‘Fleetvoltaic’ solar panels on lakes could unlock…

This story was first published by Grist.

A reservoir is many things: a source of drinking water, a playground for swimmers, a shelter for migrating birds. But if you ask solar enthusiasts, the reservoir is also not using its full potential. This open water could be covered with floating panels, an emerging technology known as floating photovoltaics, or ​“floatvoltaics.” They could simultaneously collect solar energy and shade the water, reducing evaporation – an especially welcome bonus as droughts deepen.

Now scientists have crunched the numbers and found that if humans installed floating cells in a fraction of the world’s lakes and reservoirs – covering just 10 percentage of the area of ​​each – the systems could together generate four times the amount of energy the UK uses in a year. The effectiveness of so-called FPVs varies by country, but their research showed that some could theoretically supply all their electricity this way, such as Ethiopia, Rwanda and Papua New Guinea.

“The countries around the world that have benefited most from these FPVs are low-latitude tropical countries that did not have high energy needs in the first place,” said Iestyn Woolway, an Earth system scientist at Bangor University and lead author of the new article describing the findings in the journal Nature Water. ​“This meant that if only a small percentage of their lakes — then 10 percent – ​​was covered by FPV, it could be enough to meet the energy needs of the entire country.”

For developing countries, floating-voltaic cells may prove particularly effective in generating clean electricity. Instead of building more planet-warming infrastructure based on fossil fuels such as gas-fired power plants, fledgling economies could run panels on land and water, in addition to other renewable energy sources such as wind and hydropower. Solar power provides autonomy: Utilities do not have to rely on fossil fuel supplies, but can take advantage of abundant solar energy.

Floatvoltaic solar panels – which are spreading across the world, from California to France to Taiwan – are the same ones found on roofs. ​“It’s the same electrical system, same panels, same inverters,” said Chris Bartle, director of sales and marketing at Ciel and Terre USAwhich implements floatvoltaic systems. ​“We simply provide a floating structure to accommodate the electrical system.” Solar rafts are anchored either to the bottom of a body of water or to the shore, or both, to prevent them from wandering.

In many ways, solar panels and water tanks can benefit each other. Photovoltaics become less efficient the warmer it is, so placing it on a lake or reservoir helps cool it. ​“Due to the cooling effect, we see increased efficiency of the systems,” said Sika Gadzanku, a researcher at the National Renewable Energy Laboratory in Colorado who studies swimming and was not involved in the new research. In return, the panels provide shading, reducing evaporation. If float installations are placed throughout the reservoir, this may mean more water will be available for drinking.

If the reservoir is equipped with a dam for hydropower generation, the floating voltaics can connect to the existing transmission infrastructure. (Countries like Kenya are already building more hydroelectric infrastructure). This could save local governments money because they would not have to build new transmission lines from the floating power plants to the nearest city. In the event of drought, when water levels drop too low to generate hydropower, the panels can still act as a backup power source.

To do the new modeling, Woolway and his colleagues started with more than a million lakes and reservoirs around the world that were large and deep enough for float voltaics. They then narrowed them down based on critical features. First, the body of water could not dry out, wash the panels ashore or freeze for more than six months of the year, burying the panels in ice and damaging them. The lake also could not be legally protected as a natural refuge. The site had to be close to a human population that could benefit from the energy generated.

In turn, a remote lake would require long transmission lines to connect the distant town to the float grid. This does not necessarily rule out the technology for more remote communities of people living near the relevant lake. In fact, float voltaics may prove particularly effective there as a way to provide clean energy. These cases were simply not included in the scope of this modeling.