Many countries are looking to floating systems to find space for large solar arrays. The Netherlands is now taking this a step further by developing water-based arrays that track the Sun.

A gleaming circular island floats in a Dutch lake, covered in dozens of gleaming solar panels.

But this is no ordinary solar array, nor is it one of the many new floating solar farms being installed around the world in lakes, reservoirs, and coastal areas. That’s because its panels do something that none of the other floating solar farms can: they meticulously track and follow the Sun as it moves across the sky, catching as many rays as possible.

This gleaming installation, named Proteus after the ancient Greek sea god, is among the first to combine floating solar panels with Sun-tracking technology in order to maximise the amount of clean electricity it can generate.

The island, which floats in the Oostvoornse Meer, a lake in the south-west Netherlands, is covered in 180 of these moving solar panels, totaling 73 kilowatts of peak power installed (kWp). It’s a small amount in a world trying to transition to renewable energy, but SolarisFloat, the Portuguese company that built Proteus, believes it can be scaled up to generate large amounts of clean electricity – and, crucially, without taking up valuable land.

Solar revolution

Floating solar panels are becoming increasingly popular all over the world, from the Brazilian Amazon to Japan. Floating solar capacity has increased dramatically over the last decade, from 70 MWp in 2015 to 1,300MWp in 2020. Over the next decade, the market for the technology is expected to grow at a 43% annual rate, reaching $24.5 billion (£21.7 billion) by 2031.

“Floating solar is a relatively new [renewable energy] option, but it has enormous global potential,” says Thomas Reindl, deputy chief executive of Singapore’s Solar Energy Research Institute (Seris). Covering just 10% of the world’s man-made reservoirs with floating solar would result in an installed capacity of 20 Terawatts (TW), which is 20 times the current global solar photovoltaic (PV) capacity. according to a Seris analysis seen by BBC Future Planet.

The rise of floating solar technology is one of the most recent trends in the revolutionary expansion of solar PV electricity in recent years. Global solar PV capacity has nearly tripled in the last decade, rising from 72GW in 2011 to 843GW in 2021. The technology now accounts for 3.6% of global electricity generation, up from 0.03% in 2006. At the same time, solar arrays have seen an incredible price drop, making them the world’s cheapest source of power.

Further expansions in solar energy are expected; in fact, capacity must reach six times its current level by 2030 in order to achieve a net zero-emissions world, according to the International Energy Agency. Global geopolitics are also influencing rising reliance on solar power: the European Union has proposed a massive increase in renewable energy as part of its efforts to reduce its reliance on Russian oil and gas in the aftermath of Russia’s invasion of Ukraine.

Along with this rapid expansion, researchers continue to seek advancements in solar technology. The majority of solar panels installed so far in the world are on solid ground. However, solar technologies that float on water have a distinct advantage: they do not take up land space that could be used for other purposes.

“Renewable energy production will increase all over the world,” says Antonio Duarte, SolarisFloat’s lead technical engineer. “Solar installations on water will grow much faster than on land. Why? Because land is becoming an increasingly valuable asset.”

This gives floating solar a significant advantage in a world looking to rapidly expand solar arrays, particularly in countries facing land scarcity. Conventional solar farms are frequently chastised for taking up too much land, land that could otherwise be used to grow crops to feed the world’s growing population or carbon-absorbing trees. According to Leiden University in the Netherlands, solar energy requires at least 40-50 times the space of coal plants and 90-100 times the space of gas plants.

Conservationists have also expressed concern that land-based solar and wind farms, particularly those built in species-rich areas, could have a negative impact on biodiversity.

Building sun-absorbing technology on water is thus a clever way to free up land. while also making use of unoccupied lakes and reservoirs. Because of limited land availability or high land prices, countries such as Japan and Singapore are investing heavily in floating solar farms.

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

However, according to Michael Walls, a professor at Loughborough University’s Centre for Renewable Energy Systems Technology, less than 1% of the world’s solar installations are currently floating. This is due in part to technical and financial constraints – saltwater causes corrosion, and positioning panels at an angle on a floating platform is difficult and expensive, according to Walls. He adds that installations on freshwater bodies may face opposition if they compete with other activities like swimming, boating, or angling.

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Still, floating solar farms solve another issue that plagues traditional solar energy: inefficiency when solar panels become too hot. Indeed, the cooling effect of the water over which floating solar panels float generates additional energy.

Solar panels generate electricity by utilising the Sun’s rays of light rather than its heat. However, when they become too hot, their efficiency suffers. This is because heat excites the electrons in the panel, which converts energy from the Sun into electricity, shrinking the difference between the high energy and rest states, lowering the voltage and amount of electricity generated. Solar PV panels typically operate at peak efficiency between 15 and 35 degrees Celsius (59 and 95 degrees Fahrenheit), but they can get as hot as 65 degrees Celsius (149 degrees Fahrenheit), limiting their efficiency.

According to Nuno Correia, director of composite materials at the Institute of Science and Innovation in Mechanical and Industrial Engineering in Porto, who developed the Proteus project, floating solar panels operate more efficiently and produce up to 15% more electricity.

Follow the Sun

However, there are other ways to boost solar panel energy production, such as tilting them to follow the Sun’s path in the sky, similar to how young sunflowers follow the sun from east to west during the day. Tracking technology, which is already used on some land-based solar arrays, increases overall electricity production by constantly adjusting the panels to face the Sun.

According to SERIS research, double-sided panels that track the Sun could increase energy production by 35% while lowering average electricity costs by 16%. Because of this efficiency boost, demand for tracking technology for solar panels is expected to grow by 16% per year between 2022 and 2030.

SolarisFloat claims that by combining the two technologies, it can increase electricity production by up to 40% when compared to static land installations.

SolarisFloat created Proteus as a pilot project to test this cutting-edge technology and analyse how it improves clean energy generation. This year, the prototype earned them a spot as a finalist for the European Inventor Award.

The single-sided panels of Proteus slowly rotate on two axes every few hours, using mechanical, geospatial, and light sensors to precisely follow the elevation of the Sun’s path as it moves from east to west.

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