In 2017, the USAID-NREL Partnership facilitated discussions with Ghana’s Bui Power Authority (BPA) at an NREL-hosted workshop focused on advanced photovoltaic (PV) plant capabilities, solar and wind grid integration, and best practices on integrating small-scale and utility-scale VRE into Ghana’s grid. After the workshop, BPA invited the NREL team to provide additional technical assistance to support BPA with adding power from solar PV to an existing 400 MW hydroelectric project to cut greenhouse gases, augment the hydropower and provide energy diversity.

USAID’s Power Africa West Africa Energy Program (WAEP) and NREL collaborated with BPA to operationalize 50 MW of PV within the 400 MW Bui Generating Station hydroelectric site in 2021, with plans to grow PV capacity to 250 MW. The Bui project, on the Black Volta River, is the largest hydro plant in Ghana behind 1,020 MW Akosombo. The first 50 MW of the solar plant generates energy onto the national grid during the day, with 1 MW of the installed system consisting of floating solar PV.

Scheduled for completion by late 2022, the plant will also contain a 20-MWh battery energy storage system and controls, which the NREL team suggested so the plant can meet grid codes for renewable energy resources, manage the variability of solar and increase the country’s power sector reliability.

The addition of PV to the hydro plant allows BPA to balance the variable output of solar by simultaneously increasing or decreasing hydropower output in real-time to maintain a steady power supply to meet demand, including the addition of controls and capabilities to effectively manage output. NREL worked with BPA’s renewable energy manager to provide in-depth analysis of the impacts of such hybrid hydro-PV operation and the institutional, operational, and hardware changes required to ensure the system can operate in a hybrid manner while maintaining system stability and reliability. In parallel, NREL worked with Ghana Grid Company Limited to better understand the potential operational impacts of interconnecting BPA’s hybrid system.

Once its full capacity is brought online, this hydro-solar plant will put Ghana on track to cut its power sector greenhouse gas emissions by 235,000 tons per year, NREL said.

“The global challenge of climate change, as well as the need to secure energy supply, makes the development of the hydro-solar plant very important for Ghana and West Africa,” said Peter Acheampong, deputy director of renewables at BPA.

Since 2017, the NREL-WAEP team has hosted workshops, provided technical analysis, reviewed grid impact and stability studies for the plant, modeled power flow for transient events, and evaluated plant designs to ensure compliance with Ghana’s new grid codes for VRE. They also offered guidance on utility-scale PV and worked alongside stakeholder and industry groups in Ghana to review best practices with operationalizing this VRE plant. In addition to working with BPA and the Volta River Authority (VRA, another Ghana power authority), the NREL-WAEP team collaborated with sector agencies — including distribution utilities, transmission utilities and independent power producers — in conducting analytical studies and impact assessments beyond the Bui solar project.

“We are equipping them with all the tools and lessons we learned in the United States about VRE integration, and, in some cases, helping them to avoid some of the challenges we had with the latest technology and standards. Having this type of partnership is an effective way to streamline the process of integrating advanced technologies,” said David Corbus, the Wind Grid Integration Lead at NREL and a member of the NREL-WAEP team supporting the Ghana solar project.