Solar–hydro hybrid systems combine photovoltaic (PV) generation with hydropower to deliver more stable and flexible renewable electricity. Floating PV arrays installed on hydropower reservoirs use existing surface area and benefit from water-based cooling, which can improve panel performance and avoid land-use impacts while potentially reducing water evaporation in suitable climates. Solar PV provides efficient daytime output, while hydropower offers controllable generation that compensates for rapid changes in sunlight, supports evening peaks and maintains supply during cloudy or seasonal variations. By leveraging the complementary operating profiles of both technologies, hybrid systems can increase renewable utilization, reduce reliance on thermal backup and enhance the operational flexibility of existing hydropower assets. Digital control platforms further optimize the interaction between PV output, hydropower regulation and grid requirements to smooth variability, coordinate ramping and support system reliability in regions with high shares of solar generation. 

The International Renewable Energy Agency (IRENA) notes that hybridizing hydropower with solar PV improves system operation across multiple time scales, reduces curtailment and increases transmission utilization.[1] Additional benefits are possible when hydropower is paired with battery energy storage to expand operating range and enhance grid flexibility. 

Main outcomes of the solution 

• Sustainability: Enables additional solar generation without requiring new land and can reduce water evaporation on reservoirs in favorable climates; complementary operation lowers reliance on fossil-based backup and supports broader decarbonization efforts. 
• Reliability & Flexibility: Improves balancing capability by using hydropower to stabilize variable solar output across daily and seasonal cycles, enabling more predictable renewable dispatch.  
• System Resilience: Leverages hydropower’s fast-response capability to manage solar fluctuations and maintain stability during weather-related variability or demand spikes, while making better use of existing grid and hydropower assets. 

Key deployment and scaling factors 

1. Assess site suitability for solar–hydro hybridisation by analysing local solar resources, hydropower operating profiles, hydrological constraints and demand patterns. 
2. Deploy unified control platforms to coordinate real-time interaction between PV output, hydropower regulation and grid requirements. 
3. Define clear operating strategies for joint dispatch so that both resources contribute optimally across different times of day and seasons. 
4. Establish supportive regulatory and commercial models that recognise hybrid-system benefits such as higher renewable utilisation and reduced curtailment. 
5. Adapt grid-connection and protection settings to meet technical requirements including voltage, frequency, ramp-rate and disturbance performance. 
6. Conduct environmental and reservoir-engineering assessments for floating PV, including mooring design, reservoir ecology and water-use impacts. 
7. Coordinate with hydropower operators to align hybrid operation with flood-control, irrigation and water-management obligations. 

Case Study 

The Electricity Generating Authority of Thailand (EGAT) and Siemens (2021), Thailand 

Commissioned in 2021, the Sirindhorn Dam project in Thailand is one of the world’s largest hydro–floating solar hybrid installations. The Electricity Generating Authority of Thailand (EGAT) integrated a 45 MW floating solar PV array with the existing 36 MW hydropower plant, enabling coordinated output from both resources. The floating PV panels cover part of the reservoir surface, allowing power generation without new land requirements. Siemens provided digital control and energy-management software, which forecasts solar and hydropower production, manages joint power dispatch and coordinates the combined output based on weather conditions, reservoir management needs, and grid requirements. 

According to EGAT, the project configuration enhances clean-energy production, supports national decarbonization goals, and serves as a model for maximizing the value of existing hydropower infrastructure through hybridization. The project is expected to reduce CO₂ emissions by around 47,000 tons/year. The project demonstrates how digital control systems can improve renewable utilization and deliver stable output from variable solar resources.[2,3]

References:

1. The changing role of hydropower I IRENA (2023)  
2. The World’s Largest Hydro-Floating Solar Hybrid I EGAT (July 2021) 
3. EGAT deploys Siemens’ software solutions for the world's largest Hydro-Floating Solar Hybrid Project I Siemens (January 2022)