Amid Climate Uncertainty, Floating Solar Builds Resilience
Given Southeast Asia’s rapid electricity demand growth and increasing climate uncertainty, diversification of the power supply is key for energy security
Southeast Asia is responsible for nearly a quarter of global energy demand growth through 2035, but it is currently heavily dependent on imported fossil fuels and hydropower. Given recent volatility in both fossil fuel prices and increasing severity and regularity of heatwaves and droughts which make hydropower less reliable, diversification into domestically located renewable energy sources like solar will have energy security benefits. This is particularly true for countries like Cambodia, Laos, Thailand, and Vietnam, which have significant existing hydropower in their power supply and also significant untapped solar potential. Floating solar (FPV) is a low-cost way to quickly diversify the power mix in ways that complement existing hydropower, support water conservation efforts at existing dams, and reduce the need for expensive new dams which have negative social and environmental impacts.
Southeast Asia will account for a quarter of global energy demand growth through 2035, making the region a crucial landscape for clean energy deployment. Hydropower provides most of the region’s existing and planned renewable energy potential because it is dispatchable and easier to integrate than variable solar and wind. However, increasingly severe droughts and heatwaves that reduce river flow and increase demand for air conditioning and thus electricity raise questions about the heavy reliance on hydropower.
For countries in the Mekong region, which have ample installed hydropower but struggle to meet rapidly growing electricity demand, floating solar is a low-cost way to quickly diversify the power mix in ways that complement hydropower, support water conservation efforts at existing dams, and reduce or delay the need to build new dams that displace people and can devastate fisheries. This is crucial as Mekong countries are highly dependent on freshwater fisheries for protein and micro-nutrients.
Floating solar photovoltaic (FPV) is a natural complement to existing hydropower in Cambodia, Laos, Myanmar, Thailand, and Vietnam, all of which plan to expand hydropower, with the most significant buildouts planned in Laos and Myanmar. But extreme weather events—including both seasonal and multi-year droughts—undermine hydropower’s reliability as a baseload and dispatchable power source.
In early 2023, a severe drought in Vietnam led to a 90% drop in hydropower, causing major blackouts which in turn caused Vietnam’s largest foreign investor Samsung to suspend production. In 2024, an El Nino drought drove the national utility of Vietnam to reduce hydroelectricity output for much of the dry season and to ramp up coal to avoid additional blackouts.
While improved water forecasting and management can mitigate some drought impacts, FPV offers a much more effective avenue for energy diversification and resilience.
Thailand was an early adopter of FPV, with its first project—a 45 MW FPV farm installed on the 36 MW multi-use Sirindhorn dam—coming online in 2022. It has been a success, with EGAT reporting at a conference in Ubon Ratchathani in October 2024that as well as generating electricity, FPV at Sirindhorn increased hydropower production by reducing evaporation equivalent to 500 million m3 in the first few years of operation. When coordinated directly with dam operations, FPV can also replace some daytime hydropower production and reserve reservoir water for future use.
FPV addresses some of the constraints that have limited the uptake of traditional solar power in ASEAN. Nine of the 10 ASEAN countries have stated carbon neutrality goals, all of which require rapid expansion of solar and other clean energy sources. The region has high solar radiation that can be used to generate large amounts of power domestically, a key energy security concern. Solar power is also cost-competitive. A study by Wood Mackenzie showed that by 2023 solar was the cheapest power source in Asia-Pacific. But it comes with challenges. It requires large areas of land; is variable, meaning that it produces power based on available sunshine and is not dispatchable on demand; and is unavailable at night, requiring energy storage or other energy sources to meet overnight electricity demand.
FPV addresses many of these constraints. Floating solar panels on a reservoir does not compete with other land uses. Land-scarce Singapore was an early adopter, installing 60 MW of FPV on the Tengeh Reservoir in 2021. If a FPV project is operated in conjunction with hydropower, it becomes dispatchable as solar can reliably provide power during the daytime in most seasons while hydropower can offset short drops in power production from clouds and be used to ramp up generation in the evening to provide energy overnight. FPV also enjoys energy efficiency benefits with studies indicating 5-15% increases due to the cooling effect of being located on water.
