.

The Philippine Department of Energy has already made pumped storage a major part of its renewable-energy strategy.

Under the third Green Energy Auction, the government targeted 4,250 megawatts of pumped-storage hydropower, while bids representing 6,350 MW were submitted.

Among the projects accepted under the auction are the 2,000-MW Maton pumped-storage project in Apayao, the 500-MW Kibungan project in Benguet, the 600-MW Wawa project in Rizal and the 1,400-MW Pakil project in Laguna.

The government and Japan International Cooperation Agency (JICA) are conducting a nationwide inventory of potential hydropower sites, specifically including locations suitable for pumped-storage facilities of more than 100 MW.

That makes the question less about whether the Philippines can use water batteries and more about how responsibly and intelligently it should do so.

When electricity is plentiful — say, at midday when solar farms are producing more power than the grid needs — pumps use that electricity to move water uphill.