Floating solar panels that track the sun

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Floating solar panels that track the sun

When looking for space for large solar arrays, many countries are looking for floating systems. Now, the Netherlands is going a step further, using water-based arrays that follow the sun.

On a lake in the Netherlands floats a shiny circular island covered in dozens of gleaming solar panels.

But this is no ordinary solar array, or even one of the many new floating solar farms being installed in lakes, reservoirs, and coastal areas around the world. That’s because its panels are doing something no other floating solar farm can do: carefully track and follow the sun as it moves across the sky, capturing as much light as possible.

The gleaming installation, named Proteus after the ancient Greek god of the sea, is one of the first to combine floating solar panels with sun-tracking technology — all to maximize clean electricity generation.

Floating in Oostvoornse Meer, a lake in the southwest of the Netherlands, the island is covered with 180 mobile solar panels with a total installed capacity of 73 kilowatts peak power (kW).

That’s a small amount in a world that’s rapidly trying to switch to renewable energy, but SolarisFloat, the Portuguese company that built Proteus, thinks the tiny installation could be scaled up to generate a lot of clean electricity—and, most importantly, No need to occupy valuable land.

Solar panels revolution

Floating solar panels are booming around the world, from the Brazilian Amazon to Japan. Floating solar capacity has grown substantially over the past decade, from 70 MWp in 2015 to 1,300 MWp in 2020. The market for the technology is expected to grow at an annual rate of 43% over the next decade, reaching $24.5bn (£21.7bn) by 2031.

Floating solar is a fairly new renewable energy option, but it has huge potential globally, said Thomas Reindl, deputy chief executive of the Solar Energy Research Institute of Singapore (Seris).

Covering just 10 percent of all the world’s man-made reservoirs with floating solar would generate an installed capacity of 20 terawatts (TW) – 20 times the global solar photovoltaic (PV) capacity today, according to an analysis by Seris BBC Future Planet.

The rise of floating solar technology is one of the latest trends in the revolutionary expansion of solar photovoltaics in recent years. Globally, installed solar PV capacity has grown nearly 12-fold over the past decade, from 72GW in 2011 to 843GW in 2021.

The technology now accounts for 3.6 percent of global electricity generation, up from 0.03 percent in 2006. At the same time, the price of solar arrays has dropped dramatically, making them some of the cheapest power sources in the world.

According to the International Energy Agency, solar power is expected to expand even further—in fact, capacity needs to be six times higher by 2030 to get on track to a net-zero emissions world.

Global geopolitics also play a role in increasing reliance on solar energy: the European Union has proposed a massive increase in renewable energy, to reduce its reliance on oil and gas after the country.

In addition to this tremendous growth, researchers continue to seek improvements in solar technology. Most of the solar panels installed around the world to date are on solid land. But solar technologies that float on the water have a unique advantage: They don’t take up land space that might be needed for other uses.

Renewable energy production is going to increase all over the world, said Antonio Duarte, chief technical engineer at Solaris Float. There will be more solar installations on the water and land. Why? Because land is becoming a very valuable asset.

In a world looking to rapidly scale up solar arrays, this offers important advantages to floating solar, especially for countries facing land scarcity. Conventional solar farms are often criticized for the amount of land they take up land that could be used to grow crops to feed the world’s growing population or plant carbon-absorbing trees.

Research by Leiden University in the Netherlands shows that solar energy requires a lot of space, at least 40-50 times that of coal-fired power plants and 90-100 times that of natural gas.

Environmentalists also worry about the harmful impact of onshore solar and wind farms on biodiversity, especially those built in species-rich areas.

So building solar-absorbing technology on the water is a smart way to free up land while also taking advantage of unused lakes and reservoirs. Countries such as Japan and Singapore are investing heavily in floating solar farms because the land is either limited or very expensive.

Floating solar installations have a unique advantage: they don’t take up valuable land space

But less than 1% of the world’s solar installations are currently floating, says Michael Walls, a professor at the Center for Renewable Energy Systems Technology at Loughborough University in the UK.

This is partly due to technical and financial constraints—salt water causes corrosion, and positioning panels at angles on floating platforms is tricky and expensive, Walls said.

Facilities on freshwater bodies of water could also face opposition if they compete with other activities such as swimming, boating, or fishing, he added.

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Still, floating solar farms solve another problem that plagues conventional solar: the inefficiency of solar panels when they get too hot. The floating solar panels generate additional power due to the cooling effect of their hovering over the water.

Solar panels use light from the sun rather than heat to generate electricity. But when they get so hot, their efficiency drops.

This is because heat excites the panel’s electrons, which convert energy from the sun into electricity, making the difference between high energy and resting states smaller, which in turn reduces the voltage and the amount of electricity produced. Solar PV panels typically operate at maximum efficiency between 15C and 35C but they can get as hot as 65C  affecting efficiency.

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