Both Thailand’s Electricity Generating Authority and Singapore’s Energy Market Authority plan to expand FPV. In Thailand, the first operational FPV project at Sirindhorn has consistently produced more electricity than originally expected, reducing the payback time to only five years. This was the first of a planned series of 9 FPV projects on EGAT reservoirs. But the experience was so successful that EGAT is currently considering deploying FPV more widely on hydropower reservoirs and potentially on the much larger number of irrigation reservoirs in Thailand. These would require additional transmission lines but could greatly increase domestic solar power.
The Public Utilities Board of Singapore plans to build additional FPV on the Pandan, Kranji, and Lower Seletar reservoirs. These projects will add over 200 MW of FPV to help meet a national target of 2,000 MW of solar by 2030. Conditions are ripe to expand FPV beyond Thailand and Singapore to other countries in the Mekong. The region has high solar irradiation and existing hydropower, and FPV provides a low-cost opportunity to diversify power production and reduce vulnerability to droughts. Cambodia has four reservoirs larger than 1,000 hectares suitable for FPV, Laos has 21, and Vietnam 30. While potential FPV output would vary by location and project size, these reservoirs are “low-hanging fruit” since FPV would plug into existing transmission lines and there would be zero land compensation.
The region’s governments could learn from Thailand and Singapore’s experience deploying and, critically, integrating FPV into the national grid. Singapore has expressed willingness to advise its ASEAN partners on clean energy issues, with FPV an easy opportunity. Mekong governments should establish regulations to accelerate FPV and identify priority zones for solar projects which can be operated conjunctively with existing hydropower.
This is the first of two pieces on new energy opportunities in the Mekong region. Its preparation was generously supported by the Building River Dialogue and Governance (BRIDGE) Project, which aims to build water governance capacities through learning, demonstration, leadership, and consensus building, and is funded by the Swiss Agency for Development and Cooperation (SDC) and led by IUCN.
Amid Climate Uncertainty, Floating Solar Builds Resilience
By Courtney Weatherby
Southeast Asia
Southeast Asia is responsible for nearly a quarter of global energy demand growth through 2035, but it is currently heavily dependent on imported fossil fuels and hydropower. Given recent volatility in both fossil fuel prices and increasing severity and regularity of heatwaves and droughts which make hydropower less reliable, diversification into domestically located renewable energy sources like solar will have energy security benefits. This is particularly true for countries like Cambodia, Laos, Thailand, and Vietnam, which have significant existing hydropower in their power supply and also significant untapped solar potential. Floating solar (FPV) is a low-cost way to quickly diversify the power mix in ways that complement existing hydropower, support water conservation efforts at existing dams, and reduce the need for expensive new dams which have negative social and environmental impacts.
Southeast Asia will account for a quarter of global energy demand growth through 2035, making the region a crucial landscape for clean energy deployment. Hydropower provides most of the region’s existing and planned renewable energy potential because it is dispatchable and easier to integrate than variable solar and wind. However, increasingly severe droughts and heatwaves that reduce river flow and increase demand for air conditioning and thus electricity raise questions about the heavy reliance on hydropower.
For countries in the Mekong region, which have ample installed hydropower but struggle to meet rapidly growing electricity demand, floating solar is a low-cost way to quickly diversify the power mix in ways that complement hydropower, support water conservation efforts at existing dams, and reduce or delay the need to build new dams that displace people and can devastate fisheries. This is crucial as Mekong countries are highly dependent on freshwater fisheries for protein and micro-nutrients.
Floating solar photovoltaic (FPV) is a natural complement to existing hydropower in Cambodia, Laos, Myanmar, Thailand, and Vietnam, all of which plan to expand hydropower, with the most significant buildouts planned in Laos and Myanmar. But extreme weather events—including both seasonal and multi-year droughts—undermine hydropower’s reliability as a baseload and dispatchable power source.
