A new type of photovoltaic power station is emerging. Built in reservoirs, lakes and ponds, solar panels floating on the water surface have advantages over traditional ground-mounted solar systems in terms of land conservation, efficiency and water loss reduction.
A group of researchers, led by Chinese scientist Zeng Zhenzhong, estimated the potential contribution to energy supply and water conservation by such floating photovoltaic (FPV) systems in the world, according to a Science and Technology Daily report.
Growing global energy use and the adoption of sustainability goals to limit carbon emissions from fossil fuels are increasing the demand for clean energy. FPV has become a promising clean energy provider by saving a lot of land resources and raising the efficiency of power generation through the cooling effect of water evaporation.
Zeng Zhenzhong, an environmental scientist with Southern University of Science and Technology in China, led researchers from China, the United States, Thailand and other countries in evaluating how much FPV systems can contribute to energy supply and water conservation.
Based on three global reservoir databases and a realistic climate-driven photovoltaic system simulation, the team estimated that the potential electricity generation by FPV systems, with a 30 percent coverage on 114,555 global reservoirs, is about 9,434 terawatt-hours (TWh) per year.
According to latest data from the International Hydropower Association, some 4,252 TWh of electricity had been generated by hydropower in 2021.
The regions with the highest FPV power generation potential are mainly in parts of the United States, eastern Brazil, Portugal, Spain, northern South Africa, Zimbabwe, India and eastern China, according to the study published in the journal Nature Sustainability.
Besides the power generation, the reduced evaporation caused by FPV could conserve over 100 billion cubic meters of water every year, equivalent to the annual water consumption of 300 million people.
China has more than 15,000 reservoirs with the potential to use FPV systems, ranking second in number in the world. The country's FPV power generation potential reaches 1 TWh per year, according to the study.
In western China where solar radiation flux is high, some cities should be able to fully meet their needs with FPV electricity from reservoirs, while in central and southern China, FPV electricity output levels will be far from enough, said Jin Yubin, the first author of the study paper. Jin is also from Southern University of Science and Technology.
In China, many FPV projects have been built in recent years. The project in Huainan, east China's Anhui Province, was built in a coal mining subsidence area. Its solar panels absorbed a lot of heat to curb the algae reproduction in the pond and the water environment improved as a result.
Another FPV project built in the tidal flats area in Xiangshan, east China's Zhejiang Province, can generate electricity amounting to 350 million kilowatts per year.
Through rational development and application, FPV can make an important contribution to energy development and water security, but strict environmental assessment and monitoring is required, said Zeng, adding that it is more appropriate to install FPV systems in artificial environments and on degraded land such as mines and sewage treatment plants.
The study also showed that developing countries have greater potential for FPV development. The FPV potential in 40 developing countries is higher than their current electricity demand.
For example, Brazil has an annual electricity demand of up to 538 TWh, which can be fully met by FPV development. The FPV potential in six countries with abundant reservoirs, including Zimbabwe, Laos, Ethiopia, Cameroon, Myanmar and Sudan, is three to 10 times higher than their current electricity demand.
With experience gained during domestic development, China is also working with other countries to build FPV projects.
On December 6, 2022, the FPV project jointly built by China and Thailand was connected to the grid of Thailand. It is the largest FPV project in the country at present, with an annual power generation of 95 million kWh.
The FPV project built by the two countries in the Sirindhorn Dam was put into commercial operation in October 2021. The installed capacity of the project reaches 58.5 megawatts, which can reduce carbon dioxide emissions by 47,000 tonnes every year.
Featuring a combination of two energy sources, the project in the Sirindhorn Dam generates electricity through solar energy during the daytime and via hydro power at night, prolonging the continual period of power generation and reducing fluctuations in renewable energy levels.
"Large-scale FPV applications are still in their infancy in most regions of the world. Given the cost and environmental impact, we recommend that priority be given to renewable energy projects with a mix of FPV and hydropower," Zeng said.