A study published March 13 in the journal Nature Sustainability argues that floating solar on many of the world’s reservoirs could provide a significant share of the renewable energy needed to transition away from electricity generated by burning fossil fuels. Here’s the introduction to the study:
“Growing global energy use and the adoption of sustainability goals to limit carbon emissions from fossil fuel burning are increasing the demand for clean energy, including solar. Floating photovoltaic systems on reservoirs are advantageous over traditional ground mounted solar systems in terms of land conservation, efficiency improvement, and water loss reduction. Here, based on multiple reservoir databases and a realistic climate-driven photovoltaic system simulation, we estimate the practical potential electricity generation for FPV systems with a 30% coverage on 114,555 global reservoirs is 9,434 ± 29 TWh per year.
“Considering the proximity of most reservoirs to population centers and the potential to develop dedicated local power systems, we find that 6,256 communities and/or cities in 124 countries, including 154 metropolises, could be self-sufficient with local FPV plants. Also beneficial to FPV worldwide is that the reduced annual evaporation could conserve 106 ± 1 square kilometers of water. Our analysis points to the huge potential of FPV systems on reservoirs, but additional studies are needed to assess the potential long-term consequences of large systems.
“A global commitment to curb anthropogenic global warming necessitates the development of renewable energy sources to reduce the reliance on fossil fuels for generating electricity. Solar or photovoltaic power is gaining renewable energy market share because it is economical, quick to install in a wide range of environments and is especially appropriate for smart energy networks.
“Drawbacks to solar energy expansion are that traditional ground-based PV systems require large land areas for installation, demand routine cleaning with substantial volumes of water to maintain high energy conversion efficiency and suffer from heat-related voltage losses when installed in warm climates. The lack of large tracts of available land in many densely populated areas for constructing large solar arrays capable of providing electricity to existing nearby grids limits PV application.
“Key advantages of floating photovoltaic systems installed on existing reservoirs are that they preserve land for other uses, and most reservoirs tend to be located in proximity to existing grid systems. Furthermore, the cooling effect of water in some installations enhances energy conversion efficiencies and FPV panels/floats reduce reservoir water losses from evaporation by blocking radiative energy and lowering water temperatures. The global installed FPV capacity reached 1.3 GWp at end of 2018. This capacity is expected to accelerate as the technologies mature and reach 4.8 GW by the year 2026.”
NIMBY & You
Everyone who reads CleantTechnica on a regular basis knows that solar is critical to reducing global carbon emissions. The world is reliant on electrical energy, but continuing to use thermal generation to make it is a death sentence for humanity. We have to keep our remaining reserves of coal, oil, and gas in the ground if we want to have any hope of surviving as a species.
But here’s the thing. According to Euronews, solar uses about 70 times as much land per unit of energy as methane gas. As a general rule, there is little open space available in or near most urban areas to install solar panels (although they can certainly cover every parking lot and roof) and so solar farms are sited out in rural areas and in many cases require the construction of expensive high voltage transmission lines to get the electricity to where it is needed. People who live in those rural communities are understandably annoyed that their farmlands and green spaces are being taken over by solar farms to supply electricity to those over-educated pinheads in the cities. They are all in favor of solar and wind power just as long as it isn’t in their backyard.
Drinking water reservoirs, however, tend to exist near population centers and there are no vested interests who are concerned about preserving the surface of those reservoirs. Proximity to urban areas means shorter transmission lines. Decreasing the evaporation from those reservoirs could make enough fresh water available each year to meet the needs of 300 million people.
According to The Verge, when it comes to problems that need to be solved quickly in a warming world, floating solar panels tick a lot of boxes. Droughts curtail hydroelectricity generation as water levels drop and heatwaves can reduce a solar panel’s efficiency by up to 25%. Water has a cooling effect that can keep solar cells from overheating, boosting their output. Floating solar farms and hydroelectric dams working in tandem can boost power generation during hot summer days when the demand for electricity reaches its peak. In 2020, the US Department of Energy claimed that, according to its research, combining floating solar and hydroelectric power could provide up to 40% of the world’s needs for electricity.
The study found that most communities located next to water reservoirs tend to have populations of less than 50,000 people. Examples in the United States are Burlington, Vermont, or Harrisburg, Pennsylvania. Just 15% of the cities studied with populations bigger than 1 million people would be able to meet their entire electricity demand purely with floating solar farms. The United States is the country with the most suitable reservoirs, followed by China and Brazil the researchers found.
The study acknowledges that floating solar is not a panacea. Covering too much of the surface of a reservoir might reduce oxygen levels in the water to the detriment of fish and other aquatic organisms. More research is needed to determine what the ideal ratio is between floating solar panels and open water.
Floating solar has been installed at Fort Bragg, North Carolina. “A collaboration between Fort Bragg, Duke Energy and Ameresco, this utility energy service contract project will provide carbon-free on-site generation, supplement power to the local grid, and provide backup power for Camp Mackall during electricity outages,” the Army says. The town of Cohoes, New York has also spread floating solar panels across its drinking water reservoir to bring zero emissions electricity to its residents.
In Europe, Germany’s RWE is considering a proposal to intersperse floating solar panels on the North Sea that would be located between the towers of a wind farm, which seems like a smart way to multi-task in order to create more renewable energy.
NIMBY-ism is perhaps the greatest deterrent to adding more solar energy to the world’s electrical grids and yet renewable energy will be vital to the survival of the human species. Floating solar could greatly increase how quickly new solar power resources get designed, permitted, and installed. This latest study may alert more people to the advantages of floating solar, which would be a very good thing for us all.
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