In early 2023, a severe drought in Vietnam led to a 90% drop in hydropower, causing major blackouts which in turn caused Vietnam’s largest foreign investor Samsung to suspend production. In 2024, an El Nino drought drove the national utility of Vietnam to reduce hydroelectricity output for much of the dry season and to ramp up coal to avoid additional blackouts.
While improved water forecasting and management can mitigate some drought impacts, FPV offers a much more effective avenue for energy diversification and resilience.
Thailand was an early adopter of FPV, with its first project—a 45 MW FPV farm installed on the 36 MW multi-use Sirindhorn dam—coming online in 2022. It has been a success, with EGAT reporting at a conference in Ubon Ratchathani in October 2024that as well as generating electricity, FPV at Sirindhorn increased hydropower production by reducing evaporation equivalent to 500 million m3 in the first few years of operation. When coordinated directly with dam operations, FPV can also replace some daytime hydropower production and reserve reservoir water for future use.
FPV addresses some of the constraints that have limited the uptake of traditional solar power in ASEAN. Nine of the 10 ASEAN countries have stated carbon neutrality goals, all of which require rapid expansion of solar and other clean energy sources. The region has high solar radiation that can be used to generate large amounts of power domestically, a key energy security concern. Solar power is also cost-competitive. A study by Wood Mackenzie showed that by 2023 solar was the cheapest power source in Asia-Pacific. But it comes with challenges. It requires large areas of land; is variable, meaning that it produces power based on available sunshine and is not dispatchable on demand; and is unavailable at night, requiring energy storage or other energy sources to meet overnight electricity demand.
FPV addresses many of these constraints. Floating solar panels on a reservoir does not compete with other land uses. Land-scarce Singapore was an early adopter, installing 60 MW of FPV on the Tengeh Reservoir in 2021. If a FPV project is operated in conjunction with hydropower, it becomes dispatchable as solar can reliably provide power during the daytime in most seasons while hydropower can offset short drops in power production from clouds and be used to ramp up generation in the evening to provide energy overnight. FPV also enjoys energy efficiency benefits with studies indicating 5-15% increases due to the cooling effect of being located on water.
Both Thailand’s Electricity Generating Authority and Singapore’s Energy Market Authority plan to expand FPV. In Thailand, the first operational FPV project at Sirindhorn has consistently produced more electricity than originally expected, reducing the payback time to only five years. This was the first of a planned series of 9 FPV projects on EGAT reservoirs. But the experience was so successful that EGAT is currently considering deploying FPV more widely on hydropower reservoirs and potentially on the much larger number of irrigation reservoirs in Thailand. These would require additional transmission lines but could greatly increase domestic solar power.
The Public Utilities Board of Singapore plans to build additional FPV on the Pandan, Kranji, and Lower Seletar reservoirs. These projects will add over 200 MW of FPV to help meet a national target of 2,000 MW of solar by 2030. Conditions are ripe to expand FPV beyond Thailand and Singapore to other countries in the Mekong. The region has high solar irradiation and existing hydropower, and FPV provides a low-cost opportunity to diversify power production and reduce vulnerability to droughts. Cambodia has four reservoirs larger than 1,000 hectares suitable for FPV, Laos has 21, and Vietnam 30. While potential FPV output would vary by location and project size, these reservoirs are “low-hanging fruit” since FPV would plug into existing transmission lines and there would be zero land compensation.
The region’s governments could learn from Thailand and Singapore’s experience deploying and, critically, integrating FPV into the national grid. Singapore has expressed willingness to advise its ASEAN partners on clean energy issues, with FPV an easy opportunity. Mekong governments should establish regulations to accelerate FPV and identify priority zones for solar projects which can be operated conjunctively with existing hydropower.
This is the first of two pieces on new energy opportunities in the Mekong region. Its preparation was generously supported by the Building River Dialogue and Governance (BRIDGE) Project, which aims to build water governance capacities through learning, demonstration, leadership, and consensus building, and is funded by the Swiss Agency for Development and Cooperation (SDC) and led by IUCN.
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