Maria Theresa ‘Tetchi’ Capellan, a pioneer of solar PV in the Philippines, discusses the country’s crucial turning point in its adoption of energy storage.
Tetchi Capellan is president and CEO of SunAsia, a Philippines-based solar developer founded in 2013. SunAsia’s track record includes numerous large-scale PV plants and microgrid projects, and the jewel of its current development pipeline is a 1,300MW floating solar (‘floatovoltaics’) project.
Capellan also sits as vice chair of the Global Solar Council, secretary-general of the Asian Photovoltaic Industry Association and as founder and chair of the Philippine Solar & Storage Energy Alliance.
As such, she has played a major role in the development of the solar PV industry in the Philippines and the wider ASEAN region of Southeast Asia and now advocates for the essential and urgent adoption of energy storage.
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At Energy Storage Summit Asia 2025, held in the Philippines capital, Manila, Capellan speaks with Energy-Storage.news about the next phase of the ASEAN energy transition.
You have a rich history of working with renewable energy and, more recently, with energy storage. What does that really mean for you and your business?
The Philippines’ solar surge started in 2016 when the government implemented the feed-in tariff (FiT), and that was a price signal that got a lot of developers to build solar. That was the first round. The allocation was 100MW. Within a year, it increased to 500MW, but it was not a forward contract. It was a build-first contract, which means it was a race to the FiT. There was a deadline, and if you made it, you got the purchase agreement.
There was an oversubscription that reached as high as one gigawatt. Most of the projects were in one territory. As a result of that, as early as the first round of the feed-in tariff, we were experiencing the duck curve, because in that territory, it was easy to consolidate land. Unlike in other places, where consolidating land to achieve scale was a challenge, in that particular territory, because it was comprised of former plantations, it was easier. Therefore, of the one gigawatt, over 60% was located in that region.
The surge of solar in that territory really did something weird to the grid. They were having brownouts. They were having frequency issues. There were a lot of tricky things happening to the grid, and that was when all of the solar power plants were already online. That was in 2017, 2018, something like that. It was at that point that my company, SunAsia, created another company, Megawatt Solutions, which would specialise in storage.
What was the status of the market like at that time?
We had this feeling that storage was going to be the next thing, because of that experience in the territory, but it was very early. There was no market design. There was very limited understanding of what a battery could do. There was a lack of appreciation for what the technology was like. Then came the pandemic.
Now, what is very clear, is that if we are to transition and really achieve that ambitious share, large, significant share of renewables in the energy mix of the Philippines and also of the ASEAN region, we’ve got to do storage. That is really what needs to be done. In fact, I’m also the founder of the Philippines Solar and Storage Energy Alliance (PSSEA). As early as 2018, I rebranded PSSEA to include storage, because it was really important.
Now that the Philippine government has set a 50% by 2040 renewable energy target and the regulator has promised to create energy storage-specific market rules that ‘will define the playing field for the next decade’, how have things progressed, and what needs to happen now?
We are entering that era where storage is indispensable. One of the successful things that we’ve done is to make the government realise that storage is an asset class by itself. It can be a technology that can work with generating plants, with transmission, because it supports the grid, and with distribution behind-the-meter.
So, before the first Department of Energy policy [on storage], they considered storage as a generating plant. We had to tell them like they were five-year-olds: ‘Look at your phone. You have to charge it. Without you charging it, it dies. It cannot generate energy. It has to draw energy from a source.’
We had to be that elementary for the policymakers to understand. Then came the second generation of policy. This time, they recognised solar and storage can work together, but the way that they were pairing it is just, it’s a percentage of [the generation capacity] at 20%. It doesn’t look at the function of what exactly the problem is that you’re addressing for solar and storage to be a hybrid plant. What is it? Is it a peaking plant that you discharge at peak hours, so that you cut that peak? Is it baseload? So that you can provide a base load? We are currently at that stage in the Philippines.
‘Negative pricing can be channelled into a positive for society’
Globally, relatively successful markets are those that allow for the stacking of revenues from multiple applications, and perhaps a combination of merchant and contracted sources.
So far, the majority of battery energy storage system (BESS) projects we have seen go into commercial operation in the Philippines have been paired with thermal generation plants owned by large power producers, to increase their competitiveness in delivering ancillary services. What needs to happen for more diverse types of assets to be developed for various applications?
[The BESS projects at thermal power plants] are merchant. There is a contracted market and there’s a merchant market. The merchant market is very sophisticated and only very few participants can capture what needs to be done. We want that market to be vibrant, and we want that market to reach distributed energy participants. That is the gap that we need to [bridge].
For example, we are already experiencing negative pricing in the daytime. What does that mean? We don’t know yet what’s going on, but one thing is very clear: there is a lot of solar coming in during the morning, and therefore, very cheap solar.
That excess is not being experienced by consumers because most distribution utility companies are contracting for their demand. The current policy framework ensures that only 5% of your capacity is allocated to the wholesale market, with 95% contracted. What needs to be done is to reduce that. Start with 25:75 or maybe 30:70, and get the supplies of the 30% to participate in the wholesale market so that negative pricing can then be channelled to turn it to an advantage.
This is the first time Energy Storage Summit Asia has come to the Philippines, after two years in Singapore. What do you think a show like this can achieve and what are going to be the next steps for SunAsia’s energy storage subsidiary Megawatt Solutions?
We have to really understand better what this market is all about. The market design is so open. There are a lot of opportunities. Some are specialising in the transmission service providers. Some are specialising in generating, some in the distributed residential with battery space. So many applications, so many markets that we have to ask what revenue stacking could you do, and where is it most optimised, so that you can get as much revenue to benefit your bottom line?
This is the first conference to introduce energy storage, specifically focusing on storage. What we need to do is to excite the market by providing them with more information about the technology, the market design, and the regulations in other jurisdictions, so that developers can consider it more seriously and move to the next stage of development. That’s what this can do.