The idea of floating solar panels onto bodies of water first crept into the sphere of climate solutions about 10 years ago. The field got off to a slow start at first due to technical challenges. Fortunately, now the pace is picking up, just in time to help accelerate the global energy transition. Floating solar enables PV panels to be placed in locations that would otherwise be off limits, and that includes colder parts of the world.
Floating Solar Panels Can Work In Cold Weather
The issue for floating solar arrays is that thing about floating. To the extent that cold temperatures and stormy weather raise waves and create ice on the surface of the water, floating solar arrays pose challenges for PV developers that are absent from the fields of rooftop and ground-mounted solar.
Still, those are challenges worth overcoming. The US Department of Energy published its first comprehensive report on solar panels that float in 2018, and noted that the first known installation of a commercial-scale floating solar array anywhere in the world occurred in the US, at a California winery back in 2008. After that, the idea stalled out in the US, most likely due to the large amount of land available for in-ground solar development. However, floating solar began to take off overseas, providing ample opportunity for technology improvements over the past 13 years or so.
One recent example comes from the Chinese company Mibet Energy, which has just completed a new floating solar project in Poland.
“Poland has cold and lengthy winter during which the minimum temperature can reach as low as﹣40℃ and the snow period lasts for long time. The coldness and snow/wind places high requirement on the performance of solar mounting structure,” Mibet explains.
Mibet deployed its patented “MRac G4N” mounting structure for the new array, for which it claims the ability to resist wind loads of up to 42 meters per second (about 94 miles per hour) and one kilonewton of pressure (about 220 pounds) per square meter in snow load.
So, if anyone ever tells you that floating solar arrays can’t work in cold weather, point them over to Poland.
The Hidden Benefits Of Floating Solar Arrays
Another type of challenge for floating solar involves the impact of shade on aquatic life. That problem can be partially resolved by conserving a sufficient area of the surface as open water, but of course solar developers are interested in maximizing the area covered by PV panels, and in order to do that without causing excessive negative impacts, they need more information on potential impacts.
The body of research on the shade effects of floating PV panels is beginning to grow, and there is some good news on the solar side.
In one recent example, scientists with Lancaster University and the University of Stirling modeled the potential impact of a floating solar array on the largest lake in England, Lake Windermere.
While the research team warns of the potential for negative impacts under some conditions, they found that the cooling effect of shade from the solar panels could help ward off harmful algae blooms and reduce evaporation.
Under the right conditions, the shade from solar panels could also help bodies of water avoid becoming over-stratified, which occurs when the warming effect of the sun on the surface lingers too long on the top layers of water, and the bottom layers lose oxygen.
Suddenly, A Lot More Area Available For Solar Development
Another way to avoid negative environmental impacts would be to locate floating solar on human-made structures that house little or no aquatic life of value. In that 2018 report, the Energy Department’s National Renewable Energy Laboratory calculated that approximately 24,000 human-made reservoirs in the US offer the potential for solar development, which if realized could generate about 10% of the nation’s annual electricity.
That was a conservative estimate, based partly on the cost of electricity in some areas. The US EPA recently took stock of the nation’s bodies of water and counted more than 53,000 constructed lakes and reservoirs.
Building solar arrays at hydropower reservoirs is one low hanging fruit to pick, partly because they already have a transmission infrastructure in place. The challenge is to avoid impacts on aquatic life that may have taken up residence there. However, researchers are assembling evidence that putting solar panels behind existing dams could help avoid the greater impact (and costs) of building new hydropower dams.
The potential for land conservation is also considerable. Based on the 2018 study, NREL has estimated that the US could avoid solar development on 2,141,000 hectares of land by deploying its floating solar resources.
Last year, NREL also added to its stock of floating solar studies with a new report on the global potential for the hydropower-PV combo.
The report is based on an estimate of 379,068 freshwater hydropower reservoirs around the world where solar panels could be installed, though the researchers caution that’s a preliminary estimate. “Additional siting data is needed prior to any implementation because some reservoirs may be dry during parts of the year or may not be otherwise conducive to hosting floating PV,” NREL explains.
Even if the number of available sites shrinks considerably on further analysis, the output would still be impressive. Based on its original figure, NREL estimates a potential of 10,600 terawatt-hours of clean power generation annually, not including the output from the hydropower generators. That comes pretty close to 50% of all global electricity consumption.
Piggybacking solar panels on industrial lagoons and other previously disturbed sites would be another option. Along those lines, last week the Canadian company Boralex announced that it has just commissioned its first floating solar farm, consisting of more than 43,000 PV panels at a former gravel pit.
More Ways Than One To Put Solar Out To Sea
So far, most of the floating solar activity has been focused on arrays that float on inland lakes and reservoirs. However, that’s not the only avenue for siting solar panels over water.
Ocean energy is also attracting attention for its potential to hook up with solar arrays. Among the projects crossing the CleanTechnica radar this year are a wave energy plus solar mashup and a combination of offshore wind turbines, wave energy and solar panels.
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Image: Floating PV at hydropower reservoir courtesy of NREL.
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